JPS61161018A - Displacement current compensating device of electrostatic induction thyristor - Google Patents

Abstract

PURPOSE:To prevent a gate reverse bias voltage from being decreased by detecting a reverse recovery current of a snubber diode by a transformer and applying a voltage generated based on the output between the gate and cathode of an electrostatic induction thyristor. CONSTITUTION:When an SI thyristor 1 is turned off, a main current is commutated in a snubber circuit, a diode 6 is conducted and a voltage of a capacitor 8 is increased. Since a transformer 15 and a reactor 16 are provided, when a charging current of the capacitor 8 flows to the diode 6, a current flows to the secondary side of the transformer 15 in a path of transformer 15 reactor 16 transformer 15. A voltage EC generated across the reactor 16 is applied between the gate and cathode of the SI thyristor 1 via a diode 17 in a direction the same as the reverse bias voltage. Thus, the reverse bias is not decreased to the voltage EC or below.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to gate driving of an electrostatic induction thyristor, and in particular to an electrostatic induction thyristor that eliminates defects caused by displacement current generated during reverse recovery of a snubber diode. This invention relates to a displacement current compensator.

[Prior art and its problems]

An electrostatic induction thyristor (hereinafter referred to as an 8I thyristor) is a thyristor capable of high-power, high-speed switching, and has a self-extinguishing function like a gate turn-off thyristor. When controlling this 8I thyristor with a gate signal, one of the features of the 8I thyristor is that the forward blocking voltage is determined by the value of the reverse bias voltage applied between the gate and cathode of the device. This requires different attention than when controlling. Next, the basic method of driving the S ethyristor will be explained using FIG.

FIG. 3 shows an example of the configuration of a DC switch circuit using an 8I thyristor for opening and closing an inductance load, where 1 is an 8I thyristor, 2 is a main power supply, and 3 is a load.

Here, a load 3 and an 8I thyristor l are connected in series to the main power supply 2. However, 4 indicates the inductance of the wiring, and 5 indicates the freewheel diode.

In addition, 6 is a diode, 7 is a resistor, and 8 is a capacitor. By a series circuit consisting of a diode 6 and a capacitor 8 with a resistor 7 connected in parallel, the series circuit is connected in parallel to an 8I thyristor 1 to form an SI thyristor. 1 snubber circuit is formed.

Furthermore, a resistor 9. is connected between the gate and cathode of the SI thyristor 1. An auxiliary power supply 11 is connected to supply a forward current to the gate via a switch 10, and an auxiliary power supply 13 is connected to supply a reverse current to the gate via a switch 12. However, 14 indicates the impedance of the wiring.

In order to operate the 8I thyristor 1 in the DC switch circuit having such a connection configuration, the following steps are performed.

That is, to keep the SI thyristor 1 in the blocked state, the switch 10 is turned off and the switch 12 is turned on to apply a reverse bias voltage to the gate of the SI thyristor 1. Also,
To turn on the 8I thyristor 1 in the blocked state, switch 12 is turned off and switch 10 is turned on. Here, since the forward blocking voltage of the S ethyristor is determined by the reverse bias voltage of the gate, the switching speed from off to on must be sufficiently fast.

Further, in order to turn off the 8I thyristor 1 which is in a conductive state, the switch 10 is turned off in advance, and then the switch 12 is turned on to apply a reverse voltage again between the gate and cathode of the 81 thyristor 1. At this time, the gate current flowing from the cathode to the gate of 8I thyristor 1 is applied to the gate of 8I thyristor 1.
Flows until the junction between the cathodes recovers. That game)
When the -cathode junction is restored, the cathode current is interrupted and most of the anode current flows via the diode 6 and the capacitor 8. Therefore, the capacitor 8 is charged and the anode voltage of the SI thyristor 1 increases.

Also, part of the anode current is as follows: Main power supply 2 → Load 3 → Inductance 4 → 8I thyristor 1 (anode gate) → Impedance 14 → Auxiliary power supply 13 → Switch 12 → SI thyristor 1 (cathode)
→Continues to flow through the main power supply 2 route. This current is called the Tilmi current. Furthermore, after the junction between the gate and cathode reversely recovers during turn-off, the anode voltage increases, so if the reverse bias voltage of the gate is not established sufficiently, S
This causes a decrease in the forward blocking ability of the I thyristor. Kayouna S
The waveforms during the switching operation of the I thyristor are as shown in diagrams jg4 and ig5.

Figures I@4 and 5 show the waveforms during turn-on and turn-off of the switching operation of the S Esthyristor, where vAlc is the anode-cathode voltage, M is the anode current, VGiC is the gate voltage, and G is the gate voltage. It is an electric current.

Next, in the switching operation of such an 8I thyristor, the influence of the reverse recovery current of the snubber diode on the element when the 8I thyristor is turned off will be described. This will be explained below with reference to FIGS. 3 to 5.

Now, when the SI thyristor 1 is turned off, the gate-cathode junction reversely recovers and the anode current decreases.
Load current flows through diode 6 and capacitor 8
increase the voltage.

Therefore, in FIG. 5, the freewheel current begins to flow at time To when the anode-cathode voltage YAK rises and becomes equal to the power supply voltage E. At this time, the current I8 of the diode 6 does not immediately become zero, but flows together with In e I8 due to the influence of the inductance of the circuit, and this period is between time Tea and time T1.

At time TI, the electric current 8 becomes zero, and at the same time, the anode-cathode voltage YAK fJsi & reaches a high value, and the value becomes larger than the power supply voltage Es. As a result, the charge in the capacitor 8 is discharged toward the main power supply 2 between time T1 and time T2, and the reverse recovery current of the diode 6 flows through the next path. That is, capacitor 8 → diode 6 → inductance 4 → freewheel diode 5
→ Main power supply 2 → Capacitor 8 This current becomes zero at the moment when the diode 6 recovers reversely, but at that time, due to the voltage VP induced in the inductance 4, a surge voltage is generated in the voltage VAK between the anode and cathode, and the off-voltage decreases.

On the other hand, after the junction between the gate and cathode is reversely restored, the anode-cathode voltage YAK increases, and a region where carriers do not exist, called a depletion layer, is generated inside the S ethyristor. This depletion layer is sandwiched between the anode electrode and gate electrode of the device to form a flat capacitor, and as mentioned above, when the anode-cathode voltage VAK suddenly changes, the charging current of the capacitor (hereinafter referred to as displacement current) is opposite to that of the gate. adversely affect the flow element via the bias circuit. This phenomenon will be further explained using Fig. 6. Fig. 6 is shown to explain the influence of the displacement current on the reverse bias circuit of the gate. In the capacitor, ■ is a displacement current caused by a sudden rise in the voltage YAK between the anode and cathode, and ΔVe is a voltage drop caused by the displacement current and the impedance of the gate circuit, thus the impedance 14. In the figure, the same reference numerals as in Figure 5g3 indicate parts having the same function. In other words, when the voltage between the anode and cathode of S thyristor 1 suddenly rises, a displacement current flows in the path of 8I thyristor 1 (anode gate) → impedance 14 → auxiliary power supply 13 → switch 12 → SI thyristor 1 (cathode), Impedance 14 produces a voltage drop ΔVG with the polarity shown. Since this voltage drop ΔVG reduces the reverse bias voltage EG of the gate, the reverse recovery of the snubber diode at turn-off is
When the anode-cathode voltage VAK blocks a high voltage, such as a sudden change in the anode-cathode voltage caused by a first current, the device may break down, resulting in a problem.

[Means for solving problems and their effects]

In view of the above-mentioned points, the present invention effectively shunts the displacement current generated when the anode-cathode voltage suddenly changes due to the reverse recovery current of the snubber diode when the SI thyristor turns off between the gate and the cathode. This is designed to prevent the reverse bias voltage from flowing into the circuit that applies reverse bias to the gate, thereby preventing the voltage value of the gate reverse bias from decreasing due to a voltage drop due to impedance to the wiring.

Therefore, the present invention focuses on the fact that the generation of displacement current harmful to the gate circuit is a voltage component generated by the reverse recovery current of the snubber diode and the inductance of the main circuit, and detects the reverse recovery current of the snubber diode using a transformer. The output is applied to both ends of a compensation reactor, and the voltage generated across the compensation reactor is applied between the gate and cathode of the SI thyristor via a diode, thereby acting to give a reverse bias to the gate. It is.

〔Example〕

Figure g1 shows the main part configuration of an embodiment according to the present invention, in which 15 is a transformer, 16 is a beam axle, and 17 is a diode. In the figure, the same reference numerals as in Figure 43 indicate parts having the same functions. The function of this circuit configuration is as follows. Here, detailed explanation of the same components as in FIG. 3 will be omitted.

That is, when the 8I thyristor 1 is turned off, the main current is commutated to the snubber circuit, the diode 6 becomes conductive, and the voltage of the capacitor 8 increases.

Here, a transformer 15 is arranged on the cathode side of the diode 6, and a reactor 16 is connected to the load of the transformer 15, so when the charging current of the capacitor 8 flows through the diode 6, the secondary side of the transformer 15 , terminal a of transformer 15 → reactor 16 (terminal d to terminal C) → b of transformer 15
Current flows in the path of the terminal. At this time, a voltage equation of the polarity shown is generated across the axle 16, and this voltage equation is applied through the diode 17 between the gate and cathode of the SI thyristor 1 in the same direction as the reverse bias voltage. From this, when the main current is normally commutated to the snubber circuit, a large spike voltage is generated at the anode of the S ethyristor due to the influence of the inductance component of the snubber circuit, and the rate of voltage increase at this time is quite large and the displacement current Similarly to the reverse recovery current of the snubber diode, the voltage Ec generated across the reactor 16 has an adverse effect on the gate circuit.
The gate reverse bias will not be reduced below.

Also, as the capacitor 8 charges further and reaches its maximum value,
Reverse recovery current flows through the snubber diode.

When the reverse recovery current of the snubber diode is increasing, a current flows through the transformer 15 through the path from the b terminal of the transformer 15 → the reactor 16 (terminals C to d) → the a terminal of the transformer 15, A voltage opposite to the voltage equation shown in FIG. 1 is generated across the reactor 16, but this voltage is blocked by the diode 17 and is not applied between the gate and cathode of the 8I thyristor I.

Thereafter, when the snubber diode reverse recovers and the reverse recovery current of the diode 6 decreases, the current of the handle 16 also decreases rapidly, so that a voltage with the same polarity as the voltage shown in the figure is generated again at both ends of the reactor 16. This voltage is caused by a voltage drop across the impedance 14 due to a change in the voltage between the anode and cathode of the SI thyristor l caused by the reverse recovery current of the diode 6 and the inductance 4, and the resulting displacement current flowing into the gate circuit. It works to prevent the reverse bias voltage from decreasing. That is,
8I thyristor 1 (anode gate) → reactor 1
6 (C terminal to d terminal) -> diode 17 -> 8I thyristor 1 (cathode) While bypassing the displacement current, the value of the reverse bias voltage of the S thyristor 1 is ensured.

FIG. 2 shows the main parts of another embodiment according to the present invention, in which 15' is a transformer, 16' is a beam axle, 17' is a diode, 18 is a resistor, and 19 is an auxiliary source.

In the figures, the same reference numerals as in FIGS. 1 and 3 indicate parts having the same functions. Here, the first circuit connection like this is shown.
Similarly to what is shown in FIG. 3, a transformer 15' for detecting the reverse recovery current of the snubber diode is connected in series with the capacitor 8, and a reactor 16' is connected to the load of the transformer 15'. A diode 17' is connected in series to the diode 17'.

Furthermore, the transformer 15' is provided with a tertiary winding and the resistor 18 is connected to the transformer 15'.
It is configured such that a bias current is constantly supplied from the auxiliary power supply 19 via the auxiliary power supply 19.

That is, since the reverse recovery current of the snubber diode flows through the snubber capacitor, it is clear that the device shown in this way has the same function as that shown in FIG. 1. In addition, since a bias current is passed through the transformer 15' to saturate its iron core, the inductance of the snubber circuit when current is commutated to the snubber circuit can be reduced, and the spike voltage generated at the anode of the S ethyristor can be reduced. can be lowered.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a device with a simple configuration that allows the displacement current generated during reverse recovery of the snubber diode to flow into the gate circuit to prevent a decrease in reverse bias voltage.

[Brief explanation of drawings]

Figure 5g3 is a connection diagram showing an example of the configuration of a DC switch circuit using an 8I thyristor. Figures 4 and 5 are diagrams showing waveforms at turn-on and turn-off of the switching operation of the 8I thyristor. , FIG. 6 is an explanatory diagram shown to explain the influence of the displacement current on the reverse bias circuit of the gate. l... Electrostatic induction thyristor (8I thyristor)
, 2...Main power supply, 3...Load, 4...
...Inductance, 5, 6, 17.17'...
...Diode, 8...Curved capacitor, 10.12.
...Switch, 11,13.19...Auxiliary power supply, 14...Impedance, 15.15'
... Curved transformer, 16.16'...Reactor,
CAG...Eccentric capacitor, ■...Displacement current.

Claims (1)

[Claims] A reactor is connected to a transformer that detects a reverse recovery current of a snubber diode of the electrostatic induction thyristor, and a series connection body is provided between the gate and cathode of the electrostatic induction thyristor, and a diode is connected in series with the reactor. ,
A displacement current compensator for an electrostatic induction thyristor, characterized in that a reverse bias is applied to the gate of the electrostatic induction thyristor by the voltage generated by the reactor when the reverse recovery current is stopped.