JPS6326023A - Semiconductor switch - Google Patents

Abstract

PURPOSE:To prevent malfunction due to a rate of rise of on-state voltage (dv/dt) by connecting a transient current detecting circuit comprising a PNP transistor (TR) having a dielectric strength voltage in both polarities whose base is opened between a 1st main terminal and a base of a TR of a variable impedance circuit. CONSTITUTION:The PNP TR 12 of transversal arrangement and having a bipolar dielectric strength charactristic is a transient current detection circuit whose input/output terminals 13, 14 are constituted by a collector and an emitter and is connected to a base of a TR 10 forming a variable impedance circuit and a 1st main terminal 6a. With a thyristor 9 not in operating state, if a rapid positive potential fluctuation is produced to the 1st main terminal 6a or a rapid negative potential fluctuation exists in a 2nd main terminal 6b, the transient current flows in a route of 6a 12, the TR 10 is driven and the current reaches the terminal 6b. In this case, the transient current is amplified by the PNP TR 12 and a larger current is obtained. As a result, the gate-cathode voltage of the thyristor 9 is clamped by the collector-emitter voltage of the TR 10 to prevent malfunction of the thyristor 9.

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). .

FIG. 1 shows a semiconductor switch circuit with improved characteristics over the conventional dv/d. In FIG. 1, Ia and Ib are input/output terminals of the main switch, 2 is a control signal input terminal, 3 is a capacitor for supplying displacement current to the variable impedance circuit 4, and 5 is constructed like a thyristor having a pnpn structure. There is. In Figure 1, main switch terminal 1a
If there is a sudden change in potential at If there is a relatively slow potential change in the capacitor 3, the variable impedance circuit 4 cannot be driven unless the capacitor 3 is large and the fifth capacitor 3 is large, which makes integration difficult.

On the other hand, one attempt to avoid the disadvantages due to the use of capacitors
For example, JP-A-52-43350 No. 7
There is a diagram circuit. This circuit is a transistor (transistor 1 in Fig. 2 of the main invention) in which the emitter of an open-base NPN transistor is provided between the dart and cathode of a thyristor.
0), while the collector is connected to PNP.
By connecting to the n region of the N switch (corresponding to thyristor 9 in Fig. 2 of the present invention), the voltage applied between the anode (nz region and cathode (+) 1 region) of the PNPN switch can be detected as a transient current. The charging current of this junction is added to the collector and base junction of the open-base transistor that forms the circuit, and is amplified by this transistor itself and transiently drives the transistor placed between the dirt and the cathode.
This prevents the late effect of the PNPN switch.

However, when such a circuit is used in a subscriber circuit switch in a TD exchange that requires a high withstand voltage of 350 V or more, the transient current detection circuit itself also needs a withstand voltage of 350 V or more; Since the reverse breakdown voltage between the base and emitter of the transistor forming the
For the purpose of supplementing this, take out the PNPN switch n and the electrode and pl.

n. High voltage diodes are connected in series.

Therefore, when detecting a transient current, the n1 electrode is connected to the N of the PNPN switch.
It also operates as a dirt drive trigger signal input terminal, which tends to deteriorate the pdv/dt tolerance. In addition, the diode formed by the Pi'1 region of the thyristor is connected in series with the open-base NPN transistor that forms the transient current detection circuit, which greatly reduces the total capacitance value of the equivalent capacitor, which greatly reduces the transient current. death,
There is a drawback that the transistor provided between the gate and cathode of the thyristor may not be able to be driven reliably.

The present invention provides transient current detection that satisfies bidirectional withstand voltage with a single active element in a circuit in which a variable impedance circuit that operates independently of the semiconductor switch drive circuit used in an exchange communication path is added. dv/d depending on the circuit
The present invention is characterized in that a semiconductor switch that can reliably prevent malfunctions due to t and can be integrated into an integrated circuit will be described below in detail with reference to embodiments.

FIG. 2 shows an embodiment of the present invention, in which 6a is a first main terminal;
6b is a second main terminal, 7 and 8 are drive terminals, and 9 is a thyristor. Reference numeral 10 denotes a transistor, and reference numeral 11 denotes a resistor, which are connected between the gooto cathode of the thyristor 9 to form a variable impedance circuit.

12 is a PNP type transistor with bidirectional breakdown voltage characteristics, and when integrating this cage circuit, the current amplification factor,
Due to the requirement for operating speed, NPN) transistors (usually arranged vertically) and PNP) transistors arranged horizontally are constructed on an N-type substrate with high electron mobility. Since the emitter and collector of a horizontally arranged transistor have a symmetrical structure, it can be understood without much explanation that it has bidirectional breakdown voltage characteristics. And this PNP ) transistor 1
2 is a transient current detection circuit whose collector and emitter constitute input/output terminals 13 and 14, and is connected to the first main terminal 6a and the base of a transistor 10 forming a variable impedance circuit. Further, the dart of the thyristor 9 is connected via a diode 15 to a drive circuit consisting of a transistor I6. The diode 17 is a semiconductor switch connected between the base and emitter of the transistor 10 that connects the variable impedance circuit.

Now, to explain the operation of the semiconductor switch having the transient current detection circuit of the present invention, the first main terminals 6a, 4, the second main terminals 6
When a power source is connected between terminals b and the transistor 16 is biased from the drive terminal 7°8, the gate of the thyristor 9 is driven through the diode 15, making the thyristor 9 conductive. 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 there is no state, the transient current flows along the route 6a-+12, drives the transistor IO, and reaches the transistor 6b. . At this time, the transient current is amplified by the PNP transistor 12 of the transient current detection circuit to obtain a larger current. As a result, the date-cathode voltage of the thyristor 9 is clamped to the collector-emitter voltage of the transistor 10, thereby preventing the thyristor 9 from malfunctioning.

As explained above, the effect of the present invention on malfunction prevention is that the transient current detection circuit is connected to the thyristor anode,
Since it is directly connected to the base of the F-run raster 10, there is no deterioration in dv/dt tolerance due to the application of pseudo Nl'-to, drive signals, or reduction in transient current as described above.

In other words, for the purpose of supplementing the withstand voltage of the transient current detection circuit, PNP
The dv/d caused by the pseudo N gate trigger signal from the n1 electrode taken out from the N switch is
By connecting the pj n1 diode in series with the transient current detection circuit, the transient current is greatly reduced, and the drawback of not being able to reliably drive the base of the transistor installed between the dart and cand of the thyristor is completely eliminated. It is.

In addition, since the use of active elements eliminates the need for a large area occupied by a capacitor, the degree of integration can be improved. This provides greater benefits when an array is constructed using a plurality of semiconductor switches of this type.

[Brief explanation of the drawing]

FIG. 1 is an example of a circuit diagram of a semiconductor switch with improved characteristics of a conventional d v / d, 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, 10e
10a+12e 16...transistor, 1le
lla...Resistor, 13, 1' 4...Input/output terminal, 15, 15a, 17°17ts...Diode.

Claims (1)

[Claims] (1) A variable impedance circuit consisting of a transistor in which a thyristor with a PNPN structure is connected between a first main terminal and a second main terminal, and a resistor is connected between the emitter and the erector between the second main terminal and the gate of the thyristor. is connected in such a way that the forward-biased PN junction of this thyristor is short-circuited, and the base is open between the first main terminal and the base of the transistor of the variable impedance circuit. A semiconductor switch characterized in that a transient current detection circuit composed of a PNP type transistor having bidirectional withstand voltage is connected.