JPH09312973A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the drop of conversion efficiency by making the capacitor of a snubber circuit clamp it at turn off of the first semiconductor switch element, and turning on the second switch element at turn on of the first semiconductor switch element, and discharging the energy that the snubber circuit has absorbed to load. SOLUTION: When a semiconductor switch element 2A is turned off, a snubber circuit 13 absorbs the energy accumulated in the leakage inductance and the wiring inductance of a transformer 4 through a diode 3B. Next, when semiconductor switch elements 2A and 2B are turned on, the charge accumulated in the snubber circuit 13 is discharged by the course of the snubber circuit 13 → the semiconductor switch element 2B → a transformer reset winding 42 → a DC power source 1, and the energy absorbed with the snubber circuit 13 is discharged. In short, the diode 3B performs the role of a snubber diode, and the semiconductor switch element 2b works for power regeneration.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art FIG. 24 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 2A has a diode 3A between the other terminal of the reset winding 42 of the transformer 4 and the negative terminal of the DC power supply 1, the rectifying circuit 5 in the secondary winding 43 of the transformer 4, and the rectifying circuit 5 Are connected to smoothing filters (smoothing circuits) 6.

FIG. 25 shows operation waveforms of FIG. 24 (see FIG. 24).
Such a circuit and its operation are well known, for example, as described on pages 18 to 19 and 95 to 99 of "Method of designing switching regulator and usage of power device" issued by Seibundou Shinkosha in 1984. ). Now, while the semiconductor switch element 2A 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 semiconductor switch element 2
The excitation energy of the transformer 4 is regenerated to the DC power supply 1 through the reset winding 42 and the diode 3A while A is off.

In the circuit of FIG. 24, the semiconductor switching device 2
When A is turned off, the jumping voltage of the semiconductor switch element 2A is suppressed and the voltage rising rate (dv / dt)
To reduce the switching loss by reducing the diode 71 and the capacitor 7 to the semiconductor switch element 2A.
2 is connected in series with the diode 71 in parallel with the discharge resistor 7
The snubber circuit 7 to which 3 is connected is connected in parallel. As a result, the energy absorbed by the capacitor 72 is released to the discharge resistor 73 while the semiconductor switch element 2A is next turned on.

[0005]

In the circuit of FIG. 24, the energy absorbed by the snubber capacitor is released to the discharge resistor when the semiconductor switch element is turned on next, resulting in a loss. Now, the loss of the discharge resistance is P, the capacitance of the snubber capacitor is C, the voltage of the DC power source is E, the reset voltage of the transformer is Vr, the rising voltage of the semiconductor switch element is ΔV, and the operating frequency of the semiconductor switch element is f. Then, P = (1/2) × C × (E + Vr + ΔV) ² × f. Therefore, the voltage E of the DC power supply, the reset voltage Vr of the transformer, and the operating frequency f of the semiconductor switch element
The higher the value becomes, the more the generated loss in the discharge resistance becomes, so that not only a large and expensive snubber circuit is required, but also the conversion efficiency of the device decreases. Therefore, an object of the present invention is to prevent the snubber circuit from being enlarged and the conversion efficiency of the device from being reduced.

[0006]

In order to solve such a problem, in the invention of claim 1, a DC power source, a transformer having a reset winding on the primary side, and a secondary side of the transformer are connected. A rectifying circuit and a smoothing circuit for smoothing the rectified output, and in a DC-DC converter for extracting DC power insulated from a DC power supply, one terminal of a first diode and a first semiconductor switch element. A first series arm in which one of the terminals is connected in series, a second series arm in which one terminal of the second semiconductor switch element and one terminal of the second diode are connected in series, and a first series arm A snubber circuit is connected in parallel with each other, a terminal of the transformer primary winding on the side not connected to the reset winding is connected to a connection point of the first series arm, and a transformer reset winding Connect primary winding The terminal on the side not connected is the connection point of the second series arm, and the DC power supply is the connection point of the primary winding and the reset winding of the transformer, the first semiconductor switch element and the second semiconductor switch element. Connected in parallel with the connection point of the diode.

According to the invention of claim 1, when the first semiconductor switch element is turned off, the capacitor constituting the first snubber circuit is clamped to (E + Vr), so that the first snubber circuit is absorbed. Energy P1
Becomes smaller as P1 = (1/2) × C × ΔV ² × f. Further, by turning on the second switch element while the first semiconductor switch element is on, the energy P1 absorbed by the first snubber circuit can be released to the load.

According to a second aspect of the present invention, in addition to the first aspect of the invention, a second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is provided in parallel with the first semiconductor switching element, and an auxiliary diode is provided. An auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit with an auxiliary reactor is connected in parallel with the snubber diode, and a regeneration diode is connected in parallel between the connection point between the series circuit and the auxiliary capacitor and the second semiconductor switch element. It is configured by connecting each to the connection point.

According to the second aspect of the present invention, when the first semiconductor switching element is turned off, the snubber capacitor suppresses the voltage increase rate of the first semiconductor switching element and reduces the switching loss. Next, while the first semiconductor switch element is on, the charge stored in the snubber capacitor is absorbed by the auxiliary circuit and transferred to the auxiliary capacitor. Further, while the first semiconductor switch element is off, the electric charge stored in the auxiliary capacitor is transferred to the first snubber circuit via the regenerative diode.
Then, while the first semiconductor switch element is on, the first semiconductor switch element is turned on to turn on the first semiconductor switch element.
The energy absorbed in the snubber circuit of is released to the load.

According to a third aspect of the invention, in the first or second aspect of the invention, the ON period of the second semiconductor switch element is set to the first period.
Of the resonance frequency determined by the capacitance of the capacitor and the leakage inductance of the transformer that make up the snubber circuit of
Let it be 2. As a result, a sinusoidal current having a cycle determined by the capacitance of the capacitor and the leakage inductance of the transformer that form the first snubber circuit flows through the second semiconductor switching element, but the ON period is the resonance cycle. About 1 /
2, the switching loss is reduced by cutting off the current near 0 A at turn-off.

According to a fourth aspect of the invention, there is provided a first series arm having a first diode and a first semiconductor switch element connected in series, and a second series switch having a second semiconductor switch element and a second diode connected in series. 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. In addition, in a DC-DC converter in which a rectifier circuit is connected to the secondary winding of the transformer and a smoothing circuit is connected to the rectifier circuit, the first semiconductor switch element and the second semiconductor switch element are respectively , A snubber circuit in which a snubber diode and a snubber capacitor are connected in series, respectively, and an auxiliary diode and an auxiliary reactor are connected in series to each of the snubber diodes. An auxiliary circuit in which an auxiliary capacitor is connected in series to the column circuit is connected in parallel, and a regenerative diode is further provided between the connection point of the series circuit and the auxiliary capacitor and the parallel connection point of the first and second series arms. Connect and configure.

According to the invention of claim 5, a first 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, a second series arm in which a capacitor is connected in series, and a direct current A power supply is 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 secondary winding of the transformer is connected. In a DC-DC converter in which a winding has a rectifying circuit and a smoothing circuit is connected to the rectifying circuit, a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is provided in parallel with each of the switching elements. , An auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit in which an auxiliary diode and an auxiliary reactor are connected in series to each of the snubber diodes. In parallel, further a regeneration diode and the series circuit and the connection point between the auxiliary capacitor, constituting respectively connected between the parallel connection point of said first, second series arm.

In a sixth 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 anti-parallel are connected in series, a second series arm in which a capacitor is connected in series, and a direct current A power supply is 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 secondary winding of the transformer is connected. In a DC-DC converter in which a rectifying circuit is connected to the winding and a smoothing circuit is connected to the rectifying circuit, auxiliary reactors are connected in series between the switching element and the connection point of the transformer primary winding. , A snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel to each of the switching elements, and an auxiliary diode and an auxiliary capacitor are connected in series. An auxiliary circuit is provided between the series connection point of the snubber circuit and the connection point between the auxiliary reactor and the connection point of the transformer primary winding, and a regenerative diode is provided between the series connection point of the auxiliary circuit and the first and second series. It is configured by connecting the parallel connection points of the arms.

In the inventions of claims 4 to 6, when the semiconductor switch element is turned off, the snubber capacitor suppresses the rate of voltage rise of the semiconductor switch element and reduces the switching loss. Next, while the semiconductor switch element is on, the charge stored in the snubber capacitor is absorbed by the auxiliary circuit and transferred to the auxiliary capacitor. Thereafter, while the semiconductor switch element is off, the charge accumulated in the auxiliary capacitor is regenerated to the DC power source through the regenerative diode, thereby reducing the loss generated in the snubber circuit.

According to a seventh aspect of the present invention, there is provided a first series arm in which one terminal of the first diode and one terminal of the first semiconductor switching element are connected in series, and one of the second semiconductor switching element. A second series arm in which a terminal and one terminal of a second diode are connected in series and a first snubber circuit are respectively connected in parallel, and one terminal of a transformer primary winding having an intermediate terminal To the series connection point of the first series arm, and the other terminal of the transformer primary winding to the series connection point of the second series arm,
The DC power supply is connected between the first terminal of the three-terminal switch and the parallel connection point of the first semiconductor switch element and the second diode, and the second terminal of the three-terminal switch is connected to the middle of the transformer. A third terminal of the three-terminal switch is connected to a terminal between parallel connection points of the first diode and the second semiconductor switch element, and an input voltage detection circuit is connected in parallel with the DC power supply. The control circuit is connected between the input voltage detection circuit and the three-terminal switch, the secondary terminal of the transformer is connected to a rectifying circuit, and the rectifying circuit is connected to a smoothing filter.

According to another aspect of the present invention, there is provided a first series arm in which one terminal of the first semiconductor switching element and one terminal of the second semiconductor switching element are connected in series, and the third semiconductor switching element. A second primary arm in which one terminal and one terminal of a fourth semiconductor switching element are connected in series and a first snubber circuit are connected in parallel, and a transformer primary winding having an intermediate terminal is provided. One terminal is connected to a series connection point of the first series arm, the other terminal of the transformer primary winding is connected to a series connection point of the second series arm, and a DC power supply is connected to three terminals. A first terminal of a switch, the first semiconductor switch element, and the third
The second terminal of the three-terminal switch is the intermediate terminal of the transformer, and the third terminal of the three-terminal switch is the second semiconductor switching element and the No. 4, the semiconductor switch element is connected in parallel to each other, and an input voltage detection circuit is connected in parallel with the DC power supply, and a control circuit is connected between the input voltage detection circuit and the three-terminal switch. The secondary terminal of the transformer is connected to the rectifier circuit, and this rectifier circuit is connected to the smoothing filter.

In the invention of claim 7, a second snubber circuit in which a first snubber diode and a first snubber capacitor are connected in series is provided in parallel with the first semiconductor switch element, and a first auxiliary diode is provided. And a first auxiliary reactor connected in series with a first series circuit in which a first auxiliary capacitor and a first auxiliary capacitor are connected in series, the first auxiliary circuit is connected in parallel with the first snubber diode, and the first regenerative diode is connected to the first regenerative diode. A second snubber diode and a second snubber capacitor are provided between a connection point between the first series circuit and the first auxiliary capacitor and a parallel connection point between the first diode and the second semiconductor switch element. A second series circuit in which a third snubber circuit connected in series is connected in parallel with the second semiconductor switch element, and a second auxiliary diode and a second auxiliary reactor are connected in series and a second auxiliary circuit. A second auxiliary circuit connected in series with a capacitor in parallel with the second snubber diode, a second
A regenerative diode, a connection point between the second series circuit and a second auxiliary capacitor, the second diode and the first auxiliary circuit.
Can be connected between the parallel connection points with the semiconductor switch element of (invention of claim 9).

In the above invention, the second snubber circuit in which the first snubber diode and the first snubber capacitor are connected in series is provided in parallel with the first semiconductor switch element, and the first auxiliary diode is provided. And a first auxiliary reactor connected in series, and a first auxiliary circuit in which a first auxiliary capacitor and a first auxiliary capacitor are connected in series, in parallel with the first snubber diode, and a first regenerative diode and a first auxiliary circuit. A first regenerative circuit, in which a first regenerative reactor is connected in series, is provided in parallel with a connection point between the first series circuit and the first auxiliary capacitor, the second semiconductor switch element, and the fourth semiconductor switch element. A third snubber circuit, in which a second snubber diode and a second snubber capacitor are connected in series, is provided between the connection points in parallel with the second semiconductor switch element, and a second auxiliary diode is provided. A second series circuit in which a second auxiliary reactor is connected in series and a second auxiliary circuit in which a second auxiliary capacitor is connected in series, and a second regenerative diode and a second auxiliary circuit in parallel with the second snubber diode. A second regenerative circuit in which a regenerative reactor is connected in series is connected to a connection point between the second series circuit and the second auxiliary capacitor, and a parallel connection point between the first semiconductor switching element and the third semiconductor switching element. In the meanwhile, the fourth series circuit, the fifth series circuit, the third series circuit, the fourth series circuit, the fourth series circuit, the third series circuit, the third series circuit, and the fourth series circuit are also used for the second series arm. Can be respectively connected (the invention of claim 10).

[0019]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The snubber circuit 7 is omitted from the conventional example shown in FIG. 24, one terminal of the diode 3B is connected to the connection point between the transformer primary winding 41 and the semiconductor switching element 2A, and one terminal of the semiconductor switching element 2B is connected to the transformer reset winding. At the connection point between the line 42 and the diode 3A, the diode 3B
And the snubber circuit 13 is connected between the parallel connection point of the diode 3B and the semiconductor switch element 2B and the parallel connection point of the semiconductor switch element 2A and the diode 3A, respectively. Configure. FIG. 3 shows the operation waveforms of FIG. Since the DC output operation of FIG. 1 is the same as that of FIG. 24, only the differences will be described below. That is, the semiconductor switch element 2A
Is turned off, the snubber circuit 13 absorbs the energy stored in the leakage inductance and the wiring inductance of the transformer 4 via the diode 3B. Next, the semiconductor switch element 2A and the semiconductor switch element 2B
The charges accumulated in the snubber circuit 13 are discharged through the path of the snubber circuit 13 → the semiconductor switch element 2B → the transformer reset winding 42 → the DC power supply 1 while the snubber circuit 13 absorbs the electric charge stored in the snubber circuit 13 during the period when the The released energy is released to the load. That is, the diode 3B functions as a snubber diode, and the semiconductor switch element 2B acts as a power regeneration device. FIG. 2 shows a modification of FIG. this is,
The positive electrode side terminal of the DC power supply 1 is a connection point between the semiconductor switch element 2A and the diode 3A, and the negative electrode side terminal of the DC power supply 1 is a connection point between the transformer primary winding 41 and the transformer reset winding 42. It is characterized in that it is connected, and since it is functionally the same as that in FIG. 1, its details are omitted.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention, and FIG. 6 is an operation explanation diagram thereof. The difference from FIG. 1 is that a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is provided in parallel with the semiconductor switch element 2A, and an auxiliary diode 81 and an auxiliary reactor 82 are provided.
Is connected in series with the snubber diode 71.
Further, the regenerative diode 9 is connected between the connection point between the series circuit and the auxiliary capacitor 83 and the connection point between the diode 3B and the semiconductor switch element 2B. That is, in the example shown in FIGS. 1 and 2, since the energy absorbed by the snubber circuit 13 is released to the load,
Although the snubber circuit 13 causes almost no loss, it cannot suppress the rate of voltage increase when the semiconductor switch element 2A is turned off. The one shown in FIG. 4 is intended to solve this problem.

Referring to FIG. 6, semiconductor switch element 2A
A charge energy regenerating operation of the snubber capacitor 72 connected in parallel with the above will be described. Now, when the semiconductor switching element 2A is turned off, the snubber capacitor 72 suppresses the voltage increase rate of the semiconductor switching element 2A. Next, while the semiconductor switch element 2A is on,
In addition, the charge stored in the snubber capacitor 72 is transferred to the auxiliary reactor 82 and the auxiliary capacitor 83 through the path of the snubber capacitor 72 → the auxiliary diode 81 → the auxiliary reactor 82 → the auxiliary capacitor 83 → the semiconductor switch element 2A.
To discharge. When the snubber capacitor 72 is discharged to 0 V, the energy stored in the auxiliary reactor 82 causes a current to flow in the route of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81, and the energy is transferred to the auxiliary capacitor 83. further,
While the semiconductor switch element 2A is off, the charge accumulated in the auxiliary capacitor 83 is transferred to the snubber circuit 13 through the path of the auxiliary capacitor 83 → regenerative diode 9 → snubber circuit 13 → DC power supply 1 → transformer primary winding 41. discharge. Then, while the semiconductor switch elements 2A and 2B are turned on at the same time, the charge accumulated in the snubber circuit 13 is transferred through the path of the snubber circuit 13 → the semiconductor switch element 2B → the transformer reset winding 42 → the DC power source 1. It discharges and releases the energy absorbed by the snubber circuit 13 to the load. FIG.
4 shows a modification of FIG. That is, the positive terminal of the DC power supply 1 is connected to the connection point between the semiconductor switch 2A and the diode 3A, and the negative terminal of the DC power supply 1 is connected to the connection point between the transformer primary winding 41 and the transformer reset winding 42. The description is omitted because it is exactly the same as that shown in FIG.

In any of the above examples, during the ON period of the semiconductor switching element 2B, the semiconductor switching element 2B has a period determined by the capacitance of the capacitor forming the snubber circuit 13 and the leakage inductance of the transformer 4. A sinusoidal current flows. Therefore, the ON period of the semiconductor switching element 2B is set to about 1/2 of the resonance cycle determined by the capacitance of the capacitor and the leakage inductance of the transformer (see the period shown in FIG. 6), and when the semiconductor switching element 2B is turned off, 0A is applied. Cut off the current in the vicinity. As a result, it is possible to reduce the switching loss when the semiconductor switch element 2B is turned off.

In each of FIGS. 4 and 5, a snubber circuit, an auxiliary circuit and a regenerative diode are added to the one-stone forward type converter, but application to a two-stone forward type or half-bridge type converter is also considered. To be FIG. 7 is applied to the two-stone forward type, and a snubber diode 71 and a snubber capacitor 7 are used for the basic circuit.
The semiconductor switching element 2 is a snubber circuit 7 in which 2 are connected in series.
The auxiliary circuit 8 in which the auxiliary capacitor 83 is connected in series to the snubber diode 7 is connected in parallel with A and the first series circuit in which the auxiliary diode 81 and the auxiliary reactor 82 are connected in series.
1 in parallel with the regenerative diode 9 at the connection point between the first series circuit and the auxiliary capacitor 83, and the DC power supply 1
Is connected to the positive electrode side terminal. Similarly, the snubber diode 101 and the snubber capacitor 10
The snubber diode 10 is a snubber diode in which a snubber circuit 10 in which two are connected in series is connected in parallel with the semiconductor switch element 2B, and an auxiliary capacitor 113 is connected in series in a second series circuit in which an auxiliary diode 111 and an auxiliary reactor 112 are connected in series. In parallel with 101, a regenerative diode 12
Are connected between the connection point between the second series circuit and the auxiliary capacitor 113 and the negative terminal of the DC power supply 1, respectively.

FIG. 10 shows the operation waveforms of FIG. Here, a charge energy regenerating operation of the snubber capacitor 72 attached to the semiconductor switch element 2A will be described.
When the semiconductor switch element 2A is turned off, the snubber capacitor 72 suppresses the rate of voltage increase of the semiconductor switch element 2A. Next, while the semiconductor switch element 2A is turned on, the charge accumulated in the snubber capacitor 72 is supplemented by the snubber capacitor 72 → auxiliary diode 81 → auxiliary reactor 82 → auxiliary capacitor 83 → semiconductor switch element 2A. The reactor 82 and the auxiliary capacitor 83 are discharged. Snubber capacitor 72 is 0V
When it is discharged up to the period, the period shifts, and the energy stored in the auxiliary reactor 82 causes a current to flow in the route of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81, and the energy is transferred to the auxiliary capacitor 83. Next, while the semiconductor switch element 2A is off, the charge accumulated in the auxiliary capacitor 83 is stored in the auxiliary capacitor 83 → regenerative diode 9 → DC power supply 1 → regenerative diode 12 → auxiliary capacitor 11 → transformer primary winding 41. To discharge energy to the DC power supply 1 and regenerate energy. The snubber circuit 10, the auxiliary circuit 11, and the regenerative diode 12 attached to the semiconductor switch element 2B also operate in the same manner as above.

FIG. 8 is applied to a half-bridge type, in which a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series to the basic circuit is connected in parallel with the semiconductor switch element 2A and an auxiliary diode. Auxiliary circuit 8 in which an auxiliary capacitor 83 is connected in series to a first series circuit in which 81 and an auxiliary reactor 82 are connected in series.
In parallel with the snubber diode 71, and the regenerative diode 9 is connected between the connection point between the first series circuit and the auxiliary capacitor 83 and the positive terminal of the DC power supply 1. Similarly, the snubber diode 10
1 and the snubber capacitor 102 are connected in series to the snubber circuit 10 in parallel with the semiconductor switch element 2B, and the auxiliary diode 111 and the auxiliary reactor 112 are connected in series to the second series circuit. The circuit 11 in parallel with the snubber diode 101,
Further, the regenerative diode 12 is connected between the connection point between the second series circuit and the auxiliary capacitor 113 and the negative terminal of the DC power supply 1, respectively.

FIG. 11 shows the operation waveforms of FIG. Here, a charge energy regenerating operation of the snubber capacitor 72 attached to the semiconductor switch element 2A will be described.
When the semiconductor switch element 2A is turned off, the snubber capacitor 72 suppresses the rate of voltage increase of the semiconductor switch element 2A. Next, while the semiconductor switch element 2A is turned on, the charge accumulated in the snubber capacitor 72 is supplemented by the snubber capacitor 72 → auxiliary diode 81 → auxiliary reactor 82 → auxiliary capacitor 83 → semiconductor switch element 2A. The reactor 82 and the auxiliary capacitor 83 are discharged. Snubber capacitor 72 is 0V
When it is discharged up to the period, the period shifts, and the energy stored in the auxiliary reactor 82 causes a current to flow in the route of the auxiliary reactor 82 → the auxiliary capacitor 83 → the snubber diode 71 → the auxiliary diode 81, and transfers the energy to the auxiliary capacitor 83. Next, while the semiconductor switch element 2A is off, the charge accumulated in the auxiliary capacitor 83 is discharged through the path of the auxiliary capacitor 83 → regenerative diode 9 → DC power supply 1 → capacitor 31A → transformer primary winding 41. , Regenerates energy to the capacitor 31A. The electric charge stored in the capacitor 31A is discharged to the load via the transformer 4 during the period when the semiconductor switch element 2B is on. The snubber circuit 10, the auxiliary circuit 11, and the regenerative diode 12 attached to the semiconductor switch element 2B also operate in the same manner as above.

FIG. 9 shows a modification of FIG. An auxiliary reactor 82 is provided between the semiconductor switch element 2A and the connection point of the transformer primary winding 41, a snubber circuit 7 in which a snubber diode 71 and a snubber capacitor 72 are connected in series is provided in parallel with the semiconductor switch element 2A, and an auxiliary A third series circuit in which the diode 81 and the auxiliary capacitor 83 are connected in series is provided between the connection point between the snubber diode 71 and the snubber capacitor 72 and the connection point between the auxiliary reactor 82 and the transformer primary winding 41. The regenerative diode 9 is connected between the connection point of the third series circuit and the positive terminal of the DC power supply 1, respectively. Similarly, the auxiliary reactor 112 is provided between the semiconductor switch element 2B and the connection point of the transformer primary winding 41, and the snubber circuit 10 in which the snubber diode 101 and the snubber capacitor 102 are connected in series is provided in parallel with the semiconductor switch element 2B. In addition, the auxiliary diode 111
The fourth series circuit in which the capacitor and the auxiliary capacitor 113 are connected in series is a snubber diode 101 and a snubber capacitor 102.
Between the connection point between the auxiliary reactor 112 and the primary winding 41 of the transformer, and the connection point of the fourth series circuit of the regenerative diode 12 and the negative terminal of the DC power supply 1. It is configured by connecting between each. In this example, as shown in FIG. 8, when the semiconductor switch element 2B is turned on in a state in which the snubber capacitor 72 does not sufficiently store electric charges, for example, when there is no load, the semiconductor switch element 2B is charged to charge the snubber capacitor 72. An excessive current flows through. This example is intended to prevent such inconvenience.

In the above, since the DC power supply voltage is treated as being almost constant, there remains a problem that it cannot be applied to different voltage. This will be described below. FIG. 26 shows a conventional example of a conventional two-stone forward type DC-DC converter. That is, one terminal of the semiconductor switch 2B and one terminal of the diode 3B are connected to the positive terminal of the DC power supply 1, and one terminal of the semiconductor switch 2A and the diode 3A are connected to the negative terminal of the DC power supply 1.
One terminal of the primary switch 41 of the transformer 4 and the diode 3A are connected to the other terminal of the semiconductor switch 2B.
The other terminal of the semiconductor switch 2A and the primary winding 41 of the transformer 4 are connected to the other terminal of the diode 3B.
Further, the rectifying circuit 5 is connected to the secondary winding 43 of the transformer 4, and the smoothing filter 6 is connected to the rectifying circuit 5. The operation waveforms of FIG. 26 are shown in FIG.
While the semiconductor switches 2A and 2B are on, the transformer 4 is excited in the positive direction, and 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 and the diodes 3A and 3B while the semiconductor switches 2A and 2B are turned off.

FIG. 27 shows a conventional example of a full-bridge type DC-DC converter. In the figure, one terminal of the semiconductor switches 2C and 2D is connected to the positive terminal of the DC power supply 1, one terminal of the semiconductor switches 2A and 2B is connected to the negative terminal of the DC power supply 1, and the other terminal of the semiconductor switch 2D is connected to the other terminal. The terminals include one terminal of the primary winding 41 of the transformer 4 and the semiconductor switch 2
The other terminal of B, the other terminal of the semiconductor switch 2A and the other terminal of the primary winding 41 of the transformer 4 are connected to the other terminal of the semiconductor switch 2C, and the secondary winding 43 of the transformer 4 is rectified. The circuit 5 and the smoothing filter 6 are connected to the rectifier circuit 5, respectively. The operation waveforms of FIG. 27 are shown in FIG. While the semiconductor switches 2A and 2D are on, the transformer 4 is excited in the positive direction, and the rectifier circuit 5 and the smoothing filter 6 are excited.
DC power is supplied to the load via. Next, while the semiconductor switches 2B and 2C are on, the transformer 4 is excited in the negative direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing filter 6.

In the case of FIG. 26, the maximum voltage of the DC power supply 1 is E
d1, the minimum voltage is Ed2, the period when the semiconductor switches 2A and 2B are on when the voltage is Ed1, is TS1, and the period when the semiconductor switches 2A and 2B are on when the voltage is Ed2 is TS2, and the semiconductor switch 2A. , 2B is i and the voltage drop of the semiconductor switches 2A and 2B at this time is VS, the conduction loss PON generated during the period when the semiconductor switches 2A and 2B are on is PON = 2 × (VS × i × TON). When the output voltage is constant, TS1 <TS2
Therefore, when the DC power supply voltage is Ed2, the conduction loss in the semiconductor switch increases. In addition, the turns ratio of the transformer is n1: n2, and the voltage generated in the secondary winding 43 of the transformer is V
If T2, then VT2 = Ed × n2 / n1. The diodes forming the rectifier circuit are selected so as not to exceed the withstand voltage even when the DC power supply voltage is Ed1, but a diode with a high withstand voltage has a problem that the generated loss is large and the cost is high.

The DC power supply is a single-phase alternating current (AC) power supply 100V.
Alternatively, an example of full-wave rectification from 200 V by a diode rectifier will be specifically described. Ed2 = 90V for AC100V, Ed1 = 18 for AC200V
It becomes 0V. At this time, TS2≈2 × TS1 and A
The conduction loss of the semiconductor switch in the case of AC100V is about double that in the case of C200V. Further, when the turns ratio of the transformer is 1: 1, the diode composing the rectifier is selected to have a withstand voltage of 180V or higher. This point is the same as in the case of FIG. 27, and when the DC power supply voltage is low compared to when it is high, the semiconductor switches 2A, 2
The conduction loss of B, 2C, and 2D increases, and the diode forming the rectifier circuit must be selected so as not to exceed the withstand voltage even when the DC power supply voltage is maximum. That is, in the conventional DC-DC converter, the generated loss becomes large due to the fluctuation of the DC power supply voltage, and there remains a problem that the diode forming the rectifier circuit has a large withstand voltage and is expensive.

A voltage adaptive DC-DC converter capable of avoiding the above problems will be described below. FIG. 12 shows such an embodiment (fifth embodiment).
FIG. The difference from FIG. 26 is that one terminal of the primary winding 41 of the transformer 4 is connected to the series connection point of the diode 3B and the semiconductor switch 2A, and the primary winding 42 of the transformer 4 is connected.
One terminal is connected in series with the semiconductor switch 2B and the diode 3A, and the snubber circuit 13 is connected in parallel with the diode 3B and the semiconductor switch 2B and the semiconductor switch 2A.
And the diode 3A in parallel, the positive terminal of the DC power supply 1 is connected to one terminal of the switch 30, the negative terminal of the DC power supply 1 is connected in parallel to the semiconductor switch 2A and the diode 3A, and the switch 30 is connected. The first terminal 30A is the intermediate terminal of the transformer 4, the second terminal 30B of the switch 30 is the parallel connection point of the diode 3B and the semiconductor switch 2B, and the input voltage detection circuit 40 is the DC power supply 1 in parallel. The control circuit 50 is connected between the input voltage detection circuit 40 and the switch 30, respectively.

In the configuration of FIG. 12, the voltage of the DC power supply 1 is detected by the input voltage detection circuit 40, and when the detected value exceeds a predetermined value, the control circuit 50 connects the switch 30 to the terminal 30B side. In this case, the two-stone converter configuration is the same as that in FIG. 26, and the same operation as in FIG. 26 is performed.
On the other hand, when the detected value is less than or equal to the predetermined value, the switch 30 is connected to the terminal 30A side, and the one-stone converter configuration similar to that of FIG. FIG. 20 shows operation waveforms when the switch 30 is connected to the 30A side in FIG. That is,
The DC output operation of this circuit excites the transformer 4 in the positive direction while the semiconductor switch 2A is on, and supplies DC power to the load via the rectifier circuit 5 and the smoothing circuit 6. Next, the excitation energy of the transformer 4 is regenerated to the DC power supply 1 via the transformer primary winding 42 and the diode 3A while the semiconductor switch 2A is off. The winding 42 acts as a reset winding in the case of a one-stone converter, and acts as a primary winding in the case of a two-stone converter.

Here, the energy regeneration operation by the first snubber circuit 13 will be described. Semiconductor switch 2A
Is turned off, the first snubber circuit 13 absorbs the energy stored in the leakage inductance and the wiring inductance of the transformer 4 via the diode 3B. Next, while the semiconductor switches 2A and 2B are turned on at the same time, the electric charge stored in the first snubber circuit 13 is transferred to the first snubber circuit 13 → the semiconductor switch 2
B → Primary winding 42 of transformer → Discharge in the path of DC power supply 1,
The energy absorbed by the first snubber circuit 13 is transferred to the transformer 4
To the secondary side of. FIG. 13 shows a modification of FIG.
The difference from FIG. 12 is that the positive electrode terminal of the DC power supply 1 is connected to the semiconductor switch 2A and the diode 3A in parallel, and the negative electrode terminal of the DC power supply 1 is connected to one terminal of the switch 30. However, since the operation is exactly the same as that in FIG. 12, the description will be omitted.

FIG. 14 shows a second embodiment (sixth embodiment) of a voltage adaptive DC / DC converter. This corresponds to the conventional example of FIG. 27, and the difference is that
One terminal of the primary winding 41 of the transformer 4 is connected to the series connection point of the semiconductor switch 2A and the semiconductor switch 2C, and the transformer 4
One terminal of the primary winding 42 of the semiconductor switch 2B and the semiconductor switch 2D is connected in series, the snubber circuit 13 is connected in parallel between the semiconductor switch 2C and the semiconductor switch 2D, the semiconductor switch 2A and the semiconductor switch 2B. Between the parallel connection points, the positive electrode side terminal of the DC power supply 1 is connected to one terminal of the switch 30, the negative electrode side terminal of the DC power supply 1 is connected to the parallel connection point of the semiconductor switches 2A and 2B, and the first terminal of the switch 30 is connected. The terminal 30A is the intermediate terminal of the transformer 4, the second terminal 30B of the switch 30 is the parallel connection point of the semiconductor switches 2C and 2D, the input voltage detection circuit 40 is in parallel with the DC power supply 1, and the control circuit 50 Is connected between the input voltage detection circuit 40 and the switch 30, respectively.

In the circuit of FIG. 14 as well, the voltage of the DC power supply 1 is detected by the input voltage detection circuit 40, and when the detected value exceeds a predetermined value, the control circuit 50 causes the switch 30 to switch to the terminal 30B.
To the side. In this case, the same full bridge configuration as in FIG. 27 is obtained, and the same operation as in FIG. 27 is performed. On the other hand, when the detected value is less than or equal to the predetermined value, the switch 30 is connected to the terminal 30A side and has a push-pull configuration. FIG. 21 shows operation waveforms when the switch 30 is connected to the 30A side in FIG. That is, in the DC output operation of this circuit, the transformer 4 is excited in the positive direction while the semiconductor switch 2A is turned on, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing circuit 6. Next, while the semiconductor switch 2B is on, the transformer 4 is excited in the negative direction, and DC power is supplied to the load via the rectifier circuit 5 and the smoothing circuit 6.

Here, the energy regeneration operation by the first snubber circuit 13 will be described. Semiconductor switch 2A
Is turned off, the first snubber circuit 13 absorbs the energy stored in the leakage inductance and the wiring inductance of the transformer 4 via the diode connected in anti-parallel with the semiconductor switch 2C. Next, while the semiconductor switches 2A and 2D are simultaneously turned on,
The electric charge stored in the first snubber circuit 13 is discharged through the path of the first snubber circuit 13 → the semiconductor switch 2D → the transformer primary winding 42 → the DC power source 1, and the first snubber circuit 1 is discharged.
The energy absorbed in 3 is released to the secondary side of the transformer 4. Further, the same operation as described above is performed when the semiconductor switch 2B is turned off and during the period when the semiconductor switches 2B and 2C are simultaneously turned on. FIG. 1 is shown in FIG.
4 shows a modified example. The difference from FIG. 14 is that the positive electrode terminal of the DC power supply 1 is connected in parallel to the semiconductor switches 2A and 2B, and the negative electrode terminal of the DC power supply 1 is connected to one terminal of the switch 30. However, the operation is
Since it is exactly the same as 4, the description is omitted.

FIG. 16 shows an example of a circuit (seventh embodiment) capable of suppressing the rate of voltage rise when the semiconductor switch shown in FIG. 12 is turned off. The difference from FIG. 12 is that the second snubber circuit 14 in which the snubber diode 142 and the snubber capacitor 141 are connected in series is provided in parallel with the semiconductor switch element 2A, and the auxiliary diode 151 and the auxiliary reactor 15 are provided.
An auxiliary circuit 15 in which a series circuit in which 2 is connected in series and an auxiliary capacitor 153 are connected in series is arranged in parallel with the snubber diode 142, and a regenerative diode 154 is connected to the connection point between the series circuit and the auxiliary capacitor 153, the diode 3B and a semiconductor switch. The semiconductor switching device 2B is connected to the parallel connection point with the device 2B, respectively, and in addition,
The snubber circuit 16, the auxiliary circuit 17, and the regenerative diode 174 are connected.

FIG. 22 shows the switch 30 of FIG.
The operation waveforms when connected to the A side are shown. Since the DC output operation is the same as that in FIG. 12, the energy regeneration operation of the snubber capacitor 141 attached to the semiconductor switch element 2A will be described here. When the semiconductor switch element 2A is turned off, the snubber capacitor 141 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, the period during which the semiconductor switch element 2A is on
The electric charge stored in the snubber capacitor 141 is discharged to the auxiliary reactor 152 and the auxiliary capacitor 153 along the path of the snubber capacitor 141 → the auxiliary diode 151 → the auxiliary reactor 152 → the auxiliary capacitor 153 → the semiconductor switch element 2A. When the snubber capacitor 141 is discharged to 0V, the energy stored in the auxiliary reactor 152 causes a current to flow in the route of the auxiliary reactor 152 → the auxiliary capacitor 153 → the snubber diode 142 → the auxiliary diode 151, and the energy is transferred to the auxiliary capacitor 153. Furthermore, while the semiconductor switch element 2A is off, the charge stored in the auxiliary capacitor 153 is stored in the auxiliary capacitor 153 → regenerative diode 154 →
Discharge to the first snubber circuit 13 through the path of the first snubber circuit 13 → regenerative diode 174 → auxiliary capacitor 173 → transformer primary winding 42 → transformer primary winding 41. Then, from the period when the semiconductor switching elements 2A and 2B are simultaneously turned on, the electric charge accumulated in the first snubber circuit 13 is transferred to the first snubber circuit 13 → the semiconductor switching element 2B → the transformer primary winding 42. → Discharges in the path of the DC power supply 1 and releases the energy absorbed by the first snubber circuit 13 to the load. The above operation is the same as the energy regenerating operation of the snubber capacitor 161 attached to the semiconductor switch element 2B. FIG. 17 shows a modification of FIG. The difference from FIG. 16 is that the positive electrode terminal of the DC power supply 1 is connected to the semiconductor switching element 2A and the diode 3A in parallel, and the negative electrode terminal of the DC power supply 1 is connected to one terminal of the switch 30. However, since the operation is exactly the same as that in FIG. 16, the description is omitted.

FIG. 18 shows an example of a circuit (the eighth embodiment of the present invention) for suppressing the rate of voltage rise at the time of turning off the semiconductor switch in FIG. The difference from FIG. 14 is that a second snubber circuit 14 in which a snubber diode 142 and a snubber capacitor 141 are connected in series is arranged in parallel with the semiconductor switch element 2A, and an auxiliary diode 151 and an auxiliary reactor 152 are connected in series. Auxiliary capacitor 153
The auxiliary circuit 15 in which is connected in series is a snubber diode 14
2 and a regenerative circuit 18 in which a regenerative diode 182 and a regenerative reactor 181 are connected in series, between the series connection point of the series circuit and the auxiliary capacitor 153 and the parallel connection point of the semiconductor switches 2C and 2D. For the switch 2B, the snubber circuit 19, the auxiliary circuit 20, and the regenerative circuit 21, for the semiconductor switch 2C, the snubber circuit 22, the auxiliary circuit 23, and the regenerative circuit 24, and for the semiconductor switch 2D, the snubber circuit 25,
The auxiliary circuit 26 and the regenerative circuit 27 are connected to each other as described above.

In FIG. 23, the switch 30 of FIG.
The operation waveforms when connected to the A side are shown. Since the DC output operation is the same as that in FIG. 14, the energy regeneration operation of the snubber capacitor 141 attached to the semiconductor switch element 2A will be described here. When the semiconductor switch element 2A is turned off, the snubber capacitor 141 suppresses the voltage increase rate of the semiconductor switch element 2A. Next, while the semiconductor switch element 2A is on,
The electric charge stored in the snubber capacitor 141 is discharged to the auxiliary reactor 152 and the auxiliary capacitor 153 along the path of the snubber capacitor 141 → the auxiliary diode 151 → the auxiliary reactor 152 → the auxiliary capacitor 153 → the semiconductor switch element 2A. When the snubber capacitor 141 is discharged to 0V, the energy stored in the auxiliary reactor 152 causes a current to flow in the route of the auxiliary reactor 152 → the auxiliary capacitor 153 → the snubber diode 142 → the auxiliary diode 151, and the energy is transferred to the auxiliary capacitor 153. Furthermore, from the period when the semiconductor switch elements 2B and 2C are on, the auxiliary capacitor 1
The electric charge stored in 53 is discharged to the regenerative reactor 181 through the route of the auxiliary capacitor 153 → regenerative reactor 181 → regenerative diode 182 → semiconductor switch element 2C. Then, while the semiconductor switch element 2C is off, the energy stored in the regenerative reactor 181 is regenerative reactor 181 → regenerative diode 182.
→ First snubber circuit 13 → Regenerative diode 272 → Regenerative reactor 271 → Auxiliary capacitor 263 → Transformer primary winding 42 → Transformer primary winding 41 → Auxiliary capacitor 153
An electric current is caused to flow through the path to release energy to the first snubber circuit 13. Finally, semiconductor switch elements 2A and 2D
The charges accumulated in the first snubber circuit 13 are transferred from the period when the first snubber circuits 13 are simultaneously turned on.
→ Semiconductor switch element 2D → Transformer primary winding 42 → Discharges in the path of the DC power supply 1 and releases the energy absorbed by the first snubber circuit 13 to the load. The above operation is the same for each energy regenerating operation of the snubber capacitor 191 attached to the semiconductor switching element 2B, the snubber capacitor 221 attached to the semiconductor switching element 2C, and the snubber capacitor 251 attached to the semiconductor switching element 2D. Is. FIG. 19 shows a modification of FIG. The difference from FIG. 18 is that the positive electrode side terminal of the DC power supply 1 is connected to the parallel connection point of the semiconductor switch element 2A and the semiconductor switching element 2B, and the negative electrode side terminal of the DC power supply 1 is connected to one terminal of the switch 30. In point. However, since the operation is exactly the same as that in FIG. 18, the description will be omitted.

[0042]

According to the inventions of claims 1 to 3, the energy stored in the snubber circuit is regenerated to the DC power source or discharged to the load, so that the snubber circuit causes almost no loss. Become. Further, according to the inventions of claims 4 to 6, the rate of voltage rise at the time of turning off the semiconductor switch element can be reduced, so that there is an advantage in that switching loss and heat generation are reduced. As a result, there is an advantage that the conversion efficiency of the device is improved and a cooling device for heat radiation can be downsized. Further, according to the inventions of claims 7 and 8, when the voltage of the DC power supply is below a certain value, it operates as a one-stone forward converter or a push-pull converter, and the winding ratio of the transformer is (n11 + n12): n.
Since it changes from 2 to n11: n2, there is little change in the period during which the semiconductor switch element is on even when the DC power supply voltage is low, and conduction loss is reduced. Also,
When the DC power supply voltage is equal to or higher than a certain value, the voltage generated in the secondary winding of the transformer is Ed × n2 / (n11 + n12), so that the diode composing the rectifier circuit has a lower withstand voltage than the conventional one. It is possible to select one and it is cheap. Furthermore, as in the inventions of claims 9 and 10, by adding a snubber circuit, an auxiliary circuit and a regenerative circuit to the inventions of claims 7 and 8, not only is the snubber circuit almost free of loss, There is also an advantage that the switching loss and heat generation that occur when the semiconductor switch element is turned off are reduced. As a result, the conversion efficiency of the device is improved, and the cooling device for heat dissipation can be downsized.

[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 an operation explanatory diagram of FIGS. 1 and 2;

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

FIG. 5 is a circuit diagram showing a modified example of FIG.

FIG. 6 is an operation explanatory diagram of FIGS. 4 and 5;

FIG. 7 is a circuit diagram showing a third embodiment according to the present invention.

FIG. 8 is a circuit diagram showing a fourth embodiment according to the present invention.

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

10 is an explanatory diagram of the operation of FIG.

FIG. 11 is an operation explanatory diagram of FIGS. 8 and 9;

FIG. 12 is a circuit diagram showing a fifth embodiment according to the present invention.

FIG. 13 is a circuit diagram showing a modified example of FIG.

FIG. 14 is a circuit diagram showing a sixth embodiment according to the present invention.

FIG. 15 is a circuit diagram showing a modified example of FIG.

FIG. 16 is a circuit diagram showing a seventh embodiment according to the present invention.

FIG. 17 is a circuit diagram showing a modified example of FIG.

FIG. 18 is a circuit diagram showing an eighth embodiment according to the present invention.

FIG. 19 is a circuit diagram showing a modified example of FIG.

FIG. 20 is an operation explanatory diagram of FIGS. 12 and 13;

FIG. 21 is an operation explanatory diagram of FIGS. 14 and 15;

22 is an explanatory diagram of the operation of FIGS.

FIG. 23 is an operation explanatory diagram of FIGS.

FIG. 24 is a circuit diagram showing a first conventional example.

25 is an explanatory diagram of the operation of FIG. 24.

FIG. 26 is a circuit diagram showing a second conventional example.

FIG. 27 is a circuit diagram showing a third conventional example.

28 is an explanatory diagram of the operation of FIG. 26.

29 is an explanatory diagram of the operation of FIG. 27. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2A, 2B, 2C, 2D ... Semiconductor switch element, 3A, 3B ... Diode, 4 ... Transformer, 5 ... Rectifier circuit, 6 ... Smoothing circuit (smoothing filter), 7, 10, 1
3, 14, 16, 19, 22, 25 ... Snubber circuit, 8,
11, 15, 17, 20, 23, 26 ... Auxiliary circuit, 9,
12,154,174,182,212,242,27
2 ... Regenerative diode, 18, 21, 24, 27 ... Regenerative circuit, 30 ... Switch, 30A, 30B ... Switch 30 terminal, 31A, 32A ... Capacitor, 40 ... Input voltage detection circuit, 41 ... Transformer primary winding, 42 ... Transformer reset winding, 43 ... Transformer secondary winding, 50 ... Control circuit, 71,
101, 142, 162, 192, 222, 252 ... Snubber diode, 72, 102, 141, 161, 19
1, 211, 251 ... Snubber capacitors, 73 ... Discharge resistors, 81, 111, 151, 171, 201, 231,
261 ... Auxiliary diode, 82, 112, 152, 17
2,202,232,262 ... Auxiliary reactor, 11
3, 153, 173, 203, 233, 263 ... Auxiliary capacitors, 181, 211, 241, 271 ... Regenerative reactor.

Claims (10)

[Claims] 1. A direct current power source, a transformer having a reset winding on the primary side, a rectifier circuit connected to the secondary side of the transformer, and a smoothing circuit for smoothing the rectified output thereof. In a DC-DC converter for extracting DC power isolated from a power supply, a first series arm in which one terminal of a first diode and one terminal of a first semiconductor switch element are connected in series, and a second series arm A second series arm, in which one terminal of the semiconductor switch element and one terminal of the second diode are connected in series, and a first snubber circuit are connected in parallel, and the primary winding of the transformer is reset. A terminal on the side not connected to the winding is connected to the connection point of the first series arm, and a terminal on the side not connected to the primary winding of the transformer reset winding is connected to the second series arm. At the connection point, The direct current power supply 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, respectively. -DC converter. 2. A second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel with the first semiconductor switch element, and an auxiliary capacitor is connected in series in a series circuit of an auxiliary diode and an auxiliary reactor. An auxiliary circuit is connected in parallel with the snubber diode, and a regenerative diode is connected between a connection point of the series circuit and the auxiliary capacitor and a parallel connection point of the second semiconductor switch element. The DC-DC converter according to claim 1. 3. The ON period of the second semiconductor switching element is set to be approximately 1/2 of the resonance period determined by the capacitance of the capacitor forming the first snubber circuit and the leakage inductance of the transformer. The DC-DC converter according to claim 1 or 2, characterized in that. 4. 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, and 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 DC-DC converter in which a rectifying circuit is connected to the secondary winding and a smoothing circuit is connected to the rectifying circuit, wherein a snubber diode is provided in each of the first semiconductor switching element and the second semiconductor switching element. A snubber circuit in which a snubber capacitor is connected in series is connected in parallel, and each of the snubber diodes is connected in series with an auxiliary diode and an auxiliary reactor in an auxiliary capacitor. An auxiliary circuit in which the sensors are connected in series is connected in parallel, and a regenerative diode is connected between the connection point of the series circuit and the auxiliary capacitor and the parallel connection point of the first and second series arms. Characteristic DC-DC converter. 5. A first 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, a second series arm in which a capacitor is connected in series, and a DC power supply are parallel to each other. The 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, and the secondary winding of the transformer is rectified. A circuit, a DC-DC converter in which smoothing circuits are connected to the rectifier circuit, wherein each of the switching elements includes a snubber circuit in which a snubber diode and a snubber capacitor are connected in series, and the snubber circuit is connected in parallel. In each of the diodes, in parallel, an auxiliary circuit in which an auxiliary capacitor is connected in series to a series circuit in which an auxiliary diode and an auxiliary reactor are connected in series,
Further, the regenerative diode is connected between a connection point of the series circuit and the auxiliary capacitor and a parallel connection point of the first and second series arms, respectively. 6. 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, a second series arm in which a capacitor is connected in series, and a DC power source are parallel to each other. The 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, and the secondary winding of the transformer is rectified. Circuit, a DC-DC converter in which smoothing circuits are connected to the rectifier circuit, respectively, in which auxiliary reactors are respectively connected in series between the switching element and the connection point of the transformer primary winding, Each of them has a snubber circuit in which a snubber diode and a snubber capacitor are connected in series, and an auxiliary circuit in which an auxiliary diode and an auxiliary capacitor are connected in series. A regenerative diode is provided between the series connection point of the circuit and the connection point of the auxiliary reactor and the connection point of the transformer primary winding, and the series connection point of the auxiliary circuit and the parallel connection point of the first and second series arms. A DC-DC converter characterized by being connected to each other. 7. A first circuit in which one terminal of a first diode and one terminal of a first semiconductor switching element are connected in series.
And a second series arm in which one terminal of the second semiconductor switch element and one terminal of the second diode are connected in series, and the first snubber circuit is connected in parallel. One terminal of the transformer primary winding with an intermediate terminal at the series connection point of the first series arm,
The other terminal of the transformer primary winding is connected to the series connection point of the second series arm, and a DC power supply is
Between the parallel connection point of the first terminal of the terminal switch, the first semiconductor switch element and the second diode, the second terminal of the three-terminal switch to the intermediate terminal of the transformer, the three terminals A third terminal of the switch is connected between parallel connection points of the first diode and the second semiconductor switch element, and further, an input voltage detection circuit is connected in parallel with the DC power supply, and a control circuit is connected to the control circuit. A DC-DC converter, wherein a secondary terminal of the transformer is connected to a rectifier circuit and the rectifier circuit is connected to a smoothing filter between an input voltage detection circuit and the three-terminal switch. 8. A first series arm in which one terminal of a first semiconductor switching element and one terminal of a second semiconductor switching element are connected in series, one terminal of a third semiconductor switching element and a first series arm. The second series arm in which one terminal of the semiconductor switch element of 4 is connected in series and the first snubber circuit are respectively connected in parallel, and one terminal of the transformer primary winding having an intermediate terminal is connected to the second series arm. The other terminal of the transformer primary winding is connected to the series connection point of the first series arm, and the DC power source is connected to the first connection point of the three-terminal switch. Terminal and the first
The second terminal of the three-terminal switch as the intermediate terminal of the transformer, and the three-terminal switch 7
The terminals of the second semiconductor switch element and the fourth semiconductor switch element are respectively connected in parallel,
Furthermore, an input voltage detection circuit in parallel with the DC power supply,
A DC-DC converter, wherein a control circuit is connected between the input voltage detection circuit and the three-terminal switch, the secondary terminal of the transformer is connected to a rectifying circuit, and the rectifying circuit is connected to a smoothing filter. . 9. A second snubber circuit, in which a first snubber diode and a first snubber capacitor are connected in series, is provided in parallel with the first semiconductor switch element, and a first auxiliary diode and a first auxiliary reactor are provided. Is connected in series with a first auxiliary circuit in which a first series circuit including a first auxiliary circuit and a first auxiliary capacitor connected in series is connected in parallel to the first snubber diode, and a first regenerative diode is connected to the first series circuit in the first series circuit. A third snubber in which a second snubber diode and a second snubber capacitor are connected in series between a connection point with the first auxiliary capacitor and a parallel connection point between the first diode and the second semiconductor switch element. A second series circuit in which a second auxiliary diode and a second auxiliary reactor are connected in series and a second auxiliary capacitor are connected in series, and a circuit is connected in parallel with the second semiconductor switching element. The second auxiliary circuit is connected in parallel with the second snubber diode, and the second regenerative diode is connected to the connection point between the second series circuit and the second auxiliary capacitor and the second auxiliary circuit.
8. The DC-DC converter according to claim 7, wherein the diode and the first semiconductor switch element are connected in parallel to each other. 10. A second snubber circuit, in which a first snubber diode and a first snubber capacitor are connected in series, is provided in parallel with the first semiconductor switching device, and a first auxiliary diode and a first auxiliary reactor are provided. And a first auxiliary circuit in which a first auxiliary circuit in which a first auxiliary circuit and a first auxiliary capacitor are connected in series are connected in parallel with the first snubber diode.
The first regenerative circuit in which the regenerative diode and the first regenerative reactor are connected in series, the connection point between the first series circuit and the first auxiliary capacitor, the second semiconductor switch element, and the fourth semiconductor. Between the parallel connection point with the switch element,
A third snubber circuit, in which a second snubber diode and a second snubber capacitor are connected in series, is connected in parallel with the second semiconductor switch element, and a second auxiliary diode and a second auxiliary reactor are connected in series. A second auxiliary circuit in which a second series circuit and a second auxiliary capacitor are connected in series is connected in parallel with the second snubber diode, and a second regenerative diode and a second regenerative reactor are connected in series. A regenerative circuit is provided between the connection point of the second series circuit and the second auxiliary capacitor and the parallel connection point of the first semiconductor switch element and the third semiconductor switch element with respect to the second series arm. The same as above, the fourth snubber circuit, the fifth
Snubber circuit, third auxiliary circuit, fourth auxiliary circuit, third
9. The DC-DC converter according to claim 8, wherein the regenerative circuit and the fourth regenerative circuit are connected.