JP2002191174A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the conversion efficiency of a DC-DC converter in a power supply for a vehicle. SOLUTION: A switching loss can be reduced to almost zero with a controller 20 by detecting a voltage and a current applied to switching devices 3, 4 by a first and a second voltage detectors 13, 15 and a current detector 17. A diode of a rectifying circuit 10 in the secondary side of an insulation transformer 9 is also switched with a zero voltage using a resonance operation. As a result, the switching loss is no longer generated. Moreover, the controller 20 also controls simultaneously a current flowing rate of the switching devices 3, 4 to keep an output voltage constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply comprising a DC / DC converter.

[0002]

2. Description of the Related Art A conventional auxiliary power supply device for a vehicle using a train line as an input has a configuration shown in FIG. This conventional power supply device is a DC / DC converter circuit of a full bridge circuit,
Pantograph 1, input circuit 2, switching device S
A first bridge 3 comprising A, SB and diodes connected in parallel to them, and a full bridge including switching devices SC, SD and a second arm consisting of diodes connected in parallel to these devices. Inverter circuit 30 having a configuration,
The rectifier circuit 10 is composed of an insulating transformer 9 having a primary winding connected to the output line and four diodes connected to a full bridge, and is connected to a secondary winding of the insulating transformer 9 and is serially connected to the rectifier circuit 10. , A filter capacitor 12 connected in parallel to the rectifier circuit 10 and the filter reactor 11, and a control unit 20 for controlling switching of the switching devices SA to SD.

The control unit 20 includes a filter capacitor 1
The switching devices SA to SD of the inverter circuit 30 are controlled based on the voltage detection signal (VD1) 14 of the first voltage detector 13 for detecting the voltage between the terminals 2 and 2 and the input voltage detection signal (VD3) from the input circuit 2. By performing switching control with each of the signals A to D, a DC power of a predetermined voltage is output.

In this conventional power supply device, the snubber circuit 5 is connected to the switching device of the inverter circuit 30 and the rectifier circuit 10, and the control device 20 performs hard switching (cuts off voltage and current) of each switching device.

[0005]

However, in such a conventional power supply device, the switching device in the inverter circuit and the diode in the rectifier circuit are hard-switched. When the voltage is on, the voltage area at the time of the voltage rise × the area at the time of the current drop, and when it is on, the loss at the frequency of the voltage area at the time of the voltage drop × the area at the time of the current rise is generated. Further, at the time of hard switching, a snubber circuit is required, and the snubber circuit also generates a loss. In addition, in the conventional power supply device, the conversion efficiency does not deteriorate particularly when the switching frequency is low, but when the high frequency switching is performed for the purpose of downsizing the insulating transformer and the filter reactor, the frequency is doubled. Loss increases, conversion efficiency decreases, and wasteful power consumption occurs. For this reason, the conventional power supply device has a problem that switching loss due to the switching device is large and power conversion efficiency is not sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has as its object to provide a power supply device capable of reducing switching loss due to a switching device and improving conversion efficiency.

[0007]

According to a first aspect of the present invention, there is provided a power supply apparatus comprising: an inverter circuit configured to perform DC-AC conversion, comprising four switching devices connected to a full bridge; and a serial circuit in the inverter circuit. A snubber capacitor connected in parallel to each of the two switching devices of the first arm connected thereto, and an auxiliary reactor serially connected to each of the two switching devices of the second arm serially connected in the inverter circuit. A rectifying circuit comprising a primary winding connected to two output lines of the inverter circuit, and four diodes connected to a full bridge, and connected to a secondary winding of the insulating transformer; A filter reactor serially connected to the rectifier circuit; and a rectifier circuit and a filter reactor. And connected to filter capacitors to Parallel, first to detect the voltage of the filter capacitor
A voltage detector, a current detector for detecting an output current of the inverter circuit, a second voltage detector for detecting a voltage between two output lines of the inverter circuit, and a voltage detector between the two output lines of the inverter circuit. A connected resonance reactor, a resonance capacitor serially connected between a connection point of the resonance reactor and a primary winding of the insulating transformer, and a voltage of the filter capacitor output from the first voltage detector. The duty ratio of the switching device is controlled in order to control the secondary voltage to be constant by the detection signal. A control unit that outputs a switching control signal so as to perform zero current or zero voltage switching.

According to a second aspect of the present invention, in the power supply device of the first aspect, the resonance capacitor is provided between a secondary winding of the insulating transformer and a rectifier circuit.

According to a third aspect of the present invention, in the power supply device of the first aspect, the resonance reactor is provided between secondary windings of the insulating transformer.

According to a fourth aspect of the present invention, in the power supply device of the first aspect, the auxiliary reactor is made one and connected to an intermediate point of a switching device of the second arm, and an intermediate point of the auxiliary reactor is connected to the resonance reactor. Are connected to one side of the resonance capacitor and one side of the resonance capacitor.

According to a fifth aspect of the present invention, in the power supply device of the first aspect, an intermediate tap is provided in a secondary winding of the insulating transformer, and the rectifier circuit is a half-bridge circuit composed of two diodes. It is a feature.

In the power supply device according to the first to fifth aspects of the present invention, the control unit detects the voltage applied to the switching device and the flowing current by the first and second voltage detectors and the current detector, and detects the zero voltage or By controlling the switching operation in the zero current state, the switching loss is reduced to almost zero. Also, the diode of the rectifier circuit on the secondary side of the insulating transformer performs zero voltage switching by utilizing the resonance operation, and does not generate switching loss. Further, the control unit simultaneously controls the conduction ratio of the switching device to keep the output voltage constant.

That is, (1) When the switching device of the first arm is turned off, the cutoff current is shunted to the snubber capacitor to perform zero current switching.

(2) When the switching device of the first arm is turned on, since the diode connected in parallel is turned on, the voltage applied to this switching device is in a zero state, and as a result, Zero-voltage switching occurs.

(3) On the other hand, when the switching device of the second arm is turned off, after the switching device of the first arm is turned off, the current flows through the resonance capacitor, the leakage inductance in the insulating transformer, and the secondary-side filter reactor. Resonates and gradually decays. Therefore, the zero current switching is performed by detecting that the current starts to flow in the zero direction or the reverse direction by each of the voltage detectors and the current detectors and performing off-control.

At this time, the current resonates and gradually attenuates, and flows in a direction reverse to that of the current. As a result, the amount of current flowing through each diode of the rectifier circuit on the secondary side of the insulating transformer increases. When the current amount changes to the same value as the current flowing to the load side, the off-side diode becomes Vf of the diode from which all the current flows.
Turn off with voltage. For this reason, the diode to be turned off shifts to the off state by almost zero voltage, and performs zero voltage switching.

(4) Further, when the switching device of the second arm is turned on, the rise time of the current is slower than the fall time of the voltage due to the auxiliary inductance connected in series with the switching device. This results in zero current switching.

As described above, the switching loss of the switching device of the inverter circuit is turned on or off to make the switching loss almost zero, and the resonance operation is also used for the diode of the rectifier circuit on the secondary side of the isolation transformer. Thus, zero-voltage switching is performed to prevent switching loss.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit block diagram of a vehicle power supply device according to a first embodiment of the present invention. The vehicle power supply device of this embodiment includes a pantograph 1 for collecting high-voltage DC power of an overhead line, an input circuit 2 having a protection / shutoff function of a circuit configuration shown in FIG. 2, and a full bridge for DC-AC conversion. Four connected switching devices SA, S
An inverter circuit 30 composed of B, SC, and SD, an insulation transformer 9 having a primary winding connected to two output lines of the inverter circuit 30, and four diodes connected to a full bridge. A rectifier circuit 10 connected to the secondary winding and a control unit 20 for controlling the switching devices SA to SD of the inverter circuit 30 with control signals A to D are provided, and a load 13 is connected to an output of the rectifier circuit 10. You.

In addition, a snubber capacitor 5 is connected in parallel to each of the two switching devices SA and SB of the first arm 3 serially connected in the inverter circuit 30, and is also serially connected in the inverter circuit 30. Two switching devices S of the second arm 4
An auxiliary reactor 6 is serially connected to each of C and SD. A resonance reactor 7 is connected between two output lines of the inverter circuit 30, and a resonance capacitor 8 is serially connected between a connection point of the resonance reactor 7 and a primary winding of the insulating transformer 9.

Further, a filter reactor 11 is serially connected to the output side of the rectifier circuit 10.
A filter capacitor 12 is connected in parallel with 0 and the filter reactor 11.

A first voltage detector 13 detects the voltage of the filter capacitor 12, and a second voltage detector 1 detects the voltage between two output lines of the inverter circuit 30.
5 and a current detector 17 for detecting the output current of the inverter circuit 30, respectively.

The control unit 20 controls the duty ratio of the switching devices SA to SD in order to control the secondary voltage to be constant by the voltage detection signal 14 of the filter capacitor 12 output from the first voltage detector 13; Second voltage detector 1
The switching control signals A to D are output so that the switching devices SA to SD perform zero current or zero voltage switching based on the voltage detection signal 16 of No. 5 and the current detection signal 18 of the current detector 17.

FIG. 2 is a circuit block diagram of the input circuit 2 in FIG. The input circuit 2 includes an electromagnetic contactor 201 for performing protection interruption, a DC reactor 202 for suppressing AC components, and a diode 2 for surge current protection.
03 and a resistor 205, and a thyristor 20 provided in parallel with the diode 203 and the resistor 205.
4. It is composed of a DC capacitor 206 for holding a voltage. A third voltage detector 207 for detecting a voltage between both ends of the DC capacitor 206 is provided, and a third voltage detection signal (VD3) 19 of the voltage detector 207 is provided.
Is input to the control unit 20.

FIG. 3 shows an equivalent circuit of the internal leakage inductance of the insulating transformer 9, which is represented by the insulating transformer 21 and the leakage inductance 22.

Next, the operation of the vehicle power supply device according to the first embodiment having the above configuration will be described with reference to FIGS. FIG. 4 shows the voltage / current waveforms of each part and the on / off timing of each switching device during the operation of the main circuit.

Now, from the state where the switching device SA of the first arm 3 and the switching device SD of the second arm are turned on to supply power to the secondary load 13, the control unit 20 first performs switching by the signal A. Device S
Turn A off.

When the switching device SA turns off,
The current flowing through the switching device SA is shunted to the lossless snubber capacitor 5 connected in parallel to the switching device SA, and the charging operation is started. At the same time, the lossless snubber capacitor 5 connected in parallel to the switching device SB performs a discharging operation.

Switching device SA of first arm 3
When the switch is turned off, the current is shunted to the lossless snubber capacitor 5, so that the current is not interrupted, so that zero current switching is performed, and the switching loss is zero.

When the charging / discharging operation of the lossless snubber capacitor 5 is completed, a current continues to flow due to the leakage inductance 22 in the insulating transformer 9 and the resonance reactor 7, and starts to flow to a diode connected in parallel to the switching device SB. . In this state, the control unit 20
Is detected from the fact that the voltage detection signal 16 of the second voltage detector 15 has become zero.

Switching device SB of first arm 3
Since the diode connected in parallel to the switching device SB is on and the voltage applied to the switching device SB is zero, the control unit 20 turns on the switching device SB by the signal B. As a result, the switching device SB performs zero voltage switching,
Switching loss is zero.

Next, the return current flowing through the diode connected in parallel to the switching device SB and the switching device SD by the resonance reactor 7 is gradually attenuated by the resonance phenomenon of the resonance capacitor 8 and the resonance reactor 7, and After the current becomes zero, it starts to flow in the reverse direction. At this time, the current flows through the switching device SB.
And the diode connected in parallel with the switching device SD.

The control unit 20 detects that the return current has become zero with the current detector 17, and the switching device S
At the timing when the current flowing through D becomes zero, the switching device SD is turned off by the signal D. As a result, the switching device SD performs zero voltage and zero current switching, can be turned off without providing a normal snubber circuit, and has no switching loss.

Further, the return current gradually decreases, the flow direction is reversed, and increases to the value of the current flowing on the secondary side. At the time when the return current has the same value as the current flowing on the secondary side, two diodes connected diagonally in the rectifier circuit 10 (when the switching devices SA and SD are on, the secondary side The diode that supplied power to the power supply is turned off. At this time, the application of the voltage to the diode that is turned off depends on the V of the two diodes on the opposite diagonal where the entire current starts flowing.
Since the operation is performed at the voltage f, the state shifts to the off state in the same state as the state of substantially zero voltage.

For this reason, the rectifier diode of the secondary side rectifier circuit 10 also performs zero voltage switching, and the switching loss becomes zero. In addition, at the time of the conventional hard switching, in the recovery of the diode (the timing of transition from the ON state to the OFF state), a surge voltage is generated from a sudden cutoff of the current, so that a snubber circuit or a serially connected supersaturated reactor is connected to suppress the surge voltage. Although a surge voltage suppression circuit such as that described above is required, the present embodiment eliminates the need for the surge voltage suppression circuit because of zero voltage switching, and eliminates the loss generated by the surge voltage suppression circuit.

After the switching device SD of the second arm is turned off, the control unit 20 turns on the switching device SC in response to the signal C. Switching device SC
Is turned on, the switching device SB of the first arm
At the same time, a mode for supplying power to the secondary side is set. When the switching device SC is turned on, the rise time of the load current flowing through the switching device SC is suppressed by the auxiliary reactor 6, so that the time when the voltage applied to the switching device SC starts to flow is delayed with respect to the time when the voltage applied to the switching device SC becomes zero. Then, the state shifts to the ON state in a state where the switching loss is suppressed. Therefore, the switching device SC performs zero current switching.

Thereafter, returning to the first switching mode, the switching devices SA → SB, SB → SA, S
Switching is repeated in a state where C → SD and SD → SC are replaced, and a rectangular wave voltage is output to the secondary side of the insulating transformer 9 to supply power.

As described above, the 4 in the inverter circuit 30
Since the three switching devices SA, SB, SC, and SD all repeat switching with zero current or zero voltage, switching can be performed with substantially zero switching loss, and the conversion efficiency of the device can be improved.

Next, control for making the output voltage constant and control for zero voltage and zero current switching will be described. Since the charging / discharging operation time when the switching device SA or SB of the lossless snubber capacitor 5 is off is performed by dividing the load current,
When the amount of power supplied to the load 13 changes, the time also changes. That is, when the amount of power supply to the load 13 is large, the current increases, and the charge / discharge time is short. When the amount of power supply to the load 13 is small, the current decreases, and the charge / discharge time increases.

The time from when each of the switching devices SA and SB of the first arm 3 is turned on to when each of the switching devices SD and SC of the second arm 4 is turned off depends on the current decay time of the resonance capacitor 8. You.

Therefore, in order to switch each element to zero voltage and zero current, as described above, the timing at which the switching devices SA and SB are turned on is determined by the second voltage detector 15 when the device applied voltage VD2 becomes zero. Switching devices SC, S
The timing at which D is turned off must be the timing at which the current of the device becomes zero by the current detector 17 or flows in the opposite direction.

For this reason, the control unit 20 outputs an ON / OFF signal to each switching device and satisfies the conditions necessary for the above-described zero current and zero voltage switching by the control example described below, thereby controlling the output voltage. Control to be constant.

An example of the control will be described below with reference to the control unit 2 shown in FIG.
This will be described with reference to the control block diagram of FIG. In addition, load 1
In the case where the fluctuation of the switching device 3 is small or the fluctuation of the input voltage is small, the fluctuation of the on-timing of the switching devices SA and SB and the fluctuation of the off-timing of the switching devices SC and SD are small. You can also.

From the input filter capacitor voltage VD3 based on the voltage detection signal 19 detected by the third voltage detector 207 in the input circuit 2, the transformation ratio K of the insulating transformer 9, and the rated output voltage Vout, the control reference value of the switching device is obtained. (ON time of switching device / 1 cycle time) αr
It is obtained by the following equation (1).

[0045]

(Equation 1) Here, Vrin is the rated input filter capacitor voltage.

Output reference voltage Vout and first voltage detector 13
From the load voltage VD1 based on the voltage detection signal 14 from the controller, and a correction value obtained by performing a proportional / integral operation on the difference is added to the control reference value αr to obtain a control voltage αcnt. Here, Gp is a proportional gain, and Gi is an integral gain.

[0047]

(Equation 2) This control voltage αcnt is compared with two reference sawtooth waveforms 101 and 102 which are 180 ° out of phase with each other, and the switching device SA is turned on after the switching device SD is turned on.
Is the time from when the switching device SC turns on to when the switching device SB turns off.
Calculation is performed as waves PwmA and PwmB. Reference numeral 103 denotes a triangular wave oscillator.

The switching devices SA and SB are turned on when the respective PWM waves PwmA and PwmB are at “H”, and turned off when inverted to “L”.

The timing at which each of the switching devices SA and SB of the first arm 3 is turned on and the timing at which each of the switching devices SC and SD of the second arm 4 are turned on correspond to the voltage detection signal of the second voltage detector 15, respectively. The interlock is applied by the voltage value VD2 by the reference numeral 16 and the current value CT1 by the current detection signal 18 of the current detector 17 to turn off and on at an appropriate timing.

With the above control, when the amount of power supplied to the load 13 is small and the charge / discharge time of the lossless snubber capacitor 5 is long, or after the switching devices SA and SB are turned on, the switching devices SD and SC are turned off, respectively. Even when the time until the current is longer than the current decay time of the resonance capacitor 8, the switching timing is changed to perform zero voltage and zero current switching,
The output voltage can be made constant.

Next, a vehicle power supply device according to a second embodiment of the present invention will be described with reference to FIG. The second embodiment differs from the first embodiment shown in FIG.
It is characterized in that the resonance capacitor 8 is connected to the secondary side of the insulating transformer 9. Other circuit elements are common to the first embodiment.

In the case of the second embodiment, since the secondary side of the insulating transformer 9 has a generally low grounding voltage, the conversion efficiency is improved as compared with the conventional auxiliary power supply device as in the first embodiment. And the resonance capacitor 8 used
Can have a low dielectric strength.

Next, a vehicle power supply device according to a third embodiment of the present invention will be described with reference to FIG. The third embodiment differs from the first embodiment shown in FIG.
The resonance reactor 7 and the resonance capacitor 8 are both connected to the secondary side of the insulating transformer 9. Other circuit elements are common to the first embodiment.

Also in the case of the third embodiment, the secondary side of the insulating transformer 9 generally has a low withstand voltage, so that the conversion efficiency is lower than that of the conventional auxiliary power supply device as in the first embodiment. Can be improved, and the withstand voltage of the resonance reactor 7 and the resonance capacitor 8 used can be reduced.

Next, a vehicle power supply device according to a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, the one using two auxiliary reactors 6 in the first embodiment shown in FIG. 1 is reduced to one, and a serial connection is made between the two switching devices SC and SD of the second arm 4. Characterized in that it is inserted into Other circuit elements are common to the first embodiment.

As a result, in the fourth embodiment, the first
As in the embodiment, the conversion efficiency can be improved as compared with the conventional auxiliary power supply device, and the number of circuit components can be reduced.

Next, a vehicle power supply device according to a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment differs from the first embodiment shown in FIG.
An intermediate tap is provided in the secondary winding of the insulating transformer 9 to provide two diodes in the rectifier circuit 10 to form a half bridge circuit. Other circuit elements are common to the first embodiment.

Thus, according to the fifth embodiment,
As in the first embodiment, the conversion efficiency can be improved as compared with the conventional auxiliary power supply, and the number of components can be reduced.

[0059]

As described above, according to the present invention, the switching loss of the switching device of the inverter circuit is reduced to almost zero by controlling the switching devices of the inverter circuit to zero current and zero voltage. Also for the diode, zero voltage switching is performed by utilizing the resonance operation, so that switching loss can be prevented from occurring, and power conversion efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a vehicle power supply device according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram illustrating a configuration of an input circuit in the embodiment.

FIG. 3 is an equivalent circuit diagram of the leakage inductance of the insulating transformer in the embodiment.

FIG. 4 is a timing chart of a switching operation of each element according to the embodiment.

FIG. 5 is a block diagram of a control unit in the embodiment.

FIG. 6 is a circuit block diagram of a vehicle power supply device according to a second embodiment of the present invention.

FIG. 7 is a circuit block diagram of a vehicle power supply device according to a third embodiment of the present invention.

FIG. 8 is a circuit block diagram of a vehicle power supply device according to a fourth embodiment of the present invention.

FIG. 9 is a circuit block diagram of a vehicle power supply device according to a fifth embodiment of the present invention.

FIG. 10 is a circuit block diagram of a conventional vehicle auxiliary power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pantograph 2 Input circuit 3 1st arm 4 2nd arm 5 Snubber capacitor 6 Auxiliary reactor 7 Resonant reactor 8 Resonant capacitor 9 Insulation transformer 10 Rectifier circuit 11 Filter reactor 12 Filter capacitor 13 First voltage detector 14 Voltage detection signal 15th 2 voltage detector 16 voltage detection signal 17 current detector 18 current detection signal 19 voltage detection signal 20 controller

Claims (5)

[Claims] 1. An inverter circuit comprising four switching devices connected to a full bridge for performing DC-AC conversion, and two switching devices of a first arm serially connected in the inverter circuit. A snubber capacitor connected to the inverter circuit; an auxiliary reactor serially connected to each of the two switching devices of the second arm serially connected in the inverter circuit; and a primary winding on two output lines of the inverter circuit. A rectifier circuit connected to a secondary winding of the insulating transformer, the filter reactor being serially connected to the rectifier circuit; A filter capacitor connected in parallel with the rectifier circuit and the filter reactor A first voltage detector that detects a voltage of the filter capacitor; a current detector that detects an output current of the inverter circuit; and a second that detects a voltage between two output lines of the inverter circuit.
A voltage detector; a resonance reactor connected between two output lines of the inverter circuit; a resonance capacitor serially connected between a connection point of the resonance reactor and a primary winding of the insulating transformer; The duty ratio of the switching device is controlled to keep the secondary voltage constant by the voltage detection signal of the filter capacitor output from the first voltage detector, and the voltage detection signal of the second voltage detector is controlled. And a control unit that outputs a switching control signal so that the switching device performs zero current or zero voltage switching according to a current detection signal of the current detector. 2. The power supply device according to claim 1, wherein the resonance capacitor is provided between a secondary winding of the insulating transformer and a rectifier circuit. 3. The power supply device according to claim 1, wherein the resonance reactor is provided between secondary windings of the insulating transformer. 4. The method according to claim 1, wherein the auxiliary reactor is connected to one and connected to an intermediate point of a switching device of the second arm, and the intermediate point of the auxiliary reactor is connected to one side of the resonance reactor and one side of a resonance capacitor. The power supply device according to claim 1, wherein: 5. The power supply device according to claim 1, wherein an intermediate tap is provided in a secondary winding of the insulating transformer, and the rectifier circuit is a half-bridge circuit including two diodes.