JPS63213411A - Snubber circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Purpose of the invention (Industrial field of application) The purpose of the invention is to provide a circuit (called a snubber circuit) for mitigating overvoltage and dv/dt irradiation applied to semiconductor elements in power converters. ).

(Prior art) In a power conversion device that uses semiconductor elements, a snubber circuit is always provided to prevent the semiconductor elements from being destroyed by overvoltage applied to the semiconductor elements or voltage with a rapid start-up voltage (hereinafter referred to as dv/dt). . FIG. 1 shows a conventionally used snubber circuit 1, and its operation will be explained with reference to FIG. 2 to which this circuit is applied. FIG. 2 shows an inverter using a dirt turn or thyristor (hereinafter referred to as GTO).

In the figure, 1 is the snubber circuit, which has a capacitor 11 and a diode 12.
and a resistor 13. 21 and 22 are GTOs, and j3 and 24 are diodes connected in antiparallel with the GTO.

25 is a load, and 26 and 27 are each an E/2 DC power source. The basic operation in Figure 2 is that GTO 2J and 22 alternately turn on and off, thereby causing the load 25
An alternating current is applied to the GTOJ J is on, GTO22
is off and current is flowing through load 25,
Figure 3 shows the waveform at the moment GTOJJ is turned off. GT
When a current of 1 gt is passed in the opposite direction between the dirt cathode of O, it is turned off and a voltage V is applied between the anode and cathode as shown.

(The problem to be solved by the invention is that VD in FIG. 3 is GTO,
and the anode current just before turn-off, i.e. the load current■
Determined by the size of -174 The larger the size, the higher the maD.

Also, Ma is the floating inductance Ls of the closed circuit of the power supply 26, GTO 21 and the load 25, the closed circuit of the power supply 27, the diode 22 and the load 25, the floating ai resistance Rs, and the capacitor 11.
Cano J? The capacitance C1 depends on the load current ■, and the larger t8 and I are, or the smaller C is, the smaller v is. G.T.O.
In addition, it is desirable that both D='P and D='P be small, and if Vp is high, a GTO with a high withstand voltage must be used. However, if C of capacitor 11 is increased in order to lower M, GTO21
-C(v -E J2+'-C
Most of the energy 2P 2 of 12 is consumed by the resistor 13. Here E is power supply 2
It is the sum of the voltages of 6 and 22. For example, if the frequency f is 1
000 Hz * C=21'F r vp =400
When V*E=200 V, it becomes SOW.

This causes a decrease in the efficiency of the device, and the external shape of the resistor becomes large, causing heat generation, which hinders miniaturization of the device.

An object of the present invention is to provide a snubber circuit that can improve the efficiency and downsize the device by reusing a portion of the energy of the capacitor.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention provides a power converter comprising a capacitor and a diode connected in the charging direction of the capacitor, between positive and negative DC buses constituting a power converter. In a snubber circuit connected in parallel to each of a pair of semiconductor elements connected in series, a transformer is provided in parallel to each diode of the snubber circuit, and when the capacitor is discharged, The energy of the capacitor is regenerated to the power source.

(Function) The present invention improves the efficiency of the device by several orders of magnitude by reusing the energy of the capacitor in the snubber circuit, and also enables high-density packaging by reducing the number of heat generating parts. , it becomes possible to downsize the device.

(Embodiment) FIG. 4(,)(b) is a block diagram of the snubber circuit of the present invention, and its operation will be explained using the circuit of FIG. 5 to which the snubber circuit is applied.

FIG. 5 is a configuration diagram showing one embodiment of the present invention.

The same parts as in FIG. 2 are given the same reference numerals, and their explanations will be omitted.

In Figure 5, 11a and 11b are capacitors, 12g
and 12b are diodes, 14a and 14b are transformers, 15
m and 15b are reactors or resistors (hereinafter referred to as impedance elements), and 16a and 16b are diodes.

When GTO21 is on and GTO22 is off, capacitor 11*O@, the load is 0, and capacitor Jlb is charged to E. Load current IL is from power supply 26 to GTO
It flows in a loop of 21→load 25. GT in this state
A negative signal is applied to the dunit of the O21 to turn off the GTO21't-, and a positive signal tm is applied to the dirt of the GTO22 to turn on the GTO22. As a result, the potential at the U point becomes -E/2 with respect to the 0 point.

If the load 25 is a pure resistance, the load current IL flows through the GTO 22, and if it is an inductive load, the load current IL does not change instantaneously, so the load current IL flows through the power supply 2 through the diode 24.
A loop is formed in which the load current IL flows. Immediately after the GTO21 is turned off, the capacitor lla is photovolted to Vp as shown in Fig. 3, but since the potential difference between the two points and the U point is E, the voltage of M and -H is applied to the diode 12& as a reverse voltage. The diode 12m is turned off. After this, until the voltage of capacitor l1m becomes E, transformer 14
The manner in which the capacitor energy is regenerated to the power supply 26 and 27 by advancing each of the primary winding and the secondary winding of & will be explained.

The secondary winding of the transformer 24a, whose primary winding is connected in parallel with the diode 12& with the polarity shown, has n (vp −E
) is induced. Here, n is the ratio of the secondary winding to the primary winding of the transformer 14a. If this voltage is higher than E, diode 16h is turned on and transformer J4JL's 2
A t current flows through the next winding. Impedance element 25a limits this current. During this period, the energy in the capacitor lla is regenerated to the power supply 26.27 via the primary and secondary windings of the transformer 14a, but the voltage of the primary winding of the transformer 14a is below [/n When this happens, the diode 16th turns off and regeneration to the power source 26, 27 via the secondary winding stops. Strictly speaking, regeneration stops at a value lower than E/n due to the effect of the impedance element 15a or the impedance inductance of the transformer 14a.

After this, the energy difference until the capacitor voltage reaches EVC4 is temporarily stored as excitation energy of the transformer 14h, and then consumed in the closed circuit of the transformer 14h and the diodes J and 2a.

Next, when the GTO 22 is turned on, the energy of the capacitor llb is regenerated to the power supply 26, 27, and the filtration 8 will be described. GTO with capacitor llb charged to E
22 is turned on, the voltage E is applied to the primary winding of the transformer 14b with the polarity where the marked side is positive.
ng is induced in the secondary winding of 4b, and the diode 16b
turns on.

A voltage of (n-1)E is applied to both ends of the impedance element 15b. If the impedance of the impedance element 15b is 2, a current of (n-1)E/Z flows into the transformer secondary winding. Thus, the energy in the capacitor 11b is transferred to the power supply via the transformer 14b, but the transformer Job
When the secondary voltage becomes lower than E, the diode 16b turns off and regeneration stops. If the impedance element 15b is a reactor, the function of the reactor will cause the transformer 14 to
Even if the secondary voltage of b is lower than E, the current 'fc will continue to flow, but it will eventually become O. At this time, capacitor 11b
tlC The remaining charge is transferred from capacitor llb to transformer 14 b
After being discharged in the loop of 4GTO22 and becoming 0, the excitation energy stored in the transformer 14b is transferred to the diode 12.
b and is consumed within the transformer 14b.

Even in the process where GTO22 turns off and GTO21 turns on, the respective capacitors lla and ll
Most of the energy in b can be returned to the power supply. The regeneration rate according to experiments is between 55 and 70, but it is possible to further increase the roundworm rate if the constants are selected appropriately.

[Effects of the Invention] The effects obtained by the present invention can be summarized as follows.

(a) By reusing the energy of the capacitor in the snubber circuit, the efficiency of the device can be improved by several orders of magnitude. ←) By reducing the number of heat generating parts, high-density packaging is possible, making it possible to downsize the device. This is what happened.

[Brief explanation of the drawing]

Figure 1 is a conventional snubber circuit, Figure 2 is a circuit using the circuit in Figure 1, Figure 3 is a waveform diagram showing the relationship between the GTO anode voltage and off-r-1 current, which is the second cause. Figure 4 (a)
(b) is a different configuration diagram of the snubber circuit of the present invention,
FIG. 85 is a diagram showing an embodiment of the snubber circuit of the present invention. 1... Snubber circuit, 11. Ila, llb...Capacitor, 12.12m, 12b...Diode, JJ
---Resistance, 14m, 14b...Transformer, 15a. 15b...Reactor or resistance, 21.22...G
TO123, 24...Diode, 25...Load,
26°27...Power supply. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 'Figure 5

Claims (1)

[Claims] In a snubber circuit, which is composed of a capacitor and a diode connected in the charging direction of the capacitor, and is connected in parallel to each of a pair of semiconductor elements connected in series between positive and negative DC buses constituting a power converter, each of the snubber circuits A snubber circuit characterized in that a transformer is provided in parallel to the diode, and when the capacitor is discharged, energy of the capacitor is regenerated to a power source via a secondary winding of the transformer.