JPH06209580A - Snubber energy recovery circuit of power converter - Google Patents

Abstract

PURPOSE:To regenerate energy at a power supply and to improve device effi ciency by connecting an energy absorption circuit to a snubber diode in parallel and then connecting the energy absorption circuit to a circuit with a polarity which is opposite to that where the energy absorption circuit belongs to via another energy absorption circuit. CONSTITUTION:A positive pole side energy absorption circuit 31 is connected to a snubber diode 8D in parallel. When an IGBT 4T is turned on, electric charge of a snubber capacitor 8C is discharged and accumulation energy is shifted to an auxiliary capacitor 31C. Then, when an IGBT 6T is turned on, electric charge of the auxiliary capacitor 31C is discharged, current flowing through a regeneration reactor 34 increases, and then electric charge of the auxiliary capacitor 31C decreases. Then, current flowing through the regeneration reactor 34L flows along a path, namely the regeneration reactor 34L a regeneration diode 34D an auxiliary reactor 31L an auxiliary capacitor 31C a feedback diode 4D an anode side suppression reactor 3 a DC power supply 2 and then is regenerated at the DC power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber energy recovery circuit of a power conversion device for recovering switching loss generated when power conversion is performed by turning on / off a semiconductor switching element.

[0002]

2. Description of the Related Art It is well known that power conversion can be performed by forming a power conversion device with semiconductor switching elements and turning the semiconductor switching elements on and off. Hereinafter, the present invention will be described in detail by taking an inverter that converts DC power into AC power as an example of the power converter.

FIG. 2 is a circuit diagram showing a first conventional example for one phase of an inverter. In FIG. 2, an insulated gate bipolar transistor (abbreviated as IGBT hereinafter) 4T as a semiconductor switching element and a feedback diode 4D are connected in antiparallel to form a positive-side semiconductor switch 4, and the IGBT 6T and the feedback diode 6D are connected to each other. The negative side semiconductor switch 6 is formed by connecting in antiparallel and the positive side semiconductor switch 4 and the negative side semiconductor switch 6 are connected in series and connected between the positive and negative sides of the DC power supply 2. In this state, if the IGBT 4T and the IGBT 6T are alternately turned on and off, the DC power from the DC power supply 2 can be converted into AC power and taken out from the AC terminal 7.

When a current waveform and a voltage waveform have an overlapping period when the semiconductor switching element is turned on or off (an overlapping period is a period during which a current flows while a voltage is applied), a transient power loss (so-called switching loss) Occurs. Even if the amount of this switching loss per time is small, the generated loss per unit time cannot be ignored in a power converter having a high switching frequency such as a pulse width modulation control inverter. That is, it is a wasteful waste of energy, and there arises inconveniences such as a reduction in the efficiency of the apparatus and an additional facility for processing the generated heat.
Therefore, an inductance and a capacitor are inserted in the device to reduce the above-mentioned overlap period. That is, the positive electrode side suppression reactor 3 is inserted between the DC power source 2 and the positive electrode side semiconductor switch 4, and the negative electrode side suppression reactor 5 is inserted between the DC power source 2 and the negative electrode side semiconductor switch 6 so that I
The increase rate of the current flowing into the GBT is suppressed to reduce the switching loss. Further, a positive side snubber circuit 8 is connected to the positive side semiconductor switch 4 in parallel, and a negative side snubber circuit 9 is connected to the negative side semiconductor switch 6 in parallel.
The switching loss is reduced by mitigating the rate of increase in the voltage applied to the IGBT when it is turned off.

The snubber circuit 8 on the positive electrode side is a snubber capacitor 8
C, a snubber diode 8D, and a snubber resistor 8R, and the negative side snubber circuit 9 is also a snubber capacitor 9C.
Since it is composed of the snubber diode 9D and the snubber resistor 9R, the energy stored in the suppression reactor when the IGBT is turned off is absorbed in each snubber capacitor. The energy absorbed by the snubber capacitor is released to the snubber resistor and consumed when the IGBTs next turn on. That is, the energy absorbed by the snubber capacitor is dissipated as heat. Therefore, in order to recover and reuse this energy, the circuits shown in FIGS. 3 and 4 below have been proposed.

FIG. 3 is a circuit diagram showing a second conventional example for one phase of the inverter. The second conventional circuit shown in FIG. 3 is a circuit described in Japanese Patent Application Laid-Open No. 61-210875, which includes a DC power supply 2, a positive electrode side suppression reactor 3, a positive electrode side semiconductor switch 4, and a negative electrode side suppression reactor. 5, the names, applications and functions of the negative electrode side semiconductor switch 6 and the AC terminal 7 are the same as in the case of the first conventional example circuit described in FIG.
These explanations are omitted.

In the second conventional example circuit shown in FIG. 3, a positive side snubber circuit 11 composed of a snubber capacitor 8C and a snubber diode 8D is connected in parallel to the positive side semiconductor switch 4, and the snubber capacitor 8C and the snubber diode 8D are connected.
The connecting point of the and the auxiliary DC power supply 15 on the positive electrode side are connected via the diode 12, the reactor 13, and the wiring inductance 14. With such a circuit configuration, the IG
The energy stored in the snubber capacitor 8C when the BT4T turns off is the snubber capacitor 8C → diode 12 → reactor 13 → wiring inductance 14 → positive side auxiliary DC power supply 15 → positive side suppression reactor 3 when the IGBT 4T next turns on. → IGBT4T →
Auxiliary DC power supply 15 on the positive electrode side via the snubber capacitor 8C
As it is regenerated, it becomes possible to reuse this energy. Negative side snubber 21, diode 22, reactor 2 connected in parallel to the negative side semiconductor switch 6.
The operations of the wiring inductance 24 and the negative side auxiliary DC power supply 25 are the same as described above. Furthermore, overvoltage absorption circuit 2
Although 0 is provided to absorb the overvoltage of the circuit and regenerate this energy to the positive electrode side auxiliary DC power supply 15, detailed description of these operations is omitted.

FIG. 4 is a circuit diagram showing a third conventional example for one phase of the inverter. The third conventional circuit shown in FIG. 4 is a circuit described in Japanese Patent Application Laid-Open No. 3-256569, and includes a DC power supply 2, a positive electrode side suppression reactor 3, a positive electrode side semiconductor switch 4, and a negative electrode side suppression reactor 5. The names, uses, and functions of the negative side semiconductor switch 6 and the AC terminal 7 are the same as those in the first conventional example circuit described above in FIG. 2, and the positive side snubber circuit 11, the diode 12, the reactor 13, the negative side. The names, applications, and functions of the snubber circuit 21, the diode 22, and the reactor 23 are the same as those in the case of the second conventional example circuit described above with reference to FIG.

In the third conventional circuit shown in FIG. 4, the energy stored in the snubber capacitor 8C is transferred to the diode 1
2, via the reactor 13, the diode 16, and the capacitor 17, the positive chopper 18 is provided. The positive electrode side chopper 18 converts this input energy into a desired DC voltage and returns it to the DC power supply 2. The negative electrode side chopper 28 also inputs the energy accumulated in the snubber capacitor 9C forming the negative electrode side snubber circuit 21 through the diode 22, the reactor 23, the diode 26 and the capacitor 27, and inputs this input energy into a desired direct current. Although it is converted into a voltage and returned to the DC power supply 2, detailed description of these operations is omitted.

[0010]

As shown in the first conventional example circuit of FIG. 2, a positive side snubber circuit 8 is connected in parallel to the positive side semiconductor switch 4 and a negative side is connected to the negative side semiconductor switch 6. By connecting the snubber circuit 9 in parallel, the increase rate of the voltage applied to the semiconductor switch when the semiconductor switch is turned off is moderated, and the increase rate of the current when the semiconductor switch is turned on is stored in the inductance. The energy stored in the snubber capacitor is transferred to the snubber capacitor, but conventionally, the energy stored in the snubber capacitor was wasted by the snubber resistor. In order to eliminate this useless waste of energy and recover it to the power supply,
The second conventional example circuit and the third conventional example circuit shown in FIG. 4 have been proposed. Although these conventional circuits have the effect of recovering energy, an auxiliary DC power supply and a chopper must be provided for recovering this energy. Although these auxiliary DC power supplies and choppers are not shown in the figure, since devices for controlling these are attached, the number of parts is large and the circuits are complicated, making the entire device large and expensive, and making it reliable. There is a defect that the property is lowered.

Therefore, an object of the present invention is to enable energy recovered by the snubber circuit when the power converter operates to be regenerated to a power source with a simple circuit configuration.

[0012]

In order to achieve the above object, the snubber energy recovery circuit of the power converter of the present invention has a snubber circuit composed of a series circuit of a snubber capacitor and a snubber diode connected in parallel. A plurality of semiconductor switching elements are connected in series and connected between positive and negative electrodes of a DC power supply, and in the power conversion device for performing power conversion by ON / OFF operation of the semiconductor switching element, an auxiliary diode is provided for each of the snubber diodes. An energy absorption circuit composed of a series connection of an auxiliary reactor and an auxiliary capacitor is separately connected in parallel, and any connection point of the energy absorption circuit belonging to the positive side of the DC power supply and the negative side of the DC power supply. A first energy recovery circuit composed of a first regenerative diode and a first regenerative reactor connected in series between A second regenerative diode and a second regenerative reactor are connected in series between an arbitrary connection point of the energy absorbing circuit that is connected to the negative side of the DC power source and the positive side of the DC power source. It shall be connected through the second energy recovery circuit configured by the connection.

[0013]

According to the present invention, when a plurality of semiconductor switches are connected in series and connected to a power source for power conversion, a separate snubber circuit is connected in parallel to each semiconductor switch.
An energy absorption circuit is connected in parallel to the snubber diode, which is a constituent element of this snubber circuit, and this energy absorption circuit is composed of an auxiliary capacitor, an auxiliary diode, and an auxiliary reactor connected in series. If this energy absorption circuit belongs to the positive side of the DC power supply, the connection point of any of the constituent elements of this positive side energy absorption circuit and the negative side of the DC power supply are connected via the first energy recovery circuit. To do. Here, the first energy recovery circuit is configured by connecting a regenerative diode and a regenerative reactor in series. Similarly, in the energy absorption circuit belonging to the negative side of the DC power supply, any connection point where the constituent elements are connected in series is connected to the positive side of the DC power supply via the second energy recovery circuit.

Taking the snubber circuit on the positive electrode side as an example, the energy stored in the snubber capacitor on the positive electrode side when the semiconductor switch on the positive electrode side is turned off is stored in the auxiliary capacitor which constitutes an energy absorption circuit on the positive electrode side when the semiconductor switch on the positive electrode side is turned on. To the first energy recovery circuit because the energy stored in the positive side auxiliary capacitor is discharged to the first energy recovery circuit when the negative side semiconductor switch is turned on.
The current flowing to the regenerative reactor that constitutes the energy recovery circuit increases. When the negative side semiconductor switch is turned off in this state, the current flowing in the regenerative reactor of the first energy recovery circuit flows into the DC power supply via the feedback diode forming the positive side semiconductor switch. That is, electric power is regenerated. The snubber circuit on the negative electrode side also regenerates the energy stored in the snubber capacitor to the DC power supply by the same operation.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing an embodiment of the present invention. The DC power supply 2, the positive side suppression reactor 3, the positive side semiconductor switch 4, the negative side suppression shown in the embodiment of FIG. The names, applications, and functions of the reactor 5, the negative-side semiconductor switch 6, the alternating-current terminal 7, the positive-side snubber circuit 8, and the negative-side snubber circuit 9 are already described in the conventional circuit illustrated in FIG. 2, FIG. 3, or FIG. Therefore, these explanations are omitted.

In the present invention, the snubber diode 8D constituting the positive side snubber circuit 11 is connected in parallel with the positive side energy absorbing circuit 31. The positive side energy absorbing circuit 31 is composed of the auxiliary capacitor 31C and the auxiliary diode. 31D and auxiliary reactor 31L are connected in series. Further, the auxiliary capacitor 31C and the auxiliary reactor 3
The connection point with 1L (the connection point between the auxiliary reactor 31L and the auxiliary capacitor 31C may be acceptable) and the negative electrode side of the DC power supply 2 are connected via the first energy recovery circuit 34. The first energy recovery circuit 34 is a series connection circuit of a regenerative diode 34D and a regenerative reactor 34L. Similarly, the snubber diode 9D forming the negative side snubber circuit 21 is connected in parallel with the negative side energy absorbing circuit 33. The negative side energy absorbing circuit 33 is an auxiliary capacitor 33C and an auxiliary diode 33.
It is configured by connecting D and the auxiliary reactor 33L in series. Furthermore, the auxiliary capacitor 33C and the auxiliary reactor 33L
Connection point with (auxiliary reactor 33L and auxiliary capacitor 3
3C and the positive electrode side of the DC power supply 2 are connected via the second energy recovery circuit 32. The second energy recovery circuit 32 is connected to the regenerative diode 32D and the regenerative reactor. It is configured by serial connection with 32L.

In this circuit, the positive side snubber circuit 11
The operation of how the energy stored in is regenerated will be described below. When the IGBT 4T forming the positive electrode side semiconductor switch 4 is turned off, the energy stored in the positive electrode side suppression reactor 3 is stored in the snubber capacitor 8C.
Moved to already mentioned. In the present invention, since the positive side energy absorption circuit 31 is connected in parallel to the snubber diode 8D, when the IGBT 4T is turned on next, the snubber capacitor 8C → IGBT4T → auxiliary capacitor 31C → auxiliary reactor 31L → auxiliary diode 3
Since the electric charge of the snubber capacitor 8C is discharged through the path of 1D → snubber capacitor 8C, the energy stored in the snubber capacitor 8C is transferred to the auxiliary capacitor 31C. When the IGBT 6T forming the negative side semiconductor switch 6 is turned on, the auxiliary capacitor 31C → IGBT6T is turned on.
→ Negative electrode side suppression reactor 5 → Regenerative reactor 34L → Regenerative diode 34D → Auxiliary reactor 31L → Auxiliary capacitor 31C is discharged along the path of auxiliary capacitor 31C, and the current flowing through regenerative reactor 34L increases,
The charge of the auxiliary capacitor 31C decreases.

Next, when the IGBT 6T is turned off, the current flowing through the regenerative reactor 34L is regenerative reactor 34L → regenerative diode 34D → auxiliary reactor 31.
L → Auxiliary capacitor 31C → Feedback diode 4D → Positive-side suppression reactor 3 → Reproduced to the DC power source 2 by flowing through the path of the DC power source 2, the current of the regenerative reactor 34L decreases, and the charge of the auxiliary capacitor 31C further decreases. . By repeating this operation, snubber capacitor 8
The energy stored in C can be regenerated to the DC power supply 2.

The energy stored in the snubber capacitor 9C of the negative side snubber circuit 21 connected in parallel to the negative side semiconductor switch 6 is also stored in the auxiliary capacitor 33C constituting the negative side energy absorbing circuit 33 by the same operation. Then, it is regenerated to the DC power supply 2 through the second energy recovery circuit 32 and the feedback diode 6D in conjunction with the ON / OFF operation of the IGBT 4T.

[0020]

When a plurality of semiconductor switches are connected in series and connected to a power source for power conversion, a separate snubber circuit is connected in parallel to each semiconductor switch. According to this invention, an energy absorption circuit is connected in parallel to the snubber diode which is a constituent element of this snubber circuit, and a circuit having a polarity opposite to the polarity to which this energy absorption circuit belongs is connected via an energy recovery circuit. Since it has a circuit configuration that turns on and off the semiconductor switches on the positive and negative sides
The energy stored in the snubber capacitor moves to the energy absorption circuit with the off operation, and is then regenerated to the power supply via the energy recovery circuit, so that energy is not wasted and the efficiency of the device is improved. However, heat generation can be avoided. Since both the energy absorption circuit and the energy recovery circuit are composed of only a capacitor, a diode and a reactor, the circuit is much simpler than the conventional energy recovery device, it is small and lightweight and there is no fear of failure. It also has the effect of improving reliability.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first conventional example of one phase of an inverter.

FIG. 3 is a circuit diagram showing a second conventional example for one phase of an inverter.

FIG. 4 is a circuit diagram showing a third conventional example for one phase of an inverter.

[Explanation of symbols]

2 DC power supply 3 Positive side suppression reactor 4 Positive side semiconductor switch 4D. 6D Feedback diode 4T. IGB as a 6T semiconductor switching element
T 5 Negative side suppression reactor 6 Negative side semiconductor switch 7 AC terminal 8, 11 Positive side snubber circuit 8C. 9C snubber capacitor 8D. 9D snubber diode 8R. 9R Snubber resistance 9,21 Negative side snubber circuit 15 Positive side auxiliary DC power supply 18 Positive side chopper 25 Negative side auxiliary DC power supply 28 Negative side chopper 31 Positive side energy absorption circuit 31C. 33C Auxiliary capacitor 31D. 33D Auxiliary diode 31L. 33L Auxiliary reactor 32 Second energy recovery circuit 32D. 34D regenerative diode 32L. 34L Regenerative reactor 33 Negative side energy absorption circuit 34 First energy recovery circuit

Claims (1)

[Claims] 1. A semiconductor switching device comprising a series circuit of a snubber capacitor and a snubber diode, the snubber circuit being connected in parallel, the plurality of semiconductor switching elements being connected in series and connected between the positive and negative poles of a DC power source, the semiconductor switching In a power converter that performs power conversion by on / off operation of an element, an energy absorption circuit configured by a series connection of an auxiliary diode, an auxiliary reactor, and an auxiliary capacitor is separately connected in parallel to each of the snubber diodes, and First energy constituted by a series connection of a first regenerative diode and a first regenerative reactor between an arbitrary connection point of the energy absorption circuit belonging to the positive side of the DC power source and the negative side of the DC power source. A recovery circuit is connected, and any connection point of the energy absorption circuit belonging to the negative side of the DC power source and the direct connection A snubber energy recovery circuit for a power conversion device, characterized in that the snubber energy recovery circuit is connected to a positive side of a current source via a second energy recovery circuit configured by a second regenerative diode and a second regenerative reactor connected in series. .