JPS6043692B2 - semiconductor switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch using a PNPN switch, and particularly to a semiconductor switch that is less likely to malfunction even at high temperatures and has high gate firing sensitivity.

A PNPN switch having a PNPN layer structure can withstand voltage in both directions, and is widely used as a switching element with a self-holding function. FIG. 1 schematically shows a PNPN switch with control terminals.
As shown in FIG. 1, a PNPN switch 1 is normally used with a resistor R connected between its cathode gate GK and its cathode. This resistor R has a role as a short emitter resistor, and prevents a decrease in breakdown voltage and malfunction tolerance. The equivalent circuit of the PNPN switch 1 in FIG. 1 is as shown in FIG.
It is expressed as a composite circuit with N transistor Q2. As is clear from Fig. 2, the resistor R1 is connected between the base and emitter of the NPN transistor Q2.
The collector-emitter breakdown voltage of the transistor Q2, that is, the forward breakdown voltage of the PNPN switch 1 is improved. Furthermore, although ignition of the PNPN switch 1 is normally performed by flowing current into the cathode gate GK,
Even without this gate current, the PN switch 1 has the property of erroneous firing due to a phenomenon called rate effect.
That is, when a sudden transient voltage in the forward direction is applied between the anode A and the cathode K of the PNPN switch 1, a transient current flows through the second junction capacitance Cj2 of the PNPN switch 1 to the base of the NPN transistor Q2. flowing in,
This is the characteristic that the PNPN switch 1 is turned on. The critical voltage increase rate or D
It is called v/Dt tolerance. That is, the Dv/Dt tolerance is a quantification of the malfunction tolerance due to the rate effect. In addition to improving the withstand voltage mentioned above, the resistor R1 in FIG.
It also improves v/Dt tolerance. This is the junction capacitance C
, 2 by-passing the resistor R1. However, the gate ignition sensitivity is high and Dv/D
When trying to obtain a semiconductor switch with a large t tolerance, the above-mentioned improvement by resistance B1 cannot be said to be appropriate. That is, in order to increase the gate firing sensitivity, the value of the resistor R1 must be increased. This is because this tends to reduce the Dv/Dt tolerance. Also, when considering temperature characteristics, when the temperature rises, the base-emitter voltage BE of the NPN transistor Q2 in Figure 2 decreases, so P
The ignition sensitivity of the NPN switch 1 increases. This is D
This means that the v/Dt tolerance decreases. As mentioned above, conventional semiconductor switches using PNPN switches are as follows.
There is a limit to increasing both the gate ignition sensitivity and the Dv/Dt tolerance, and this is particularly exacerbated under high temperature conditions. An object of the present invention is to provide a semiconductor switch which has a high Dv/Dt tolerance even at high temperatures and also has a high gate firing sensitivity, while eliminating the drawbacks of the prior art described above.

That is, the present invention connects a resistor to one main terminal of a PNPN switch, and short-circuits this resistor and the PN junction of the PNPN switch including the main terminal by an electrical shorting means,
Furthermore, by using a capacitive circuit to detect the rate of voltage increase applied to the PNPN switch and allowing the displacement current to flow into the connection point between the main terminal and the resistor, the Dv/Dt withstand capability can be maintained even at high temperatures. To obtain a semiconductor switch which has a high gate ignition sensitivity and a high gate firing sensitivity.

The present invention will be described in detail below using the drawings.

FIG. 3 is a circuit diagram showing a first embodiment of a semiconductor switch according to the present invention. A resistor R2 is connected to the cathode K1, which is one of the main terminals of the semiconductor switch 1 shown in FIG. , and a capacitor C1 is connected as a capacitive circuit between the anode gate GA and the cathode K1.
When a rapidly rising forward transient voltage is applied to this semiconductor switch, a transient current flows through the second junction capacitance of the PNPN switch 1 to the cathode gate GK.
However, on the other hand, a transient current flows into the resistor R2 through the capacitor C1, so the potential of the cathode K1 also rises.Here, the condition for erroneous firing of the PNPN switch 1 is the voltage between the cathode gate and the cathode. reaches the activation voltage of the PN junction (0.6 to 0.7 V for Si). Therefore, in the circuit shown in FIG. 3, both the potential of the cathode gate GK< and the potential of the cathode K1 rise. Therefore, the voltage between the cathode gate and the cathode does not increase so much, and the Dv/Dt withstand capability becomes high.At this time, the resistance R2
The resistance value cannot be increased if the on-voltage and on-resistance as a semiconductor switch are not desired to be too large. On the other hand, in order to increase the gate firing sensitivity of the PNPN switch 1, it is necessary to increase the resistance R1 and decrease the resistance R2. All of these conditions tend to lower the Dv/Dt tolerance.

However, when the second junction capacitance of the thyristor 1 is C,2, if the value of the capacitor C1 is selected so that CJ2,Rl:Cl*R2, a sufficiently large Dv/Dt tolerance can be obtained.

This is because the potentials generated at the cathode gate GK and the cathode K1 become approximately the same when a sudden transient voltage is applied. Since the above is hardly affected by temperature, it is possible to obtain a semiconductor switch that has sufficiently large Dv/Dt tolerance even in high temperature conditions and has high gate firing sensitivity. However, since the circuit shown in FIG. 3 includes the capacitor C1, it is not suitable for fabrication into a monolithic IC. The following embodiment takes this into consideration. FIG. 4 is a circuit diagram showing a second embodiment of the semiconductor switch according to the present invention.

The difference in Fig. 4 from Fig. 3 is the PNPN switch 1.
The base of an equivalent PNP transistor (N base layer)
A capacitive circuit connected to three diodes Dl, D2,
The point is that it is composed of D3 and one transistor Q3.
In the circuit shown in FIG. 4, when a sudden forward transient voltage is applied, the diodes Dl, D2, D3 act as capacitors because they are all in a reverse bias state, and the transient current flows through the diodes Dl, D2, D3 and Flows into resistor R2 through transistor Q3. At this time, a portion of the transient current flowing through the diode D2 flows to the base of the transistor Q3, so that the transient current flowing through the transistor Q3 is amplified and flows into the resistor R2. Therefore, if the current amplification factor of the transistor Q3 is made large, a large Dv/Dt tolerance can be obtained for the same reason as explained in FIG. 3. Here, diode D1 is transistor Q3
Since there is a slight delay time until the amplification effect occurs,
This is to compensate for the gap and allow a transient current to flow. Furthermore, when a repeated transient voltage is applied, diode D3 connects diode D2 and the collector of transistor Q3.
By rapidly discharging the charge accumulated in the base junction, Dv
This is to prevent the protective effect against /Dt from being impaired. The semiconductor switch shown in Figure 4 does not include a capacitor, so it can be easily integrated into an IC, and the current amplification factor of the transistor has a positive temperature characteristic even at high temperatures, so it has a sufficiently large Dv/Dt tolerance. is obtained. FIG. 5 is a circuit diagram showing a third embodiment of the semiconductor switch according to the present invention, in which electrical shorting means consisting of diodes D4, D5 and a transistor Q4 is added to the circuit shown in FIG. be.

In the circuit shown in FIG. 5, a resistor R1 and a transistor O are connected between the cathode gate GK and the new sort K2.
The parallel circuit with this becomes a kind of variable impedance circuit. That is, normally the transistor α is in a cut-off state, so the only impedance between the cathode gate GK and the cathode K2 is the resistor R1, but when a transient voltage is applied between the anode A and the cathode K2, the transient current passing through the diode D4 flows through the transistor The impedance between the cathode gate GK and the cathode K2 becomes extremely small because it flows into the base of Q4 and turns on the transistor Q4. Therefore, the potential rise of cathode gate GK when a transient voltage is applied is only slight. On the other hand, the effect of the large transient current amplified by the action of the transistor O flowing into the resistor 2 and raising the potential of the cathode K1 as described in FIG. 4 remains unchanged.

From these facts, Dv/Dt of the semiconductor switch in Fig. 5
The tolerance will be very large. Here, diode D
5 is for discharging the charge accumulated in the diode D4, and since a discharge path is also provided in the capacitive circuit including the transistor O, the Dv/Dt withstand capacity does not decrease even if a transient voltage is repeatedly applied. In addition, in the circuit shown in FIG. 5, the resistance R1 becomes Dv/
Since it has almost no relation to the Dt tolerance, the resistor R1 can be set to a fairly large value, and as a result, a semiconductor switch with very high gate firing sensitivity and Dv/Dt tolerance can be obtained.

Further, even in a high temperature state, a high Dv/Dt tolerance can be maintained in the same manner as explained in FIG. 4. In addition to the features described so far, the semiconductor switch of the present invention has resistor B2.
It also has the feature that the gate potential is increased by the addition of , making gate turn-off easier.

In addition, although the above embodiment shows an example in which the capacitive circuit is connected to the N base layer of the PNPN switch, it may also be connected to a multi-collector provided in the N base layer, or a multi-collector that does not require bidirectional withstand voltage. A similar effect can be obtained by connecting to the anode.

As explained above, according to the present invention, a semiconductor j-switch with extremely high gate firing sensitivity and d■/Dt tolerance can be obtained, and these characteristics are maintained even under high temperature conditions.

At the same time, this semiconductor switch also has the effect of easy gate turn-off.

[Brief explanation of drawings]

FIG. 1 is a schematic illustration of a conventional PNPN switch. FIG. 2 is an equivalent circuit diagram of the switch shown in FIG. FIG. 2 is a circuit diagram showing the second and third embodiments. 1...PNPN switch, A...anode, K, Kl, K2...cathode, GA...
Anode gate, GK...Cathode gate, R
l, R2...Resistor, C1...Capacitor, D1-D5...Diode, Q1-Q4...
・Transistor.

Claims (1)

[Claims] 1. A PNPN switch and a resistor having a four-layer PNPN structure;
The PNP is provided with an electrical shorting means and a capacitive circuit.
Connect one end of the resistor to one main terminal of the N switch to form the other end of the resistor as a new main terminal, and connect the electrical connection between the resistor and the PN junction of the PNPN switch including the main terminal. A structure configured to short-circuit by the short-circuiting means, detect the rate of increase in forward voltage applied to the PNPN switch by using the capacitive circuit, and cause the displacement current to flow into the connection point between the main terminal and the resistor. A semiconductor switch characterized by: 2. The semiconductor switch according to claim 1, wherein the electrical shorting means comprises one resistor. 3. The electrical shorting means consists of one resistor, two diodes, and one transistor, and the transistor of the electrical shorting means becomes conductive when the rate of increase in forward voltage applied to the PNPN switch is detected. A semiconductor switch according to claim 1 or 2, characterized in that the semiconductor switch is configured so that: 4. The semiconductor switch according to claim 1 or 2, wherein the capacitive circuit consists of one capacitor. 5. A patent characterized in that the capacitive circuit consists of three diodes and one transistor, and the capacitive circuit is configured to amplify the displacement current due to the forward voltage increase rate applied to the PNPN switch. A semiconductor switch according to claim 1 or 2.