JPH035691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC switch circuit using an electrostatic induction thyristor, and more particularly to an improved snubber circuit device suitable for use with an electrostatic induction thyristor.

A static induction thyristor (hereinafter referred to as an SI thyristor) is a type of self-extinguishing thyristor that has the same self-extinguishing function as a gate turn-off thyristor (GTO thyristor), but it has various advantages compared to a GTO thyristor. This is something that is attracting attention. That is, (1) the switching speed is fast.

(2) Resistant to thermal damage during turn-off.

(3) Forward voltage rise rate immediately after turn-off (dV/dt)
Has a large tolerance.

On the other hand, the one shown in FIG. 1 is known as a typical snubber circuit device.

FIG. 1 shows a device equipped with a known snubber circuit device.
This shows the main part configuration of a DC switch circuit example that uses a GTO thyristor. 1 is a DC power supply, 2 is a GTO
A thyristor, 3 is a load, and 4 is a main circuit floating inductance. Further, in the figure, 5 is a snubber diode, 6 is a snubber capacitor, and 7 is a snubber resistor.

Further, FIGS. 2 and 3 are explanatory diagrams showing waveforms of various parts when the DC switch circuit shown in FIG. 1 is in an OFF operation and in an ON operation.

That is, the operation of the snubber circuit when performing a switch operation using the GTO thyristor 2 is as follows.

First, the anode current I _T and anode voltage when the load current I _L is cut off by the GTO thyristor 2.
In Fig. 2, which shows the time course of V _AK , it is assumed that an off-gate pulse is applied to the GTO thyristor 2 at the current time T _OF , and the anode current I during the falling time T _F after the accumulation time T _S has elapsed. Most of _T decays and the remaining current disappears after the tail period T _T . Furthermore, the change in the anode voltage _VAK of the GTO thyristor 2 during this period is as shown in the example.

The functions of the snubber capacitor 6 in this operation are as follows. The first point is to reduce the power loss during the tail period T _T by suppressing the anode voltage V _AK immediately after turn-off, and the second point is to limit the rate of increase in the anode voltage V _AK to reduce the power loss during the tail period T T. The third point is to prevent erroneous firing of the thyristor 2, and the third point is to suppress the spike voltage ΔV _C occurring in the anode voltage V _AK by absorbing the energy stored in the inductance component of the main circuit.

Next, the anode current I _T when GTO thyristor 2 is turned on and the voltage of snubber capacitor 6
The change in V _C is as shown in Figure 3.

Here, I _TP indicates the peak value of the anode current _IT . That is, when the gate is turned on at time T _ON , the charge stored in the snubber capacitor 6 is discharged through the snubber resistor 7, and the energy is consumed as heat. At this time, the power W _R applied to the snubber resistor 7 is as follows _, where C _S is the capacitance of the snubber capacitor 6, and _F is the operating _frequency ^. F...(1) It can be expressed by the following relational expression. Therefore, the heat generated by the snubber resistor 7 increases significantly as the circuit voltage and operating frequency increase.

Now, if an SI thyristor were to be used in place of the GTO thyristor in such a DC switch circuit, the snubber capacitor 6 would be used because it is less likely to be thermally destroyed during turn-off and has a large (dV/dt) tolerance as described above. It should be possible to reduce the snubber resistance 7 by reducing the capacitance of the snubber resistor 7. However, simply replacing the GTO thyristor 2 with an SI thyristor in the circuit configuration shown in Figure 1 increases the overcharge voltage of the snubber capacitor caused by the energy stored in the main circuit stray inductance 4 when the thyristor is disconnected. It becomes something that influences us.

This indicates that the spike voltage ΔV _C has the following relationship, where _LS is the value of the main circuit stray inductance 4, ΔV _C ≒ _IT ·√( _{S S} )...(2). However, the anode current I _T is the value when the anode current is cut off. For this reason, the snubber capacitor 6
If the capacitance C _S is made small, the spike voltage ΔV _C becomes extremely large, resulting in a problem in which it exceeds the allowable forward voltage of the SI thyristor.

The present invention has been made with attention to the above-mentioned points, and it is an object of the present invention to provide a snubber circuit device with a simple configuration that is compatible with the SI thyristor and exhibits effects in a DC switch circuit employing the SI thyristor. Hereinafter, the present invention will be explained based on the drawings.

FIG. 4 shows the configuration of essential parts of an embodiment of the present invention, in which 5' is a snubber diode, 6' is a snubber capacitor, 7' is a snubber resistor as an example of an impedance element, and S is an SI thyristor. In the figure, the same reference numerals as in FIG. 1 indicate the same components. In contrast to Fig. 1 for the snubber circuit component of an SI thyristor, the snubber resistor 7' connects to the connection point between the two series-connected bodies consisting of the snubber diode 5' and the snubber capacitor 6'. The difference is that it is placed between the positive electrode of the power source 1. Regarding this configuration, the time transition of the waveform of each part is
Figures 5 and 6 are similar to Figures 3 and 3.
A detailed explanation will be given below with reference to the drawings.

Here, FIG. 5 shows the waveforms of the anode current I _T ′ and anode voltage _{V AK} ′ during OFF operation in the circuit shown in FIG. 4, and FIG. 6' voltage
It shows V _C ′.

In other words, when an off-gate pulse is given to the SI thyristor 8 at time T _OF , most of the anode current I _T ' attenuates during the fall time T _F after the accumulation time T _S has elapsed, and the remaining current is reduced after the tail period T _T. Disappear. Therefore, this change results in the anode current shown in Figure 2.
Although it is similar to _IT , both the anode voltage V _AK and V _AK ' characteristics are significantly different. This is because the snubber capacitor 6' is always charged to the DC power supply 1 voltage E _S during the conduction period of the SI thyristor 8 due to the snubber resistor 7' in which the snubber capacitor 6' is connected to the DC power supply 1 as shown in the figure. Therefore, the anode voltage V _AK ' immediately exceeds the power supply voltage value after the fall period ends. Note that the spike voltage ΔV _C ' at this time occurs in the inductance component of the above-mentioned main circuit and is given by equation (2). Furthermore, when the SI thyristor 8 is turned on at time T _ON , the anode current I _T ' increases as shown in the figure, so that
Since there is no connection for discharging the charge stored in the snubber capacitor 6', no power loss occurs due to the snubber resistor 7'.

As described above, this embodiment allows the SI thyristor 8 to fully demonstrate its performance, does not generate power loss in the impedance element part of the snubber circuit, and allows selection of a high circuit voltage and operating frequency. This is a snubber circuit device that is ideal for the DC switch circuit used. Furthermore, to illustrate this point more specifically, SI thyristors are less susceptible to thermal breakdown (dV/dt) and have a large withstand capacity, so they can withstand a sudden increase in anode voltage immediately after turn-off, and the overcharge voltage of the snubber capacitor at turn-off of the SI thyristor. Even if the capacitor capacity is selected to be large in order to lower the power, it is possible to do so without causing any problem in power loss at turn-on.

FIG. 7 shows the main part configuration of another embodiment of the present invention, in which 5'' is a snubber diode, 6'' is a snubber capacitor, 7'' is a snubber resistor, and 8' is an SI thyristor. The one shown in the figure is the fourth
For the example of the DC switch circuit shown in the figure, the SI thyristor 8 is connected to the DC power supply 1 from the positive side of the DC power supply 1 via the load 3 etc.
This is an example in which the SI thyristor 8' is placed on the positive potential side of the load 3. It is clear that the configuration of the snubber circuit consisting of the snubber diode 5'', the snubber capacitor 6'' and the snubber resistor 7'' is the same as that shown in FIG. 4. Therefore, the device shown in FIG. 4
It has the same function as the figure device.

FIG. 8 shows a modification of the device shown in FIG.
In the drawings, the same reference numerals as in FIGS. 1 and 4 indicate the same components. That is, what is shown in FIG. 8 is an example of a configuration in which the known snubber circuit portion provided in the device shown in FIG. 1 is installed in conjunction with the device shown in FIG. Therefore, it is clear that this example also provides the same effect as the device shown in FIG. 4.

As explained above, according to the present invention, it is possible to provide a special and useful device for a DC switch circuit employing an SI thyristor.

[Brief explanation of the drawing]

1, 2, and 3 are circuit diagrams showing an example of a DC switch circuit employing a GTO thyristor equipped with a known snubber circuit device, and explanatory diagrams showing the time course of the waveforms of each part, respectively. 5 and 6 are circuit diagrams showing one embodiment of the present invention and explanatory diagrams showing time transitions of waveforms of each part, respectively. FIG. 7 is a circuit diagram showing another embodiment of the present invention, and FIG. FIG. 4 is a circuit diagram showing a modified example of the device. 3...Load, 4...Main circuit floating inductance, 5, 5', 5''...Snubber diode, 6,
6', 6''... Snubber capacitor, 7, 7', 7''...
...Snubber resistor, 8,8',8''...Static induction thyristor (SI thyristor).

Claims (1)

[Claims] 1. In a DC switch circuit comprising at least a DC power source, a load, and an electrostatic induction thyristor, a series connection body consisting of a diode and a capacitor connected in series is connected in parallel to the electrostatic induction thyristor, and a connection point between the diode and the capacitor is connected in parallel to the electrostatic induction thyristor. A snubber circuit device for a static induction thyristor, characterized in that one end of an impedance element is connected, and the other end of the impedance element is connected to the DC power supply so as to charge the capacitor during the conduction period of the static induction thyristor. .