JPH09252576A - Sunbber circuit of dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the loss in a snubber circuit by suppressing the voltage rise of a semiconductor switching element thereby lessening the loss. SOLUTION: Loss generation is reduced by making the effective use of snubber energy, by suppressing the voltage rise percentage at the time of turn off of a semiconductor switch element 21 so as to reduce the switching loss, and reversely charging the capacitor at the time of turn on of the semiconductor element 21d, while enabling the application of a clamp snubber circuit 7 by connecting a semiconductor switch 22 and a diode 32 as shown in the Fig. and also, connecting a snubber circuit 8 and an auxiliary circuit 9 to the one- stone forward type converter consisting of a DC power source 1, a semiconductor switch element 21, a diode 31, and a converter 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber circuit of a DC-DC converter for extracting DC power insulated from a DC power supply, and more particularly to a snubber circuit of small size and low loss.

[0002]

2. Description of the Related Art FIG. 11 shows a conventional example of a one-stone forward type DC-DC converter. As shown in FIG.
Is connected to the primary winding 41 and the reset winding 42 of the transformer 4, and a semiconductor switch is provided between the other terminal of the primary winding 41 of the transformer 4 and the negative terminal of the DC power supply 1. The element 21, the diode 32 between the other terminal of the reset winding 42 of the transformer 4 and the negative terminal of the DC power supply 1, the rectifier circuit 5 in the secondary winding 43 of the transformer 4, the rectifier circuit 5 Are connected to smoothing filters 6 respectively.

FIG. 18 shows the operation waveforms of FIG. 11 (FIG. 11
Such a circuit and its operation are well known including, for example, the description on pages 18 to 19 and 95 to 99 of "Method of designing switching regulator and use of power device" published by Seibundou Shinkosha Co., Ltd. in 1984. ing). Now, while the semiconductor switch element 21 is on, the transformer 4 is excited in the positive direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6. On the other hand, the excitation energy of the transformer 4 is regenerated to the DC power supply 1 via the reset winding 42 and the diode 32 while the semiconductor switch element 21 is off.

In the circuit of FIG. 11, the semiconductor switching element 2
1 is turned off, the jumping voltage of the semiconductor switch element 21 is suppressed and the voltage rising rate (dv / dt)
To reduce the switching loss, the snubber circuit 12 as shown in FIGS. 17A and 17B is connected in parallel to the semiconductor switch element 21. Note that FIG.
17A shows a series circuit of a capacitor 121 and a resistor 122, and FIG. 17B shows a capacitor 123 and a diode 12
5 is connected in series, and the discharge resistance 124 is connected in parallel with the diode 125. As a result, the energy absorbed by the capacitors 121 and 123 is applied to the discharge resistor 12 while the semiconductor switch element 21 is turned on next time.
It is released to 2,124.

FIG. 12 shows a modification of FIG. The difference from FIG. 11 is that the snubber circuit 12 is omitted and the diode 31
One terminal is connected to the transformer primary winding 41 and the semiconductor switching element 21, one terminal of the semiconductor switching element 22 is connected to the transformer reset winding 42 and the diode 32, and the diode 31 And the snubber circuit 7 is connected between the connection point between the diode 31 and the semiconductor switch element 22 and the connection point between the semiconductor switch element 21 and the diode 32, respectively. Here, the snubber circuit 7 is shown as a capacitor.

FIG. 19 shows the operation waveform of FIG. The DC output operation is the same as that in the case of FIG. 11, and is omitted, and the energy regeneration operation by the snubber circuit 7 will be described. When the semiconductor switch element 21 is turned off, the diode 31 conducts to suppress the jump voltage of the semiconductor switch element 21, and the snubber circuit 7 absorbs energy corresponding to the jump voltage. Next, the semiconductor switch element 22 is turned on while the semiconductor switch element 21 is on, and the energy absorbed by the snubber circuit 7 is released to the load.

FIG. 13 shows a conventional example of a two-stone forward type DC-DC converter. As shown in the figure, one terminal of the semiconductor switch element 22 is connected to the positive terminal of the DC power supply 1, and one terminal of the transformer primary winding 41 is connected to the other terminal of the semiconductor switch element 22. The other terminal of the primary winding 41 is one terminal of the semiconductor switching element 21, the other terminal of the semiconductor switching element 21 is the negative terminal of the DC power supply 1, the positive terminal of the DC power supply 1 and the transformer primary. A diode 31 is provided between the connection point between the winding 41 and the semiconductor switching element 21, and the transformer primary winding 41 and the semiconductor switching element 2 are connected.
A diode 32, a rectifier circuit 5 is connected to the transformer secondary winding 43, and a smoothing filter 6 is connected to the rectifier circuit 5 between the connection point 2 and the negative terminal of the DC power supply 1.

FIG. 20 shows the operation waveform of FIG. That is, the transformer 4 is excited in the positive direction while the semiconductor switch elements 21 and 22 of FIG. 13 are turned on, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6. Next, the excitation energy of the transformer 4 is regenerated to the DC power supply 1 via the transformer primary winding 41, the diode 31 and the diode 32 while the semiconductor switch elements 21 and 22 are off. In the circuit of FIG. 13 as well, the semiconductor switch elements 21 and 22 have the semiconductor switch elements 21 and 22 for suppressing the rising voltage and the voltage rising rate.
A snubber circuit as shown in FIG. 17 is connected in parallel to and 22.

FIG. 14 shows a conventional example of a half-bridge type DC-DC converter. Here, one terminal of the semiconductor switch element 22 and one terminal of the capacitor 18 are connected to the positive terminal of the DC power supply 1, and one terminal of the semiconductor switch element 21 and the transformer are connected to the other terminal of the semiconductor switch element 22. One terminal of the primary winding 41, one terminal of the capacitor 17 at the other terminal of the capacitor 18 and the other terminal of the transformer primary winding 41, and the rectifying circuit 5 at the transformer secondary winding 43. The smoothing filters 6 are connected to the rectifier circuit 5, respectively.

FIG. 21 shows the operation waveform of FIG. That is, the transformer 4 is excited in the positive direction while the semiconductor switch element 22 of FIG. 14 is turned on, and the transformer 4 is excited in the negative direction while the semiconductor switch element 21 is turned on. By repeating such operations, the DC power supply 1
To supply DC power to the load via the rectifier circuit 5 and the smoothing filter 6. In the circuit of FIG. 14 as well, snubber circuits as shown in FIG. 17 are connected in parallel to the semiconductor switch elements 21 and 22 in order to suppress the voltage rise and the voltage increase rate of the semiconductor switch elements 21 and 22.

FIG. 15 shows a conventional example of a push-pull DC / DC converter. Here, the center side terminal (intermediate terminal) of the transformer 4 is connected to the positive electrode side terminal of the DC power supply 1 via the DC reactor 19, and one terminal of the transformer primary winding 41 is connected to one of the semiconductor switch elements 21. The semiconductor switching element 2 is connected to one terminal of the transformer primary winding 44.
2, the other terminal of the semiconductor switching element 21 is the other terminal of the semiconductor switching element 22 and the negative terminal of the DC power supply 1, the rectifier circuit 5 is the rectifier circuit 5 in the transformer secondary winding 43, A smoothing filter 6 is connected to the circuit 5, respectively.

FIG. 22 shows the operation waveform of FIG. That is, energy is stored in the DC reactor 19 during the period when the semiconductor switching devices 21 and 22 of FIG. 15 are simultaneously turned on, and the transformer 4 is excited in the positive direction during the period when the semiconductor switching device 21 is turned on. The transformer 4 is magnetized in the negative direction while the switch element 22 is on. By repeating this operation, the DC power supply 1
To supply DC power to the load via the rectifier circuit 5 and the smoothing filter 6. In the circuit of FIG. 15 as well, snubber circuits as shown in FIG. 17 are connected in parallel to the semiconductor switch elements 21 and 22 in order to suppress the voltage rise and the voltage increase rate of the semiconductor switch elements 21 and 22.

FIG. 16 shows a modification of FIG. The difference from FIG. 15 is that the snubber circuits 12 and 13 are omitted, one terminal of the semiconductor switching element 23 is used as a connection point between the transformer primary winding 41 and the semiconductor switching element 21, and one of the semiconductor switching elements 24 is used. The terminal is a connection point between the transformer primary winding 44 and the semiconductor switching element 22, the other terminal of the semiconductor switching element 23 is the other terminal of the semiconductor switching element 24,
The snubber circuit 7 is connected to a connection point between the semiconductor switch element 23 and the semiconductor switch element 24 and a connection point between the semiconductor switch element 21 and the semiconductor switch element 22, respectively. In FIG. 16, the snubber circuit 7 is shown by a capacitor.

FIG. 23 shows the operation waveform of FIG. The DC output operation is the same as in the case of FIG. 15 and is omitted, and the energy regeneration operation by the snubber circuit 7 will be described here. When the semiconductor switching element 21 is turned off, the diode connected in anti-parallel to the semiconductor switching element 23 is turned on, the rising voltage of the semiconductor switching element 21 is suppressed, and the snubber circuit 7 absorbs energy corresponding to the rising voltage. Next, the semiconductor switch element 24 is turned on while the semiconductor switch element 21 is on, and the energy absorbed by the snubber circuit 7 is released to the load.

[0015]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Compared with the conventional example shown in FIGS. 14 and 15, FIG.
When such a snubber circuit is used, the voltage rising rate of the semiconductor switch element cannot be suppressed, and the energy absorbed by the snubber capacitor is consumed by the discharge resistance. Also,
When the snubber circuit as shown in FIG. 17B is used, the voltage increase rate of the semiconductor switch element can be suppressed,
The point that the energy absorbed by the snubber capacitor is consumed by the discharge resistance is the same. In the conventional example shown in FIGS. 12 and 16, the energy absorbed by the snubber capacitor can be regenerated, but the voltage increase rate of the semiconductor switch element cannot be suppressed.

That is, in the conventional circuit, when the voltage of the DC power supply and the operating frequency of the semiconductor switching element become high, the switching loss of the semiconductor switching element becomes large in the snubber circuit of FIG. 17A and the circuits of FIGS. Moreover, in the snubber circuits of FIGS. 17A and 17B, the generated loss in the discharge resistance becomes large. As a result, the conventional device has a problem that the conversion efficiency of the device is reduced and the snubber circuit is increased in size. Therefore, an object of the present invention is to suppress the voltage rise rate of the semiconductor switching element, prevent the snubber circuit from becoming large, and improve the conversion efficiency of the device.

[0017]

In order to solve such a problem, in the invention of claim 1, a first series arm in which a first diode and a first semiconductor switch element are connected in series, and a second series arm are provided. The second series arm in which the semiconductor switch element and the second diode are connected in series and the first snubber circuit are connected in parallel to each other, and the second winding arm of the transformer primary winding not connected to the reset winding is connected. A terminal at the series connection point of the first series arm, a terminal on the side not connected to the primary winding of the transformer reset winding at the series connection point of the second series arm, and a direct current A power source is connected in parallel between a connection point between the primary winding and the reset winding of the transformer and a connection point between the first semiconductor switching element and the second diode, and in addition, the secondary winding of the transformer is connected. Rectifier circuit on the line, smooth on this rectifier circuit In a DC-DC converter in which paths are connected to each other, a second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected to a series connection point of the first series arm and a series of the second series arm. The auxiliary circuit is connected to the connection point and is formed of a series circuit of an auxiliary diode and an auxiliary reactor.
Is connected between the series connection point of the snubber circuit and the terminal of the first snubber circuit on the side to which the DC power source is not connected.

According to a second aspect of the present invention, a first series arm having a first diode and a first semiconductor switching element connected in series and a second series switching element having a second semiconductor switching element and a second diode connected in series are provided. Two series arms and a DC power source are connected in parallel with each other, and a transformer primary winding is connected between the series connection point of the first series arm and the series connection point of the second series arm. Also, in a DC-DC converter in which a rectifier circuit is connected to the transformer secondary winding and a smoothing circuit is connected to the rectifier circuit, the DC power supply is divided into first and second DC power supplies. A first snubber circuit, which is connected in series with each other and in which a first snubber diode and a first snubber capacitor are connected in series, is connected to the series connection point of the first series arm, the first DC power supply and the second DC power supply. Between the power supply and the series connection point A second snubber circuit connected in series with a second snubber diode and a second snubber capacitor connected in series to the first DC power supply and the second DC power supply; and the second series arm. And a first auxiliary circuit composed of a series circuit of a first auxiliary diode and a first auxiliary reactor, the first auxiliary circuit being connected to the second connection point of the first snubber circuit and the second auxiliary circuit. A second auxiliary circuit composed of a series circuit of a second auxiliary diode and a second auxiliary reactor is provided between the negative side terminal of the DC power supply and the series connection point of the second snubber circuit and the first auxiliary circuit. And the positive-side terminal of the DC power source.

According to the third aspect of the present invention, a first series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in antiparallel are connected in series and a second series arm in which two capacitors are connected in series are provided. , A DC power source are connected in parallel with each other, a transformer primary winding is connected between a series connection point of the first series arm and a series connection point of the second series arm, and a transformer In a DC-DC converter in which a rectifier circuit is connected to the next winding and a smoothing circuit is connected to the rectifier circuit, a first snubber circuit in which a first snubber capacitor and a first snubber diode are connected in series is provided. A second snubber circuit, in which a second snubber diode and a second snubber capacitor are connected in series, are respectively connected between the transformer primary winding terminals, and
Connecting a first auxiliary circuit composed of a series circuit of the auxiliary diode and the first auxiliary reactor between the series connection point of the first snubber circuit and the negative electrode side terminal of the DC power supply, A second auxiliary circuit composed of a series circuit of a diode and a second auxiliary reactor is connected between the series connection point of the second snubber circuit and the positive terminal of the DC power supply.

According to a fourth aspect of the present invention, first and second series arms in which two sets of switching elements, each of which is a semiconductor switching element and a diode, are connected in anti-parallel, are connected in series.
A first primary snubber circuit is connected in parallel with each other, and a transformer primary winding having an intermediate terminal is provided between a series connection point of the first series arm and a series connection point of the second series arm. And a DC power supply is connected between one terminal of the first snubber circuit and the transformer intermediate terminal via a DC reactor, and a rectifier circuit is provided in the transformer secondary winding. Is connected to a smoothing circuit.
In the DC converter, the first snubber diode and the first snubber diode
A second snubber circuit in which the snubber capacitor is connected in series, and a third snubber circuit in which a second snubber diode and a second snubber capacitor are connected in series are respectively connected between the transformer primary winding terminals. At the same time, a series connection point of the second snubber circuit and a direct current power source of the first snubber circuit are connected to a first auxiliary circuit including a series circuit of a first auxiliary diode and a first auxiliary reactor. A second auxiliary circuit, which is connected between the terminal on the other side and a series circuit of a second auxiliary diode and a second auxiliary reactor, is connected to the series connection point of the third snubber circuit and the first auxiliary circuit. The snubber circuit is connected between the snubber circuit and the terminal on the side to which the DC power source is not connected.

In any of the above inventions, when the semiconductor switch element is turned off, the snubber capacitor suppresses the rate of voltage increase of the semiconductor switch element, and while the semiconductor switch element is on, the snubber capacitor and the auxiliary circuit are connected. By constructing a resonance circuit and reversely charging the snubber capacitor, energy is not wasted and the generated loss is reduced. This improves the conversion efficiency of the device without increasing the size of the snubber circuit.

[0022]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This is configured by adding a snubber circuit 8 and an auxiliary circuit 9 to the one shown in FIG. That is, the snubber circuit 8 is configured by connecting the snubber diode 81 and the snubber capacitor 82 in series, and is connected between one end of the transformer primary winding 41 and one end of the transformer reset winding 42. The auxiliary circuit 9 is configured by connecting an auxiliary diode 91 and an auxiliary reactor 92 in series, and is connected between a series connection point of the snubber circuit 8 and a terminal of the snubber circuit 7 on the side not connected to the DC power supply 1.

FIG. 7 shows the operation waveforms of FIG. Hereinafter, differences from FIG. 12 will be mainly described. That is, when the semiconductor switch element 21 is turned off, the snubber capacitor 82 changes from a negative voltage (high potential on the side not connected to the snubber diode 81) to a positive voltage (snubber diode 81).
The side connected to is gradually charged to a high potential), and the voltage increase rate of the semiconductor switch element 21 is suppressed. Next, the semiconductor switch element 22 is turned on while the semiconductor switch element 21 is on, and the electric charge stored in the snubber capacitor 82 is transferred to the snubber capacitor 82 → auxiliary diode 91 → auxiliary reactor 92 → semiconductor switch element 22.
And discharges energy to the auxiliary reactor 92. When the snubber capacitor 82 reaches 0 V, the period shifts, the current continues to flow due to the energy stored in the auxiliary reactor 92, and the snubber capacitor 8 follows the same path as above.
Charge 2 in the opposite direction.

FIG. 2 shows a modification of FIG. This is because the positive side terminal of the DC power supply 1 is connected to the connection point between the semiconductor switch element 21 and the diode 32, and the negative side terminal of the DC power supply 1 is connected to the transformer primary winding 41 and the transformer reset winding 42. The configuration is the same as that of FIG. 1 except that the auxiliary circuit 9 is connected between the series connection point of the snubber circuit 8 and the terminal of the snubber circuit 7 on the side not connected to the DC power supply 1, and its operation is also the same. The details are omitted because they are the same as in FIG. 7.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention, which is configured by providing snubber circuits 8 and 10 and auxiliary circuits 9 and 11 in place of the snubber circuits 12 and 13 shown in FIG. . That is, the DC power supply 1 is divided into a DC power supply 1A and a DC power supply 1B, which are connected in series, and a snubber circuit 8 in which a snubber diode 81 and a snubber capacitor 82 are connected in series is connected to one of the transformer primary windings 41. The auxiliary circuit 9 is connected between the terminals and the series connection point of the DC power supply 1A and the DC power supply 1B, and the auxiliary diode 91 and the auxiliary reactor 92 are connected in series, and the series connection point of the snubber circuit 8 and the DC power supply 1B.
A snubber circuit 10 in which a snubber diode 101 and a snubber capacitor 102 are connected in series by being connected between the negative terminals of
Is connected between the other terminal of the transformer primary winding 41 and the series connection point of the DC power supply 1A and the DC power supply 1B, and the auxiliary circuit 11 in which the auxiliary diode 111 and the auxiliary reactor 112 are connected in series is connected to the snubber circuit 10 in series. It is configured by being connected between the connection point and the positive electrode side terminal of the DC power supply 1A.

FIG. 8 shows the operation waveforms of FIG. Hereinafter, the operation that is different from FIG. 13 will be mainly described. That is, when the semiconductor switch elements 21 and 22 are turned off, the snubber capacitor 82 gradually changes from a negative voltage (high potential on the side not connected to the snubber diode 81) to a positive voltage (high potential on the side connected to the snubber diode 81). It is charged to suppress the rate of increase in voltage of the semiconductor switch elements 21 and 22. Next, the electric charge stored in the snubber capacitor 82 while the semiconductor switch elements 21 and 22 are on is discharged through the path of the snubber capacitor 82 → semiconductor switch element 21 → auxiliary reactor 92 → auxiliary diode 91 to obtain auxiliary power. Energy is released to reactor 92. When the snubber capacitor 82 reaches 0 V, the period starts, and the current stored in the auxiliary reactor 92 continues to flow, and the snubber capacitor 82 is charged in the opposite direction through the same path as described above. The snubber circuit 10 and the auxiliary circuit 11 operate in exactly the same manner as above.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention, which is configured by adding snubber circuits 8 and 10 and auxiliary circuits 9 and 11 in place of the snubber circuits 12 and 13 shown in FIG. It That is, the snubber circuit 8 in which the snubber diode 81 and the snubber capacitor 82 are connected in series is connected between the terminals of the transformer primary winding 41, and the auxiliary circuit 9 in which the auxiliary diode 91 and the auxiliary reactor 92 are connected in series is used as the snubber circuit 8. Of the snubber diode 101 and the snubber capacitor 102.
And the snubber circuit 10 connected in series with the transformer primary winding 41
The auxiliary circuit 11 in which the auxiliary diode 111 and the auxiliary reactor 112 are connected in series is connected between the serial connection point of the snubber circuit 10 and the positive electrode side terminal of the DC power supply 1.

FIG. 9 shows the operation waveforms of FIG. Hereinafter, differences from FIG. 14 will be mainly described. That is, when the semiconductor switch element 21 is turned off, the snubber capacitor 82 changes from a negative voltage (high potential on the side not connected to the snubber diode 81) to a positive voltage (snubber diode 8).
The side connected to 1 is gradually charged to a high potential), and the rate of voltage rise of the semiconductor switch element 21 is suppressed. Next, while the semiconductor switch element 21 is on, the charge accumulated in the snubber capacitor 82 is transferred to the snubber capacitor 82 → the semiconductor switch element 21 → the auxiliary reactor 9
2 → Discharges in the path of the auxiliary diode 91, and releases energy to the auxiliary reactor 92. Snubber capacitor 82
When the voltage reaches 0 V, the current shifts to the period, the current continues to flow with the energy stored in the auxiliary reactor 92, and the snubber capacitor 82 is charged in the opposite direction through the same path as described above. Also,
The snubber circuit 10 and the auxiliary circuit 11 also operate on the same principle as above.

FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention, which is constructed by adding snubber circuits 8 and 10 and auxiliary circuits 9 and 11 to the one shown in FIG. That is, the snubber circuit 8 in which the snubber diode 81 and the snubber capacitor 82 are connected in series is connected between the transformer primary windings 41 and 44, and the auxiliary diode 91 and the auxiliary reactor 92 are connected.
An auxiliary circuit 9 in which is connected in series is connected between a series connection point of the snubber circuit 8 and a terminal of the snubber circuit 7 that is not connected to the DC power supply 1, and a snubber diode 101 and a snubber capacitor 102 are connected in series. The circuit 10 is connected between the primary windings 41 and 44 of the transformer, and the auxiliary circuit 11 in which the auxiliary diode 111 and the auxiliary reactor 112 are connected in series is connected to the series connection point of the snubber circuit 10 and the snubber circuit 7.
The DC power supply 1 is connected between terminals on the side not connected.

FIG. 10 shows the operation waveforms of FIG. Hereinafter, differences from FIG. 16 will be mainly described. That is, when the semiconductor switch element 21 is turned off, the snubber capacitor 82 changes from a negative voltage (high potential on the side not connected to the snubber diode 81) to a positive voltage (snubber diode 8).
The side connected to 1 is gradually charged to a high potential), and the rate of voltage rise of the semiconductor switch element 21 is suppressed. Next, while the semiconductor switch elements 21 and 24 are simultaneously turned on, the electric charge stored in the snubber capacitor 82 is discharged through the path of the snubber capacitor 82 → auxiliary diode 91 → auxiliary reactor 92 → semiconductor switch element 24. , Releases energy to the auxiliary reactor 92. When the snubber capacitor 82 reaches 0 V, the period starts, and the current stored in the auxiliary reactor 92 continues to flow, and the snubber capacitor 82 is charged in the opposite direction through the same path as described above. Further, the snubber circuit 10 and the auxiliary circuit 11 also operate on the same principle as above.

FIG. 6 shows a modification of FIG. This is because the positive side terminal of the DC power source 1 is connected to the connection point between the semiconductor switching element 21 and the semiconductor switching element 22 via the DC reactor 19, and the negative side terminal of the DC power source 1 is the center tap terminal of the transformer 4 ( Intermediate terminal), the auxiliary circuit 9 is connected between the series connection point of the snubber circuit 8 and the terminal of the snubber circuit 7 on the side not connected to the DC power source 1, and the auxiliary circuit 11 is connected to the series connection point of the snubber circuit 10. And the snubber circuit 7 is connected between the terminals of the snubber circuit 7 on the side not connected to the DC power supply 1, and the operation thereof is the same as that of FIG.

[0032]

According to the present invention, since the snubber capacitor is gradually charged from the reverse voltage to the positive voltage when the semiconductor switching element is turned off, the rate of voltage increase of the semiconductor switching element is suppressed, and thus the snubber capacitor is suppressed. Switching losses and heat generation are reduced. Further, since the resonance circuit is configured by the snubber capacitor and the auxiliary circuit so that the snubber capacitor is reversely charged, almost no loss occurs in the snubber circuit. Therefore, the snubber circuit can be constructed in a small size, the conversion efficiency of the device can be improved, and the cooling device for heat dissipation can be made small in size.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment according to the present invention.

FIG. 2 is a circuit diagram showing a modified example of FIG.

FIG. 3 is a circuit diagram showing a second embodiment according to the present invention.

FIG. 4 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 5 is a circuit diagram showing a fourth embodiment according to the present invention.

FIG. 6 is a circuit diagram showing a modified example of FIG.

FIG. 7 is an operation waveform diagram of FIGS. 1 and 2.

FIG. 8 is an operation waveform diagram of FIG.

9 is an operation waveform diagram of FIG.

FIG. 10 is an operation waveform diagram of FIGS. 5 and 6;

FIG. 11 is a circuit diagram showing a conventional example of a one-stone forward type DC-DC converter.

FIG. 12 is a circuit diagram showing a modified example of FIG.

FIG. 13 is a circuit diagram showing a conventional example of a two-stone forward type DC-DC converter.

FIG. 14 is a circuit diagram showing a conventional example of a half-bridge type DC-DC converter.

FIG. 15 is a circuit diagram showing a conventional example of a push-pull type DC-DC converter.

16 is a circuit diagram showing a modified example of FIG.

FIG. 17 is a circuit diagram showing a specific example of a snubber circuit.

FIG. 18 is an operation waveform diagram of FIG. 11.

19 is an operation waveform diagram of FIG.

20 is an operation waveform diagram of FIG.

FIG. 21 is an operation waveform diagram of FIG. 14.

22 is an operation waveform diagram of FIG.

FIG. 23 is an operation waveform diagram of FIG. 16.

[Explanation of symbols]

1, 1A, 1B ... DC power supply, 4 ... Transformer, 5 ... Rectifier circuit, 6 ... Smoothing filter, 7, 8, 10, 12, 13 ... Snubber circuit, 9, 11 ... Auxiliary circuit, 17, 18 ... Capacitor, 19 ... DC reactor, 21, 22, 23, 24 ...
Semiconductor switch elements, 31, 32 ... Diodes, 41,
44 ... Transformer primary winding, 42 ... Transformer reset winding, 4
3 ... Transformer secondary winding, 81, 101, 125 ... Snubber diode, 82, 102, 121, 123 ... Snubber capacitor, 91, 111 ... Auxiliary diode, 92, 112
... Auxiliary reactor, 122,124 ... Discharge resistance.

Claims (4)

[Claims] 1. A first series arm in which a first diode and a first semiconductor switch element are connected in series, and a second series arm in which a second semiconductor switch element and a second diode are connected in series. , The first snubber circuit is connected in parallel with each other, and the terminal of the transformer primary winding on the side not connected to the reset winding is connected to the series connection point of the first series arm,
Further, a terminal on the side not connected to the primary winding of the transformer reset winding is connected to a series connection point of the second series arm,
Further, a DC power source is connected in parallel between a connection point between the primary winding and the reset winding of the transformer and a connection point between the first semiconductor switch element and the second diode, and in addition, the transformer In a DC-DC converter in which a rectifier circuit is connected to the secondary winding and a smoothing circuit is connected to the rectifier circuit, a second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is provided in the first series. An auxiliary circuit, which is connected between the series connection point of the arms and the series connection point of the second series arm, and which includes a series circuit of an auxiliary diode and an auxiliary reactor is connected to the series connection point of the second snubber circuit. , A snubber circuit of the DC-DC converter, wherein the snubber circuit is connected between the first snubber circuit and a terminal on the side not connected to the DC power supply. 2. A first series arm in which a first diode and a first semiconductor switch element are connected in series, and a second series arm in which a second semiconductor switch element and a second diode are connected in series. , A DC power source are connected in parallel with each other, a transformer primary winding is connected between a series connection point of the first series arm and a series connection point of the second series arm, and a transformer In a DC-DC converter in which a rectifier circuit is connected to the next winding and a smoothing circuit is connected to the rectifier circuit, the DC power supply is divided into a first DC power supply and a second DC power supply, which are connected in series. A first snubber circuit, in which a first snubber diode and a first snubber capacitor are connected in series, is connected in series to the series connection point of the first series arm, and the first DC power supply and the second DC power supply are connected in series. Connect between the point and the second switch A second snubber circuit in which a diode and a second snubber capacitor are connected in series is provided between a series connection point of the first DC power supply and the second DC power supply and a series connection point of the second series arm. A first auxiliary diode connected between the first auxiliary diode and the first auxiliary reactor in series.
Between the series connection point of the first snubber circuit and the negative electrode side terminal of the second DC power source, and a second series circuit of a second auxiliary diode and a second auxiliary reactor. 2. A snubber circuit for a DC-DC converter, wherein two auxiliary circuits are connected between a series connection point of the second snubber circuit and a positive electrode side terminal of the first DC power supply, respectively. 3. A first series arm in which two sets of switching elements in which a semiconductor switching element and a diode are connected in anti-parallel are connected in series, a second series arm in which two capacitors are connected in series, and a DC power supply are provided. Connect to each other in parallel,
A transformer primary winding is connected between a series connection point of the first series arm and a series connection point of the second series arm, and a rectifier circuit is provided in the transformer secondary winding. In a DC-DC converter in which a smoothing circuit is connected to the first snubber circuit, a first snubber circuit in which a first snubber capacitor and a first snubber diode are connected in series, a second snubber diode and a second snubber diode, respectively. A second snubber circuit in which a capacitor is connected in series is connected between the transformer primary winding terminals, respectively, and a first auxiliary circuit including a series circuit of a first auxiliary diode and a first auxiliary reactor is connected. A second auxiliary circuit, which is connected between a series connection point of the first snubber circuit and a negative electrode side terminal of the DC power supply and includes a series circuit of a second auxiliary diode and a second auxiliary reactor, is provided. Two The snubber circuit of the DC-DC converter, wherein the snubber circuit is connected between the serial connection point of the snubber circuit and the positive electrode side terminal of the DC power supply. 4. A first snubber circuit and a first and a second series arm in which two sets of switching elements in which a semiconductor switch element and a diode are connected in anti-parallel are connected in series, respectively, and a first snubber circuit are connected in parallel to each other, and an intermediate A transformer primary winding having a terminal is connected between a series connection point of the first series arm and a series connection point of the second series arm, and a DC power supply is connected to one of the first snubber circuits. Between the terminal and the intermediate terminal of the transformer via a DC reactor,
A rectifier circuit is connected to the secondary winding of the transformer, and a smoothing circuit is connected to the rectifier circuit. In a DC-DC converter, a second snubber diode and a first snubber capacitor are connected in series. A snubber circuit, a third snubber circuit in which a second snubber diode and a second snubber capacitor are connected in series are connected between the transformer primary winding terminals, respectively, and a first auxiliary diode and a first auxiliary diode are connected. A first auxiliary circuit consisting of a series circuit with an auxiliary reactor is connected between a series connection point of the second snubber circuit and a terminal of the first snubber circuit on the side to which the DC power source is not connected, In addition, a second auxiliary circuit composed of a series circuit of a second auxiliary diode and a second auxiliary reactor is connected to the series connection point of the third snubber circuit and the DC power supply of the first snubber circuit. A snubber circuit for a DC-DC converter, characterized in that it is connected between the terminal on the side not connected and the terminal.