JPS628075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drive circuit for a semiconductor communication path switch using a four-terminal thyristor.

Generally, when a communication path switch in an automatic telephone exchange is configured with a four-terminal thyristor, in order to maintain the thyristor in a conductive state, a constant current source is used to flow current through at least one of the anode gate and cathode gate of the four-terminal thyristor. I need to continue.

For this reason, a semiconductor switch drive circuit having a configuration as shown in FIG. 1 has conventionally been used. More specifically, the drive circuit shown in FIG. 1 includes a transistor Q1 connected to a semiconductor communication path switch (four-terminal thyristor) SW through a current absorption terminal 1 so as to absorb a constant current, and a base emitter of this transistor Q1. A constant current absorbing section including a resistor R1 and a reference voltage generating diode D1 connected in series therebetween, and a transistor Q2 connected to supply a constant current to the semiconductor channel switch SW via a current supply terminal 2. and a constant current supply section including a resistor R2 and a reference voltage generating diode D2 connected in series between the base and emitter of the transistor Q2. This drive circuit is controlled by the conduction/non-conduction state of transistor Q3 of control circuit 5 connected via control terminals 3 and 4. Note that terminals A and B of the semiconductor communication path switch SW are each connected to a communication line. Since the reference voltage generating diodes D1 and D2 used in this drive circuit do not have ideal characteristics, their terminal voltages vary depending on the current value.
Therefore, when the voltage of the power supply E fluctuates, the terminal voltages of the reference voltage generating diodes D1 and D2 fluctuate, and as a result, both the absorption current value and the output current value for the semiconductor channel switch SW fluctuate. In order to prevent this, a constant current circuit is used in the control circuit 5, and reference voltage generation diodes D1 and D2 are used.
Although it is possible to keep the current flowing through the circuit constant regardless of fluctuations in the power supply voltage, the control circuit 5 is inevitably complicated.

On the other hand, a two-terminal type circuit as shown in FIG. 2a is used as a circuit that supplies a constant current to a load without being affected by fluctuations in power supply voltage. This drive circuit makes the current to the reference voltage generating diode D11 a constant current by the transistor Q12, and also makes the current to the reference voltage generating diode D12 a constant current by the transistor Q11, thereby controlling the current to the load 6. is kept constant regardless of fluctuations in the power supply voltage. However, since this drive circuit is of a two-terminal type, in order to drive the switch SW by applying a constant current to at least one gate of the semiconductor communication path switch SW using a four-terminal thyristor, the circuit shown in Fig. 2b is used. As shown, two identical circuits are required, which is not economical.

Therefore, an object of the present invention is to provide a semiconductor switch drive circuit that can drive a semiconductor communication path switch at a constant current without being affected by fluctuations in power supply voltage, and that facilitates integration into a semiconductor integrated circuit. shall be.

The semiconductor switch driving circuit of the present invention has first and second collectors, a base, and an emitter.
a current supply type constant current circuit comprising a PNP multi-collector transistor; a series circuit of a first resistor and a first diode connected between the base and emitter of the multi-collector transistor; a resistor connected between the collector and the base; first and second resistors whose bases and emitters are commonly connected to each other;
an NPN transistor, a second resistor connected between the commonly connected base and emitter, and a second
a current absorbing constant current circuit having a series circuit of diodes; connecting the second collector of the multi-collector transistor and the bases of the first and second NPN transistors; connecting the base of the transistor and the collector of the first NPN transistor; a connection point between the first resistor and the first diode; and a connection point between the second resistor and the second diode. a voltage is applied to; the first collector of the multi-collector transistor is used as a current supply terminal to the semiconductor switch;
The semiconductor switch is characterized in that the collector of the NPN transistor is used as a current absorption terminal from the semiconductor switch, and the semiconductor switch is driven with a constant current.

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

FIG. 3 is a circuit diagram showing an embodiment of a semiconductor switch driving circuit according to the present invention.

As shown in the figure, the semiconductor communication path switch SW is connected via the current supply terminal 21 and the current absorption terminal 22.
The drive circuit of this invention connected to the current supply terminal 21 includes a multi-collector transistor Q21 whose first collector is connected to the current supply terminal 21,
a current value setting resistor R21 connected in series to the emitter of transistor Q1, and a reference voltage generating diode D connected to the base of the transistor Q21 and the emitter of the transistor Q21 via the resistor R21.
21, a current supply type constant current circuit in which the connection point between the resistor R21 and the diode D21 is connected to the control circuit 25 via the control terminal 23, and the collector is connected to the current absorption terminal 22 and the base is connected to the transistor Q21. A pair of transistors Q22a connected to the second collector of
The transistor Q21 has a base and an emitter commonly connected to the base and emitter of the transistor Q2a.
A pair of transistors Q22b whose collector is connected to the base of the transistor Q22b and the transistors Q22a and Q
22b, a current value setting resistor R22 connected in series to the common emitter of the transistors Q22b, and a reference voltage generating diode D22 connected to the common base of the transistors Q22a and Q22b and the common emitter of the transistors Q22a and Q22b via the resistor R22. a current absorption type constant current circuit including a connection point between the resistor R22 and the diode D22 and connected to a control circuit 25 via a control terminal 24;
It consists of a starting resistor R23 connected between the base and second collector of the transistor Q21.

In this drive circuit configured as described above, the currents flowing out from the pair of collectors of the multi-collector transistor Q21 are equal to each other,
The value is determined by the base-emitter voltage of multi-collector transistor Q21. Further, the current value flowing into the collector of paired transistor Q22a is equal to the current value flowing into the collector of paired transistor Q22b, and these current values are defined by the base-emitter voltages of paired transistors Q22a and Q22b. The base-emitter voltage of each of the multi-collector transistor Q21 and the paired transistors Q22a and Q22b is the value obtained by subtracting the voltage across the current value setting resistor R21 or R22 from the voltage across the reference voltage generating diode D21 or D22. . Here, the current flowing through the reference voltage generating diode D21 is made constant by the paired transistor Q22b, and the current flowing through the reference voltage generating diode D22 is made constant by the pair transistor Q22b.
A current made constant by the multi-collector transistor Q21 flows through the transistor Q21. Therefore, the voltage generated across each of these reference voltage generating diodes D21 and D22 remains constant regardless of fluctuations in the power supply voltage. Therefore, both the current value supplied to the semiconductor communication path switch SW from the current supply terminal 21 and the current value absorbed from the current absorption terminal 22 can be kept constant.

Note that 25 is a control circuit that controls the operation of the drive circuit described above. That is, the operation of the drive circuit is controlled by controlling the transistor Q23 in the control circuit 25 to be conductive or non-conductive. In addition, semiconductor communication path switches
Terminals A and B of SW are each connected to a communication line.

As described above, according to the present invention, a semiconductor switch drive circuit is provided which can drive a semiconductor communication path switch at a constant current without being affected by fluctuations in power supply voltage and which facilitates integration into a semiconductor integrated circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional semiconductor switch drive circuit, FIGS. 2a and b are circuit diagrams showing another example of a circuit for driving a load with constant current, and FIG. 3 is a circuit diagram showing an example of a semiconductor switch drive circuit according to the present invention. FIG. 1 is a circuit diagram showing an example of a circuit. 21...Current supply terminal, 22...Current absorption terminal, 23, 24...Control terminal, Q21...Multi-collector transistor, Q22a, Q22b...
Pair transistor, D21, D22...Reference voltage generation diode, R21, R22...Resistor for current value setting, R23...Starting resistor.

Claims (1)

[Scope of Claims] 1. A PNP multi-collector transistor having first and second collectors, a base, and an emitter; a first resistor connected between the base and the emitter of the multi-collector transistor;
a current supply constant current circuit having a series circuit of diodes; a resistor connected between the second collector and the base of the multi-collector transistor; first and second NPNs whose bases and emitters are commonly connected to each other; a current absorbing constant current circuit comprising a transistor and a series circuit of a second resistor and a second diode connected between the commonly connected base and emitter; the second collector of the multi-collector transistor; and the bases of the first and second NPN transistors; the base of the multi-collector transistor and the collector of the first NPN transistor; the first resistor and the first diode; applying a voltage to a connection point between the second resistor and the second diode; using the first collector of the multi-collector transistor as a current supply terminal to the semiconductor switch; The collector of the second NPN transistor is used as a current absorption terminal from the semiconductor switch,
A semiconductor switch driving circuit characterized in that the semiconductor switch is driven with a constant current.