JPS6255729B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch using a thyristor or the like in an exchange communication path, and more particularly to a semiconductor switch with improved off-voltage rise rate tolerance (hereinafter abbreviated as DV/DT tolerance). .

Figure 1 shows a semiconductor switch circuit with improved conventional dv/dt characteristics. 1a, 1b in Figure 1
2 is an input/output terminal of the main switch, 2 is a control signal input terminal, 3 is a capacitor for supplying a displacement current to a variable impedance circuit 4, and 5 is constructed like a thyristor having a pnpn structure. In FIG. 1, when there is a sudden change in potential at the main switch terminal 1a, a transient current passes through the capacitor 3, drives the variable impedance circuit 4, and drives the thyristor 5.
The voltage between the gate and cathode of the capacitor 3 can be clamped to a low voltage to prevent malfunction, but if there is a relatively slow potential fluctuation at the main switch terminal 1a, the capacitor 3
This has the drawback that the variable impedance circuit 4 cannot be driven unless the impedance is extremely large, which makes integration difficult.

The present invention further adds a transient current detection circuit with a circuit configuration using active elements to a semiconductor switch drive circuit used for an exchange communication path, etc., in which a variable impedance circuit that operates independently of the semiconductor switch drive circuit is added. In addition, by making the input/output terminals of this transient current detection circuit bidirectional in terms of voltage resistance and operation, a semiconductor switch is obtained which can reliably prevent malfunctions due to DV/DT and which can be integrated into an integrated circuit. This will be explained in detail below according to examples.

FIG. 2 shows an embodiment of the present invention, in which 6a is the first
Main terminal, 6b is the second main terminal, 7 and 8 are drive terminals,
9 is a thyristor. 10 is a transistor, 1
A resistor 1 is connected between the gate and cathode of the thyristor 9 to constitute one variable impedance circuit. A thyristor 9a is connected between the first main terminal 6a and the second main terminal 6b with the opposite polarity to the thyristor 9. 10a is a transistor, 11a is a resistor, and is connected between the gate and cathode of the thyristor 9a.
It constitutes two variable impedance circuits.
Further, the diodes 17 and 17a are connected to the respective transistors 10 and 10 forming the variable impedance circuit.
It is connected between the base and emitter of a. Furthermore, each gate of each of the thyristors 9 and 9a is connected to a drive circuit consisting of a transistor 16 via a diode 15 and 15a, respectively. One of the characteristic configurations of this invention is that one input/output terminal 13 of the transient current detection circuit is connected to the base of a transistor 10a forming another variable impedance circuit.

Now, to explain the operation of the semiconductor switch having the transient current detection circuit of the present invention, a power supply is connected between the first main terminal 6a and the second main terminal 6b, and the drive terminal 7,
When the transistor 16 is forward biased from the thyristor 9 through the diode 15 or 15a,
Or drive the gate of 9a, thyristor 9 or 9
A is made conductive, but thyristor 9 or 9
If there is a sudden positive potential change at the first main terminal 6a or a negative potential at the second main terminal 6b when terminal a is not in the operating state, the transient current will change from 6a to 17a (if this is not added, the emitter of 10a - between bases)→
12, drives the transistor 10, and reaches the second main terminal 6b.

In addition, when there is a sudden change in potential that is negative at the first main terminal 6a or positive at the second main terminal 6b, the transient current
Transistor 10 flows through the route b → 17 (if this is not available, between the emitter and base of 10) → 12
a to the first main terminal 6a.

At this time, in either case, the transient current is amplified by the transistor 12 to obtain a larger current. As a result, the voltage between the gate and cathode of thyristor 9 or 9a is clamped to the voltage between the collector and emitter of transistor 10 or 10a, and malfunction of either thyristor 9 or 9a can be prevented.

As explained above, the semiconductor switch of the present invention has
Even if a sudden potential change occurs in the thyristor 9 or 9a, or even if the change is not far away, the transient current detection circuit can reliably operate the variable impedance circuit to prevent malfunctions due to dv/dt. can.

Furthermore, since the transient current detection circuit in the semiconductor switch of the present invention has the same configuration at the input and output terminals, bidirectional operation can be achieved. In this case, one transient current circuit can be shared in the same way as with unidirectional semiconductor switches, and the number of parts can be reduced, and when an array is constructed using a plurality of switches of this type, high integration can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an example of a circuit diagram of a conventional semiconductor switch with improved dv/dt characteristics, and FIG. 2 is a circuit diagram of an embodiment of the present invention. 6a...first main terminal, 6b...second main terminal, 7,8
...Control terminal, 9,9a...Thyristor, 10,10
a, 12, 16...transistor, 11, 11a...
Resistor, 13, 14... Input/output terminal, 15, 15a,
17, 17a...diode.

Claims (1)

[Claims] 1 1 with PNPN structure between the 1st main terminal and the 2nd main terminal
A pair of thyristors are connected in parallel with opposite polarity, and the second
A pair of variable impedance circuits consisting of transistors with a resistor connected between the emitter and collector are connected between the main terminal and the gates of the pair of thyristors so that the forward biased PN junction of each thyristor is short-circuited. The semiconductor switch is characterized in that a transient current detection circuit consisting of a PNP type transistor with an open base and having a bidirectional withstand voltage is connected between the bases of the transistors of the variable impedance circuit. semiconductor switch.