JPH0133973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch circuit including a PNPN switch, and in particular to a semiconductor switch that has easy gate turn-off operation, low on-voltage, and occupies a small area.

In general, a PNPN switch as a semiconductor switch has advantages over a transistor switch, such as being able to obtain a high breakdown voltage in both directions, having a low on/off resistance, and being able to have a low on-state voltage even when a large current is applied. However, at the same time, since the PNPN switch has a self-holding function, it has the disadvantage that when used as an on/off switch, it is relatively difficult to control the switch off. There are two ways to turn off a PNPN switch: one is to reduce the load current to below the holding current value, and the other is to cut off the load current by applying a reverse current to the gate (gate turn-off method). Generally, the former method is used, but the latter method is used to turn off the load without changing the load current.

FIG. 1 shows a circuit configuration using this PNPN switch so that the gate turn-off operation can be performed more easily. In this circuit configuration, equivalently the PNP transistor _Q1
PNPN switches Q1 _and Q2 (hereinafter simply referred to as PNPN switch Q
1, Q2. ) and Darlington-connected transistors Q4 and Q5, most of the current between the anode A and cathode K flows to the transistors Q4 and Q5, so that the cutting transistor Q3 draws it out from the gate G. Gate turn-off operation can be performed even with a small collector current. That is, it is possible to cut off a relatively large load current with a small off-control current.

However, the semiconductor switch circuit having the circuit configuration shown in FIG. 1 has the following problems.
First, on the premise of semiconductor integration, if we want to obtain a semiconductor switch with a high cutting current capacity, that is, a semiconductor switch that can cut a large current, the required area of each component transistor must be increased, as shown in Figure 1. Since the circuit configuration has a large number of elements, the overall degree of integration cannot be increased. Also, the on-voltage as a semiconductor switch is V _ON (PNPN switch) +
V _BE Q5, which is large.

As described above, gate turn-off type semiconductor switches using PNPN switches according to the prior art have disadvantages in that the degree of integration cannot be improved due to the large number of elements and that the on-state voltage is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor switch which has a high cutting current capacity, has a relatively small overall area, and has a low on-voltage.

The present invention is equivalent to a PNP transistor and an NPN transistor.
An additional transistor for current shunting whose emitter and base are commonly connected to the PNP transistor constituting the PNPN switch, and a transistor for operating the additional transistor are provided for the PNPN switch consisting of a transistor. Add the collector to the collector of the transistor for operating the transistor, the gate terminal of the PNPN switch to one main terminal of the switch element for gate/turn-off, and the base of the transistor for operating the additional transistor to the other main terminal of the switch element for gate/turn-off. By connecting each of the additional transistor operating transistors to the gate and setting the emitter potential of the additional transistor operating transistor to be lower than the potential of the cathode terminal of the PNPN switch, the additional transistor operating transistor was configured to be controlled by the current flowing through the gate turn-off switch element. It is characterized by

Hereinafter, the present invention will be explained in detail using the figures. FIG. 2 is a circuit diagram showing a first embodiment of a semiconductor switch according to the present invention. In the figure, Q1, Q2
are the PNP transistor and NPN transistor that make up the PNPN switch, Q3 is the NPN transistor that is the gate turn-off switch element, _Q6
is a PNP transistor that constitutes a PNPN switch
An additional PNP for current shunting that commonly connects the emitter and base to Q ₁ and shunts the load current from the anode of the PNPN switch to reduce the load current flowing to the PNPN switches Q ₁ and Q ₂ .
The transistor _Q7 is an NPN transistor for operating the additional transistor that operates the additional transistor _Q6 only during OFF control, and R1 is a resistor for preventing malfunction of the PNPN switch. Further, A is an anode, K is a cathode, G is a gate, B is an off control terminal, and E is a power supply terminal.

In this circuit configuration, ON control is performed by supplying a gate drive current from the gate G.
PNPN switches Q1 and Q2 are turned on,
Load current flows from anode A to cathode K.
At this time, gate turn-off transistor Q
3 is in an off state, and transistors Q6 and Q7 are also in an off state. Next, for off control, turn off control terminal B.
When current flows into the gate turn-off transistor Q3, the gate turn-off transistor Q3 is turned on, and then the emitter current of the transistor Q3 flows to the base of the transistor Q7, which turns on and draws the collector current of the transistor _Q6 from its collector. Turn on _Q6 .
By turning on this additional current shunting transistor Q ₆ , a part of the load current flowing from the anode of the PNPN switch is shunted to transistor Q ₆ - transistor Q ₇ and flows through PNP transistor Q ₁ - NPN transistor. The load current flowing into Q ₂ decreases. In this state NPN transistor _Q2
transistor for gate turn-off from the base of
Since current is drawn to the collector of _Q3 , NPN transistor _Q2 -PNP transistor _Q1 are easily turned off, turning off the PNPN switch.

However, as a condition for the above operation, it is necessary to set the emitter potential of the transistor _Q7 (potential of the power supply terminal E) lower than the potential of the cathode terminal K of the PNPN switch in the on state.

As is clear from the above explanation, the additional transistor operating transistor Q ₇ is controlled by the current flowing through the gate turn-off transistor Q ₃ , so the additional current shunting transistor Q ₆ is turned on only during off control. Thus, the load current flowing from the anode of the PNPN switch is shunted to reduce the load current flowing to the PNPN switches Q ₁ and Q ₂ .
Since there is a proportional relationship between the load current of the PNPN switch and the gate turn-off current required for disconnection at an almost constant ratio (called gate turn-off gain), according to the circuit configuration shown in Figure 2,
The cutting current capability can be greatly improved compared to the case of a PNPN switch alone. In addition, the on-voltage is the on-state, and the on-operating element is
Since there are only PNPN switches Q1 and Q2, V _ON
(PNPN switch) alone, and is smaller than in the case of the circuit shown in FIG. Furthermore, this PNPN
When manufacturing the switch and the additional transistor for current shunting, if the PNP transistor Q1 has a horizontal structure, the emitter and base regions of the PNP transistors Q1 and Q6 may be the same, and the collector of the transistor Q6 is connected to the PNPN switches Q1 and Q2. It can be formed by simply adding areas, so
It only requires a slight increase in area compared to a PNPN switch. As a result, the cutting current capability is high, the on-voltage is low, and the overall area occupied is small, so when integrated with semiconductors, high performance is achieved.
Furthermore, an economical semiconductor switch with a high degree of integration can be obtained. Although the circuit shown in FIG. 2 uses a transistor as the gate turn-off switch element, the same effect can be obtained by using a PNPN switch instead of the transistor.

In addition, when preventing dv/dt malfunction only with resistor R1 as in the circuit shown in Figure 2, the resistance value conflicts with the dv/dt tolerance and gate firing sensitivity, so high sensitivity and high dv/dt are required. Although it is not possible to obtain a semiconductor switch with high durability, it is possible to improve the characteristics of the semiconductor switch by adding another circuit element to the circuit configuration shown in FIG.

Figure 3 shows the disadvantages of the PNPN switch.
This is another embodiment of the present invention in which a circuit for preventing malfunction due to the dv/dt effect is added.
1 is a circuit for preventing malfunction due to the dv/dt effect. According to this embodiment, a semiconductor switch having high sensitivity, high dv/dt tolerance, and the characteristics described in FIG. 2 can be obtained.

As explained above, the present invention is equivalent to
For a PNPN switch composed of a PNP transistor and an NPN transistor, an additional transistor for current shunting whose emitters and bases are commonly connected to the PNP transistor constituting the PNPN switch, and the additional transistor is operated only during off control. By providing a transistor for operating an additional transistor, it is possible to obtain a semiconductor switch with a high cutting current capacity and a low on-voltage.Moreover, since the entire occupied area is small, it is possible to obtain a semiconductor switch with a high performance when integrated with semiconductors. It is possible to obtain an economical semiconductor switch that can be integrated.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional semiconductor switch.
FIGS. 2 and 3 are circuit configuration diagrams showing first and second embodiments of the semiconductor switch according to the present invention, respectively. Q1, Q2: Transistors for PNPN switch configuration, Q3 to Q8: Transistors, D1, D
2: Diode, R1: Resistor, A: Anode terminal, K: Cathode terminal, G: Gate terminal, B: OFF control terminal, E: Power supply terminal.

Claims (1)

[Scope of Claims] 1. A PNPN switch comprising anode and cathode main electrode terminals and a control gate terminal and equivalently composed of a PNP transistor and an NPN transistor, and a PNP transistor constituting the PNPN switch. an additional transistor for current shunting whose emitters and bases are commonly connected, a transistor for operating the additional transistor, and a switch element for gate turn-off of the PNPN switch, and the collector of the additional transistor is connected to the additional transistor. Connect the gate terminal of the PNPN switch to the collector of the transistor for operating the transistor, connect the gate terminal of the PNPN switch to one main terminal of the switch element for gate/turn-off, and connect the base of the transistor for operating the additional transistor to the other main terminal of the switch element for gate/turn-off. and the emitter potential of the transistor for operating the additional transistor is set lower than the potential of the cathode terminal of the PNPN switch, and the transistor for operating the additional transistor is controlled by the current flowing through the gate turn-off switch element. Features of semiconductor switches. 2 The emitter region of the PNP transistor constituting the above PNPN switch and the emitter region of the above additional transistor for current shunting, and the base region of the PNP transistor composing the above PNPN switch and the base region of the above additional transistor for current shunting are integrated, respectively. A semiconductor switch according to claim 1, characterized in that the semiconductor switch has the following structure.