JPH10271822A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the conversion efficiency of a DC-DC converter from lowering without need for increasing the size of a snubber circuit. SOLUTION: A snubber circuit 51A consisting of a diode and a capacitor and an auxiliary circuit 52A constituted of a serial circuit consisting of an auxiliary reactor and an auxiliary switching element are connected to the semiconductor switching element 5A of this DC-DC converter consisting of a DC power source 1, the semiconductor switching elements 5A, 7B, diodes 9A, 9B, a transformer 2, a rectifier circuit 3, a filter 4 and so on, and the energy absorbed in the snubber circuits 8, 51A is finally discharged to the DC power source 1 or the load, thus it is possible to attain size reduction and higher efficiency of the device.

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 insulated DC power from a DC power supply, and more particularly to a snubber attached to the semiconductor switch when performing power conversion by turning on and off a semiconductor switch. The present invention relates to a DC-DC converter having an energy recovery function for recovering energy stored in a circuit.

[0002]

2. Description of the Related Art FIG. 12 shows a conventional example of a single-forward type DC-DC converter. As shown in FIG.
The connection point between the primary winding 21A of the transformer 2 and the reset winding 21B is connected to the positive terminal of the transformer 2 and a semiconductor switch is connected between the other terminal of the primary winding 21A of the transformer 2 and the negative terminal of the DC power supply 1. An element 5A includes a diode 9B between the other terminal of the reset winding 21B of the transformer 2 and the negative terminal of the DC power supply 1.
However, the rectifier circuit 3 is connected to the secondary winding 22 of the transformer 2, and the rectifier circuit 3 is connected to a smoothing filter (smoothing circuit) 4.

FIG. 17 shows operation waveforms of FIG. Now
While the semiconductor switch element 5A is ON, the transformer 2 is excited in the positive direction, and supplies DC power to the load via the rectifier circuit 3 and the smoothing filter 4. On the other hand, while the semiconductor switch element 5A is off, the excitation energy of the transformer 2 is regenerated to the DC power supply 1 via the reset winding 21B and the diode 9B.

FIG. 13 shows a conventional example of a dual-forward DC-DC converter. In the figure, one terminal of the semiconductor switch element 5D is connected to the positive terminal of the DC power supply 1, and the transformer primary winding 21 is connected to the other terminal of the semiconductor switch element 5D.
A, one terminal of the semiconductor switching element 5A is connected to the other terminal of the transformer primary winding 21A, the negative terminal of the DC power supply 1 is connected to the other terminal of the semiconductor switching element 5A, 1 positive terminal and transformer primary winding 21A
A diode 9A is provided between the connection point of the switching element 5A and the semiconductor switching element 5A.
A diode 9B is connected between the connection point of D and the negative terminal of the DC power supply 1, a rectifier circuit 3 is connected to the transformer secondary winding 22, and a smoothing filter 4 is connected to the rectifier circuit 3. . The operation of FIG. 13 is the same as that of FIG. 17, and during the period when the semiconductor switch elements 5A and 5D are on, the transformer 2
In the positive direction, and supplies DC power to the load via the rectifier circuit 3 and the smoothing filter 4. Next, while the semiconductor switch elements 5A and 5D are off, the transformer 2
Is regenerated to the DC power supply 1 through the transformer primary winding 21A and the diodes 9A and 9B.

FIG. 14 shows a conventional example of a push-pull type DC-DC converter. In the figure, the connection point between the primary windings 21A and 21C of the transformer 2 is connected to the positive terminal of the DC power supply 1 between the other terminal of the primary winding 21A of the transformer 2 and the negative terminal of the DC power supply 1. Is a semiconductor switch element 5A, and a semiconductor switch element 5B is provided between the other terminal of the primary winding 21C of the transformer 2 and the negative terminal of the DC power supply 1, and a transformer secondary winding 22
The rectifier circuit 3 is connected to the smoothing filter 4. FIG. 18 shows the operation waveforms of FIG. Now, when the semiconductor switch element 5A is on, the transformer 2 is excited in the positive direction, and when the semiconductor switch element 5B is on, the transformer 2 is excited in the negative direction, and the rectifier circuit 3 and the smoothing filter 4 are activated. Supply DC power to the load via the power supply.

FIG. 15 shows a conventional example of a half-bridge type DC-DC converter. In the figure, one terminal of the semiconductor switch element 5C and one terminal of the capacitor 6B are connected to the positive terminal of the DC power supply 1 and one terminal of the semiconductor switch element 5A is connected to the other terminal of the semiconductor switch element 5C. One terminal of the transformer primary winding 21A, one terminal of the capacitor 6A and the other terminal of the transformer primary winding 21A at the other terminal of the capacitor 6B, and a semiconductor switching element at the negative terminal of the DC power supply 1. 5A other terminal and capacitor 6
A is connected to the transformer secondary winding 22 by the rectifier circuit 3.
However, a smoothing filter 4 is connected to the rectifier circuit 3. The operation of FIG. 15 is the same as that of FIG. 18, in which the transformer 2 is excited in the negative direction while the semiconductor switch element 5A is on, and the transformer 2 is excited in the positive direction while the semiconductor switch element 5C is on. To supply DC power to the load via the rectifier circuit 3 and the smoothing filter 4.

FIG. 16 shows a conventional example of a full-bridge type DC-DC converter. In the figure, the positive terminal of the DC power supply 1 has one terminal of the semiconductor switching element 5C and one terminal of the semiconductor switching element 5D, and the negative terminal of the DC power supply 1 has one terminal of the semiconductor switching element 5A. One terminal of the semiconductor switch element 5B is connected to the semiconductor switch element 5D.
Is connected to one terminal of the primary winding 21A of the transformer 2 and the other terminal of the semiconductor switch element 5B, and to the other terminal of the semiconductor switch element 5C.
A rectifier circuit 3 is connected to the other terminal of A and the other terminal of the primary winding 21A of the transformer 2, the rectifier circuit 3 is connected to the transformer secondary winding 22, and the smoothing filter 4 is connected to the rectifier circuit 3. I have. The operation of FIG. 16 is also the same as that of FIG. 18, except that the transformer 2 is excited in the positive direction while the semiconductor switch elements 5A and 5D are on, and the semiconductor switch elements 5B and
When the transformer 2 is turned on, the transformer 2 is excited in the negative direction,
DC power is supplied to the load via the rectifier circuit 3 and the smoothing filter 4.

In the circuits shown in FIGS. 12 to 16, when the semiconductor switch elements 5A, 5B, 5C and 5D are turned off, the surge voltage of the semiconductor switch elements is suppressed, and
In order to reduce the voltage rise rate (dv / dt) and reduce the switching loss, a snubber circuit composed of snubber capacitors 531A, 531B, 531C, 531D and discharge resistors 532A, 532B, 532C, 532D and the like is provided in the semiconductor switch element. 53A, 53B, 53C, 53
D are connected in parallel. As a result, the energy absorbed by snubber capacitors 531A, 531B, 531C, 531D finally becomes the discharge resistors 532A, 532B, 5
32C and 532D.

[0009]

In any of the above circuits, the energy absorbed by the snubber capacitor is released to the discharge resistor when the semiconductor switch element is turned on next time, resulting in a loss. Now, let P be the loss of the discharge resistor, C be the capacitance of the snubber capacitor, E be the voltage of the DC power supply, Vr be the reset voltage of the transformer, ΔV be the jump voltage of the semiconductor switch element, and f be the operating frequency of the semiconductor switch element. Then, in the circuit of FIG. 12, P = (1/2) × C × (E + Vr + ΔV) ² × f, and in the case of FIGS. 13, 15 and 16, P = (1/2) × C × (E + ΔV) ² × f, and in the case of FIG. 14, P = (１ ／) × C × (2E + ΔV) ² × f. Therefore, when 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 increase, the loss P generated in the discharge resistor increases, and only a large and expensive snubber circuit is required. Therefore, there is a problem that the conversion efficiency of the device is reduced. 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.

[0010]

In order to solve such a problem, according to the present invention, there is provided a first semiconductor device in which one terminal of a first diode and one terminal of a first semiconductor switch element are connected in series. A serial arm, a second serial 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 snubber circuit connected in parallel with each other; The terminal of the transformer primary winding on the side where the reset winding is not connected is connected to the series connection point of the first series arm, and the terminal on the side where the primary winding of the transformer reset winding is not connected is connected. A DC power supply is further connected to a series connection point of the second series arm and a connection point of a primary winding and a reset winding of a transformer and a connection point of the first semiconductor switch element and the second diode. Connected in parallel between In the current-DC converter, a second snubber circuit in which a snubber diode and a snubber capacitor are connected in series is connected in parallel with a semiconductor switch element on the side connected to the DC power supply, and an auxiliary reactor and an auxiliary switch are connected in series. A second regenerative diode is connected between a series connection point of the series circuit and a parallel connection point of the semiconductor switch element on the side not connected to the DC power supply, and a first regenerative diode is connected in parallel with the snubber diode. Each is connected in parallel with the snubber capacitor.

According to the second aspect of the present invention, the first series arm in which the first diode and the first semiconductor switching element are connected in series, and the second series arm in which the second semiconductor switching element and the second diode are connected in series. And a DC power supply is connected in parallel to each other, and a primary transformer of the transformer is connected between the series connection point of the first series arm and the series connection point of the second series arm. In the DC-DC converter, a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is individually and in parallel with each of the first semiconductor switch element and the second semiconductor switch element.
In each of the snubber diodes, a series circuit in which an auxiliary reactor and an auxiliary switch are connected in series is individually and in parallel, and is connected between a series connection point of the series circuit and a parallel connection point of the first and second series arms. Has a first regenerative diode connected individually and a second regenerative diode connected to each of the snubber capacitors individually and in parallel.

According to a third aspect of the present invention, a first series arm in which one terminal of the first semiconductor switch element and one terminal of the second semiconductor switch element are connected in series, One terminal of a transformer primary winding having an intermediate terminal and a second series arm in which one terminal and one terminal of a fourth semiconductor switch element are connected in series, and a first snubber circuit, respectively. To the series connection point of the first series arm, the other terminal of the primary winding of the transformer to the series connection point of the second series arm, and a DC power supply to the intermediate terminal of the transformer and the second terminal. In a DC-DC converter connected between parallel connection points of a semiconductor switch element and a fourth semiconductor switch element, a snubber die is connected to each of the second semiconductor switch element and the fourth semiconductor switch element. And a snubber circuit connected in series with a snubber capacitor, a series circuit in which an auxiliary reactor and an auxiliary switch are connected in series to each of the snubber diodes, individually and in parallel, and a series connection point of the series circuit. And a first regenerative diode individually between each of the parallel connection points of the first and second series arms on which the DC power supply is not connected, and a second regenerative diode separately for each of the snubber capacitors. They are connected in parallel.

According to a fourth aspect of the present invention, a first series arm in which one terminal of the first semiconductor switch element and one terminal of the second semiconductor switch element are connected in series, and a second series arm in which a capacitor is connected in series. And a DC power supply 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 the DC-DC converter, in each of the switching elements, a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is individually and in parallel, and in each of the snubber diodes, an auxiliary reactor and an auxiliary switch are provided. A first regenerative die is connected to the series circuit connected in series individually and in parallel, and further between a series connection point of the series circuit and a parallel connection point of the first series arm. Individually over de, and a second regenerative diode respectively connected to individual and parallel to each of the snubber capacitor.

According to a fifth aspect of the present invention, a first series arm in which one terminal of the first semiconductor switch element and one terminal of the second semiconductor switch element are connected in series, A second series arm in which one terminal and one terminal of the fourth semiconductor switch element are connected in series, and a DC power supply are connected in parallel with each other, and a primary transformer is connected in series with the first series arm. In a DC-DC converter connected between a connection point and a series connection point of the second series arm, each of the semiconductor switch elements includes a snubber circuit in which a snubber diode and a snubber capacitor are connected in series. Individually and in parallel, and in each of the snubber diodes, a series circuit in which an auxiliary reactor and an auxiliary switch are connected in series is individually and in parallel, and furthermore, a series circuit of the series circuit is connected. Individually first regenerative diode respectively between the parallel connection point between the series arm and attachment point, and a second regenerative diode respectively connected to individual and parallel to each of the snubber capacitor. According to the above-described first to fifth aspects, the on-period of the auxiliary switch element can be set to about １ ／ of the resonance cycle of the capacitance of the snubber capacitor and the auxiliary reactor (claim 6).
Invention).

According to the first and third aspects of the present invention, when the semiconductor switching element is turned off, the rate of voltage rise of the semiconductor switching element is suppressed by the snubber capacitor, and the switching loss is reduced. Next, while the auxiliary switch element is on, the electric charge stored in the snubber capacitor is transferred to the auxiliary reactor. Then, by turning off the auxiliary switch element, the energy stored in the auxiliary reactor is transferred to the first snubber circuit via the first and second regenerative diodes. Further, the charge stored in the first snubber circuit is released to the load while the semiconductor switch element is on.

According to the second, fourth and fifth aspects of the present invention, when the semiconductor switch element is turned off, the rate of voltage rise of the semiconductor switch element is suppressed by the snubber capacitor, and the switching loss is reduced. Next, while the auxiliary switch element is on, the electric charge stored in the snubber capacitor is transferred to the auxiliary reactor. Then, by turning off the auxiliary switch element, the energy stored in the auxiliary reactor is regenerated to the DC power supply via the first and second regenerative diodes.

Further, in the sixth invention, the ON period of the auxiliary switch element is set to about １ ／ of the resonance cycle of the snubber capacitor capacitance and the auxiliary reactor. During the ON period of the auxiliary switch element, a sinusoidal current having a period determined by the snubber capacitor capacity and the auxiliary reactor flows,
Next, after the snubber capacitor discharges to zero voltage, the circulating current continues to flow in the auxiliary switch element and the snubber diode due to the energy stored in the auxiliary reactor, and conduction loss occurs in the auxiliary switch element and the snubber diode during this period. I do. Therefore, by setting the on-period of the auxiliary switch element to about 1/4 of the resonance cycle, the period during which the circulating current flows is made substantially zero, and the conduction loss of the auxiliary switch element and the snubber diode can be reduced.

[0018]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This is because the snubber circuit 53A is omitted from the conventional example shown in FIG. 12, one terminal of the diode 9A is connected to a connection point between the transformer primary winding 21A and the semiconductor switch element 5A, and one terminal of the semiconductor switch element 7B is transformed. The other terminal of the diode 9A is connected to the other terminal of the semiconductor switch element 7B at the connection point between the reset coil 21B and the diode 9B, and the first snubber circuit 8 is connected to the parallel connection point of the diode 9A and the semiconductor switch element 7B. Between the semiconductor switch element 5A and the parallel connection point of the diode 9B and the snubber diode 512A and the snubber capacitor 51A.
1A is connected in series with the semiconductor switch element 5A, a series circuit in which the auxiliary reactor 522A and the auxiliary switch element 521A are connected in series is connected in parallel with the snubber diode 512A, and the regenerative diode 524.
A is an auxiliary reactor 522A and an auxiliary switch element 521
A regenerative diode 523A is connected in parallel with a snubber capacitor 511A between a series connection point A and a connection point between the diode 9A and the semiconductor switch element 7B.

FIG. 8 shows the operation waveforms of FIG. FIG.
12 is the same as the case of FIG. 12, the energy regeneration operation of the snubber capacitor 511A attached to the semiconductor switch element 5A and the snubber capacitor attached to the snubber circuit 8 will be mainly described below. That is, when the semiconductor switch element 5A is turned off, the snubber capacitor 511A suppresses the voltage increase rate of the semiconductor switch element 5A. Next, while the semiconductor switch element 5A and the auxiliary switch element 521A are on, the electric charge stored in the snubber capacitor 511A is transferred to the snubber capacitor 511A → the auxiliary reactor 522.
A → Auxiliary switch element 521A → Semiconductor switch element 5
Transfer to the auxiliary reactor 522A along the route A. During the period after the snubber capacitor 511A has discharged to zero voltage, the energy stored in the auxiliary reactor 522A
Auxiliary reactor 522A → Auxiliary switch element 521A →
Current continues to flow through the path of snubber diode 512A.
Further, while the auxiliary switch element 521A is off,
The energy stored in the auxiliary reactor 522A is converted into the auxiliary reactor 522A → the regenerative diode 524A → the first
Of the snubber circuit 8 → regeneration diode 523A
To the snubber circuit 8 of FIG. Also, the semiconductor switch element 5A
During the period in which the semiconductor switch element 7B is simultaneously turned on, the electric charge stored in the first snubber circuit 8 is
First snubber circuit 8 → semiconductor switch element 7B → transformer reset winding 21B → discharge in the path of DC power supply 1
The energy absorbed by the snubber circuit 8 is released to the load.

FIG. 2 shows a modification of FIG. This is because the positive terminal of the DC power supply 1 is connected to a connection point between the semiconductor switch element 5A and the diode 9B, and the negative terminal of the DC power supply 1 is connected to the primary winding 21A of the transformer and the reset winding 21B of the transformer. It is characterized in that it is connected to each point, and its function is exactly the same as that of FIG. The operation is also shown in FIG.
Is the same as

FIG. 3 is a circuit diagram showing a second embodiment of the present invention, and corresponds to FIG. 13 is different from FIG. 13 in that the snubber circuits 53A and 53D are omitted, a snubber circuit 51A in which a snubber diode 512A and a snubber capacitor 511A are connected in series is connected in parallel with a semiconductor switch element 5A, an auxiliary reactor 522A and an auxiliary switch element 521.
A is connected to the first series circuit connected in series with the snubber diode 5.
In parallel with 12A, a regenerative diode 524A is connected between the connection point between the auxiliary reactor 522A and the auxiliary switch element 521A and the positive terminal of the DC power supply 1.
Are connected in parallel with the snubber capacitor 511A, respectively.
Similarly, a snubber circuit 51D in which a snubber capacitor 511D and a snubber diode 512D are connected in series is connected in parallel with a semiconductor switch 5D, and a second series circuit in which an auxiliary reactor 522D and an auxiliary switch element 521D are connected in series is connected in parallel with a snubber diode 512D. , Regenerative diode 52
4D is connected to the auxiliary reactor 522D and the auxiliary switch element 52
The point lies in that the regenerative diode 523D is connected in parallel with the snubber capacitor 511D between the connection point with 1D and the negative terminal of the DC power supply 1.

Referring to FIG. 9, the energy regenerating operation of snubber capacitor 511A attached to semiconductor switch element 5A, which is different from FIG. 13, will be described. Now, when the semiconductor switch element 5A turns off, the snubber capacitor 511A suppresses the rate of voltage increase of the semiconductor switch element 5A. Next, while the semiconductor switch element 5A is on, the electric charge stored in the snubber capacitor 511A is transferred to the auxiliary reactor 522A via the snubber capacitor 511A → auxiliary reactor 522A → auxiliary switch element 521A → semiconductor switch element 5A. Transfer to During the period after the snubber capacitor 511A has discharged to zero voltage, current continues to flow through the path of the auxiliary reactor 522A → the auxiliary switch element 521A → the snubber diode 512A due to the energy stored in the auxiliary reactor 522A. Further, while the auxiliary switch element 521A is off, the energy stored in the auxiliary reactor 522A is discharged through the path of the auxiliary reactor 522A → the regenerative diode 524A → the DC power supply 1 → the regenerative diode 523A, and the energy is regenerated to the DC power supply 1. I do. The snubber circuit 51D and the auxiliary circuit 52D attached to the semiconductor switch element 5D operate on the same principle.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention, and corresponds to FIG. The difference from FIG. 14 is that the snubber circuits 53A and 53B are omitted, and one terminal of the transformer primary winding 21A is connected to the series connection point of the semiconductor switch element 7A and the semiconductor switch element 5A, and the transformer primary winding 21C Is connected to the series connection point of the semiconductor switch element 7B and the semiconductor switch element 5B, and the snubber circuit 8 is connected to the semiconductor switch element 7A and the semiconductor switch element 7B.
The positive terminal of the DC power supply 1 is connected to the intermediate terminal of the transformer 2 and the negative terminal of the DC power supply 1 is connected to the semiconductor switch element 5A between the connection point of the DC power supply 1 and the connection point of the semiconductor switch element 5B. A snubber diode 512A and a snubber capacitor 51 are connected to a connection point with the semiconductor switch element 5B.
1A in parallel with the semiconductor switch element 5A, a series circuit in which the auxiliary reactor 522A and the auxiliary switch element 521A are connected in series with the snubber diode 512A, and a regenerative diode 524A with the auxiliary reactor 522A and the auxiliary switch. A regenerative diode 523A is connected in parallel with the snubber capacitor 511A between the connection point with the element 521A and the connection point between the semiconductor switch elements 7A and 7B.
The snubber circuit 51B and the auxiliary circuit 52B attached to B are connected in the same manner as described above.

FIG. 10 shows operation waveforms of FIG. Since this operation is the same as that of FIG. 14, mainly the energy regeneration operation of the snubber capacitor 511A attached to the semiconductor switch element 5A will be described. Now, when the semiconductor switch element 5A is turned off, the snubber capacitor 511A
Suppresses the voltage rise rate of the semiconductor switch element 5A. Next, the semiconductor switch element 5A and the auxiliary switch element 5
While the 21A is on, the snubber capacitor 51
1A is stored in the snubber capacitor 511A.
→ Auxiliary reactor 522A → Auxiliary switch element 521A
→ Auxiliary reactor 52 on the path of semiconductor switch element 5A
Transfer to 2A. During the period after the snubber capacitor 511A has discharged to zero voltage, current continues to flow through the path of the auxiliary reactor 522A → the auxiliary switch element 521A → the snubber diode 512A due to the energy stored in the auxiliary reactor 522A. Further, the auxiliary switch element 52
During the period when 1A is off, the auxiliary reactor 522A
The energy stored in the auxiliary reactor 522A →
Discharge is performed on the path of the regenerative diode 524A → the snubber circuit 8 → the regenerative diode 523A, and energy is transferred to the snubber circuit 8.

The semiconductor switch elements 5A and 7B
During the period when is simultaneously turned on, the electric charge stored in the snubber circuit 8 is discharged through the path of the snubber circuit 8 → the semiconductor switch element 7B → the transformer primary winding 21C → the DC power supply 1; Releases absorbed energy to the load. During the period (10) when the semiconductor switch elements 5A and 5B are simultaneously turned off, the snubber capacitor 5
11A is stored in the snubber capacitor 51
1A → auxiliary reactor 522A → regenerative diode 524
A → discharge in the path of the snubber circuit 8 and the auxiliary reactor 52
Transfer energy to 2A and snubber circuit 8. After the snubber capacitor 511A reaches 1/2 of the DC power supply voltage, the energy stored in the auxiliary reactor 522A is changed from the auxiliary reactor 522A to the regenerative diode 524A.
→ Snubber circuit 8 → DC power supply 1 → Transformer primary winding 21A →
A current flows through the path of the snubber diode 512A and transfers energy to the snubber circuit 8. The snubber circuits 51B and 52B attached to the semiconductor switch element 5B also
It operates exactly as described above.

FIG. 5 shows a modification of FIG. The difference from FIG. 4 is that the positive terminal of the DC power supply 1 is connected to the semiconductor switch element 5.
A DC power supply 1 is connected to the connection point between A and the semiconductor switch element 5B.
The other point is the same as that of FIG. 4 in that the negative electrode side terminal is connected to the intermediate terminal of the transformer 2. In addition, about the operation,
This is the same as FIG.

FIG. 6 shows a fourth embodiment of the present invention corresponding to FIG. The difference from FIG. 15 is that the snubber circuit 5
3A and 53C are omitted, and a snubber circuit 51 in which a snubber diode 512A and a snubber capacitor 511A are connected in series.
A is connected in parallel with the semiconductor switch element 5A, and a first series circuit in which the auxiliary reactor 522A and the auxiliary switch element 521A are connected in series is connected in parallel with the snubber diode 512A.
The regenerative diode 524A is connected in parallel with the snubber capacitor 511A between the connection point between the auxiliary reactor 522A and the auxiliary switch element 521A and the positive terminal of the DC power supply 1, and similarly, the snubber capacitor 511C and the snubber diode are connected. The auxiliary reactor 522C and the auxiliary switch element 52C are connected in parallel with the semiconductor switch element 5C by connecting a snubber circuit 51C having the 512C connected in series.
1C in series with the snubber diode 512C, and a regenerative diode 524C between the series connection point of the auxiliary reactor 522C and the auxiliary switch element 521C and the negative terminal of the DC power supply 1. Are connected in parallel with the snubber capacitor 511C.

FIG. 11 shows the operation waveforms of FIG. Since the operation is the same as that of FIG. 15, here, the operation of regenerating the energy of the snubber capacitor 511A attached to the semiconductor switch element 5A will be mainly described. That is, when the semiconductor switch element 5A turns off, the snubber capacitor 511A suppresses the rate of voltage increase of the semiconductor switch element 5A. Next, while the semiconductor switch element 5A and the auxiliary switch element 521A are on, the electric charge stored in the snubber capacitor 511A is transferred through the path of the snubber capacitor 511A → the auxiliary reactor 522A → the auxiliary switch element 521A → the semiconductor switch element 5A. To the auxiliary reactor 522A. Snubber capacitor 511
During the period after A discharges to zero voltage, current continues to flow on the path of auxiliary reactor 522A → auxiliary switch element 521A → snubber diode 512A due to the energy stored in auxiliary reactor 522A. Further, while the auxiliary switch element 521A is off, the energy stored in the auxiliary reactor 522A is changed from the auxiliary reactor 522A → the regenerative diode 524A → the DC power supply 1 →
The power is regenerated to the DC power supply 1 through the path of the regenerative diode 523A. During the period (10) when the semiconductor switch elements 5A and 5C are simultaneously turned off, the snubber capacitor 51
The electric charge stored in 1A is a snubber capacitor 511
A → Auxiliary reactor 522A → Regenerative diode 524A
→ Discharge in the path of DC power supply 1, auxiliary reactor 522A
Transfer energy to After the snubber capacitor 511A reaches 1/2 of the DC power supply voltage, the auxiliary reactor 522
The energy stored in A is the auxiliary reactor 522A
A current flows through the path of the regenerative diode 524A → the capacitor 6B → the primary winding 21A of the transformer → the snubber diode 512A to transfer energy to the capacitor 6B. The snubber circuits 51C, 5C attached to the semiconductor switch element 5C
In 2C, the operation is exactly the same as described above.

FIG. 7 shows a fifth embodiment of the present invention corresponding to FIG. The difference from FIG. 16 is that the snubber circuit 5
3A, 53B, 53C and 53D are omitted, a snubber circuit 51A in which a snubber diode 512A and a snubber capacitor 511A are connected in series is connected in parallel with a semiconductor switch element 5A, and an auxiliary reactor 522A and an auxiliary switch 521 are provided.
A is connected in series with the snubber diode 512A, the regenerative diode 524A is connected between the connection point between the auxiliary reactor 522A and the auxiliary switch 521A and the positive terminal of the DC power supply 1, and the regenerative diode 523A is connected to the snubber diode 512A. The point is that each is connected in parallel with the capacitor 511A. Similarly, a snubber circuit 51C in which a snubber capacitor 511C and a snubber diode 512C are connected in series.
In parallel with the semiconductor switch element 5C,
A second series circuit in which the second switch 22C and the auxiliary switch 521C are connected in series is connected in parallel with the snubber diode 512C, and the regenerative diode 524C is connected between the connection point between the auxiliary reactor 522C and the auxiliary switch 521C and the negative terminal of the DC power supply 1. The diode 523C is connected to the snubber capacitor 511.
C and connected in parallel. Further, the semiconductor switch elements 5B and 5D are similarly connected to the snubber circuits 51B and 5D.
1D and the auxiliary circuits 52B and 52D are connected.

FIG. 11 shows the operation waveforms of FIG. Since the operation is the same as that of FIG. 16, here, the regenerative operation of the energy of the snubber capacitor 511A attached to the semiconductor switch element 5A will be mainly described. When the semiconductor switch element 5A is turned off, the snubber capacitor 51
1A suppresses the voltage rise rate of the semiconductor switch element 5A. Next, while the semiconductor switch element 5A and the auxiliary switch element 521A are on, the electric charge stored in the snubber capacitor 511A is transferred to the path of the snubber capacitor 511A → auxiliary reactor 522A → auxiliary switch element 521A → semiconductor switch element 5A. Then, it is transferred to the auxiliary reactor 522A. During the period after the snubber capacitor 511A has discharged to zero voltage, the auxiliary reactor 522
A, the auxiliary reactor 52
2A → auxiliary switch element 521A → snubber diode 5
Current continues to flow through the 12A path. Further, when the auxiliary switch element 521A is off, the auxiliary reactor 52
The energy stored in 2A is the auxiliary reactor 522
The power is regenerated to the DC power supply 1 through a path of A → regeneration diode 524A → DC power supply 1 → regeneration diode 523A. During the period (10) in which the semiconductor switch elements 5A, 5B, 5C and 5D are off, the electric charge stored in the snubber capacitor 511A is transferred through the path of the snubber capacitor 511A → the auxiliary reactor 522A → the regenerative diode 524A → the DC power supply 1. Discharges and transfers energy to auxiliary reactor 522A. The snubber capacitor 511A is connected to 1 / DC power supply voltage.
After reaching 2, the energy stored in the auxiliary reactor 522A is converted to the auxiliary reactor 522A → the regenerative diode 524A → DC power supply 1 → the regenerative diode 524D → the auxiliary reactor 522D → the snubber diode 512D → the transformer primary winding 21A → the snubber diode The power is regenerated to the DC power supply 1 through the path of 512A. Semiconductor switch element 5B, 5
The snubber circuits 51B, 51C and 51D and the auxiliary circuits 52B, 52C and 52D attached to C and 5D operate in the same manner as described above.

In the above example, the auxiliary switch element 52
The ON periods of 1A, 521B, 521C and 521D are determined by the capacitance of snubber capacitors 511A, 511B, 511C and 511D and the auxiliary reactors 522A and 522.
B, about ４ of the resonance frequency with 522C and 522D
And In this way, the period described with reference to FIGS. 8 to 11 can be made substantially zero, and the conduction loss of the auxiliary switch elements 521A to 521D and the snubber diodes 512A to 512D during this period can be reduced.

[0032]

According to the present invention, the energy stored in the snubber circuit is regenerated to the DC power supply or released to the load, so that almost no loss occurs in the snubber circuit. Further, since the rate of voltage rise at the time of turning off the semiconductor switch element can be reduced, there is obtained an advantage 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.

[Brief description of the 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 modified example of FIG.

FIG. 6 is a circuit diagram showing a fourth embodiment according to the present invention.

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

FIG. 8 is an operation waveform diagram of FIGS. 1 and 2;

9 is an operation waveform diagram of FIG.

FIG. 10 is an operation waveform diagram of FIGS. 4 and 5;

FIG. 11 is an operation waveform diagram of FIGS. 6 and 7;

FIG. 12 is a circuit diagram showing a first conventional example.

FIG. 13 is a circuit diagram showing a second conventional example.

FIG. 14 is a circuit diagram showing a third conventional example.

FIG. 15 is a circuit diagram showing a fourth conventional example.

FIG. 16 is a circuit diagram showing a fifth conventional example.

FIG. 17 is an operation waveform diagram of FIGS.

FIG. 18 is an operation waveform diagram of FIGS. 14, 15, and 16;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Transformer, 21A, 21C ... Transformer primary winding, 21B ... Transformer reset winding, 22 ... Transformer secondary winding, 3 ... Rectifier circuit, 4 ... Smoothing circuit (smoothing filter) , 5A, 5B, 5C, 5D, 7A, 7B ... Semiconductor switch elements, 51A, 51B, 51C, 51D, 53
A, 53B, 53C, 53D, 8 ... snubber circuit, 511
A, 511B, 511C, 511D, 531A, 531
B, 531C, 531D ... snubber capacitor, 512
A, 512B, 512C, 512D ... snubber diodes, 52A, 52B, 52C, 52D ... auxiliary circuits, 52
1A, 521B, 521C, 521D ... auxiliary switches,
522A, 522B, 522C, 522D ... Auxiliary reactors, 523A, 523B, 523C, 523D, 52
4A, 524B, 524C, 524D: Regenerative diode, 532A, 532B, 532C, 532D: Discharge resistance, 6A, 6B: Capacitor, 9A, 9B: Diode.

Claims (6)

[Claims] A first terminal connected in series with one terminal of the first diode and one terminal of the first semiconductor switch element;
A serial arm, a second serial 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 snubber circuit connected in parallel with each other; The terminal of the transformer primary winding on the side where the reset winding is not connected is connected to the series connection point of the first series arm, and the terminal on the side where the primary winding of the transformer reset winding is not connected is connected. A DC power supply is further connected to a series connection point of the second series arm and a connection point of a primary winding and a reset winding of a transformer and a connection point of the first semiconductor switch element and the second diode. In a DC-DC converter having a snubber diode and a snubber capacitor connected in series, a second snubber circuit is connected in parallel with the semiconductor switch element on the side connected to the DC power supply. A series circuit in which a reactor and an auxiliary switch are connected in series is connected in parallel with the snubber diode, and a first regenerative diode is connected in series between the series connection point of the series circuit and the semiconductor switch element on the side not connected to the DC power supply. A DC-DC converter, wherein a second regenerative diode is connected in parallel with the snubber capacitor. 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. , DC-DC power supply connected in parallel with each other, and a transformer primary winding connected between the series connection point of the first series arm and the series connection point of the second series arm. In the conversion device, a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is individually and in parallel with each of the first semiconductor switch element and the second semiconductor switch element, and an auxiliary reactor is provided in each of the snubber diodes. A series circuit with the auxiliary switch connected in series individually and in parallel,
A first regenerative diode is separately provided between a series connection point of the series circuit and a parallel connection point of the first and second series arms, and a second regenerative diode is separately provided for each of the snubber capacitors. A DC-DC converter, wherein the DC-DC converters are connected in parallel. 3. A first series arm in which one terminal of a first semiconductor switch element and one terminal of a second semiconductor switch element are connected in series, and one terminal of a third semiconductor switch element and a second terminal. 4 and a first snubber circuit in parallel with one terminal of one of the semiconductor switch elements of No. 4 and a first snubber circuit, respectively, and one terminal of a transformer primary winding having an intermediate terminal is connected to the first terminal. The other terminal of the primary winding of the transformer is connected to the series connection point of the second arm, and the DC power supply is connected to the intermediate terminal of the transformer, the second semiconductor switch element, A DC-DC converter connected between the parallel connection points of the fourth semiconductor switch element and the fourth semiconductor switch element respectively, wherein the second semiconductor switch element and the fourth semiconductor switch element each have a snubber diode and a snubber converter. And a snubber circuit connected in series with a sensor, and a serial circuit in which an auxiliary reactor and an auxiliary switch are connected in series to each of the snubber diodes individually and in parallel. A first regenerative diode is individually connected between each parallel connection point of the second series arm on which the DC power supply is not connected, and a second regenerative diode is individually and parallelly connected to each of the snubber capacitors. A DC-DC converter, characterized in that: 4. A first series arm in which one terminal of a first semiconductor switch element and one terminal of a second semiconductor switch element are connected in series, a second series arm in which capacitors are connected in series, Connect the DC power supply in parallel with each other,
In a DC-DC converter in which 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, in each of the switching elements, A snubber circuit in which a snubber diode and a snubber capacitor are connected in series is individually and in parallel, and a series circuit in which an auxiliary reactor and an auxiliary switch are connected in series is individually and in parallel in each of the snubber diodes. Wherein a first regenerative diode is individually connected between each of the series connection points of the first series arm and a parallel connection point of the first series arm, and a second regenerative diode is individually and parallelly connected to each of the snubber capacitors. DC-DC converter. 5. A first series arm in which one terminal of a first semiconductor switch element and one terminal of a second semiconductor switch element are connected in series, and one terminal of a third semiconductor switch element and a first series arm. A second series arm in which one terminal of the semiconductor switch element of No. 4 is connected in series and a DC power supply are connected in parallel with each other, and a primary transformer of a transformer is connected to a series connection point of the first series arm and the second arm. A DC-DC converter connected between the serial connection points of the two serial arms, wherein a snubber circuit in which a snubber diode and a snubber capacitor are connected in series is individually and in parallel with each of the semiconductor switch elements; Also, a series circuit in which an auxiliary reactor and an auxiliary switch are connected in series is individually and in parallel with each of the snubber diodes, and a series connection point of the series circuit and the series circuit are connected to each other. A first regenerative diode individually to each of the inter-parallel connection point of the beam, direct current, characterized in that the second regenerative diode respectively connected to individual and parallel to each of said snubber capacitor - DC converter. 6. The apparatus according to claim 1, wherein an on-period of said auxiliary switch element is set to be about １ ／ of a resonance cycle between a capacity of said snubber capacitor and said auxiliary reactor. DC-DC converter.