JPH03113914A - Semiconductor switch - Google Patents

Abstract

PURPOSE:To make the on-off detection characteristic of a main current suitable and to reduce the area occupied of an element by detecting the on-off state of a flowing current to a 1st anode terminal with a flowing current of a 2nd anode terminal. CONSTITUTION:The emitter of a transistor(TR) Q1 being a component of a PNPN switch 1 and the emitter of a TR Q51 are connected to form a 1st anode terminal A1 for the main electrode. Furthermore, the emitter of a TR Q52 whose collector and base are connected in common to those of the TR Q51 is used as a 2nd anode terminal A2 for on/off detection. The on/off detection of a main current is implemented by the presence of a current flowing to the emitter of the TR Q52 whose collector and base are connected in common to those of the TR Q51 turned finally off at the off-control. Thus, the on/off state of the main current is detected more accurately. Moreover, the TRs Q51, Q52 are integrated the same as the PNPN switch and the area occupied by the element is made small.

Description

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

(Prior art) In general, a PNPN switch as a semiconductor switch is
Compared to transistor switches, they have advantages such as high bidirectional breakdown voltage, low on-resistance, and 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, the off control is relatively distant.

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.

Now, 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. PNPN
The switch enters the off state with a delay of the turn-off time caused by the charge accumulation time from the time of off-drive, but
Depending on the application of the switch, this delay time may cause problems with 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 pulsed manner, and then the other switch is driven on in a pulsed manner to control the load current. When trying to switch, there are cases where the switch that receives the OFF drive does not completely turn off, and the other switch turns on, causing both switches to remain on at the same time. This is a phenomenon caused by the self-holding function of the PNPN switch, which continues to operate as long as the main electrodes are externally conductive even without gate control, and the fact that the turn-off time is generally longer than the turn-on time. be. In order to prevent such malfunctions, a method is required to detect at what point the load current of the switch is turned off.

Figure 1 shows the circuit configuration of an on/off switch with an off detection function. Control is achieved by applying drive current to gate G and off control input terminal B, respectively, and as a result, load resistance R2 and ff of the external circuit
The load current determined by the i source v1 can be turned on and off. Here, the resistor R1 prevents the PNPN switch 1 from malfunctioning due to the dv/dt effect, and the gate firing sensitivity of the PNPN switch 1 is determined by this resistor R1.

The transistor Q3 temporarily short-circuits the gate G and cathode of the PNPN switch 1 to increase the minimum holding current value of the PNPN switch 1 and shift it to the off state.

Furthermore, the transistor Q4 is for detecting the on/off state of the PNPN switch 1.

That is, transistor Q2. Since the base and emitter of transistor Q4 are connected in common, transistors Q2. Q4 has substantially the same base bias condition, and their respective collector currents also become substantially equal. Here, since the collector current of transistor Q2 is a part of the 7-node current of PNPN switch 1,
If the collector current of transistor Q4 is monitored, PNP
This means that the on/off state of the N switch can be detected.

FIG. 2 schematically shows the above operating waveforms, where ◇ indicates the on-drive current, 3 indicates the off-drive current, ^ indicates the anode current, and Ic indicates the collector current of the transistor Q4. As is clear from Fig. 2, PNPN switch 1
The on/off information of the anode current can be inspected from the presence or absence of the collector current Ic of the transistor Q4, that is, 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 I and the transistor Q4 are separate devices, and therefore have different sizes and shapes.

Since the external load conditions cannot always be the same, the turn-off time will vary. Furthermore, PNPN switch 1
Since the turn-off time of the transistor Q1 tends to be the sum of the turn-off times of the component transistors Ql and Q2, accurate off-detection cannot be performed with the transistor Q4. That is, when driven off in FIG. 1, transistor Q2. Q4
Since the base and emitter of the transistor Q3 are short-circuited at the same time, the PNP transistor Q1 quickly turns off, but the PNP transistor Q1 turns off from that point.

As a result, as shown as t4t t in Fig. 2, PN
Since the off detection is performed before the PN switch 1 is completely turned off, the 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.

An object of the present invention is to obtain a semiconductor switch which has accurate main current on/off detection characteristics, has a small element occupation area, 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 diagram showing an example of a semiconductor switch that is an improved version of the conventional semiconductor switch.

Qll, Q12. Q2 is 4-terminal PNPN switch 2
Two PNP transistors and one NPN
transistor, Q3 is an NPN transistor for turn-off, R1 is a resistor to prevent malfunction due to dv/dt effect,
Vl and R2 are the load power supply and resistance, respectively, and V2. R3 is a power supply and a resistor for on/off detection, respectively. Also,
A1 is the first anode terminal, A2 is the second 7-node terminal, K is the cathode terminal, G is the gate terminal, and B is the off control input terminal. In this embodiment, the transistor Ql
4-terminal PNPN switch 2 consisting of 1, Q12, and Q2
A main current switch circuit of the semiconductor switch is constituted by this, and a turn-off switch circuit of the semiconductor switch is constituted by the NPN transistor Q3 and the resistor R1.

In the circuit configuration shown in FIG. 3, on control is achieved by supplying an on drive current from the gate G, Qll, Q
The PNPN switch constituted by 2 is turned on, and a load current determined by the voltage IIXV1 of the external rgJ path and the resistor R2 flows from the anode A1 to the cathode. Also, at the same time, Q12. The PNPN switch composed of Q2 is also turned on.

An on-detection current determined by the external circuit power supply v2 and resistor R3 flows from the anode A2 to the cathode. Then, off control is performed by flowing an off drive current from the off control input terminal B, and the transistor Q3 becomes on. ,
By shorting the gate G and cathode of the PNPN switch 2, that is, the base and emitter of the transistor Q2, the holding current value of the PNPN switch is increased, and the load current flowing from the anode A1 to the cathode K is turned off. . At the same time, the on-detection current flowing from the anode A2 toward the cathode K is also turned off.

Now, in the circuit configuration shown in Figure 3, the main current is on/off.
Off detection is performed using a PNP transistor Qll through which the main current flows and a PNP transistor Q whose base and collector are commonly connected.
12 depending on the presence or absence of emitter current. 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 Qll and Q12 are turned off at the same time.
The times during which the inflow currents from the anodes Al and A2 are turned off are approximately the same. Similarly, regarding the turn-on operation of the PNPN switch, after the NPN transistor Q2 is turned on, the PNP transistors Qll and Q12 are turned on.
turns on at the same time. 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;
A semiconductor switch with accurate off-detection characteristics can be obtained.

Furthermore, the four-terminal PNPN switch 2 shown in FIG. 3 can be a device of integral construction. FIG. 4 shows the cross-sectional structure of this four-terminal PNPN switch 2, in which 10 is an N-type semiconductor substrate, 11° 12, 13 is a P-type scattering layer, 14 is an N-swelling diffusion layer, and 15 is an N-type semiconductor substrate. is an oxide film, 16a
, 16b, 16c, and 16d indicate metal wiring layers, respectively. The first anode terminal A1 of the four-terminal PNPN switch 2 is connected to the wing wiring N16a via the P-type scattering layer 11.
Similarly, the second anode terminal A2. A P-type wave diffusion layer 13 is provided at the gate terminal G and the cathode terminal, respectively. P-type diffusion N12. Metal wiring layer 16b via N-type wave diffusion layer 14
, 16c, 16d.

Since the four-terminal PNPN switch 2 can be formed into an integral structure as shown in FIG. 4, the circuit shown in FIG. 3 can occupy a small area. Furthermore, according to the prototype experiments conducted by the present inventors, the operation of the circuit shown in FIG.
After ll turns off, transistor Q12 turns off,
It was found that there was sufficient time to detect the main current off. In other words, when the circuit shown in FIG. 5 is integrated into 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 example of a semiconductor switch that is a further improvement to the semiconductor switch shown in FIG. 3, and includes a current shunting transistor Q5 in the circuit configuration shown in FIG. Q6
In addition, the current cutting ability as a semiconductor switch is further improved.

That is, in this example, transistors Qll, Q12
, Q2, and first and second current shunt transistors Q5 and Q6 constitute a main current switch circuit of the semiconductor switch. In FIG. 5, the same parts as in FIG.
and resistors R2 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 transistor Q5. Q6 is turned on, and a load current flows from the first anode A1 to the cathode. Furthermore, since the transistor Q12 is also in the on state at the same time, a heon detection current flows from the second anode A2 to the cathode.

Next, OFF control is also performed by injecting an immediate OFF current from OFF control input terminal B. First, transistor Q3 is turned on, and 4-terminal PNPN switch 2 is turned OFF.
Next, a current shunt transistor Q5. Q6 turns off, cutting off the load current flowing from anode A1 to the cathode. At the same time, the on-detection current flowing from the second anode A2 toward the cathode K is also turned off.

In the improved example of FIG. 5, the load current is connected to the PNPN switch 2 and the transistor Q5. Since the current is divided into Q6, a semiconductor switch having a greater current cutting ability than the improved example shown in FIG. 3 can be obtained. Further, as described in FIGS. 3 and 4, since the four-terminal PNPN switch 2 can be formed into an integral structure, the device occupies a small area. However, regarding the off detection time, transistor Q5.
The turn-off time due to Q6 tends to cause an error.

The present invention improves this point.

FIG. 6 is a circuit configuration diagram showing an embodiment of the semiconductor switch according to the present invention, in which the four-terminal PNPN switch 2 in FIG. It was added.

In this embodiment, the emitter of the transistor Q1 constituting the PNPN switch 1 and the emitter of the transistor Q51 are connected to form the first anode terminal A1 for the main electrode,
It is characterized in that the emitter of a transistor Q52 whose collector and base are commonly connected to the transistor Q51 is used as a second anode terminal A2 for on/off detection.

That is, in this embodiment, 'P N P N switch 1
, a current detection transistor Q52, and a first and second
Current shunting transistor Q51. Q6 constitutes the main current switch circuit of the semiconductor switch.

The other parts are the same as those shown in FIG. 5, and the operation is the same as that described in FIG. However, since the on/off detection of the main 4 current is carried out based on the presence or absence of current flowing into the emitter of the transistor Q52, whose base and collector are commonly connected to the transistor Q51 that turns off at the end during off control, it is possible to detect the main 4 current more accurately. Can detect on/off status of current. Also, PNPN transistor Q51.
Q52 can be made of an integral bridge structure like the 4-terminal PNPN switch described in FIG. 3, and the area occupied by the element can be kept small. Furthermore, it has a feature of high current cutting ability.

〔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@path, thereby making the detection characteristics accurate, and Since the area occupied by the elements can be reduced, high integration is possible, and a semiconductor switch with excellent characteristics and economical efficiency can be provided.

[Brief explanation of drawings]

Figure 1 is a circuit configuration diagram of a conventional semiconductor switch, Figure 2 is an operating waveform diagram of the circuit configuration in Figure 1, and Figure 3 is a circuit configuration diagram showing an example of a semiconductor switch that is an improvement on the conventional semiconductor switch. , FIG. 4 is a structural sectional view of the four-terminal NPNP switch shown in FIG. 3. FIG. 5 is a circuit configuration diagram showing an example of a further improved semiconductor switch of FIG. 3, and FIG. 6 is a circuit configuration diagram showing an embodiment of the semiconductor switch according to the present invention. 1...PNPN switch, 2...4-terminal PNPN switch. Ql, Q2. Qll, Ql2... PNPN switch configuration transistor, Q3. Q5. QB, Q51. Q52...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 a main electrode, a cathode terminal,
A semiconductor switch comprising: a main current switch circuit having a gate terminal for control and a second anode terminal for current detection; and a turn-off switch circuit connected between the gate and cathode terminals of the main current switch circuit. The main current switch circuit includes a PNPN switch, a current detection transistor, and first and second current shunting transistors, and one main electrode terminal of the PNPN switch is connected to the first current switch. The other main electrode terminal of the PNPN switch is connected to the emitter of the shunt transistor, and the other main electrode terminal of the PNPN switch is connected to the base of the second current shunt transistor;
The bases and collectors of the first current shunting transistor and the current detecting transistor are commonly connected to the collector and emitter of the second current shunting transistor, respectively, and the first current shunting transistor The emitter and collector of the main current switch circuit are
The anode terminal and cathode terminal of the PNPN switch, the gate terminal of the PNPN switch, and the emitter of the current detection transistor are configured as a gate terminal for controlling the main current switch circuit and a second anode terminal for current detection, respectively, A semiconductor switch characterized in that the on/off state of the inflow current of the first anode terminal is detected by the inflow current of the second anode terminal.