JP2008253075A - Switching power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply device which can be made compact, the cost reduced, and which can detect an input overvoltage with high accuracy. <P>SOLUTION: The switching power supply device 1 includes its power body part 10 that performs switching operation and generates an output voltage obtained by converting an input voltage, a control part 17 that controls the switching operation, an auxiliary power supply part 30 that generates power voltage of the control part 17 from the input voltage and a voltage-detecting part 20 for detecting the input voltage. The auxiliary power supply part 30 changes a first level of power voltage to a second level, different from the first level, according to the output voltage from the voltage detecting part 20. The control part 17 controls so as to perform the switching operation for stabilizing output voltage of the power body part 10, when power voltage is at the first level. When power voltage goes into a second level, the control part controls the system to perform prescribed operations that are different from stabilization. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a switching power supply device having an input overvoltage detection function.

  In general, a hybrid vehicle (HybridElectric Vehicle) has a low-voltage DC voltage of, for example, about 12 volts as a power source for driving on-vehicle equipment such as wipers, headlights, room lights, audio equipment, air conditioners, and various instruments. Is mounted as a power source for driving the motor. For example, a high-voltage battery that outputs a high-voltage DC voltage of about 400V is mounted. Usually, such a low-voltage battery is charged by rectifying an AC output voltage from an AC generator driven by the rotation of the engine to obtain a high-voltage DC voltage, and using this DC input voltage as a switching power supply. It is performed by using a low-voltage DC voltage after being converted to a lower-voltage battery. Note that the high-voltage battery is charged by supplying the DC input voltage from the engine side to the high-voltage battery. In this switching power supply device, as described in Patent Document 1, for example, a DC input voltage is once converted into an AC voltage by an inverter circuit, and then the AC voltage is transformed by a voltage conversion transformer and is again DC by a rectifier circuit or the like. Voltage conversion is performed by converting the voltage.

  By the way, if the DC input voltage supplied from the engine side exceeds the withstand voltage of the internal circuit of the switching power supply device, the internal circuit may be destroyed. Therefore, it is important to always monitor the DC input voltage so that the internal circuit is not destroyed. This is not limited to the switching power supply device mounted on the hybrid car, but also applies to a general switching power supply device.

For example, in Patent Document 2, a voltage detection circuit for detecting a DC input voltage is provided. Since this voltage detection circuit estimates the DC input voltage by calculation after detecting the voltage generated in the output winding of the voltage conversion transformer, the voltage detection circuit is connected to the control circuit to which the power supply voltage is applied from the low voltage battery side. When the detection signal is input, it is not necessary to use an input / output insulation circuit such as a photocoupler, and the size and price can be reduced.
Japanese Patent Laid-Open No. 2003-259637 JP 2003-33015 A

  However, in the switching power supply device described in Patent Document 2, the voltage generated in the output winding of the voltage conversion transformer varies due to fluctuations in the leakage inductance of the voltage conversion transformer, and the DC input voltage is highly accurate. It was difficult to detect.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a switching power supply apparatus that can be reduced in size and price, and that can detect an input overvoltage with high accuracy.

  The switching power supply device of the present invention includes: (a) a power supply main body that generates an output voltage obtained by converting the input voltage by performing a switching operation; (b) a control unit that controls the switching operation; An auxiliary power supply unit that generates a power supply voltage from the input voltage; and (d) a voltage detection unit that detects the input voltage. (E) the auxiliary power supply unit supplies the power supply voltage according to the output voltage from the voltage detection unit. The first level is changed to a second level different from the first level, and (f) the control unit stabilizes the output voltage of the power source main unit when the power source voltage is the first level. Control is performed to perform a switching operation, and control is performed to perform a predetermined operation different from the stabilization when the power supply voltage reaches the second level.

  Generally, in a switching power supply device, the control unit may use a power supply voltage on the output side (secondary side). In this case, the voltage detection unit is connected to the input side (primary side) in order to improve the detection accuracy of the input overvoltage. ), The voltage detection unit must send the output signal to the control unit via an input / output insulation circuit (primary-secondary insulation circuit) such as a photocoupler.

  However, according to this switching power supply device, since the auxiliary power supply unit changes the level of the power supply voltage of the control unit according to the output voltage of the voltage detection unit, the control unit can detect the voltage detection unit from the level of the power supply voltage. Can detect whether or not an input overvoltage has been detected. Therefore, according to this switching power supply device, even if the voltage detection unit is provided on the input side, it is not necessary to separately provide an input / output insulation circuit for the voltage detection unit, and it is possible to reduce the size and the price.

  Further, according to this switching power supply device, the amount of change in the power supply voltage at the time of the input overvoltage, that is, the difference between the second level at the time of the input overvoltage and the first level at the normal time is increased, thereby increasing the leakage inductance. The input overvoltage can be detected with high accuracy without depending on fluctuations. Furthermore, in this switching power supply apparatus, the voltage detection unit can be provided on the input side by the above-described configuration, and the input voltage can be directly detected, so that the input overvoltage detection accuracy can be further increased.

  The predetermined operation different from the stabilization performed by the control unit at the time of input overvoltage is to prevent the internal circuit of the switching power supply device from being destroyed due to the input overvoltage. For example, it means that the duty ratio of the switching power supply device is lowered, the output of the switching power supply is lowered, or the switching power supply device is stopped. The control unit performs control so as to perform a predetermined operation different from these stabilization operations. The switching signal is generated so as to lower the duty ratio, or the switching signal itself is stopped.

  The auxiliary power supply unit described above preferably increases the power supply voltage to the second level when the input voltage detected by the voltage detection unit becomes equal to or higher than a predetermined voltage. When the second level is reached, it is preferable to stop the operation of the power supply main body.

  According to this configuration, when the input overvoltage is applied, the control unit stops the operation of the power supply main body, so that the internal circuit of the switching power supply device can be appropriately prevented from being destroyed. Here, the predetermined voltage is set in advance from, for example, the breakdown voltage of the internal circuit element of the switching power supply device.

  According to the present invention, it is possible to obtain a switching power supply apparatus that can be reduced in size and price and can detect input overvoltage with high accuracy.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a circuit block diagram showing a switching power supply device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing in detail the switching power supply device shown in FIG. The switching power supply device 1 shown in FIGS. 1 and 2 converts the high-voltage DC input voltage Vin supplied from the high-voltage battery HB (first power supply) into a lower DC output voltage Vout, and outputs the low-voltage battery LB (second output). The secondary side is a switching power supply with a center tap type cathode common connection, as will be described later. The switching power supply device 1 includes a power supply main body 10, a control unit 17, a voltage detection unit 20, and an auxiliary power supply unit 30.

  The power supply main body 10 has a three-winding transformer 11 that includes a primary winding 11A and secondary windings 11B and 11C. A smoothing capacitor 12, an inverter circuit 13, and a resonance inductor 14 are provided on the primary side of the transformer 11, and a rectifier circuit 15 and a smoothing circuit 16 are provided on the secondary side, respectively. The smoothing capacitor 12 and the inverter circuit 13 are provided between the primary side high voltage line L1H and the primary side low voltage line L1L, and the resonance inductor 14 is provided between the inverter circuit 13 and the primary side winding 11A. .

  An input terminal T1 is provided on the primary high voltage line L1H, and an input terminal T2 is provided on the primary low voltage line L1L. These input terminals T1 and T2 are connected to the output terminal of the high voltage battery HB. It has become. Further, an output terminal T3 is provided on the output line L0 which is a high voltage side line of the smoothing circuit 16, and an output terminal T4 is provided on the ground line LG which is a low voltage side line of the smoothing circuit 16, respectively. T4 is connected to the input / output terminal of the low voltage battery LB.

  The inverter circuit 13 is a single-phase inverter circuit that converts the DC input voltage Vin output from the high-voltage battery HB into a substantially rectangular wave-shaped single-phase AC voltage. This inverter circuit 13 is a full-bridge type switching circuit formed by full-bridge connection of four switching elements 13A, 13B, 13C, and 13D that are respectively driven by switching signals supplied from the control unit 17. As these switching elements 13A, 13B, 13C, and 13D, for example, elements such as a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor) are used.

  The switching element 13A is provided between one end of the primary side winding 11A of the transformer 11 and the primary side high voltage line L1H, and the switching element 13B is the other end of the primary side winding 11A and the primary side low voltage line L1L. Between. The switching element 13C is provided between the other end of the primary winding 11A and the primary high voltage line L1H, and the switching element 13D is provided between one end of the primary winding 11A and the primary low voltage line L1L. Is provided. The resonance inductor 14 described above is connected between the connection point of the switching elements 13A and 13D and one end of the primary side winding 13A.

  Thus, the inverter circuit 13 turns to the primary low voltage line L1L through the switching element 13A, the primary winding 11A and the switching element 13B in order from the primary high voltage line L1H by the ON operation of the switching elements 13A and 13B. While the current flows through the first current path, the switching elements 13C and 13D are turned on, so that the switching element 13C, the primary winding 11A, the resonance inductor 14 and the switching element 13D are sequentially turned from the primary high-voltage line L1H. A current flows through a second current path that passes through to the primary low-voltage line L1L.

  The transformer 11 is a magnetic element magnetically coupled so that the polarities of the primary side winding 11A and the secondary side windings 11B and 11C are in the same direction. The pair of secondary windings 11B and 11C of the transformer 11 are connected to each other by a center tap C, and the center tap C is connected to the output terminal T4 via a ground line LG. That is, this switching power supply device is of a center tap type. As a result, the transformer 11 transforms (steps down) the AC voltage converted by the inverter circuit 13, and the AC is 180 degrees out of phase with the ends A and B of the pair of secondary windings 11 </ b> B and 11 </ b> C. The voltages VO1 and VO2 are output. In this case, the degree of transformation is determined by the turn ratio between the primary side winding 11A and the secondary side windings 11B and 11C.

  The resonance inductor 14 may actually be provided with a coil component, but instead of or together with this, a series inductance including a leakage inductance (not shown) or wiring of the transformer 11 is used. May be configured.

  The rectifier circuit 15 is a single-phase full-wave rectifier type composed of a pair of diodes 15A and 15B. The anode of the diode 15A is connected to one end A of the secondary winding 11B, and the anode of the diode 15B is connected to one end B of the secondary winding 11C. The cathodes of the diodes 15A and 15B are connected to each other at the connection point D and to the output line LO. That is, the rectifier circuit 15 has a cathode common connection structure, and the DC voltage is obtained by individually rectifying the half-wave periods of the AC output voltages VO1 and VO2 of the transformer 11 by the diodes 15A and 15B, respectively. It has become.

  The smoothing circuit 16 includes a choke coil 16A and a smoothing capacitor 16B. The choke coil 16A is inserted into the output line LO, and one end thereof is connected to the connection point D and the other end is connected to the output terminal T3. The smoothing capacitor 16B is connected between the other end of the choke coil 16A and the ground line LG. With such a configuration, the smoothing circuit 16 smoothes the DC voltage rectified by the rectifying circuit 15 to generate the DC output voltage Vout, and supplies the DC output voltage Vout to the low voltage battery LB from the output terminals T3 and T4. Yes.

  Next, the voltage detection unit 20 detects whether or not the DC input voltage Vin has reached an overvoltage (predetermined voltage) level. The voltage detection unit 20 includes resistors 21 to 24, a comparator 25, and a transistor 26.

  The resistors 21 and 22 are connected in series between the primary side high voltage line L1H and the primary side low voltage line L1L, and a node between them is connected to the plus input terminal of the comparator 25. The reference voltage Vr 1 is input to the negative input terminal of the comparator 25, and the output terminal is connected to the node between the base of the transistor 26 and the resistors 23 and 24. The resistors 23 and 24 are connected in series between the reference voltage Vr2 and the primary side low-voltage line L1L. The emitter of the transistor 26 is connected to the primary low-voltage line L 1 L, and the collector is connected to the auxiliary power supply unit 30.

  The overvoltage level may be set in advance from the breakdown voltage of the circuit element inside the switching power supply device 1, for example, and is set by the reference voltage Vr 1 and the resistors 21 and 22.

  The auxiliary power supply unit 30 generates a power supply voltage for the control unit 17 from the DC input voltage Vin. Further, when the voltage detection unit 20 detects an input overvoltage, the auxiliary power supply unit 30 increases the level of the power supply voltage and notifies the control unit 17 of the increase. The auxiliary power supply unit 30 includes a transformer 31, a switching element 32, an auxiliary control unit 33, resistors 34 to 36, a rectifier circuit 37, and a capacitor 38.

  The transformer 31 includes a primary side winding 31A, a secondary side winding 31B, and a tertiary side winding 31C, and the polarity of the primary side winding 31A, the secondary side winding 31B, and the tertiary side winding 31C. Are three-winding type flyback transformers that are magnetically coupled so that their polarities are opposite to each other. That is, the secondary winding 31B and the tertiary winding 31C have the same polarity, and the primary winding 31A has a polarity opposite to the polarity of the secondary winding 31B and the tertiary winding 31C. It will have.

  One end of the primary winding 31A is connected to the primary high voltage line L1H, and the other end is connected to the primary low voltage line L1L via the switching element 32. That is, the primary winding 31A and the switching element 32 are connected in series between the primary high voltage line L1H and the primary low voltage line L1L. Specifically, the drain of the switching element 32 is connected to the other end of the primary winding 31A, the source is connected to the primary low-voltage line L1L, and the gate is connected to the output terminal of the auxiliary control unit 33. Yes. A capacitor 38 is connected in parallel to the series circuit of the primary winding 31 </ b> A and the switching element 32.

  Resistors 34 to 36 are connected in series between both ends of the tertiary winding 31C. One terminal of the tertiary winding 31C is connected to the first control terminal of the auxiliary control unit 33, and the other end is connected to the primary low voltage line L1L. The node between the resistors 34 and 35 is connected to the second control terminal of the auxiliary control unit 33, and the node between the resistors 35 and 36 is connected to the output terminal of the voltage detection unit 20, that is, the collector of the transistor 26. ing.

  A rectifier circuit 37 is connected to the secondary winding 31B, and the rectifier circuit 37 includes a diode 37A and a capacitor 37B. One end of the secondary winding 31B is connected to one end of the capacitor 37B via the diode 37A, and the other end is connected to the other end of the capacitor 37B. Specifically, the anode of the diode 37A is connected to one end of the secondary winding 31B, and the cathode is connected to one end of the capacitor 37B. The diode 37A and the capacitor 37B constitute a peak detection circuit, and the peak voltage of the voltage across the secondary winding 31B can be held in the capacitor 37B. The rectifier circuit 37 supplies the voltage of the capacitor 37 </ b> B as the power supply voltage of the control unit 17.

  The auxiliary control unit 33 supplies the power supply voltage of the control unit 17 in a normal state, that is, when the output of the voltage detection unit 20 is high impedance (the transistor 26 is off) according to the voltage across the tertiary winding 31C. To the first level. Specifically, the auxiliary control unit 33 controls the duty of the switching signal supplied to the switching element 32 by PWM control.

  On the other hand, when the input overvoltage occurs, that is, when the output voltage of the voltage detection unit 20 is at a low level (transistor 26 is on), the auxiliary control unit 33 sets the node voltage between the resistor 34 and the resistor 35. Based on the increase, the power supply voltage of the control unit 17 is increased to the second level. Specifically, the auxiliary control unit 33 widens the ON width of the switching signal.

  For example, the second level is about 1.5 times the first level. As a result, the difference between the second level and the first level can be made sufficiently larger than the fluctuation amount of the power supply voltage caused by the fluctuation or fluctuation of the leakage inductance of the transformer 31. Overvoltage detection accuracy can be increased.

  The control unit 17 controls the power supply body unit 10 to perform a switching operation in order to stabilize the DC output voltage Vout of the power supply body unit 10. Further, when the voltage detection unit 20 detects an input overvoltage, the control unit 17 controls the power supply main body unit 10 to stop the switching operation, that is, to perform a predetermined operation different from stabilization. The control unit 17 includes an overvoltage information reading circuit 40 and a stabilization circuit 50.

  The overvoltage information reading circuit 40 reads information on whether or not the primary side voltage detection unit 20 has detected an input overvoltage on the secondary side from the power supply voltage from the auxiliary power supply unit 30 and notifies the stabilization circuit 50 of the information. . Specifically, the overvoltage information reading circuit 40 detects the input overvoltage depending on whether or not the power supply voltage from the auxiliary power supply unit 30 has reached the second level. The overvoltage information reading circuit 40 includes resistors 41 and 42 and a comparator 43. The resistors 41 and 42 are connected in series between the output terminals of the auxiliary power supply unit 30, and the node between them is connected to the plus input terminal of the comparator 43. The reference voltage Vr3 is input to the negative input terminal of the comparator 43, and the output terminal is connected to the second control terminal of the stabilization circuit 50.

  The stabilization circuit 50 is a switching signal (for example, PWM control) for stabilizing the DC output voltage Vout of the power supply main body 10 at normal time, that is, when the output voltage of the overvoltage information reading circuit 40 is at a low level. Is supplied to the inverter circuit 13. On the other hand, at the time of input overvoltage, that is, when the output voltage of the overvoltage information reading circuit 40 is at a high level, the control unit 17 supplies a switching signal for stopping switching to the inverter circuit 13.

Next, the operation of the switching power supply device 1 will be described with reference to FIGS. FIG. 3 is a diagram illustrating operation waveforms of each part of the switching power supply device.
(Non-input overvoltage)

  First, the operation at the time of non-input overvoltage (normal time) will be described. Since the DC input voltage Vin is less than the overvoltage level Vov at the normal time (left side from the time t1 in FIG. 3A), the output voltage Vd1 of the comparator 25 in the voltage detector 20 is at the low level (FIG. 3B). ) On the left side from time t1), the collector of the transistor 26, that is, the output of the voltage detector 20 is high impedance. Therefore, the auxiliary control unit 33 in the auxiliary power supply unit 30 stabilizes the power supply voltage Vs for the control unit 17 at the first level Vs1. Specifically, the auxiliary control unit 33 controls the duty of the switching element 32 while monitoring the voltage of the tertiary winding 31C of the transformer 31 and stabilizes the voltage of the tertiary winding 31C. Then, since the tertiary winding 31C and the secondary winding 31B have the same polarity, the voltage of the secondary winding 31B is also stabilized and the power supply voltage Vs rectified by the rectifier circuit 37 is obtained. Is stabilized to the first level Vs1 (left side from time t1 in FIG. 3C).

  At this time, since the power supply voltage Vs is less than the overvoltage level (resistance ratio multiple of Vr3), the output voltage Vd2 of the comparator 43 in the overvoltage information reading circuit 40 of the control unit 17 is at the low level (in FIG. 3D). Left side from time t1). Then, the stabilization circuit 50 stabilizes the DC output voltage Vout. Specifically, the stabilization circuit 50 controls the inverter circuit 13 in the power supply main body 10 as follows.

  When the switching elements 13A and 13B of the inverter circuit 13 are turned on, a current flows from the switching element 13A to the switching element 13B, and the voltages VO1 and VO2 appearing in the secondary windings 11B and 11C of the transformer 11 are applied to the diode 15B. The reverse direction, and the forward direction with respect to the diode 15A. Therefore, a current flows from the secondary winding 11B through the diode 15A to the output line LO.

  Next, when the switching element 13B is turned off and the switching element 13C is turned on, the voltage [−VO2] appearing on the secondary winding 11C of the transformer 11 becomes substantially zero.

  Thereafter, when the switching elements 13C and 13D are turned on, current flows from the switching element 13C to the switching element 13D, and the voltages [−VO1] and [−VO2] appearing in the secondary windings 11B and 11C of the transformer 11 are diodes. While the forward direction is to 52, the reverse direction is to diode 15A. Therefore, a current flows from the secondary winding 11C through the diode 15B to the output line LO.

  Next, when the switching element 13C is turned off and the switching element 13B is turned on, the voltage [−VO1] appearing at the secondary winding 11B of the transformer 11 becomes substantially zero.

  The stabilization circuit 50 stabilizes the DC output voltage Vout by causing the power supply main unit 10 to repeat the above-described operation and adjusting the duty of the switching signal of the inverter circuit 13 while monitoring the DC output voltage Vout.

In this way, the power supply main body 10 transforms (steps down) the DC input voltage Vin supplied from the high voltage battery HB to the DC output voltage Vout, and supplies the transformed DC output voltage Vout to the low voltage battery LB.
(At input overvoltage)

  Next, the operation at the time of input overvoltage will be described. As shown in FIG. 3A, when the DC input voltage Vin rises and the DC input voltage Vin reaches the overvoltage level Vov at time t2, the output voltage Vd1 of the comparator 25 in the voltage detector 20 becomes high level. (Time t2 in FIG. 3B), the collector of the transistor 26, that is, the output voltage of the voltage detection unit 20 becomes low level. As a result, the resistor 36 is short-circuited, the node voltage between the resistor 34 and the resistor 35 rises, and the auxiliary control unit 33 in the auxiliary power supply unit 30 sets the power supply voltage Vs for the control unit 17 to the first level. 2 to the level Vs2 (time t2 to t3 in FIG. 3C). The specific operation of the auxiliary control unit 33 is the same as described above. In the present embodiment, the power supply voltage Vs rises to about 1.5 times R35 × (R34 + R35 + R36) / ((R34 + R35) × (R35 + R36)).

  Then, the power supply voltage Vs reaches the overvoltage level, and the output voltage Vd2 of the comparator 43 in the overvoltage information reading circuit 40 of the control unit 17 becomes the high level (time t3 in FIG. 3D). As a result, the stabilization circuit 50 outputs a switching signal for turning off all the inverter circuits 13 and stops the operation of the power supply main body 10.

  As described above, according to the switching power supply device 1 of the present embodiment, the auxiliary power supply unit 30 changes the level of the power supply voltage of the control unit 17 according to the output voltage of the voltage detection unit 20, and thus the control unit 17 From this power supply voltage level, it can be determined whether or not the voltage detection unit 20 has detected an input overvoltage. Therefore, according to the switching power supply device 1 of the present embodiment, even if the voltage detection unit 20 is provided on the input side (primary side), the input / output insulation circuit for the voltage detection unit 20 (primary-secondary insulation circuit: There is no need to provide a separate photocoupler, relay, etc., and the size and cost can be reduced. In the present embodiment, the transformer 31 in the auxiliary power supply unit 30 serves as both power supply unit insulation and voltage detection unit insulation of the control unit 17.

  Further, according to the switching power supply device 1 of the present embodiment, the amount of change in the power supply voltage at the time of input overvoltage, that is, the difference between the second level at the time of input overvoltage and the first level at the time of normal is about 1.5. By doubling the input overvoltage, it is possible to detect the input overvoltage with high accuracy without depending on fluctuations and variations in the leakage inductance of the transformer 31. Furthermore, in the switching power supply device 1 according to the present embodiment, the voltage detection unit 20 can be provided on the input side with the above-described configuration, and the DC input voltage Vin can be directly detected. Can be further enhanced.

  Further, according to the switching power supply device 1 of the present embodiment, the control unit 17 stops the operation of the power supply main body unit 10 at the time of an input overvoltage, so that the internal circuit of the switching power supply device 1 can be appropriately prevented from being destroyed. .

  The present invention is not limited to the above-described embodiment, and various modifications can be made.

  In the above embodiment, the operation of the power supply main body 10 is stopped when the input overvoltage is detected, but the on-time of the inverter circuit 13 is adjusted to the extent that the destruction of the circuit elements can be suppressed without shutting down the power supply main body 10. However, the duty ratio may be lowered. In the above embodiment, the switching signal for turning off all the inverter circuits 13 is output when the operation of the power supply main body 10 is stopped. However, when the operation of the power supply main body 10 is stopped, the switching is performed. A configuration in which no signal is output may be used.

  In the above-described embodiment, the circuit configuration of the switching power supply device 1 is specifically described. However, the circuit configuration is not limited to this. For example, the inverter circuit may be configured by a full bridge type using eight switching elements, a forward type using two switching elements, or a half bridge type using two or four switching elements.

  In the above embodiment, the case where the power supply main body 10 is configured by the step-down DC-DC converter that converts the high-voltage DC input voltage Vin to the lower DC output voltage Vout has been described. The power supply main body may be constituted by a boost DC-DC converter that converts a low-voltage DC input voltage Vin into a higher DC output voltage Vout.

  In the above embodiment, the auxiliary power supply 30 controls the power supply voltage by monitoring the voltage across the tertiary winding 31C of the transformer 31, but the voltage across the secondary winding 31B and the power supply directly. Even if the voltage is monitored, the same control is possible.

1 is a circuit block diagram showing a switching power supply device according to a first embodiment of the present invention. It is a circuit diagram which shows the switching power supply device shown in FIG. 1 in detail. It is a figure which shows each part operation | movement waveform of a switching power supply device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Switching power supply device, 10 ... Power supply main-body part, 11 ... Transformer, 12 ... Smoothing capacitor, 13 ... Inverter circuit, 13A-13D ... Switching element, 14 ... Resonance inductor, 15 ... Rectifier circuit, 16 ... Smoothing circuit, 17 DESCRIPTION OF SYMBOLS ... Control part, 20 ... Voltage detection part, 25 ... Comparator, 30 ... Voltage detection part, 31 ... Transformer, 32 ... Switching element, 33 ... Auxiliary control part, 37 ... Rectifier circuit, 40 ... Overvoltage information reading circuit, 43 ... Comparator, 50 ... Stabilization circuit, HB ... High voltage battery, LB ... Low voltage battery.

Claims (2)

A power supply main body for generating an output voltage obtained by performing a switching operation and converting the input voltage into a voltage;
A control unit for controlling the switching operation;
An auxiliary power supply unit that generates a power supply voltage of the control unit from the input voltage;
A voltage detector for detecting the input voltage;
With
The auxiliary power supply unit changes the power supply voltage from a first level to a second level different from the first level according to an output voltage from the voltage detection unit,
The control unit controls the switching operation to stabilize the output voltage of the power supply main body unit when the power supply voltage is at the first level, and the power supply voltage is set to the second level. If it becomes, control to perform a predetermined operation different from the stabilization,
A switching power supply device. The auxiliary power supply unit increases the power supply voltage to the second level when the input voltage detected by the voltage detection unit exceeds a predetermined voltage,
The control unit stops the operation of the power supply main body when the power supply voltage reaches the second level.
The switching power supply device according to claim 1, wherein:

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