JPH04285466A - Power converter - Google Patents

Abstract

PURPOSE:To prevent a decrease in an efficiency due to consumption of energy stored in a snubber capacitor by a resistor in a snubber circuit connected to a power conversion semiconductor switching element for constituting a power converter. CONSTITUTION:A capacitor 4 is connected in parallel with a GTO 1, and a series circuit of a GTO 6, a reactor 7 and a pulse transformer 8 is connected in parallel with the capacitor 4. A secondary side of the transformer 8 is connected to a DC circuit 10 through a diode 9. Charge stored in the capacitor 4 at the time of turning off the GTO 1 is discharged by turning on the GTO 6 at the time of turning off the GTO 1. Thus, snubber energy can be transferred to the circuit 10.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion device, and more particularly to a snubber circuit that transfers energy from a snubber circuit connected to a power conversion semiconductor switching element of a main circuit of the device to a DC circuit.

0002

2. Description of the Related Art As a prior art, FIG. 5 shows an example of the configuration of a snubber circuit for a gate turn-off thyristor (hereinafter referred to as GTO).

[0003] A diode 2 is connected in antiparallel to the GTO1. Directly connected diodes 3 capacitors 4 are connected in parallel to GTO1. Further, a resistor 5 is connected in parallel to the diode 3.

[0004] When GTO1 turns off, the G
The current flowing through the TO1 flows through the diode 3 and the capacitor 4 to charge the capacitor 4, and the rate of increase in the voltage across the GTO1 is limited to a certain value or less. At this time, energy is stored in the capacitor 4.

When GTO1 is turned on, the charge in capacitor 4 is discharged through resistor 5 and GTO1, and the main current flows through GTO1. Then, the voltage across the capacitor 4 becomes approximately 0V. At this time, capacitor 4
The energy stored in the resistor 5 is consumed by the resistor 5.

[0006]

In the conventional snubber circuit as described above, all the energy of the capacitor 4 is consumed by the resistor 5.

[0007] This resistance loss is proportional to the square of the voltage applied to the GTO 1 and proportional to the number of interruptions (switching frequency). Therefore, as the voltage cut off by GTO1 increases and the switching frequency increases,
The energy consumed by resistor 5 also increases. As described above, there is a problem in that the efficiency of the entire power conversion device is reduced.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the problem of consuming energy stored in a snubber capacitor in a resistor in a snubber circuit of series-connected or parallel-connected power conversion semiconductor switching elements constituting a power conversion device. The present invention provides a power conversion device equipped with a snubber circuit that can be used effectively without any problems. [Structure of the invention]

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention is composed of a capacitor, a semiconductor switching element, a reactor, a pulse transformer, and a diode.

0010

[Operation] The charge in the snubber capacitor is converted into a pulse current by turning on the semiconductor switching element, and is transferred as a pulse current to the DC circuit connected to the secondary side of the pulse transformer via a diode.

[0011]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings.

FIG. 1 shows a first embodiment, in which GT
A diode 2 is connected in antiparallel to O1. GT
The anode of O1 is further connected to the anode of diode 3. The cathode of diode 3 is capacitor 4
connected to one end of the The other end of capacitor 4 is GT
Connected to the cathode of O1. The cathode of the diode 3 is further connected to the anode of the second GTO 6. This GTO6 cathode is connected to one end of the reactor 7. The other end of the reactor 7 is connected to one end of the primary winding of a pulse transformer 8. The other end of the primary winding of the pulse transformer 8 is connected to the other end of the capacitor 4, GTO1.
connected to the cathode of One end of the secondary winding of the pulse transformer 8 is connected to the anode of a diode 9, and the cathode of the diode 9 is connected to the positive electrode side of the DC circuit 10. The other end of the secondary winding of the pulse transformer 8 is connected to the negative electrode side of the DC circuit 10. The snubber circuit 11 includes a diode 3, a capacitor 4, a GTO 6, a reactor 7, a pulse transformer 8, and a diode 9.

An arm circuit 12 is composed of the GTO 1, the diode 2, the snubber circuit 11, and the DC circuit 10. Two arm circuits 12 are connected in series and inserted between PN, which is a DC power source, and an alternating current terminal (AC) is provided between the connections of each arm circuit 12. In this way, a half bridge of the power conversion device is configured.

The operation of this embodiment will be explained below. G.T.O.
When GTO 1 turns off, the current that had been flowing through GTO 1 flows through diode 3 and capacitor 4, charging capacitor 4. In this way, the rate of voltage increase across the GTO1 is limited to a certain value or less. At this time, capacitor 4
can store energy.

When GTO6 of the snubber circuit 11 is turned on during the turn-on period of GTO1, capacitor 4 and GTO6
, a reactor 7, and a pulse transformer 8 form a resonant circuit. Therefore, the charge in capacitor 4 is discharged,
A current flows through the reactor 7, and the energy stored in the capacitor 4 is transferred to the reactor 7. At this time, while the voltage of capacitor 4 is positive, the current flows between capacitor 4 and GT
It flows through the loop of the primary winding of O6, reactor 7, and pulse transformer 8, but when the voltage of capacitor 4 drops below OV, it flows through the loop of capacitor 4, diode 2, and diode 3. In this way, the voltage of capacitor 4 is approximately 0V.
It decreases to a constant value. The energy of reactor 7 is
The current becomes a pulsed current and is transferred from the secondary side of the pulse transformer 8 to the DC circuit 10 via the diode 9. Note that the discharge of the charge in the capacitor 4 is completed during the turn-on period of the GTO 6, and also during the turn-on period of the GTO 6, the capacitor 4, the reactor 7, and the pulse transformer 8.
Set constants for .

Since the snubber energy of the capacitor 4 needs to be transferred at high speed, the inductance of the reactor 7 may be small, and the reactor 7 can be made smaller. The pulse transformer 8 may also be small. Therefore, according to this embodiment, a small, lightweight, and inexpensive snubber circuit can be constructed. Further, since the pulse transformer 8 provides insulation, the GTO 1 and the DC circuit path 10 are electrically disconnected. Therefore, the configuration of the GTO 1 and the configuration of the DC circuit 10 can be determined independently. Moreover, energy can be regularly supplied to the DC circuit 10 which is a load. FIG. 2 shows a second embodiment of the invention. The snubber circuit 11 in the figure has the same configuration as in FIG.

[0017] n GTO1s are connected in series. n
A diode 2 is connected in antiparallel to each of the GTOs 1. Furthermore, a snubber circuit 11 is connected to each GTO 1. Each snubber circuit 1
1 is connected in series to the DC circuit 10 in such a way that one end of the secondary side of the pulse transformer 8 is connected to the cathode of the diode 9 of the snubber circuit 11 at the next stage.

[0018] n series-connected GTO1, each GTO
An arm circuit 13 is constituted by a diode 2 connected to the diode 2, a snubber circuit 11, and a DC circuit 10. Two arm circuits 13 are connected in series and inserted between PN, and the connection between the two arm circuits 13 becomes an AC side terminal.

GTO 6 of snubber circuit 11 is fired during the ON period of GTO 1 connected to snubber circuit 11 . Furthermore, the GTOs 6 of the snubber circuits 11 in the same arm circuit 13 are fired at the same timing. The way in which energy is transferred by the capacitor 4 is similar to that of the previous embodiment.

According to this embodiment, the present invention can be applied to the GTOs 1 connected in series within the arm circuit 13. In addition, in this embodiment, the DC circuit 10 is
It is not necessary that each arm circuit 13 be independent, and the DC circuit 10 portions of two arm circuits 13 may be connected in parallel to be common. FIG. 3 shows a third embodiment of the present invention, in which snubber circuits 11 are connected in parallel. Note that the snubber circuit 11 in the figure has the same configuration as the first embodiment.

[0021] n GTO1s are connected in series, and a diode 2 is connected antiparallel to each GTO1. A snubber circuit 11 is connected to each GTO 1. The cathodes of the diodes 9 of each snubber circuit 11 are connected to the positive electrode side of the DC circuit 10, and the other ends of the pulse transformer 8 to which the diodes 9 are not connected are respectively connected to the negative electrode side of the DC circuit 10. In this way, each snubber circuit 11 is connected in parallel and connected to the DC circuit 10.

GTO 6 of snubber circuit 11 is fired during the on period of GTO 1 to which it is connected. Furthermore, when the snubber circuits 11 are connected in parallel, the GTOs 6 of each snubber circuit 11 do not need to be fired at the same time. Note that this embodiment can be applied even when the GTOs 1 are connected in parallel. FIG. 4 shows a fourth embodiment of the present invention, and is an example in which the energy of each snubber circuit 11 is regenerated to the DC power supply to which the GTO 1 is connected.

The cathode of the diode 9 in the snubber circuit 11 is connected to the positive electrode side of the DC power supply. One end of the pulse transformer 8 that is not connected to the diode 9 is connected to the negative electrode side of the DC power supply. The way in which energy is transferred by the capacitor 4 is the same as in the first embodiment. According to this embodiment, since snubber energy is regenerated into the DC power supply, it is possible to provide an efficient power conversion device without resistance loss.

[0024]

As explained above, the present invention can be applied regardless of the configuration of the semiconductor switching element for power conversion, and the snubber energy can be transferred and used, thereby providing an efficient power conversion device. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a main circuit diagram of a power conversion device showing a first embodiment according to the present invention.

FIG. 2 is a main circuit diagram of a power conversion device showing a second embodiment of the present invention.

FIG. 3 is a main circuit diagram of a power conversion device showing a third embodiment of the present invention.

FIG. 4 is a main circuit diagram of a power conversion device showing a fourth embodiment according to the present invention.

FIG. 5 is a main circuit diagram of a conventional power conversion device.

[Explanation of symbols]

1,6...GTO
2, 3, 9...Diode 4...Capacitor
5...Resistor 7...Reactor
8...Pulse transformer 10...DC circuit
11... Snubber circuit 12, 13... Arm circuit

Claims (1)

[Claims] 1. A power conversion device having a converter configured with a semiconductor switching element for power conversion, comprising: a snubber capacitor connected in parallel to the semiconductor switching element for power conversion; and a snubber energy capacitor connected in parallel to the snubber capacitor. It has a series circuit in which a semiconductor switching element for transfer, a reactor, and the primary side of a pulse transformer are connected in series, and a DC circuit connected to the secondary side of the pulse transformer of this series circuit via a diode. A power conversion device characterized in that it turns on and transfers the energy of a snubber capacitor to this DC circuit.