JPS6029348Y2 - 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 so that its di/dt and dv/dt tolerances are 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 main thyristor 1 is ignited with the current.

Since the main circuit current does not flow through this auxiliary thyristor 2, it is easy to obtain coordination between the light ignition sensitivity and the amount of di/dti=J.
In addition, since the temperature rise of the element is small, the light ignition sensitivity and dv/d are
It is also easy to coordinate with the t 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 FIG. 1, when a sudden voltage of dv/dt is applied between the anode and cathode of the main thyristor 1, the same dv/dt is applied to the auxiliary thyristor 2 as well.

Then, the displacement current of the auxiliary thyristor 2 Cjdv/dt (
Cj is the junction capacitance) given to the gate of the main silicon risk,
If this current is large, the main thyristor 1 is also likely to fire due to its own displacement current, resulting in erroneous firing.

In particular, when the main thyristor 1 is required to have a high withstand voltage, the auxiliary thyristor 2 must also have an equivalent withstand voltage, and the creepage distance is increased, which increases the joint area and increases the displacement current.
This risk is greater.

In order to prevent erroneous firing of the main thyristor due to such displacement current of the auxiliary thyristor, a capacitor 5 is connected between the cathode of the main thyristor 1 and the cathode of the auxiliary thyristor 2, as shown in FIG. It has already been proposed to attract the displacement current of the thyristor 2.

However, since the junction capacitance -77yj of the auxiliary thyristor 2 increases when the applied voltage is low, the displacement current increases in the low voltage region, and even if the capacitor 5 is connected, there is a risk of erroneous firing.

An object of the present invention is to provide a thyristor ignition circuit in which a large displacement current does not flow into the gate of the main thyristor even in a low voltage region.

In addition to connecting the capacitor mentioned above, the purpose of is to block current between the electrode of the auxiliary thyristor and the gate of the main thyristor while the voltage between them is low, and to conduct current when it exceeds a predetermined value. Moreover, this can be achieved by connecting a semiconductor element having a junction capacitance smaller than that of the auxiliary thyristor.

Such semiconductor elements include Zener diodes and SSS, and the junction capacitance of these semiconductor elements is several tenths of the junction capacitance Cj of the auxiliary thyristor.

Therefore, the displacement current flowing through it during the rise of dv/dt is extremely small, so that the displacement current flowing through the capacitor is large, eliminating the risk of false firing of the main thyristor and increasing the dv/dt withstand capability.

An example of a Zener diode will be described below with reference to the drawings.

In FIG. 3, the main thyristor 1 has a withstand voltage of 4 kv, for example.
, the current capacity is 1000 A, and the auxiliary thyristor 2 that is ignited by light has a breakdown voltage of 4 kV and a current capacity, for example,
Approximately 3C71! It has a joint area of .

Between the cathode of the main thyristor 1 and the cathode of the auxiliary thyristor 2, a capacitor 5 having a capacitance of, for example, 5/AF is connected as in FIG.

Furthermore, the cathode of the auxiliary thyristor 2 and the main thyristor 1
In addition to the resistor 3 that suppresses the peak value of the gate current, a Zener diode 6 is connected between the gates of the gate according to the present invention.
is connected.

The Zener diode used has a Zener voltage of about 10 V, for example, but its junction area is several times smaller than the junction area of the auxiliary silice, and therefore its junction capacitance is also much smaller.

Therefore, as described above, the displacement current flowing to the gate circuit becomes small, and erroneous firing due to dv/dt in the low voltage region is prevented.

Then, the auxiliary thyristor 2 is ignited by the light 4 and applied to the Zener diode 6! When the voltage exceeds the Zener voltage, a gate current flows and the main thyristor 1 fires.

In FIG. 4, a resistor 3 is connected between the anode of the main thyristor 1 and the anode of the auxiliary thyristor 2, and similarly to FIG. Block the arc.

In FIG. 5, instead of the Zener diode 6 in FIG.
I am inserting ss 7.

If a voltage having a breakover voltage comparable to the Zener voltage is used, an effect similar to that shown in FIG. 3 will be obtained.

As mentioned above, the present invention prevents erroneous firing of a circuit in which the main thyristor is not ignited by light but is ignited via a light ignition auxiliary thyristor by inserting an easily available semiconductor element such as a Zener diode or SSS. Therefore, an economically reliable ignition circuit can be obtained.

[Brief explanation of drawings]

Figures 1 and 2 are connection diagrams of conventional circuits for igniting an electric ignition main thyristor by an optical ignition auxiliary thyristor, respectively, and Figures 3 to 5 are connection diagrams showing different embodiments of the present invention, respectively. It is a diagram. 1... Main thyristor, 2... Auxiliary thyristor, 5... Capacitor, 6... Zener diode, 7... SSS0

Claims (1)

[Scope of utility model registration request] One electrode of the optical ignition auxiliary thyristor is connected to the gate of the electric ignition main thyristor, and the main thyristor is ignited by the current flowing when the auxiliary thyristor is irradiated with light, in which one electrode of the auxiliary thyristor is connected to the gate of the auxiliary thyristor. connected to the main electrode on the side closer to the gate of the main thyristor via a capacitor, and connected to the gate of the main thyristor via a semiconductor element that conducts current only when a voltage of a predetermined value is applied on the other side; Moreover, the thyristor ignition circuit is characterized in that the semiconductor element has a junction capacitance smaller than that of the auxiliary thyristor.