JPS604618B2 - thyristor firing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thyristor ignition circuit for igniting an electrical ignition main thyristor via an optical ignition auxiliary thyristor.

It is difficult for a thyristor that is directly ignited by light to maintain high ignition sensitivity while maintaining di/dt and dv/dt tolerances on the same level as ordinary electric ignition thyristors.

Therefore, as shown in Fig. 1, the cathode of the optical ignition auxiliary thyristor 2, which is an individual element, is connected to the gate circuit of the electric ignition main thyristor 1 via a resistor 3 that suppresses the peak value of the gate current, and the light 4 is auxiliary. A circuit has been proposed in which the thyristor 2 is irradiated and ignited, and the current is used to ignite the main thyristor. Since the main circuit current does not flow through this auxiliary thyristor 2, the temperature rise of the element is small, so it is easy to coordinate the light ignition sensitivity and the dv/dt tolerance. Furthermore, since the main thyristor 1 can be a general electric ignition thyristor as it is, it is economically advantageous. However, in the circuit shown in Figure 1, there is a sudden dv/dt between the anode and cathode of main thyristor 1.
When the voltage is applied, the same dv/dt is also applied to the auxiliary thyristor 2. In this case, if the junction capacitance of the auxiliary thyristor 2 is Ci, then the displacement current Cidv/dt
is applied to the gate of the main thyristor, and if this current is large, the main thyristor 1 is also in a state where it is likely to be fired by its own displacement current, resulting in false firing. In particular, when the main thyristor 1 is required to have a high withstand voltage, the auxiliary thyristor 2 must also have a similar withstand voltage, and the creepage distance is increased, so the joint area is also increased and the displacement current becomes large, making this risk even greater.
The object of the present invention is to propose an ignition circuit that prevents the main thyristor from being accidentally ignited due to the displacement current of the auxiliary thyristor.

The purpose of this is to create a series circuit of a light ignition auxiliary thyristor and a resistor between the gate electrode of the electric ignition main thyristor and the main electrode on the side farther from the gate electrode. When connected so that the ignition current of the main thyristor is If the breakover voltage is 2000V or more, the junction area of the auxiliary thyristor is 1.
This can be achieved by connecting a capacitor with a capacitance of 0.02 F or more.

Embodiments of the present invention will be described below with reference to the drawings.

As is clear from FIG. 2 when compared with FIG. 1, a capacitor 5 is inserted between the cathode of the electric ignition main thyristor 1 and the cathode of the optical ignition auxiliary thyristor 2. Third
In the figure, the resistor 3 is connected between the anode of the main thyristor 1 and the anode of the auxiliary thyristor 2, unlike in Figures 1 and 2, and the capacitor 5 is connected between both thyristors as in Figure 2. It is inserted between the evening cathodes. In FIG. 4, a resistor 6 is further connected to the gate of the main thyristor 1 via a resistor 3 connected in series with the auxiliary thyristor 2, and a capacitor 5 is connected to the cathode of the main thyristor. This capacitor 5 is the auxiliary thyristor 2
absorbs the displacement current and prevents the main thyristor from firing.
The capacitance of the capacitor 5 is determined based on the experimental results shown in FIG.

This is based on an experiment conducted using the circuit shown in Figure 4. A light-ignition thyristor with a junction area of 3 was used as the auxiliary thyristor 2, a 200 Ω resistor was inserted as the resistor 3, and the resistance value of the resistor 6 was used as a parameter. dv of 1500V/mountain s when
Main thyristor breakover voltage Vs due to /dt
The relationship between o and the capacitance C of the capacitor 5 is shown in a diagram on a logarithmic scale. The numerical value attached to each line indicates the resistance value of the resistor 6. From this diagram, even if the resistance value of the resistor 6 changes, the capacitance of the capacitor 5 is dv/
It was found that breakover does not occur at low forward voltages due to dt. In other words, the junction area 1 of the auxiliary thyristor 2
It is sufficient to connect a capacitor 5 with a capacity of 0.02 F or more per . However, if the capacity is too large, the auxiliary thyristor 2
When ignited by light, the current flowing through the resistor 6 becomes too small and the main thyristor does not ignite, and the price of the capacitor increases. A capacitor with a capacity of 1 F or less is used. The relationship curve shown in FIG. 5 hardly changes even if the value of the resistor 3 changes. However, if this resistance value becomes large, the current flowing into the gate of the main thyristor 1 when the auxiliary thyristor 2 is turned on becomes too small, so that it is usually suppressed to about 1000 or less. From these facts, it can be understood that the value of capacitance of 0.02 F or more per total rear area of the auxiliary thyristor applies to any of the cases shown in FIGS. 2 to 4. There is another advantage that the resistor 3 is connected in series with the capacitor 5 as in FIG. 3 or 4. In other words, this resistance is
Since the main circuit current with a sudden rise is suppressed from flowing through the auxiliary thyristor 2 and the capacitor 5, it is possible to reduce the di/d ratio of the auxiliary thyristor 22, and the firing sensitivity of the auxiliary thyristor 2 is reduced. This makes it easier to coordinate di/dt tolerance. This resistor is even more effective when a snapper circuit consisting of a parallel capacitor 7 and resistor 8 is connected to protect the main thyristor 1 from surge voltage as shown in FIG. In this case, when the auxiliary thyristor 2 is ignited by the light 4, the charge stored in the capacitor 7 is discharged via the resistor 8, the auxiliary thyristor 2 and the capacitor 5. This discharge current has a sudden rise and puts a heavy burden on the auxiliary thyristor 2.
The resistor 3 connected in series with the capacitor 5 also functions to suppress the discharge current from the snubber circuit and prevent damage to the auxiliary thyristor 2 due to its sudden and slow rise. As described above, according to the present invention, by simply inserting a capacitor between the main electrodes of the auxiliary thyristor and the main thyristor, V ignition can be achieved in a circuit that ignites a normal electric ignition main thyristor using an optical ignition auxiliary thyristor. It is also possible to prevent this, making it significantly more advantageous in terms of characteristics and economy than when the main thyristor is directly ignited with light.

[Brief explanation of drawings]

Fig. 1 is a connection diagram of a conventional circuit in which an electric ignition thyristor is ignited by an optical ignition thyristor, Fig. 2 is a connection diagram of an embodiment of the present invention, and Figs. 3, 4, and 6 are respectively 5 is a connection diagram of different embodiments, and FIG. 5 is a relationship diagram between breakover voltage and capacitance of a capacitor according to the present invention. 1... Electric ignition main thyristor, 2... Optical ignition auxiliary thyristor, 3, 6... Resistor, 5...
...Capacitor. Spear' figure - Sai 2 Kajiru 3 figure Sai 4 figure O J figure O 5 figure

Claims (1)

[Claims] 1. A series circuit of an optical ignition auxiliary thyristor and a resistor is connected between the gate electrode of the electric ignition main thyristor having a breakover voltage of 2000 V or more and the main electrode on the side farther from the gate electrode. In a device connected such that the forward current of the auxiliary ignition thyristor becomes the ignition current of the main electric ignition thyristor, the main electrode of the main electrode of the electric ignition main thyristor closer to the gate electrode and the auxiliary light ignition thyristor A junction area 1c of the auxiliary thyristor between the gate electrode and the electrode connected to the gate electrode.
A thyristor ignition circuit characterized by connecting a capacitor with a capacitance of 0.02 μF or more per m^2. 2. A thyristor ignition circuit according to claim 1, characterized in that a resistor is connected in series to the optical ignition auxiliary thyristor and the capacitor.