JPH056932B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor switch including a PNPN switch, and in particular, it is capable of accurately detecting the on/off state of the main current from the outside and is easy to integrate into semiconductors. This relates to semiconductor switches.

[Conventional technology]

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-resistance, and having a low on-voltage even when a large current is applied. However, since it also has a self-holding function, it has the disadvantage that when used as an on-off switch, it is relatively difficult to control off.

To turn off a PNPN switch without changing the load current, there are two methods: transiently shorting the gate and cathode to temporarily increase the holding current, making it impossible to hold the load current, and applying a reverse current to the gate. There are different ways to turn it off, which can be used depending on the current cutting ability and external circuit conditions.

Since the on/off switch constructed using these methods has a self-holding function, it may be necessary to detect the on/off state of the switch. A PNPN switch turns off with a delay of a turn-off time caused by charge accumulation time from the time of off-drive, but depending on the application of the switch, this delay time may cause problems in terms of external control. For example, when a current selection switch is configured with two on/off switches using PNPN switches, first one switch is driven off in a pulse manner, and then the other switch is driven on in a pulse manner to control the load current. When attempting to switch, there are cases where the switch that receives the OFF drive is not completely turned off, and the other switch is turned on, causing two switches to remain on at the same time. This is a phenomenon caused by the self-holding function of the PNPN switch, which continues its on-holding operation even without gate control as long as the main electrodes are externally energized, and the fact that the turn-off time is generally longer than the turn-on time. In order to prevent such malfunctions, a method is required to detect at what point the switch's load current is turned off.

FIG. 1 shows the circuit configuration of an on/off switch equipped with an off detection function. In Figure 1,
PNP transistor Q1 and NPN transistor Q2
The on control and off control of the PNPN switch 1, which is equivalently constituted by
As a result, the load current determined by the load resistance R2 of the external circuit and the power supply V1 can be turned on and off. here,
Resistor R1 is to prevent malfunction due to dv/dt effect of PNPN switch 1.
The gate firing sensitivity of is determined by this resistance R1.
In addition, the transistor Q3 temporarily shorts the gate G and cathode K of the PNPN switch 1,
This increases the minimum holding current value of the PNPN switch 1 and shifts it to the off state.

Furthermore, the transistor Q4 is for detecting the on/off state of the PNPN switch 1. In other words, since the bases and emitters of transistors Q2 and Q4 are connected in common, transistors Q2 and Q4
The base bias conditions are almost the same, and the respective collector currents are also almost the same. Here, the collector current of transistor Q2 is PNPN
Since it is part of the anode current of switch 1, if the collector current of transistor Q4 is monitored,
The on/off state of the PNPN switch 1 can be detected. Figure 2 schematically shows the above operating waveforms, where I _C is the on-drive current, I _B is the off-drive current, I _A is the anode current, and I _C is the transistor Q4.
The collector current of is shown respectively. As is clear from Fig. 2, the anode current I _A of PNPN switch 1
The on/off information can be detected from the presence or absence of the collector current I _C of the transistor Q4, that is, from the voltage drop across the resistor R3 in FIG.

[Problem to be solved by the invention]

However, the circuit configuration shown in FIG. 1 has the following drawbacks. The first drawback is that off detection is not temporally accurate. Normally, the PNPN switch 1 and the transistor Q4 are separate devices, so their turn-off times differ because they have different sizes and shapes, and because the external load conditions cannot always be the same. moreover,
Since the turn-off time of the PNPN switch 1 tends to be the sum of the turn-off times of the component transistors Q1 and Q2, accurate off detection cannot be performed with the transistor Q4. That is, when the transistors Q2 and Q4 are turned off in FIG. 1, their bases and emitters are simultaneously short-circuited by the transistor Q3, so they are quickly turned off.
PNP transistor Q1 turns off from that point on. As a result, as shown at t4 _{and t5} in FIG. 2, the OFF detection is performed before the PNPN switch 1 is completely turned off, and its purpose is not fully achieved. The second drawback is that the number of elements increases because the transistor Q4 is added for off-detection. This increases the area occupied by the element when considering semiconductor integrated circuits, which is undesirable from an economical point of view.

As described above, the semiconductor switches according to the prior art have disadvantages in that the off-detection characteristics are insufficient and the device occupies a large area.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor switch which has accurate main current on/off detection characteristics, has a small area occupied by the element, and is suitable for integration.

[Means to solve the problem]

For this purpose, the present invention provides a main current switch circuit with a second anode terminal for detecting the on/off state of the main current, so that it can accurately detect the on/off state of the main current. It is characterized by

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.
FIG. 3 is a circuit configuration diagram showing an example of a semiconductor switch that is an improvement on the conventional semiconductor switch described above.
NPN transistor, Q3 is for turn-off
In the NPN transistor, R1 is a resistor for preventing malfunction due to the dv/dt effect, V1 and R2 are a load power source and a resistor, respectively, and V2 and R3 are a power source and a resistor for on/off detection, respectively. Further, A1 is a first anode terminal, A2 is a second anode terminal, K is a cathode terminal, G is a gate terminal, and B is an off control input terminal. In this embodiment, a main current switch circuit of the semiconductor switch is configured by a four-terminal PNPN switch 2 consisting of transistors Q11, Q12, and Q2, and a turn-off switch circuit of the semiconductor switch is configured by an NPN transistor Q3 and a resistor R1. There is. In the circuit configuration shown in Fig. 3, this is achieved by supplying an on-drive current from the on-control gate G, and the PNPN switch consisting of Q11 and Q2 is turned on, which is determined by the power supply V1 and resistor R2 of the external circuit. A load current flows from anode A1 to cathode K. At the same time, the PNPN switch composed of Q12 and Q2 is also turned on, and the external circuit power supply V2 and resistor R3 are turned on.
An on-detection current determined by , flows from the anode A2 to the cathode K. Next, off control is performed by injecting an off drive current from off control input terminal B, and transistor Q3 is turned on.
Between gate G and cathode K of PNPN switch 2,
That is, by short-circuiting the base and emitter of transistor Q2, the holding current value of the PNPN switch is increased, and the load current flowing from anode A1 to cathode K is turned off. Also,
At the same time, the on-detection current flowing from the anode A2 to the cathode K is also turned off.

Now, in the circuit configuration shown in Figure 3, the on/off detection of the main current is carried out by connecting the base collector of the PNP transistor Q11 through which the main current flows.
This is done depending on the presence or absence of emitter current of PNP transistor Q12. In the turn-off operation of the PNPN switch, first, the NPN transistor Q2 is turned off by shorting its base and emitter by the transistor Q3, and then the PNP transistors Q11 and Q12 turn off at the same time, so that the anodes A1 and A2 are turned off. The time during which the inflow current is turned off is approximately the same. Similarly, regarding the turn-off operation of the PNPN switch,
After NPN transistor Q2 turns on, PNP
Transistors Q11 and Q12 turn on simultaneously. As a result, the presence or absence of an inflow current from the second anode A2 indicates the on/off state of the main current at an appropriate time, making it possible to obtain a semiconductor switch with accurate on/off detection characteristics. be.

In addition, the 4-terminal PNPN switch 2 shown in FIG.
can be a unitary device. Fourth
The figure shows the cross-sectional structure of this 4-terminal PNPN switch 2, in which 10 is an N-type semiconductor substrate,
11, 12, 13 are P-type diffusion layers, 14 is an N-type diffusion layer, 15 is an oxide film, 16a, 16b, 16
c and 16d indicate metal wiring layers, respectively. 4 terminals
The first anode terminal A1 of the PNPN switch 2 is
Similarly, the second anode terminal A2, gate terminal G, and cathode terminal K are taken out from the metal wiring layer 16a through the P-type diffusion layer 11, and the P-type diffusion layer 13,
It is taken out from the metal wiring layers 16b, 16c, and 16d via the P-type diffusion layer 12 and the N-type diffusion layer 14. 4 terminals
Since the PNPN switch 2 can be formed into an integral structure as shown in FIG. 4, the circuit shown in FIG. 3 can have a small element occupation area. Further, according to the test experiments conducted by the present inventors, it was found that the operation of the circuit shown in FIG. 3 is that the transistor Q12 is turned off after the transistor Q11 is turned off, and there is a time margin for detecting the main current off. That is, when the circuit shown in FIG. 3 is integrated with a semiconductor, an economical design with a high degree of integration can be achieved, and a semiconductor switch can be obtained that can accurately detect on/off of the main current.

FIG. 5 is a circuit configuration diagram showing an embodiment of the semiconductor switch according to the present invention. Transistors Q5 and Q6 for current shunting are added to the circuit configuration shown in FIG. 3 to further enhance the current cutting ability as a semiconductor switch. It is something that

That is, in this embodiment, the transistor Q1
A main current switch circuit of a semiconductor switch is constituted by a four-terminal PNPN switch 2 consisting of transistors Q1, Q12, and Q2, and first and second transistors Q5 and Q6 for current shunting. In Fig. 5, the same symbols are used for the same parts as in Fig. 3, but the external circuit power supplies V1 and V2 and the resistor R shown in Fig.
2 and R3 are omitted. In this circuit configuration as well, on-control is achieved by supplying an on-drive current from the gate G, first turning on the four-terminal PNPN switch 2, then turning on the transistors Q5 and Q6.
is turned on, and a load current flows from the first anode A1 to the cathode K. Moreover, since the transistor Q12 is also in the on state at the same time, the second
An on-detection current flows from the anode A2 to the cathode K. Next, off control is also performed by injecting an off drive current from off control input terminal B, first transistor Q3 is turned on, 4-terminal PNPN switch 2 is turned off, and then current shunting transistors Q5 and Q6 are turned off. , anode A
The load current flowing from 1 to cathode K is cut off. At the same time, the on-detection current flowing from the second anode A2 to the cathode K is also turned off.

In this embodiment, since the load current is divided into the PNPN switch 2 and the transistors Q5 and Q6, a semiconductor switch having a greater current cutting ability than the semiconductor switch shown in FIG. 3 can be obtained. Also, similar to the explanation in Figures 3 and 4, 4
Since the terminal PNPN switch 2 can have an integral structure,
The device occupies a small area.

〔Effect of the invention〕

As described in detail above, the present invention detects the on/off of the main current from the second anode terminal of the main current switch circuit, thereby making the detection characteristics accurate, and Since the area occupied by the device can be reduced, high integration is possible, and a semiconductor switch with excellent characteristics and economy can be provided.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional semiconductor switch.
Figure 2 is an operating waveform diagram of the circuit configuration shown in Figure 1, Figure 3 is a circuit configuration diagram showing an example of a semiconductor switch that is an improvement on a conventional semiconductor switch, and Figure 4 is a four-terminal diagram of the circuit configuration shown in Figure 3. Structural cross section of PNPN switch,
FIG. 5 is a circuit diagram showing an embodiment of a semiconductor switch according to the present invention. 1...PNPN switch, 2...4 terminal PNPN
Switch, Q1, Q2, Q11, Q12...
Transistor for PNPN switch configuration, Q3, Q
5, Q6...transistor, A1...first anode terminal, A2...second anode terminal, K...
Cathode terminal, G...gate terminal, B...off control input terminal.

Claims (1)

[Claims] 1. A first anode terminal for the main electrode, a cathode terminal, a gate terminal for control, and a second terminal for current detection.
A semiconductor switch comprising: a main current switch circuit having an anode terminal; and a turn-off switch circuit connected between the gate and cathode terminals of the main current switch circuit; , a current detection transistor whose base and collector are respectively connected to the same polarity parts of the N layer and P layer of the PNPN switch excluding the main electrode terminal, and first and second current shunting transistors, One main electrode terminal of the PNPN switch is connected to the emitter of the first current shunting transistor,
The other main electrode terminal of the PNPN switch is connected to the base of the second current shunting transistor, and the base and collector of the first current shunting transistor are connected to the collector and emitter of the second current shunting transistor, respectively. The emitter and collector of the first current shunting transistor are connected to the first anode terminal and cathode terminal for the main electrode of the main power switch circuit, respectively, and the gate terminal of the PNPN switch and the current The emitters of the detection transistors are configured as a gate terminal for controlling the main power switch circuit and a second anode terminal for current detection, respectively, and the on/off state of the inflow current of the first anode terminal is controlled by the second anode terminal. A semiconductor switch characterized in that detection is performed by an inflow current to an anode terminal of the switch.