JP6458235B2 - Switching power supply - Google Patents

Description

  The present invention relates to a switching power supply device used for a DC-DC converter or the like, and more particularly to an insulating switching power supply device in which a primary circuit and a secondary circuit are electrically insulated by a transformer.

  A switching power supply device such as a DC-DC converter is characterized by being highly efficient while being small and light, and has recently been widely used as a power source for various electronic devices and devices. Such a switching power supply device generally has a configuration in which a primary side circuit and a secondary side circuit are electrically insulated using a transformer.

FIG. 10 is a schematic circuit configuration diagram of a conventional full-bridge switching power supply device (see Patent Documents 1 and 2, etc.).
As shown in the figure, in this switching power supply device, the transformer 21 insulates the circuit on the primary winding 211 side (primary side circuit) from the circuit on the secondary winding 212 side (secondary side circuit). Yes. The primary side circuit includes a first arm in which two switching elements 151 and 161 are connected in series between a positive power supply line 11 and a negative power supply line 12 connected to the DC power supply 10; 2 switching elements 171 and 181 connected in series with each other, a connection point 13 of the two switching elements 151 and 161 on the first arm, and 2 on the second arm. A primary winding 211 of the transformer 21 is connected between the connection points 14 of the switching elements 171 and 181. Each switching element 151, 161, 171, 181 is connected in reverse parallel with diodes 152, 162, 172, 182 for reverse conduction, and capacitors 60, 61, 62, 63 that function as snubber capacitors are also connected in parallel. It is connected. As the diodes 152, 162, 172, 182 for reverse conduction and the capacitors 60 to 63, parasitic diodes of the switching elements 151 to 181 themselves (when the switching elements are MOS-FETs) and parasitic capacitances are used. Can do.

  On the other hand, the secondary circuit includes a diode bridge circuit for rectification composed of a series circuit of two diodes 22 and 23 and another series circuit of two diodes 24 and 25, an inductor (reactor) 26 and a capacitor 27. And an LC filter circuit comprising: The secondary winding 212 of the transformer 21 is connected between the connection point of the two diodes 22 and 23 and the connection point of the other two diodes 24 and 25, and DC power is supplied to the subsequent stage of the LC filter circuit. A load 28 that is an object to be supplied is connected.

  In this switching power supply device, a control unit (not shown) detects the voltage output to the load 28 and turns on / off the four switching elements 151 to 181 so that the detected voltage becomes a set target voltage. To control each. By the on / off control of the switching elements 151 to 181, the direct current supplied from the direct current power supply 10 to the primary winding 211 of the transformer 21 is controlled so that the direction is alternately and alternately reversed. An alternating current voltage is induced in the secondary winding 212 by the alternating current flowing in the primary winding 211, and the current flowing by the voltage is rectified and smoothed by the diode bridge circuit and the LC filter circuit, that is, converted into a direct current and loaded. 28.

  As the switching elements 151 to 181, a power MOSFET, an insulated gate bipolar transistor (IGBT) or the like is used. Generally, however, a surge voltage may be generated when these switching elements are turned on and turned off. On the other hand, in the circuit shown in FIG. 10, capacitors 60 to 63 as snubber capacitors are connected in parallel to the switching elements 151 to 181, and the surge voltage and surge current are reduced by the capacitors 60 to 63. . In the switching power supply device described above, the switching elements having a full bridge configuration are subjected to phase shift control for soft switching, so that zero voltage switching is performed when the switching elements are turned off (hereinafter referred to as “ZVS” according to common usage). Operation can be realized. In such ZVS operation, power consumption in a transient state between ON and OFF of the switching element is suppressed, so that switching loss is reduced, power is used effectively, and heat generation due to loss is also suppressed. Is done.

  However, the ZVS operation based on the phase shift control as described above is limited to a circuit using a switching element having a full bridge configuration, and is applied to a circuit having a half bridge configuration or a push-pull configuration commonly used for a small-scale switching power supply device. Can not do it.

  Further, as pointed out in Patent Document 3 and Non-Patent Document 1, when such a full-bridge switching element is subjected to phase shift control, a current having a waveform as shown in FIG. 11 flows in the primary circuit. FIG. 12 is a waveform of a current flowing in the primary circuit when the switching power supply device having the same circuit configuration is subjected to PWM control. As can be seen from a comparison between FIG. 11 and FIG. 12, in the phase shift control, the conduction loss of the switching element increases as the circulating current indicated by the hatched area in FIG. Due to this loss, the switching element and the primary winding generate heat, and it is difficult to miniaturize these components. Note that these problems occur more in switching power supply devices that are designed so that the normal duty ratio of the pulse signal that drives the switching element is small because the variable range of voltage and current is wide and the load changes over a wide range. It is remarkable.

  Furthermore, in the above conventional switching power supply device, since the ZVS operation is realized by utilizing the energy of the circulating current, when the circulating current is small because the load current is small, the switching elements 151 to 181 are connected in parallel. Charging / discharging of the capacitors 60 to 63 that have been performed may be incomplete, and an appropriate ZVS operation may not be performed. On the contrary, if the circulating current is small, a short-circuit surge current of the capacitors 60 to 63 is generated via the switching elements 151 to 181 and the switching loss may be increased. In addition, the occurrence of such a short-circuit surge current impairs the stability of the switching operation and generates noise.

U.S. Pat. No. 4,864,479 JP 2004-56971 A JP 2009-118648 A

Matsushita et al., “Characteristic Analysis and Prototype Experiment of High Frequency AC Link DC-DC Converter with Secondary Phase Shift PWM Control 2. Principle 2-1 Features and Problems of Phase Shift PWM Control”, Kobe National College of Technology, [May 2014 Search 14th of March], Internet <URL: http://www.kobe-kosen.ac.jp/~michi/matsushita/1/2-1_feature_and_problem.html>

The present invention has been made to solve the above-mentioned problems, and its main purpose is not limited to the full-bridge method, but also realizes the ZVS operation without performing phase shift control in the half-bridge method and the push-pull method. An object of the present invention is to provide a switching power supply device that can reduce power loss.
Another object of the present invention is to provide a switching power supply device that can avoid the occurrence of a surge current even when the load current is small, and can achieve the stability of switching operation and the suppression of noise generation. There is to do.

The switching power supply device according to the first aspect of the present invention, which has been made to solve the above problems, has two arms each having an even number of main switching elements each having a diode connected in anti-parallel, connected in series, A full bridge circuit in which both ends of each of the two arms are connected to a positive and negative DC power supply line, and a transformer having a primary winding connected between the midpoints of the two arms, In the full bridge circuit , the main switching element on the positive DC power supply line side with the midpoint on one of the two arms and the negative DC on the other arm with the midpoint on the other side A drive signal for PWM control is given to the main switching element on the power supply line side, and on the negative DC power supply line side across the middle point on the one of the two arms. A drive signal whose phase is delayed by 180 ° from the drive signal is applied to the main switching element and the main switching element on the positive DC power supply line side with the middle point on the other arm. A full bridge that operates the element to supply a current that alternates its direction to the primary winding of the transformer, thereby supplying power to the load based on the voltage induced in the secondary winding of the transformer Switching power supply device of the type,
a) a snubber circuit formed by connecting an auxiliary switch and a capacitor connected in series between the middle points of the two arms and capable of supplying a current alternatively and bidirectionally;
b) a main switching element driving unit for driving the main switching element of the full bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
With
The switching control unit is configured to switch the auxiliary switch when all the main switching elements are turned off by switching a pair of main switching elements included in different arms of the two arms from an on state to an off state. Is turned on in a predetermined direction for a predetermined period , and is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off, and passes through the auxiliary switch. The capacitor is charged by the flowing current, and then the auxiliary switch is switched from the on state to the off state, and the other pair of main switching elements included in different arms of the two arms are switched from the off state to the on state. The main switching element drive unit and the snubber switch drive Is characterized in that control each section.

Further, the switching power supply device according to the second aspect of the present invention, which has been made to solve the above-mentioned problems, has an even number of main switching elements each having a diode connected in anti-parallel, connected in series, and both ends are positive and negative. A half-bridge circuit connected to a direct current DC power supply line, a capacitor series circuit in which an even number of capacitors are connected in series, and both ends are connected to positive and negative DC power supply lines, and the half-bridge circuit And a transformer having a primary winding connected between the center point of the capacitor series circuit and a PWM control drive signal to a main switching element on one side across the center point of the half-bridge circuit. And a drive signal whose phase is delayed by 180 ° relative to the drive signal to the main switching element on the other side across the midpoint. That direction to the primary winding of the transformer to supply current to alternately reversed by operating the switching element, thereby supplying electric power based on the voltage induced in the secondary winding of the transformer to a load half A bridge-type switching power supply,
a) An auxiliary switch connected between the midpoint of the half-bridge circuit and the midpoint of the capacitor series circuit, which can alternatively supply current bidirectionally, and a capacitor are connected in series. Snubber circuit,
b) a main switching element driving unit for driving the main switching element of the half-bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit sets the auxiliary switch in a predetermined direction when all the main switching elements are turned off by switching one main switching element in the half-bridge circuit from an on state to an off state. By turning on for a period of time, the snubber is caused by the current flowing through the auxiliary switch , which is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off. The main switching element is charged so that the capacitor constituting the circuit is charged and then the auxiliary switch is switched from the on state to the off state, and the other main switching element in the half-bridge circuit is switched from the off state to the on state. A drive unit and the snubber switch drive unit; It is characterized by controlling each.

A switching power supply device according to a third aspect of the present invention, which has been made to solve the above problems, includes a transformer including a primary winding having an intermediate tap connected to a positive DC power supply line, and the primary winding. A first main switching element connected between one end of the wire and the negative DC power supply line and having a diode connected in reverse parallel; the other end of the primary winding; and a negative DC power supply line A second main switching element having a diode connected in antiparallel, and operating the first and second main switching elements to the primary winding of the transformer. A push-pull type switching power supply device that controls on / off of a current to be supplied, and thereby supplies power based on a voltage induced in a secondary winding of the transformer to a load;
a) alternatively connected between a connection point between the primary winding and the first main switching element and a connection point between the primary winding and the second main switching element; A snubber circuit in which an auxiliary switch capable of supplying current in both directions and a capacitor are connected in series;
b) a main switching element driving unit for driving the first and second main switching elements, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit is configured to turn the auxiliary switch in a predetermined direction when all the main switching elements are turned off by switching one of the first or second main switching elements from an on state to an off state. By turning on the power source for a predetermined period of time, it is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off , and the current flowing through the auxiliary switch Charging the capacitor, and then switching the auxiliary switch from the on-state to the off-state, and switching the other of the first or second main switching elements from the off-state to the on-state; The snubber switch driving unit is controlled.

In addition, the switching power supply device according to the fourth aspect of the present invention, which has been made to solve the above-mentioned problems, has two arms each having an even number of main switching elements each having a diode connected in antiparallel, connected in series, A full bridge circuit in which both ends of the two arms are connected to positive and negative DC power supply lines, and a transformer in which a primary winding is connected between the midpoints of the two arms. In the full-bridge circuit , the main switching element on the positive DC power supply line side with the middle point on one arm of the two arms and the negative polarity with the middle point on the other arm A drive signal for PWM control is given to the main switching element on the DC power supply line side, and a negative DC power supply line with a middle point on the one of the two arms. A drive signal whose phase is delayed by 180 ° relative to the drive signal is applied to the main switching element located on the other arm and the main switching element located on the positive DC power supply line side with the middle point on the other arm. By operating the switching element, a current whose direction is alternately reversed is supplied to the primary winding of the transformer, thereby supplying power based on the voltage induced in the secondary winding of the transformer to the load. A bridge-type switching power supply,
a) A serial circuit of an even number of capacitors connected in parallel to one arm, and alternatively, current can be supplied bidirectionally connected between the midpoint of the series circuit and the midpoint of the arm A first snubber circuit comprising: a first auxiliary switch;
b) A serial circuit of an even number of capacitors connected in parallel to the other arm, and alternatively, current can be supplied bidirectionally connected between the midpoint of the series circuit and the midpoint of the arm A second snubber circuit comprising: a second auxiliary switch,
c) A main switching element driving unit for driving the main switching element of the full bridge circuit and a snubber for independently turning on and off the first and second auxiliary switches of the first and second snubber circuits for each current direction. A switch drive unit,
d) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
With
The switching control unit, when all of the main switching element at Rukoto switching a pair of main switching elements included in different arms ones of the two arms from the ON state to the OFF state is turned off, the first 1 and a second auxiliary switch by the Tokoro periodically between oN state, derived from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off , by a current flowing through the first and second auxiliary switches, the capacitor is in the state of being connected in parallel to the pair of main switching elements of the plurality of capacitors included in the first and second snubber circuits while charging, to discharge the capacitor is in the state of being connected in parallel to the other pair of main switching elements, their After with switching off state them auxiliary switch from the on state, before Symbol to switch the other pair of main switching element from the off state to the on state, control the main switching element driving unit and the snubber switch driving section, respectively It is characterized by doing.

Further, the switching power supply device according to the fifth aspect of the present invention, which has been made to solve the above-mentioned problems, has an even number of main switching elements each having a diode connected in anti-parallel, connected in series, and both ends are positive and negative. A half-bridge circuit connected to a direct current DC power supply line, a capacitor series circuit in which an even number of capacitors are connected in series, and both ends are connected to positive and negative DC power supply lines, and the half-bridge circuit And a transformer having a primary winding connected between the center point of the capacitor series circuit and a PWM control drive signal to a main switching element on one side across the center point of the half-bridge circuit. And a drive signal whose phase is delayed by 180 ° from the drive signal is applied to the other main switching element across the midpoint. That direction to the primary winding of the transformer to supply current to alternately reversed by operating the main switching element, thereby supplying electric power based on the voltage induced in the secondary winding of the transformer to a load A half-bridge type switching power supply
a) a series circuit of an even number of capacitors connected in parallel to the half-bridge circuit, and alternatively bidirectional current connected between the midpoint of the series circuit and the midpoint of the half-bridge circuit. A snubber circuit comprising an auxiliary switch capable of supplying
b) a main switching element driving unit for driving the main switching element of the half-bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit comprises a, when the all of the main switching element at Rukoto turned OFF the main switching element one which is separated at the midpoint of the half-bridge circuit from the ON state is turned off, the auxiliary by switching to a predetermined regular between the on state, and from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off, it flows through the auxiliary switch Among the even number of capacitors included in the snubber circuit, the capacitor that is connected in parallel to the one main switching element is charged by the current, while being connected in parallel to the other main switching element. The capacitor is discharged, and then the auxiliary switch is switched from on to off. The to switch the other main switching device from the OFF state to the ON state, it is characterized by controlling the main switching element driving unit and the snubber switch driving section, respectively.

Furthermore, a switching power supply device according to a sixth aspect of the present invention, which has been made to solve the above problems, includes a transformer including a primary winding having an intermediate tap connected to a positive DC power supply line, and the primary A first main switching element connected between one end of the winding and the negative DC power supply line and having a diode connected in reverse parallel; the other end of the primary winding and the negative DC power supply line And a second main switching element having a diode connected in antiparallel, and operating the first and second main switching elements to operate a primary winding of the transformer A push-pull type switching power supply device that controls on / off of a current supplied to the transformer, thereby supplying power based on a voltage induced in the secondary winding of the transformer to a load,
a) A first snubber comprising a first auxiliary switch connected between both ends of the first main switching element and capable of supplying a current alternatively and bidirectionally and a capacitor connected in series. Circuit,
b) a second snubber in which a second auxiliary switch connected between both ends of the second main switching element and capable of supplying a current in both directions and a capacitor are connected in series; Circuit,
c) The main switching element driving section for driving the first and second main switching elements, and the first and second auxiliary switches of the first and second snubber circuits are turned on and off independently for each current direction. A snubber switch drive unit that is driven off;
d) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit comprises a, when the all of Rukoto switched one from the ON state to the OFF state of the main switching element of the first or second main switching element is turned off, the first and the second auxiliary switch by the Tokoro periodically between oN state, derived from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off, the first The current flowing through the first and second auxiliary switches charges the capacitor that is connected in parallel to the main switching element that has been switched off immediately before, while being connected in parallel to the other main switching element. The capacitor in the closed state is discharged, and then the auxiliary switches are switched from the on state to the off state, and the other To switch the main switching element from the OFF state to the ON state, it is characterized by controlling the main switching element driving unit and the snubber switch driving section, respectively.

  In the switching power supply device according to the first to third aspects of the present invention, the primary side circuit connected to the primary winding of the transformer is different from the full bridge method, the half bridge method, and the push-pull method. A snubber circuit in which an auxiliary switch and a capacitor are connected in series is provided in parallel with the primary winding. In any of the first to third aspects, the switching control unit turns off the auxiliary switch in a state where some of the main switching elements are turned on so that a current flows through the primary winding of the transformer. . Therefore, at this time, the capacitor included in the snubber circuit is substantially disconnected from the primary side circuit of the transformer, and no current flows through the capacitor. keep.

  The switching controller turns off some of the main switching elements that are in the on state, and turns on the auxiliary switch when all of the main switching elements are in the off state. As a result, the capacitor included in the snubber circuit is connected to the primary side circuit, specifically, the path including the primary winding and the main switching element. Only when all the main switching elements are in the OFF state, this capacitor is connected to the path, so that the capacitor is charged or discharged by the energy stored in the leakage inductance of the primary winding of the transformer.

  The direction of charging or discharging of the capacitor is reversed every time the main switching element or the main switching element pair to be turned on is alternately switched. Therefore, when the auxiliary switch is turned on, the voltage gradually increases or decreases so that the polarity of the voltage across the capacitor (the polarity of the potential of the other terminal with respect to the potential of one terminal) is alternately inverted. Always pass through zero. Accordingly, the voltage applied to the main switching element that is turned off prior to or substantially simultaneously with the turn-on of the auxiliary switch gradually increases from zero, while the voltage applied to the other main switching elements is a predetermined voltage (for example, a power supply). The voltage gradually decreases from zero to zero. Thereby, zero voltage switching operation in these main switching elements can be achieved, and switching loss can be suppressed. The on / off drive of the main switching element may be performed by normal PWM control.

  On the other hand, in the switching power supply devices according to the fourth to sixth aspects of the present invention, the primary side circuit connected to the primary winding of the transformer is different from the full-bridge method, the half-bridge method, and the push-pull method. A capacitor is provided for each main switching element so that a capacitor that functions as a snubber capacitor is connected in parallel to the main switching element only when the auxiliary switch is in the ON state. The timing of the on / off control of the auxiliary switch by the switching control unit is the same as that of the switching power supply according to the first to third aspects.

  That is, also in the switching power supply devices according to the fourth to sixth aspects, in the state where some of the main switching elements are turned on in order to pass current through the primary winding of the transformer, It is disconnected from the path including the primary winding and maintains the charged or discharged voltage just before it. When all the main switching elements are turned off, the auxiliary switch is turned on, and each capacitor is connected to a path including the corresponding main switching element, so that the leakage inductance of the primary winding of the transformer is reduced. The stored energy charges or discharges the capacitor, and the voltage across the capacitor gradually increases from zero or gradually decreases from a predetermined voltage to zero. Accordingly, as in the switching power supply device according to the first to third aspects, the voltage applied to the main switching element turned off prior to or substantially simultaneously with the turning on of the auxiliary switch gradually increases from zero, while the others The voltage applied to the main switching element gradually decreases from a predetermined voltage to zero.

  In the switching power supply according to any one of the first to sixth aspects of the present invention, each auxiliary switch has a unidirectional switching element in which a unidirectional switching element in which a current flows only in one direction is connected in reverse parallel, and the unidirectional dedicated drive according to the current direction. It is preferable that the unidirectional switching element is independently turned on / off by a signal.

  In this configuration, the current flows through the auxiliary switch in a direction opposite to the current direction when one of the unidirectional switching elements is turned on, that is, when the switching element is in a negative polarity, the switching element is gate-driven. When the switching element is turned off spontaneously regardless of the presence or absence of a signal, or when the switching element is switched from an on state to an off state by a drive signal, the current flowing through the switching element is zero, so that a zero current switching operation is performed. As a result, the timing at which one unidirectional switching element is switched from the on state to the off state by the drive signal is after a predetermined period in which the switching element spontaneously turns off, and the other one that performs complementary operation with a phase delay of 180 °. The main switching element may be at an arbitrary time until the main switching element switches from the off state to the on state.

  In the switching power supply according to the present invention, the configuration of the secondary circuit is not particularly limited, and includes, for example, a rectifier circuit and a smoothing circuit, and a DC voltage generated by the rectifier circuit and the smoothing circuit is used as a load. It can be set as the structure which supplies, or can be set as the structure which supplies alternating current power to load as it is.

  According to the switching power supply according to the present invention (full-bridge, half-bridge, and push-pull switching power supplies driven by PWM control), a main switching element for PWM control can be provided without performing phase shift control. Switching can be performed with zero voltage. That is, a ZVS operation can be realized. As a result, it is possible to avoid a circulating current from flowing through the main switching elements, so that it is possible to reduce the loss generated in the primary winding of the switching elements and the transformer, and to reduce the size of the parts by reducing the heat generation of these parts. Can also be realized.

  Further, according to the switching power supply device according to the present invention, the snubber capacitor functions only when the main switching element is turned off. Therefore, even when the load current is small, the snubber capacitor is short-circuited via the main switching element. Generation of surge current can be avoided. As a result, the power loss can be further reduced, the stability of the switching operation can be improved, and the occurrence of noise due to the surge current can be suppressed.

  Note that these actions and effects are caused by driving the added auxiliary switch unit at an appropriate timing, so it is irrelevant to the switching control method, and phase shift control is performed for zero voltage switching operation. The present invention can also be applied to a full-bridge switching power supply device. That is, since the switching control device according to the present invention does not depend on the switching control method, it is a double active bridge (DAB) type that operates the phase of the switching between the primary side circuit and the secondary side circuit by phase shift control. The present invention can also be applied to a bidirectional DC-DC converter. In addition, since the effect of the switching control device according to the present invention is not affected by the configuration of the secondary side circuit, the DC-DC converter having not only the DC-DC converter having the rectifier circuit in the secondary side circuit but also the DC- The present invention can also be applied to an AC inverter.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic circuit block diagram of the switching power supply device which is 1st Example of this invention. The signal waveform diagram of each part of the vicinity of the period immediately after the turn-off of the main switching element in the switching power supply device of 1st Example. The schematic circuit block diagram of the switching power supply which is 2nd Example of this invention. The schematic circuit block diagram of the switching power supply which is 3rd Example of this invention. The schematic circuit block diagram of the switching power supply which is 4th Example of this invention. The signal waveform diagram of each part of the vicinity of the period immediately after the turn-off of the main switching element in the switching power supply device of 4th Example. The schematic circuit block diagram of the switching power supply which is 5th Example of this invention. The schematic circuit block diagram of the switching power supply which is 6th Example of this invention. The figure which shows the specific circuit example of the auxiliary switch in the switching power supply device of each Example. The schematic circuit block diagram of the conventional full bridge type switching power supply device. The signal waveform figure of the electric current which flows into the primary winding of a transformer in the case of phase shift control in the conventional switching power supply device. The signal waveform figure of the electric current which flows into the primary winding of a transformer at the time of PWM control in the conventional switching power supply device.

[First embodiment]
A switching power supply device according to a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic circuit diagram of the switching power supply device of the first embodiment, and FIG. 2 is a signal waveform diagram of each part in the vicinity of the period immediately after the main switching element is turned off in the switching power supply device of the first embodiment. The switching power supply according to the first embodiment is a full-bridge switching power supply.
1, the same components as those in the conventional switching power supply device shown in FIG. 10 are denoted by the same reference numerals. The same applies to the following second to sixth embodiments.

Since the secondary circuit connected to the secondary winding 212 of the transformer 21 is exactly the same as the conventional switching power supply device, description thereof is omitted. In the primary circuit connected to the primary winding 211 of the transformer 21, instead of the capacitors 60 to 63 respectively connected in parallel to the main switching elements 151 to 181 in the conventional device shown in FIG. The auxiliary switch 19 and the snubber are connected between the connection point 13 of the two switching elements 151 and 161 that are the midpoint of the arm and the connection point 14 of the two switching elements 171 and 181 that are the midpoint of the second arm. A series circuit with a capacitor 20 that functions as a capacitor is connected. In other words, a series circuit of the auxiliary switch 19 and the capacitor 20 is connected in parallel with the primary winding 211 of the transformer 21.
Here, the auxiliary switch 19 is not composed of a single power MOSFET or IGBT, but typically to obtain a unidirectional characteristic with a switching element such as a power MOSFET or IGBT, as will be described later with reference to FIG. And a unidirectional switching element including (or consisting of) a diode, and can alternatively supply current in both directions.

  The four main switching elements 151 to 181 are on / off controlled by a drive signal generated by the main switching element driving unit 31 based on an instruction from the switching control unit 30. On the other hand, the auxiliary switch 19 is ON / OFF controlled by a drive signal generated by the snubber switch drive unit 32 based on an instruction from the switching control unit 30. There are two drive signals supplied to the auxiliary switch 19, and each drive signal determines the direction of current flowing through the auxiliary switch 19. The switching control unit 30 includes a CPU and a memory (for example, a flash ROM) in which a control program is stored in order to perform characteristic switching control to be described later.

Next, the operation of the switching power supply device according to the first embodiment will be described.
The operation of the main switching elements 151 to 181 that are turned on / off according to the drive signal from the main switching element driving unit 31, and thereby the voltage induced in the secondary winding 212 due to the current flowing in the primary winding 211. On the other hand, the operation performed in the secondary circuit is exactly the same as the PWM control in the existing full bridge switching power supply. That is, another pair of main switching elements 161 and 171 is switched by PWM control with a drive signal whose phase is delayed by 180 ° with respect to the pair of main switching elements 151 and 181 on different arms.

  2, (a) shows the waveform of the gate drive signal Vg1 applied to the gate terminal of the main switching element 151, (b) shows the waveform of the gate drive signal Vg11 applied to the gate terminal corresponding to the current direction of the auxiliary switch 19, (C) is the waveform of the current Iq1 flowing through the main switching element 151, (d) is the waveform of the current Id2 flowing through the diode 162 connected in reverse parallel to the main switching element 161, (e) is the waveform of the current Iq11 flowing through the auxiliary switch 19, f) is a voltage Vq11 waveform across the auxiliary switch 19, (g) is a voltage Vq1 waveform across the main switching element 151, and (h) is a voltage Vc11 waveform across the capacitor 20. The voltage and current waveforms related to the main switching element 181 are the same as the voltage and current waveforms related to the main switching element 151, and the current waveform related to the diode 172 connected in reverse parallel to the main switching element 171 is the same as the current waveform related to the diode 162. is there.

  As shown in FIG. 2A, since the gate drive signal Vg1 is at the high level in the period before time t0, the main switching elements 151 and 181 are in the conductive state, as shown in FIG. In addition, the voltage Vq1 of the main switching element 151 is almost zero. At this time, a current Iq1 corresponding to the load current as shown in FIG. 2C passes from the positive electrode of the DC power supply 10 through the positive power supply line 11 to the primary switching element 151 and the primary winding of the transformer 21. 211, the main switching element 181, and the negative power supply line 12, and then flows in a closed loop reaching the negative electrode of the DC power supply 10.

  As shown in FIG. 2B, since the gate drive signal Vg11 is at the low level in the period before time t0, the auxiliary switch 19 is in the OFF state. Therefore, the capacitor 20 connected in series to the auxiliary switch 19 is disconnected from the closed loop including the connection points 13 and 14 of the two arms, and the current Iq11 flowing through the capacitor 20 as shown in FIG. Zero. The voltage Vc11 at both ends of the capacitor 20 at this time is charged by the energy accumulated in the leakage inductance (not shown) of the transformer 21 during the off period of the main switching elements 161 and 171 immediately before the voltage Vc11. Is equal to the voltage E1 from the DC power source 10. Here, the polarity of the voltage Vc11 across the capacitor 20 is positive when the potential on the connection point 14 side is higher than that on the connection point 14 side with respect to the connection point 13 side. The voltage Vq11 applied to the auxiliary switch 19 in the off state is a series composite value in consideration of the polarity of the voltage difference E1 between the connection points 13 and 14 and the voltage Vc11 across the capacitor 20, and in this case, as shown in FIG. It is zero as shown.

  At time t0, when the gate drive signal Vg1 for the main switching elements 151 and 181 becomes a low level, both the main switching elements 151 and 181 are turned off, and all the main switching elements 151 to 181 are turned off to increase the impedance. At substantially the same time, the gate drive signal Vg11 for the auxiliary switch 19 becomes high level (see FIG. 2B), and the switch 19 is turned on, so that the capacitor 20 is connected to the above-mentioned high impedance two arms. 13 and 14 are connected. At this time, the direction of the current flowing through the primary winding 211 of the transformer 21 is opposite to the direction of the current flowing through the primary winding 211 during the off period of the immediately preceding main switching elements 161 and 171. The direction of energy stored in the leakage inductance of the winding 211 is reversed so that the connection point 13 side of the first arm is negative and the connection point 14 side of the second arm is positive. Charging of the capacitor 20 is started in the direction opposite to the polarity of the voltage that has been applied. Therefore, as shown in FIG. 2 (h), the voltage Vc11 across the capacitor 20 gradually increases from -E1.

  The voltage Vq1 applied to the main switching elements 151 and 181 is an equal value of the series composite value in consideration of the polarities of the voltage E1 from the DC power supply 10 and the voltage Vc11 across the capacitor 20, and the voltage Vc11 across the capacitor 20 described above is equal. As the voltage rises, the voltage Vc11 between both ends passes through zero and gradually rises to the voltage E1 while all the main switching elements 151 to 181 are in the off state. Therefore, the main switching elements 151 and 181 operate in ZVS, and the switching-off loss is reduced. At the same time, the voltage applied to the main switching elements 161 and 171 gradually decreases from the voltage E1 to zero with the same slope that complements the voltage increase of the main switching elements 151 and 181. Since the voltage Vq11 applied to the switch 19 when the auxiliary switch 19 is turned on is almost zero, the auxiliary switch 19 also performs ZVS operation.

  At time t1, when the voltage Vc11 across the capacitor 20 tries to exceed the voltage E1 from the DC power supply 10, the diodes 162 and 172 connected in reverse parallel to the main switching elements 161 and 171 are turned on, as shown in FIG. A current Id2 shown flows from the diodes 162 and 172 to the DC power supply 10. For this reason, the voltage Vc11 at both ends of the capacitor 20 is clamped to the voltage by the DC power supply 10 and therefore does not become E1 or more. At this time, the current Ic11 does not flow through the series circuit of the auxiliary switch 19 and the capacitor 20.

  At time t2, when the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21 disappears and the current Id2 flowing through the diodes 162 and 172 disappears, the potentials of the connection points 13 and 14 in the two arms are both It converges to an equal value E1 / 2 of the voltage E1. The voltage Vq11 applied to the auxiliary switch 19 is a series composite value in consideration of the polarities of the voltage between the connection points 13 and 14 and the voltage Vc11 across the capacitor 20, and at this time, the voltage E1 charged in the capacitor 20 immediately before that. However, the polarity is opposite to that of the current Iq11 flowing through the switch 19. Since the auxiliary switching element in the auxiliary switch 19 is a unidirectional switching element, even if the gate drive signal Vg11 to the switch 19 is at a high level, the switch 19 is spontaneously turned off in the state where the current Iq11 does not flow. To do. As a result, the capacitor 20 retains the voltage value Vc11 = E1 charged during the off period of the immediately preceding main switching elements 151 and 181 and the polarity thereof.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching elements 161 and 171 are turned on (not shown). At substantially the same time, the gate drive signal Vg11 to the auxiliary switch 19 becomes low level, the switch 19 is turned off, and the capacitor 20 maintains the voltage value Vc11 = E1 and its polarity while the connection points 13 and 14 are connected. Disconnected from the closed loop containing. Since the current Iq11 does not flow when the auxiliary switch 19 is turned off, zero current switching (hereinafter referred to as “ZCS” according to common usage) is performed. In addition, a current flows through the primary winding 211 of the transformer 21 in a direction opposite to the period in which the main switching elements 151 and 181 are in the ON state.

  Since the operation immediately after the main switching elements 161 and 171 are turned off is the same as the operation of the main switching elements 151 and 181 except that the phase is different by 180 °, detailed description is omitted.

  In the switching power supply device of the first embodiment, due to the configuration and operation described above, a series circuit of the auxiliary switch 19 and the capacitor 20 is provided only during the off period of the main switching elements 151 to 181 as shown in FIG. Current flows. For this reason, the average current flowing through the auxiliary switch 19 is small, and since the auxiliary switch 19 performs ZVS operation when turned on and ZVS and ZCS operations when turned off, a small switching element can be used with little loss. The loss generated in the auxiliary switch 19 is sufficiently small compared with the improvement of the switching-off loss of the main switching elements 151 to 181. The effect becomes more remarkable as the switching frequency is higher. Therefore, the switching power supply device of this embodiment is simple. It can be said that the circuit configuration is suitable for high-frequency switching.

  Further, in the switching power supply device of the present embodiment, the ZVS operation can be realized by general PWM control without performing phase shift control. Therefore, since it is not necessary to flow a circulating current to the primary side circuit, the loss of the main switching elements 151 to 181 and the primary winding 211 of the transformer 21 can be reduced. In addition, since the load current is small, the energy stored in the leakage inductance of the primary winding 211 of the transformer 21 is small, so that the voltage charged and held in the capacitor 20 when the main switching elements 151 to 181 are turned off is at the time of steady operation. Even if the voltage is lower than that, the operation of the auxiliary switch 19 avoids the occurrence of a short-circuit surge current that compensates for insufficient charging of the capacitor 20 via the switching elements 151 to 181 every time the main switching elements 151 to 181 are turned on. it can. Therefore, it is possible to suppress the generation of noise while maintaining the stability of the switching operation, and to avoid an increase in loss due to a short-circuit surge current. If the load current is extremely small, control may be performed such that the auxiliary switch 19 is not operated at all.

[Second Embodiment]
A switching power supply apparatus according to a second embodiment of the present invention will be described with reference to a schematic circuit configuration diagram shown in FIG. The switching power supply of the second embodiment is a half-bridge type switching power supply.

  In the switching power supply device of the second embodiment, instead of the arm including the main switching elements 171 and 181 in the switching power supply device of the first embodiment, a circuit in which two capacitors 40 and 41 are connected in series is provided. Similar to the first embodiment, a series circuit of an auxiliary switch 19 and a capacitor 20 is provided between a connection point 14 which is the middle point of the power supply and a connection point 13 which is the middle point of the Harbridge circuit.

  Next, the operation of the switching power supply device according to the second embodiment will be described with reference to FIG. 2 used in the description of the operation according to the first embodiment. However, since the voltage distribution between the switching element and the capacitor is different between the full bridge method and the half bridge method, the relative comparison of the voltage values is ignored here.

  The operation of the main switching elements 151 and 161 which are turned on / off according to the drive signal from the main switching element driving unit 31, and thereby the voltage induced in the secondary winding 212 due to the current flowing in the primary winding 211. On the other hand, the operation performed by the secondary circuit is exactly the same as the PWM control in the existing half-bridge switching power supply. That is, another main switching element 161 is switched by PWM control with a drive signal whose phase is delayed by 180 ° with respect to the main switching element 151.

  In the period before time t0, as shown in FIG. 2A, the gate drive signal Vg1 of the main switching element 151 is at the high level, so the main switching element 151 is in the on state and the voltage Vq1 is as shown in FIG. It is zero as shown in (g). At this time, as shown in FIG. 2C, a current Iq1 corresponding to the load current passes from the positive electrode of the DC power supply 10 through the positive power supply line 11 to the main switching element 151, the primary winding 211 of the transformer 21, It flows to the negative electrode of the DC power supply 10 through the capacitor 41 and the negative power supply line 12. On the other hand, since the gate drive signal Vg11 for the auxiliary switch 19 is at a low level, the auxiliary switch 19 is in an OFF state. Therefore, the capacitor 20 connected in series to the auxiliary switch 19 is disconnected from the closed loop including the connection points 13 and 14, and the current Iq11 flowing through the capacitor 20 is zero as shown in FIG.

  The voltage Vc11 at both ends of the capacitor 20 at this time is charged by the energy accumulated in the leakage inductance (not shown) of the primary winding 211 of the transformer 21 during the off period of the main switching element 161 immediately before that. The voltage value is equal to the equal value E1 / 2 of the voltage E1 from the DC power source 10. In the circuit configuration diagram shown in FIG. 3, as in FIG. 1, the positive and negative voltages of the capacitor 20 are represented with the connection point 13 as a reference. The voltage Vq11 applied to the auxiliary switch 19 in the off state is a series composite value in consideration of the polarities of the voltage difference E1 / 2 between the connection points 13 and 14 and the voltage Vc11 across the capacitor 20, and in this case, FIG. ) Is zero.

  At time t0, when the gate drive signal Vg1 for the main switching element 151 becomes low level, the main switching element 151 is turned off, and the two main switching elements 151 and 161 are both turned off to increase the impedance. At substantially the same time, the gate drive signal Vg11 for the auxiliary switch 19 becomes high level (see FIG. 2B), and the switch 19 is turned on, so that the capacitor 20 is connected between the connection points 13 and 14. At this time, the direction of the current flowing through the primary winding 211 of the transformer 21 is opposite to the off period of the immediately preceding main switching element 161, and the direction of the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21. Is inverted so that the connection point 13 side is negative and the connection point 14 side is positive, and charging of the capacitor 20 is started in the direction opposite to the polarity of the charged voltage.

  The voltage Vq1 applied to the main switching element 151 is an average value of a series composite value in consideration of the polarities of the equalized value E1 / 2 of the voltage E1 from the DC power supply 10 and the voltage Vc11 across the capacitor 20, and the capacitor 20 described above. As the both-end voltage Vc11 rises, the both-end voltage Vc11 passes through zero and gradually rises to the voltage E1 / 2 in a period in which both the main switching elements 151 and 161 are in the OFF state. Therefore, the main switching element 151 performs ZVS operation, and the switching-off loss is reduced. At the same time, the voltage applied to the main switching element 161 gradually decreases from the voltage E1 to zero with the same slope that complements the voltage increase of the main switching element 151. Since the voltage Vq11 applied when the auxiliary switch 19 is turned on is almost zero, the auxiliary switch 19 also performs the ZVS operation.

  At time t1, when the voltage Vc11 across the capacitor 20 tries to exceed the voltage E1 / 2, the diode 162 connected in reverse parallel to the main switching element 161 becomes conductive, and the current Id2 shown in FIG. To the DC power supply 10. For this reason, the voltage Vc11 across the capacitor 20 is clamped to the voltage value E1 / 2 and does not exceed it, and the current Ic11 does not flow through the series circuit of the auxiliary switch 19 and the capacitor 20.

  At time t2, when the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21 disappears and the current Id2 flowing through the diode 162 disappears, the potential at the connection point 13 becomes the equal value E1 / 2 of the voltage E1. Converge. The voltage Vq11 applied to the auxiliary switch 19 is a series composite value in consideration of the polarities of the voltage between the connection points 13 and 14 and the voltage Vc11 across the capacitor 20, and at this time, the voltage E1 / 2 charged in the capacitor 20 immediately before that. However, the polarity is opposite to that of the current Iq11 flowing through the switch 19. Since the auxiliary switching element in the auxiliary switch 19 is a unidirectional switching element, even if the gate drive signal Vg11 to the switch 19 is at a high level, the switch 19 is spontaneously turned off in the state where the current Iq11 does not flow. To do. As a result, the capacitor 20 maintains the voltage value Vc11 = E1 / 2 and the polarity charged during the off period of the main switching element 151 immediately before.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching element 161 is turned on although not shown. At substantially the same time, the gate drive signal Vg11 to the auxiliary switch 19 becomes low level, the switch 19 is turned off, and the capacitor 20 maintains the voltage value Vc11 = E1 / 2 and its polarity, and the connection point 13, 14 is disconnected from the closed loop including 14. At the time when the auxiliary switch 19 is turned off, the current Iq11 does not flow, so the ZCS operation is performed. In addition, a current flows through the primary winding 211 of the transformer 21 in the direction opposite to the period in which the main switching element 151 is in the on state.

  With the above operation, the switching power supply of the second embodiment can obtain the same operations and effects as the switching power supply of the first embodiment.

[Third embodiment]
A switching power supply apparatus according to a third embodiment of the present invention will be described with reference to a schematic circuit configuration diagram shown in FIG. The switching power supply of the third embodiment is a push-pull type switching power supply.

  In the switching power supply device of the third embodiment, an intermediate tap 503 is provided in the primary winding 501 of the transformer 50, and the main switching element 151 is connected between one end of the primary winding 501 and the negative power supply line 12. Another main switching element 161 is connected between the other end of the primary winding 501 and the negative power supply line 12, and the intermediate tap 503 is connected to the positive power supply line 11. The auxiliary switch 19 is the same as that of the first embodiment between the connection point 51 between the primary winding 501 and the main switching element 151 and the connection point 52 between the primary winding 501 and the main switching element 161. And a capacitor 20 are provided in series.

  Next, the operation of the switching power supply device of the third embodiment will be described with reference to FIG. 2 used in the description of the operation of the first embodiment. However, since the voltage distribution between the switching element and the capacitor is different between the full bridge method and the push-pull method, the relative comparison of the voltage values is ignored here.

  The operation of the main switching elements 151 and 161 which are turned on / off according to the drive signal from the main switching element driving unit 31, and thereby the voltage induced in the secondary winding 212 due to the current flowing in the primary winding 211. On the other hand, the operation performed in the secondary circuit is exactly the same as the PWM control in the existing push-pull type switching power supply. That is, another main switching element 161 is switched by PWM control with a drive signal whose phase is delayed by 180 ° with respect to the main switching element 151.

  As shown in FIG. 2A, since the gate drive signal Vg1 is at the high level in the period before time t0, the main switching element 151 is in the ON state, and as shown in FIG. The voltage Vq1 applied to the switching element 151 is almost zero. At this time, the current Iq1 corresponding to the load current as shown in FIG. 2C is evenly distributed from the positive electrode of the DC power supply 10 through the positive power supply line 11 by the intermediate tap 503 of the transformer 50. The current flows in a closed loop through the next winding 501a, the main switching element 151, and the negative power supply line 12 to the negative electrode of the DC power supply 10.

  As shown in FIG. 2B, since the gate drive signal Vg11 is at the low level in the period before time t0, the auxiliary switch 19 is in the OFF state. Therefore, the capacitor 20 connected in series to the auxiliary switch 19 is disconnected from the closed loop including the connection points 51 and 52, and the current Iq11 flowing through the capacitor 20 is zero as shown in FIG. The voltage Vc11 at both ends of the capacitor 20 at this time is charged by the energy accumulated in the leakage inductance (not shown) of the primary winding 501 of the transformer 50 during the off period of the main switching element 161 immediately before that. The voltage value becomes twice the voltage E1 from the DC power supply 10 by the boosting action of the primary windings 501a and 501b divided by the intermediate tap 503. In the circuit configuration diagram shown in FIG. 4, the sign of the voltage of the capacitor 20 is determined based on the connection point 52 side. The voltage Vq11 applied to the auxiliary switch 19 in the off state is a series composite value in consideration of the polarity of the voltage difference 2E1 between the connection points 51 and 52 and the voltage Vc11 across the capacitor 20, and in this case, as shown in FIG. It is zero as shown.

  At time t0, when the gate drive signal Vg1 for the main switching element 151 becomes low level, the main switching element 151 is turned off, and the two main switching elements 151 and 161 are both turned off to increase the impedance. At substantially the same time, the gate drive signal Vg11 for the auxiliary switch 19 becomes high level (see FIG. 2B), and the switch 19 is turned on, so that the capacitor 20 is connected between the connection points 51 and 52. At this time, the direction of the current flowing through the primary windings 501a and 501b of the transformer 50 is opposite to the direction of the current flowing through the primary windings 501a and 501b during the off period of the main switching element 161 immediately before. The direction of the energy accumulated in the leakage inductance of the primary winding 501 is reversed so that the connection point 51 side is positive and the connection point 52 side is negative. Therefore, the polarity of the charged voltage is reversed. In the direction, charging of the capacitor 20 is started.

  The voltage Vq1 applied to the main switching element 151 is a series composite value in consideration of the polarity of 2E1 which is twice the voltage E1 from the DC power supply 10 and the voltage Vc11 across the capacitor 20, and the voltage Vc11 across the capacitor 20 described above is obtained. Along with the increase, the both-ends voltage Vc11 passes through zero and gradually increases to the voltage 2E1 during a period in which both the main switching elements 151 and 161 are in the OFF state. Therefore, the main switching element 151 performs ZVS operation, and the switching-off loss is reduced. At the same time, the voltage of the main switching element 161 gradually decreases from the voltage 2E1 to zero with the same slope that complements the voltage increase of the main switching element 151. Since the voltage Vq11 applied to the switch 19 when the auxiliary switch 19 is turned on is almost zero, the auxiliary switch 19 also performs ZVS operation.

  If the voltage Vc11 across the capacitor 20 is about to exceed the voltage 2E1 at time t1, the voltage across the primary winding 501b divided by the intermediate tap 503 becomes equal to or higher than the voltage E1. Therefore, the diode 162 connected in reverse parallel to the main switching element 161 is turned on, and the current Id2 shown in FIG. 2 (d) flows from the diode 162 to the DC power source 10. For this reason, the voltage Vc11 across the capacitor 20 is clamped to the voltage value 2E1 and does not exceed it. At this time, the current Ic11 does not flow through the series circuit of the auxiliary switch 19 and the capacitor 20.

  When the energy accumulated in the leakage inductance of the primary winding 501 of the transformer 50 disappears at time t2 and the current Id2 flowing through the diode 162 disappears, the potentials at the connection points 51 and 52 converge to the voltage E1. The voltage Vq11 applied to the auxiliary switch 19 is a series composite value in consideration of the polarities of the voltage between the connection points 51 and 52 and the voltage Vc11 across the capacitor 20, and at this time, the voltage Vq11 becomes the voltage 2E1 charged in the capacitor 20 immediately before that. However, the polarity is opposite to that of the current Iq11 flowing through the switch 19. Since the auxiliary switching element in the auxiliary switch 19 is a unidirectional switching element, even when the gate drive signal Vg11 to the auxiliary switch 19 is at a high level, the switch 19 is spontaneously turned off in a state where no current Iq11 flows. To do. As a result, the capacitor 20 retains the voltage value Vc11 = 2E1 charged during the off period of the main switching element 151 and the polarity thereof.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching element 161 is turned on although not shown. At substantially the same time, the gate drive signal Vg11 to the auxiliary switch 19 becomes low level, the switch 19 is turned off, and the capacitor 20 maintains the above voltage value Vc11 = 2E1 and its polarity, and the connection points 51, 52 Is disconnected from the closed loop. At the time when the auxiliary switch 19 is turned off, the current Iq11 does not flow, so the ZCS operation is performed. In addition, a current flows through another primary winding 501b that is divided by the intermediate tap 503 of the transformer 50.

  With the above operation, the switching power supply of the third embodiment can obtain the same operations and effects as the switching power supply of the first and second embodiments.

[Fourth embodiment]
A switching power supply according to a fourth embodiment of the present invention will be described with reference to the schematic circuit configuration diagram shown in FIG. 5 and the signal waveform diagram shown in FIG. The switching power supply of the fourth embodiment is a full-bridge switching power supply as in the first embodiment, but the configuration of the snubber circuit is different from that of the first embodiment.

  In the switching power supply device of the fourth embodiment, 2 functions as a snubber capacitor between the positive power supply line 11 and the negative power supply line 12 in the primary circuit connected to the primary winding 211 of the transformer 21. A series circuit of the capacitors 42 and 43 and a series circuit of two capacitors 44 and 45 that also function as snubber capacitors are connected. A first auxiliary switch 48 is connected between a connection point 46 which is the middle point of the series circuit of the two capacitors 42 and 43 and a connection point 13 between the main switching elements 151 and 161, and another two capacitors. A second auxiliary switch 49 is connected between a connection point 47 that is the middle point of the series circuit of 44 and 45 and a connection point 14 between the main switching elements 171 and 181.

Next, the operation of the switching power supply device according to the fourth embodiment will be described.
The operation of the main switching elements 151 to 181 that are turned on / off according to the drive signal from the main switching element driving unit 31, and thereby the voltage induced in the secondary winding 212 due to the current flowing in the primary winding 211. On the other hand, the operation performed in the secondary circuit is exactly the same as the PWM control in the existing full bridge switching power supply. That is, another pair of main switching elements 161 and 171 is switched by PWM control with a drive signal whose phase is delayed by 180 ° with respect to the pair of main switching elements 151 and 181 on different arms.

  6A to 6G are the same as FIGS. 2A to 2G. 6H shows the voltage Vc12 waveform across the capacitors 42 and 45, and FIG. 6I shows the voltage Vc13 waveform across the capacitors 43 and 44. FIG. Although the polarities are different, the voltage and current waveforms relating to the first auxiliary switch 48 and the second auxiliary switch 49 are the same.

  As shown in FIG. 6A, since the gate drive signal Vg1 is at the high level in the period before time t0, the main switching elements 151 and 181 are in the ON state, as shown in FIG. The voltage Vq1 applied to the main switching element 151 is almost zero. At this time, a current Iq1 corresponding to the load current as shown in FIG. 6C passes from the positive electrode of the DC power supply 10 through the positive power supply line 11 to the main switching element 151 and the primary winding of the transformer 21. 211, the main switching element 181, and the negative power supply line 12, and then flows in a closed loop reaching the negative electrode of the DC power supply 10.

  As shown in FIG. 6B, since the gate drive signal Vg11 for the auxiliary switches 48 and 49 is at a low level in the period before the time t0, both the auxiliary switches 48 and 49 are in the off state. Therefore, the connection point 13 of the series circuit of the main switching elements 151 and 161 and the connection point 46 of the series circuit of the capacitors 42 and 43 are disconnected, and the connection point 14 and the capacitor 44 of the series circuit of the main switching elements 171 and 181 are separated. , 45 are disconnected from the connection point 47 of the series circuit. Therefore, as shown in FIG. 6E, the current Iq11 flowing through the capacitor 42 is zero, and the other capacitors 43 to 45 are the same.

  At this time, the voltage across the capacitors 42 to 45 is charged by the energy accumulated in the leakage inductance (not shown) of the primary winding 211 of the transformer 21 during the off period of the main switching elements 161 and 171 immediately before that. The voltage Vc12 across the capacitors 42 and 45 is zero due to discharge (see FIG. 6 (h)), and the voltage Vc13 across the capacitors 43 and 44 is equal to the voltage E1 from the DC power supply 10 due to charging. . Since the potentials of the connection points 13 and 46 are both E1, the voltage Vq11 applied to the first auxiliary switch 48 in the off state is zero as shown in FIG. 6 (f). Further, since the potentials of the connection points 14 and 47 are both zero, the voltage Vq13 applied to the second auxiliary switch 49 in the off state is also zero.

  At time t0, when the gate drive signal Vg1 for the main switching elements 151 and 181 becomes a low level, both the main switching elements 151 and 181 are turned off, and all the main switching elements 151 to 181 are turned off to increase the impedance. At substantially the same time, the gate drive signals Vg11 for the auxiliary switches 48 and 49 are both at a high level (see FIG. 6B), and the switches 48 and 49 are turned on, so that the series circuit of the main switching elements 151 and 161 is connected. The point 13 and the connection point 46 of the series circuit of the capacitors 42 and 43 are connected, and the connection point 14 of the series circuit of the main switching elements 171 and 181 and the connection point 47 of the series circuit of the capacitors 44 and 45 are connected. Thereby, the main switching element 151 and the capacitor 42, the main switching element 161 and the capacitor 43, the main switching element 171 and the capacitor 44, and the main switching element 181 and the capacitor 45 are connected in parallel.

  At this time, the direction of the current flowing through the primary winding 211 of the transformer 21 is opposite to the off period of the immediately preceding main switching elements 161 and 171, and the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21. Since the direction is reversed so that the connection point 13 side of the first arm is a negative electrode and the connection point 14 side of the second arm is a positive electrode, charging of the capacitors 42 and 45 is started. For this reason, as shown in FIG. 6 (h), the voltage Vc12 across the capacitors 42 and 45 gradually increases from zero, and the voltage Vq1 applied to the main switching elements 151 and 181 connected in parallel thereto gradually gradually. To rise. Therefore, the main switching elements 151 and 181 operate in ZVS, and the switching-off loss is reduced. In addition, the capacitors 43 and 44 start to discharge, and the voltage at both ends thereof gradually decreases from E1 to zero with the same slope that complements the charging of the capacitors 42 and 45. Since the voltage Vq11 applied to the switches 48 and 49 when the auxiliary switches 48 and 49 are turned on is substantially zero, the auxiliary switches 48 and 49 also perform ZVS operation.

  When the voltage Vc12 across the capacitors 42 and 45 tries to exceed the voltage E1 from the DC power source 10 at time t1, the diodes 162 and 172 connected in reverse parallel to the main switching elements 161 and 171 become conductive, and FIG. The current Id2 shown in d) flows from the diodes 162 and 172 to the DC power source 10, respectively. For this reason, the voltage Vc12 across the capacitors 42 and 45 is clamped to the voltage by the DC power supply 10 and therefore does not exceed E1, and at this time, the current Iq11 does not flow through the auxiliary switches 48 and 49.

  When the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21 disappears at time t2 and the current Id2 flowing through the diodes 162 and 172 disappears, the potentials at the connection points 13 and 14 in the two arms are both It converges to an equal value E1 / 2 of the voltage E1. Since the potential at the connection point 46 of the series circuit of the capacitors 42 and 45 at this time is zero and the potential at the connection point 13 is E1 / 2, the voltage Vq11 applied to the first auxiliary switch 48 is E1 / 2. Since the point 46 side is negative and the connection point 13 side is positive, the polarity is opposite to that of the current Iq11 flowing through the switch 48. Further, since the potential at the connection point 47 of the series circuit of the capacitors 43 and 44 is E1, and the potential at the connection point 14 is E1 / 2, the voltage Vq12 applied to the second auxiliary switch 49 is E1 / 2, and the connection point 47 side is Since the polarity is positive and the connection point 14 side is negative, the polarity is opposite to that of the current Iq11 flowing through the switch 49. Since the auxiliary switching elements in the auxiliary switches 48 and 49 are unidirectional switching elements, the current Iq11 does not flow through the switches 48 and 49 even when the gate drive signal Vg11 to the auxiliary switches 48 and 49 is at a high level. Turn off spontaneously in the state. As a result, the voltage across the capacitors 42 and 45 holds E1, and the voltage across the capacitors 43 and 44 holds zero.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching elements 161 and 171 are turned on (not shown). At substantially the same time, when the gate drive signal Vg11 to the auxiliary switches 48 and 49 becomes low level, the switches 48 and 49 are turned off, the voltage across the capacitor 42 remains E1, and the voltage across the capacitor 43 remains zero. The connection point 46 and the connection point 13 are disconnected. Similarly, the connection point 47 and the connection point 14 are disconnected while the voltage across the capacitor 45 is E1 and the voltage across the capacitor 44 remains zero. At the time when the auxiliary switches 48 and 49 are turned off, the current Iq11 does not flow, so the ZCS operation is performed. In addition, a current flows through the primary winding 211 of the transformer 21 in a direction opposite to the period in which the main switching elements 151 and 181 are in the ON state.

  With the above operation, the switching power supply of the fourth embodiment can obtain the same operations and effects as the switching power supply of the first to third embodiments.

[Fifth embodiment]
A switching power supply apparatus according to a fifth embodiment of the present invention will be described with reference to a schematic circuit configuration diagram shown in FIG. The switching power supply of the fifth embodiment is a half-bridge type switching power supply as in the second embodiment, but the configuration of the snubber circuit is the same as that of the fourth embodiment, not the second embodiment.

  That is, in the switching power supply of the fifth embodiment, a snubber capacitor is provided between the positive power supply line 11 and the negative power supply line 12 in the primary circuit connected to the primary winding 211 of the transformer 21. A series circuit of two capacitors 42 and 43 that function is connected, and an auxiliary switch 48 is connected between a connection point 46 that is a middle point of the series circuit and a connection point 13 between the main switching elements 151 and 161. It is connected.

  Next, the operation of the switching power supply device of the fifth embodiment will be described with reference to FIG. 6 used in the description of the operation of the fourth embodiment. However, since the voltage distribution between the switching element and the capacitor is different between the full bridge method and the half bridge method, the relative comparison of the voltage values is ignored here.

  As shown in FIG. 6A, since the gate drive signal Vg1 is at a high level in a period before time t0, the main switching element 151 is in a conductive state, and as shown in FIG. The voltage Vq1 of the switching element 151 is almost zero. At this time, a current Iq1 corresponding to the load current as shown in FIG. 6C passes from the positive electrode of the DC power supply 10 through the positive power supply line 11 to the main switching element 151 and the primary winding of the transformer 21. 211, the capacitor 41, and the negative power supply line 12, and then flows in a closed loop that reaches the negative electrode of the DC power supply 10.

  As shown in FIG. 6B, since the gate drive signal Vg11 for the auxiliary switch 48 is at the low level in the period before time t0, the auxiliary switch 48 is in the OFF state. Therefore, the connection point 13 of the series circuit of the main switching elements 151 and 161 and the connection point 46 of the series circuit of the capacitors 42 and 43 are disconnected. Therefore, as shown in FIG. 6E, the current Iq11 flowing through the capacitors 42 and 43 is zero.

  At this time, the voltage Vc12 across the capacitor 42 is zero because it is discharged by the energy accumulated in the leakage inductance (not shown) of the primary winding 211 of the transformer 21 during the off period of the main switching element 161 immediately before that. Yes (see FIG. 6H), the voltage Vc13 across the capacitor 43 is equal to the voltage E1 of the DC power supply 10 due to charging by the energy stored in the same leakage inductance. Since the potentials of the connection points 13 and 46 are both E1, the voltage Vq11 applied to the auxiliary switch 48 in the off state is zero as shown in FIG. 6 (f).

  At time t0, when the gate drive signal Vg1 for the main switching element 151 becomes low level, the main switching element 151 is turned off, and both the main switching elements 151 and 161 are turned off to increase the impedance. At substantially the same time, the gate drive signal Vg11 for the auxiliary switch 48 becomes high level (see FIG. 6B), and the switch 48 is turned on. Therefore, the connection point 13 of the series circuit of the main switching elements 151 and 161 and the capacitor 42 , 43 are connected to the connection point 46 of the series circuit. Therefore, the main switching element 151 and the capacitor 42, and the main switching element 161 and the capacitor 43 are connected in parallel.

  At this time, the direction of the current flowing through the primary winding 211 of the transformer 21 is opposite to the direction of the current flowing through the primary winding 211 during the off period of the immediately preceding main switching element 161. Since the direction of energy accumulated in the leakage inductance 211 is reversed so that the connection point 13 side is negative and the connection point 46 side is positive, charging of the capacitor 42 is started. For this reason, as shown in FIG. 6 (h), the voltage Vc12 across the capacitor 42 gradually increases from zero, and the voltage Vq1 of the main switching element 151 connected in parallel also gradually increases. Therefore, the main switching element 151 performs ZVS operation, and the switching-off loss is reduced. At the same time, the capacitor 43 starts to discharge, and the voltage at both ends gradually decreases from E1 to zero with the same slope that complements the charging of the capacitor 42. Since the voltage Vq11 applied to the switch 48 when the auxiliary switch 48 is turned on is substantially zero, the auxiliary switch 48 also performs ZVS operation.

  When the voltage Vc12 across the capacitor 42 attempts to exceed the voltage E1 from the DC power source 10 at time t1, the diode 162 connected in reverse parallel to the main switching element 161 becomes conductive, and the current Id2 shown in FIG. The current flows from the diode 162 to the DC power supply 10. For this reason, the voltage Vc12 across the capacitor 42 is clamped to a voltage by the DC power supply 10 and therefore does not exceed E1, and at this time, the current Iq11 does not flow through the auxiliary switch 48.

  At time t2, when the energy accumulated in the leakage inductance of the primary winding 211 of the transformer 21 disappears and the current Id2 flowing through the diode 162 disappears, the potential at the connection point 13 becomes the equal value E1 / 2 of the voltage E1. Converge. Since the potential at the connection point 46 of the series circuit of the capacitor 42 at this time is zero, the voltage Vq11 applied to the auxiliary switch 48 is E1 / 2, and the polarity is opposite to the current Iq11 flowing through the switch 48. It is. Since the auxiliary switching element in the auxiliary switch 48 is a unidirectional switching element, even when the gate drive signal Vg11 to the switch 48 is at a high level, the switch 48 is spontaneously turned off in a state where no current Iq11 flows. To do. As a result, the voltage across the capacitor 42 is E1, and the voltage across the capacitor 43 is zero.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching element 161 is turned on although not shown. At substantially the same time, when the gate drive signal Vg11 to the auxiliary switch 48 becomes low level, the switch 48 is turned off, the voltage across the capacitor 42 is E1, and the voltage across the capacitor 43 is kept at zero while the connection point 46 is maintained. And the connection point 13 are disconnected. At the time when the auxiliary switch 48 is turned off, the current Iq11 does not flow, so the ZCS operation is performed. In addition, a current flows through the primary winding 211 of the transformer 21 in a direction opposite to the period in which the main switching element 151 is in the ON state.

  With the above operation, the switching power supply of the fifth embodiment can obtain the same operations and effects as the switching power supply of the first to fourth embodiments.

[Sixth embodiment]
A switching power supply apparatus according to a sixth embodiment of the present invention will be described with reference to a schematic circuit configuration diagram shown in FIG. The switching power supply of the sixth embodiment is a push-pull type switching power supply as in the third embodiment, but the configuration of the snubber circuit is not the third embodiment but the same as the fourth and fifth embodiments.

  That is, in the switching power supply of the sixth embodiment, a capacitor that functions as a snubber capacitor in parallel with the main switching element 151 connected between one end of the primary winding 501 of the transformer 50 and the negative power supply line 12. 42 and the first auxiliary switch 48 are connected in series, and in parallel with the main switching element 161 connected between the other end of the primary winding 501 of the transformer 50 and the negative power supply line 12, A series circuit of a capacitor 43 functioning as a snubber capacitor and a second auxiliary switch 49 is connected.

  Next, the operation of the switching power supply device of the sixth embodiment will be described with reference to FIG. 6 used in the description of the operation of the fourth embodiment. However, since the voltage distribution between the switching element and the capacitor is different between the full bridge method and the push-pull method, the relative comparison of the voltage values is ignored here.

  The operation of the main switching elements 151 and 161 which are turned on / off according to the drive signal from the main switching element driving unit 31 and the current flowing in the primary windings 501 (501a and 501b) thereby cause the secondary winding 502 to The operation performed in the secondary side circuit with respect to the induced voltage is exactly the same as the PWM control in the existing push-pull type switching power supply. That is, another main switching element 161 is switched by PWM control with a drive signal whose phase is delayed by 180 ° with respect to the main switching element 151.

  As shown in FIG. 6A, since the gate drive signal Vg1 is at the high level in the period before time t0, the main switching element 151 is in the ON state, and as shown in FIG. The voltage Vq1 applied to the switching element 151 is almost zero. At this time, the current Iq1 corresponding to the load current as shown in FIG. 6C is evenly distributed from the positive electrode of the DC power supply 10 through the positive power supply line 11 by the intermediate tap 503 of the transformer 50. The current flows in a closed loop through the next winding 501a, the main switching element 151, and the negative power supply line 12 to the negative electrode of the DC power supply 10.

  As shown in FIG. 6B, since the gate drive signal Vg11 is at the low level in the period before time t0, both the auxiliary switches 48 and 49 are in the off state. Therefore, the capacitors 42 and 43 connected in series to the auxiliary switches 48 and 49 are disconnected from the main switching elements 151 and 161, respectively, and the current Iq11 flowing through the capacitor 42 is zero as shown in FIG. The same applies to the capacitor 43. The voltage Vc12 across the capacitor 42 at this time is discharged by the energy accumulated in the leakage inductance (not shown) of the primary winding 501 of the transformer 50 in the off period of the main switching element 161 just before that. Zero. On the other hand, the voltage Vc13 at both ends of the capacitor 43 is charged by the energy stored in the same leakage inductance, and the voltage value is DC by the step-up action of the primary windings 501a and 501b that are divided by the intermediate tap 503. This is twice the voltage E1 of the power supply 10. Therefore, the voltage Vq11 applied to the first auxiliary switch 48 in the off state is zero as shown in FIG. 6F, and the voltage applied to the second auxiliary switch 49 is also zero.

  At time t0, when the gate drive signal Vg1 for the main switching element 151 becomes low level, the main switching element 151 is turned off, and both the main switching elements 151 and 161 are turned off to increase the impedance. At substantially the same time, the gate drive signal Vg11 for the auxiliary switches 48 and 49 becomes high level (see FIG. 6B), and both the switches 48 and 49 are turned on, so that the main switching element 151, the capacitor 42, and the main switching element 161 and the capacitor 43 are connected in parallel.

At this time, the direction of the current flowing through the primary windings 501a and 501b of the transformer 50 is opposite to the direction of the current flowing through the primary windings 501a and 501b during the off period of the main switching element 161 immediately before. Since the direction of energy accumulated in the leakage inductance of the primary winding 501 is reversed so that the connection point 51 side is positive and the connection point 52 side is negative, charging of the capacitor 42 is started. Therefore, as shown in FIG. 6 (h), the voltage across Vc12 of the capacitor 4 2 gradually increases from zero, the voltage Vq1 likewise rises gradually applied to the main switching element 151 connected in parallel thereto . Therefore, the main switching element 151 performs ZVS operation, and the switching-off loss is reduced. Further, the capacitor 43 starts discharging, and the voltage at both ends thereof gradually decreases from E1 to zero with the same slope that complements the charging of the capacitor 42. Since the voltage Vq11 applied to the auxiliary switches 48 and 49 when they are turned on is almost zero, the auxiliary switches 48 and 49 also perform the ZVS operation.

  At time t1, if the voltage Vc12 across the capacitor 42 tries to exceed the voltage 2E1, the voltage across the primary winding 501b divided by the intermediate tap 503 becomes equal to or higher than the voltage E1. Therefore, the diode 162 connected in reverse parallel to the main switching element 161 is turned on, and the current Id2 shown in FIG. 6 (d) flows from the diode 162 to the DC power supply 10. For this reason, the voltage Vc12 across the capacitor 42 is clamped to the voltage value 2E1 and does not exceed it. At this time, the current Ic11 does not flow through the series circuit of the first auxiliary switch 48 and the capacitor 43.

  When the energy accumulated in the leakage inductance of the primary winding 501 of the transformer 50 disappears at time t2, and the current Id2 flowing through the diode 162 disappears, the potentials at the connection points 51 and 52 converge to E1. Since the voltage Vc12 across the capacitor 42 at this time is 2E1, the voltage Vq11 applied to the first auxiliary switch 48 is E1, and the connection point 51 side is negative and the capacitor 42 side is positive. The polarity is opposite to that of the current Iq11 that has been flowing. Further, since the voltage Vc13 across the capacitor 43 is zero, the voltage Vq12 applied to the second auxiliary switch 49 is also E1, and the connection point 52 side is positive and the capacitor 43 side is negative. The polarity is opposite to that of the current Iq11. Since the auxiliary switching elements in the auxiliary switches 48 and 49 are unidirectional switching elements, the current Iq11 does not flow through the switches 48 and 49 even when the gate drive signal Vg11 to the switches 48 and 49 is at a high level. Turn off spontaneously in the state. As a result, the voltage across the capacitor 42 remains E1, and the voltage across the capacitor 43 remains zero.

  At time t3, the operation proceeds to the next operation at a time determined by the PWM control, and the main switching element 161 is turned on although not shown. At substantially the same time, when the gate drive signal Vg11 to the auxiliary switch 48 becomes low level, the switch 48 is turned off, the voltage across the capacitor 42 is E1, and the voltage across the capacitor 43 is kept at zero, respectively. 51 and 52 are separated. At the time when the auxiliary switches 48 and 49 are turned off, the current Iq11 does not flow, so the ZCS operation is performed. In addition, a current flows through the primary winding 501 of the transformer 50 in a direction opposite to the period in which the main switching element 151 is in the ON state.

  By the above operation, the switching power supply of the sixth embodiment can obtain the same operations and effects as the switching power supply of the first to fifth embodiments.

A specific configuration example of the auxiliary switches 19, 48, and 49 in the switching power supply devices of the first to sixth embodiments will be described with reference to FIG.
The auxiliary switches 19, 48 and 49 must alternatively be able to supply current in both directions. In order to make this possible, in the configuration shown in FIG. 9A, the source terminals (S) of the two power MOS-FETs are connected in common, and a reverse conducting element by a parasitic diode of the element itself is provided. Connected in series. In the configuration shown in FIG. 9B, two reverse blocking circuits of a power MOS-FET and a diode are connected in antiparallel. In the configuration shown in FIG. 9C, reverse conduction circuits of IGBTs and diodes are connected in series. Further, in the configuration shown in FIG. 9D, two reverse blocking IGBTs are connected in antiparallel. That is, the circuits shown in FIGS. 9A to 9D are all configured by antiparallel connection of unidirectional circuits. The gate drive signal used in these circuits is a combination of unidirectional dedicated signals that match the current direction of the auxiliary switch.

The above-described embodiment is merely an example of the present invention, and it is a matter of course that modifications, corrections, and additions may be appropriately made within the scope of the present invention, and included in the scope of the claims of the present application.
For example, in each of the above embodiments, the switching power supply device according to the present invention is applied to a DC-DC converter that converts a DC voltage into an AC voltage, converts the AC voltage into a DC voltage, and supplies the converted voltage to a load. The DC power supply 10 may be a battery or the like, but it is obvious that the DC power supply 10 may be a power supply that rectifies and smoothes AC power from a commercial AC power supply to convert it to DC. Further, it is obvious that the switching power supply apparatus according to the present invention may be applied to a DC-AC converter that supplies an AC voltage to a load without converting the AC voltage into a direct current in the secondary side circuit of the transformer.

  The switching power supply according to the present invention can be used not only as a general-purpose DC power supply, but also as a power supply for various processing apparatuses such as a plasma processing power supply, a surface treatment power supply, and an arc machining power supply. be able to.

DESCRIPTION OF SYMBOLS 10 ... DC power supply 11 ... Positive power supply line 12 ... Negative power supply line 13, 14, 46, 47, 51, 52 ... Connection point 151, 161 ... Main switching element 152, 162, 172, 182, 22, 24 ... Diode 19, 48, 49 ... auxiliary switches 20, 27, 40, 41, 42, 43, 44, 45 ... capacitors 21, 50 ... transformers 211, 501 (501a, 501b) ... primary windings 212, 502 ... secondary windings Line 503 ... Intermediate tap 26 ... Inductor 28 ... Load 30 ... Switching control unit 31 ... Main switching element drive unit 32 ... Snubber switch drive unit

Claims (6)

A full bridge with two arms connected in series with an even number of main switching elements each connected in antiparallel with a diode, and both ends of the two arms connected to a positive and negative DC power supply line A circuit and a transformer having a primary winding connected between the midpoints of the two arms, the midpoint being sandwiched between one of the two arms in the full bridge circuit. The PWM switching drive signal is given to the main switching element on the positive DC power supply line side and the main switching element on the negative DC power supply line side with the middle point on the other arm, and the two The main switching element on the negative DC power supply line side across the middle point on the one arm and the positive DC power line side across the middle point on the other arm Gives some driving signal main switching element by 180 ° than the drive signal to the phase is delayed, the supply current reverses its direction alternately in the primary winding of the transformer by operating their main switching element and thereby a switching power supply unit of a full bridge type supplying electric power based on the voltage induced in the secondary winding of the transformer to the load,
a) a snubber circuit formed by connecting an auxiliary switch and a capacitor connected in series between the middle points of the two arms and capable of supplying a current alternatively and bidirectionally;
b) a main switching element driving unit for driving the main switching element of the full bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
With
The switching control unit is configured to switch the auxiliary switch when all the main switching elements are turned off by switching a pair of main switching elements included in different arms of the two arms from an on state to an off state. Is turned on in a predetermined direction for a predetermined period , and is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off, and passes through the auxiliary switch. The capacitor is charged by the flowing current, and then the auxiliary switch is switched from the on state to the off state, and the other pair of main switching elements included in different arms of the two arms are switched from the off state to the on state. The main switching element drive unit and the snubber switch drive Switching power supply device and controls each section. An even number of main switching elements each connected in reverse parallel are connected in series, a half-bridge circuit whose both ends are connected to positive and negative DC power supply lines, and an even number of capacitors are connected in series. A capacitor series circuit having both ends connected to positive and negative DC power supply lines, and a transformer having a primary winding connected between the midpoint of the half bridge circuit and the midpoint of the capacitor series circuit, And providing a PWM control drive signal to one of the main switching elements sandwiching the midpoint of the half-bridge circuit, and applying the drive signal to the other main switching element sandwiching the midpoint supplies driving signals whose phase is delayed by 180 °, to the inverting its direction alternately in the primary winding of the transformer by operating their main switching element Current supply, whereby a switching power supply device of the half-bridge type supplying electric power based on the voltage induced in the secondary winding of the transformer to the load,
a) An auxiliary switch connected between the midpoint of the half-bridge circuit and the midpoint of the capacitor series circuit, which can alternatively supply current bidirectionally, and a capacitor are connected in series. Snubber circuit,
b) a main switching element driving unit for driving the main switching element of the half-bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit sets the auxiliary switch in a predetermined direction when all the main switching elements are turned off by switching one main switching element in the half-bridge circuit from an on state to an off state. By turning on for a period of time, the snubber is caused by the current flowing through the auxiliary switch , which is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off. The main switching element is charged so that the capacitor constituting the circuit is charged and then the auxiliary switch is switched from the on state to the off state, and the other main switching element in the half-bridge circuit is switched from the off state to the on state. A drive unit and the snubber switch drive unit; A switching power supply device that is controlled individually. A transformer including a primary winding having an intermediate tap connected to a positive DC power supply line, and a diode connected between one end of the primary winding and the negative DC power supply line in antiparallel A first main switching element connected, a second main switching element connected between the other end of the primary winding and the negative-polarity DC power supply line and having a diode connected in reverse parallel; The current supplied to the primary winding of the transformer is controlled on and off by operating the first and second main switching elements, thereby being induced in the secondary winding of the transformer A push-pull switching power supply that supplies power based on voltage to a load,
a) alternatively connected between a connection point between the primary winding and the first main switching element and a connection point between the primary winding and the second main switching element; A snubber circuit in which an auxiliary switch capable of supplying current in both directions and a capacitor are connected in series;
b) a main switching element driving unit for driving the first and second main switching elements, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit is configured to turn the auxiliary switch in a predetermined direction when all the main switching elements are turned off by switching one of the first or second main switching elements from an on state to an off state. By turning on the power source for a predetermined period of time, it is derived from the energy accumulated in the leakage inductance of the primary winding of the transformer immediately before all the main switching elements are turned off , and the current flowing through the auxiliary switch Charging the capacitor, and then switching the auxiliary switch from the on-state to the off-state, and switching the other of the first or second main switching elements from the off-state to the on-state; A switching power supply unit that controls the snubber switch driving unit. A full bridge with two arms connected in series with an even number of main switching elements each connected in antiparallel with a diode, and both ends of the two arms connected to a positive and negative DC power supply line A circuit and a transformer having a primary winding connected between the midpoints of the two arms, the midpoint being sandwiched between one of the two arms in the full bridge circuit. The PWM switching drive signal is given to the main switching element on the positive DC power supply line side and the main switching element on the negative DC power supply line side with the middle point on the other arm, and the two The main switching element on the negative DC power supply line side across the middle point on the one arm and the positive DC power line side across the middle point on the other arm Gives some driving signal main switching element by 180 ° than the drive signal to the phase is delayed, the supply current reverses its direction alternately in the primary winding of the transformer by operating their main switching element and thereby a switching power supply unit of a full bridge type supplying electric power based on the voltage induced in the secondary winding of the transformer to the load,
a) A serial circuit of an even number of capacitors connected in parallel to one arm, and alternatively, current can be supplied bidirectionally connected between the midpoint of the series circuit and the midpoint of the arm A first snubber circuit comprising: a first auxiliary switch;
b) A serial circuit of an even number of capacitors connected in parallel to the other arm, and alternatively, current can be supplied bidirectionally connected between the midpoint of the series circuit and the midpoint of the arm A second snubber circuit comprising: a second auxiliary switch,
c) A main switching element driving unit for driving the main switching element of the full bridge circuit and a snubber for independently turning on and off the first and second auxiliary switches of the first and second snubber circuits for each current direction. A switch drive unit,
d) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
With
The switching control unit, when all of the main switching element at Rukoto switching a pair of main switching elements included in different arms ones of the two arms from the ON state to the OFF state is turned off, the first 1 and a second auxiliary switch by the Tokoro periodically between oN state, derived from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off , by a current flowing through the first and second auxiliary switches, the capacitor is in the state of being connected in parallel to the pair of main switching elements of the plurality of capacitors included in the first and second snubber circuits while charging, to discharge the capacitor is in the state of being connected in parallel to the other pair of main switching elements, their After with switching off state them auxiliary switch from the on state, before Symbol to switch the other pair of main switching element from the off state to the on state, control the main switching element driving unit and the snubber switch driving section, respectively A switching power supply device characterized in that: An even number of main switching elements each connected in reverse parallel are connected in series, a half-bridge circuit whose both ends are connected to positive and negative DC power supply lines, and an even number of capacitors are connected in series. A capacitor series circuit having both ends connected to positive and negative DC power supply lines, and a transformer having a primary winding connected between the midpoint of the half bridge circuit and the midpoint of the capacitor series circuit, And providing a PWM control drive signal to one of the main switching elements sandwiching the midpoint of the half-bridge circuit, and applying the drive signal to the other main switching element sandwiching the midpoint 180 supplies a drive signal whose phase is delayed by °, that direction alternately to the primary winding of the transformer by operating a plurality of main switching elements The current rolling supplied, whereby a switching power supply device of the half-bridge type supplying electric power based on the voltage induced in the secondary winding of the transformer to the load,
a) a series circuit of an even number of capacitors connected in parallel to the half-bridge circuit, and alternatively bidirectional current connected between the midpoint of the series circuit and the midpoint of the half-bridge circuit. A snubber circuit comprising an auxiliary switch capable of supplying
b) a main switching element driving unit for driving the main switching element of the half-bridge circuit, and a snubber switch driving unit for independently driving on and off the auxiliary switch of the snubber circuit for each current direction;
c) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit comprises a, when the all of the main switching element at Rukoto turned OFF the main switching element one which is separated at the midpoint of the half-bridge circuit from the ON state is turned off, the auxiliary by switching to a predetermined regular between the on state, and from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off, it flows through the auxiliary switch Among the even number of capacitors included in the snubber circuit, the capacitor that is connected in parallel to the one main switching element is charged by the current, while being connected in parallel to the other main switching element. The capacitor is discharged, and then the auxiliary switch is switched from on to off. The to switch the other main switching device from the OFF state to the ON state, the switching power supply apparatus characterized by controlling the main switching element driving unit and the snubber switch driving section, respectively. A transformer including a primary winding having an intermediate tap connected to a positive DC power supply line, and a diode connected between one end of the primary winding and the negative DC power supply line in antiparallel A first main switching element connected, a second main switching element connected between the other end of the primary winding and the negative-polarity DC power supply line and having a diode connected in reverse parallel; The current supplied to the primary winding of the transformer is controlled on and off by operating the first and second main switching elements, thereby being induced in the secondary winding of the transformer A push-pull switching power supply that supplies power based on voltage to a load,
a) A first snubber comprising a first auxiliary switch connected between both ends of the first main switching element and capable of supplying a current alternatively and bidirectionally and a capacitor connected in series. Circuit,
b) a second snubber in which a second auxiliary switch connected between both ends of the second main switching element and capable of supplying a current in both directions and a capacitor are connected in series; Circuit,
c) The main switching element driving section for driving the first and second main switching elements, and the first and second auxiliary switches of the first and second snubber circuits are turned on and off independently for each current direction. A snubber switch drive unit that is driven off;
d) a switching control unit for controlling the main switching element driving unit and the snubber switch driving unit;
The switching control unit comprises a, when the all of Rukoto switched one from the ON state to the OFF state of the main switching element of the first or second main switching element is turned off, the first and the second auxiliary switch by the Tokoro periodically between oN state, derived from the all of the energy which the main switching element is accumulated in the primary winding leakage inductance of the transformer immediately before turned off, the first The current flowing through the first and second auxiliary switches charges the capacitor that is connected in parallel to the main switching element that has been switched off immediately before, while being connected in parallel to the other main switching element. The capacitor in the closed state is discharged, and then the auxiliary switches are switched from the on state to the off state, and the other To switch the main switching element from the OFF state to the ON state, the switching power supply apparatus characterized by controlling the main switching element driving unit and the snubber switch driving section, respectively.

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