JPH022331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor switch circuit that uses a thyristor with a pnpn four-layer structure as a switch and has improved dv/dt tolerance.

Thyristors can obtain high blocking voltage,
It has the feature of being able to control a large amount of power with a small amount of control power due to its self-holding action, and is useful as a semiconductor switch.

On the other hand, if the transistors are different and vulnerable to noise, and the change is steep when a surge occurs,
It has the disadvantage of causing false ignition even if it is within the blocking voltage. Normally, to prevent this, the gate and cathode of the thyristor are short-circuited with a resistor, but because of this, part of the ignition current flows to the cathode via the short-circuit resistor, increasing the power required for ignition. , it loses its characteristics as a thyristor.

Therefore, in the prior art, circuits as shown in FIGS. 1 and 2 are used to compensate for the above drawbacks.

In FIG. 1, a p emitter layer 2, an n base layer 3,
Between the gate 8 and cathode 7 of the thyristor 1, four layers, the p base layer 4 and the n emitter layer 5, are successively adjacent to each other.
A transistor 10 having an npn three layer structure is connected, and the base of the transistor 10 is driven by a transistor 9 having a pnp three layer structure. In this circuit, when a rapidly changing noise voltage v _A enters between the anode 6 and cathode 7 of the thyristor 1, a transient current i _B flows through the transistor 9, immediately saturating the transistor 10, and the transient current i _J in the thyristor 1 flows through the transistor 9. Since it flows into the collector, it appears as if the gate and cathode are short-circuited, and erroneous firing of the thyristor 1 can be prevented.

The resistor 11 is provided to absorb the leakage current from the thyristor 1. It is sufficient that it can absorb the leakage current at high temperatures, and it can have a relatively high resistance. When the transistor 10 is in the off state, the gate firing current is reduced.
Since i _G can be used as it is as an ignition signal for the thyristor 1, the ignition current i _G can be lowered. That is, the circuit shown in FIG. 1 has the advantage of being resistant to noise and requiring low control power.

Diode 12 has anode 6 and cathode 7
This is provided in order to prevent the base of the transistor 10 from becoming deeply negatively saturated through the transistor 9 and causing breakdown between the base and emitter when the signal voltage of the transistor 10 fluctuates.

The circuit configuration shown in FIG. 2 is a bidirectional version of the circuit shown in FIG. 1, and the driving transistor 9 is common in both forward and reverse directions. In the figure, 15 is a thyristor, 20 is a transistor, 21 is a resistor, 22 is a diode, and 88 is a second gate.

This circuit has the features of the circuit shown in FIG. 1, and at the same time has the feature of being able to constitute a bidirectional switch.

Although the circuits shown in FIGS. 1 and 2 have the above-mentioned features, the above-mentioned features may not be fully utilized depending on the type of noise voltage _vA that is applied.
For example, if the noise voltage v _A applied to both terminals 6 and 7 of the thyristors 1 and 15 is as shown in FIG. 3, the thyristors 1 and 15 are likely to malfunction.

In Fig. 3, when the signal voltage v _AS is applied at time t ₀ and the on signal is applied to gate 8 or 88 at time t ₁ , thyristor 1 or 15 is turned on at this point, and the switch current i _A suddenly increases. It increases to , and remains constant thereafter. At time t ₂ , the signal voltage v _AS is 0V
When the voltage returns to , the switch current i _A also becomes 0,
Thyristor 1 or 15 is turned off.

Between times _t1 and _t2 , the voltage between the anode and cathode of thyristor 1 or 15 constituting the switch is in the on state, and the voltage at that time is constant at about 1V.If thyristor 1 is in the on state, the voltage is as shown in Figure 4. Source 3
0 indicates this. On the other hand, each pn junction of the transistor 9 is connected to the diodes 31 and 3 in FIG.
2, and the diode 31 connects the pn junction between the base and emitter of the transistor by 32
each represents a pn junction between the base and collector.

Between times _t1 and _t1 , the diode 31 is on and the diode 32 is off, and charges are accumulated in the pn junction of the diode 32. When the thyristor ₁ turns on at time t1, the anode 6 has almost the same potential as the cathode 7, so the diode 3
1 and 32 are both in a reverse bias state, and the charge in the diode 32 has only a discharge path through the circuit a in the figure.
This is a reverse bias state for the diode 31, so the charge cannot escape and the diode 32
The charge remains for a long time. That is,
Charge remains between the collector and base of the transistor 9, and even if the thyristor 1 is turned on, this charge does not disappear, and this charge continues even after time _t2 .

On the other hand, since thyristor 1 is in the on state, in order to turn off at time _t2 , it can be considered that the charge exists in thyristor 1 only during the turn-off time of thyristor 1. In this state, that is, after time _t2 , no charge remains inside the thyristor 1.

This state (charge remains in transistor 9 and no charge remains in thyristor 1)
As shown at time t ₃ , when the noise voltage v _A is applied, the thyristor 1 malfunctions, and the thyristor 1 turns on even if there is no on signal to the gate 8 .
This is because the current flowing through transistor 9 decreases due to the noise voltage _vA due to the residual charge in transistor 9, and the base current of transistor 10 decreases, making it impossible to effectively short the gate 8 and cathode 7 of thyristor 1. It is.

An object of the present invention is to provide a semiconductor switch circuit having a circuit configuration that eliminates such malfunctions.

FIG. 5 shows an embodiment of the present invention.

Components that are the same as the previous components are given the same numbers.

This embodiment is a specific example of a bidirectional semiconductor switch circuit.

Diodes 35 and 36 are for charge discharge. That is, the electric charge accumulated in the base and collector of the transistor 9 is absorbed into the thyristor 1 through the n-base layer 3 of the thyristor 1 the moment the thyristor 1 is turned on, so that no electric charge remains. When the reverse direction thyristor 15 operates, that is, when the cathode 7 is at a positive voltage with respect to the anode 6, the n-base layer 37 is passed through the diode 36.
The charge in transistor 9 is discharged. In this way, the charge is discharged and there is no charge remaining inside, so even if a pulse noise voltage arrives, the current flowing inside increases, and the short-circuiting operation of the transistor 10 described above can be completed. It is something.

As is clear from the equivalent circuit in Figure 4, if there is a charge, both diodes 31 and 32 will be reverse biased when a pulsed noise voltage arrives, and the current flowing through this p-n junction will be due to the junction static voltage between them. It is proportional to the series value of capacitance, and if there is no charge, only diode 32 will be reverse biased and its pn
This is because the current flowing through the junction is proportional only to the value of the capacitance of the diode 32.

From the above, the semiconductor switch circuit shown in FIG. 5 can reliably prevent malfunctions due to the noise voltage shown in FIG. 3, which has been a problem up to now.

FIG. 6 shows another embodiment of the invention.

In this case, both thyristors 1 and 15 have their respective n base layers 38 in common, and such a structure is used for bidirectional thyristors. In this case, only one diode 35 is required to connect the base of the transistor 9 to the n base layer 38 of the thyristors 1 and 15.

FIG. 7 shows another embodiment of the present invention.

The circuit configuration in this case is almost the same as the embodiment shown in FIG. 5, but resistors 39 and 40 are used in place of diodes 35 and 36. In this case as well, as in the previous embodiment, the residual charge of the transistor 9 can be released through the resistor 39 or 40, making it possible to create a circuit that is resistant to noise.

FIG. 8 shows another embodiment of the present invention.

In order to protect thyristors 1 and 15 from noise voltage, this circuit uses the p emitter layer of thyristors 1 and 15 and the n
The base layer is short-circuited with a transistor 40 having a pnp three layer structure, and is driven by a transistor 50. That is, in this embodiment, the transistors 10 and 20 in the embodiment of FIG.
43, the transistor 9 is replaced with a transistor 50, and a complementary structure is formed in which the conductivity types of the semiconductor layers are mutually exchanged.

This circuit configuration is often used when integrating a circuit and manufacturing a circuit using a P-type single crystal semiconductor as a starting material. In this embodiment, residual charges are discharged using diodes 51 and 52. However, unlike the previous examples, the diode 5
The connection points on the anode side of thyristors 1 and 52 are the P gates 8 and 88 of both thyristors 1 and 15. In this case, the diodes 51 and 52 may be replaced with resistors as in the embodiment of FIG.

In the above embodiments, a bidirectional semiconductor switch circuit has been described, but it is also applicable to a unidirectional semiconductor switch circuit as shown in FIG.
It may have an npn three-layer structure.

As explained above, according to the present invention, it is possible to further improve the noise resistance performance, which is of great industrial advantage.

[Brief explanation of drawings]

1 and 2 are diagrams showing conventional semiconductor switch circuits, FIGS. 3 and 4 are explanatory diagrams of the operation of the semiconductor switch circuits shown in FIGS. 1 and 2, and FIGS. 5 to 8
Each figure shows a different embodiment of the invention. 1...thyristor, 2...p emitter layer, 3...
...n base layer, 4...p base, 5...n emitter layer, 6...anode, 7...cathode, 8...
Gate, 9, 10...Transistor, 11...Resistor, 12,35...Diode.

Claims (1)

[Claims] 1. The first and second main terminals are connected in parallel with opposite polarity between the first and second main terminals, and each has a p-emitter layer, an n-base layer, a p-base layer and a separately formed first and second thyristors having four consecutive layers of n-emitter layers; first and second gate terminals connected to the p-base layers of the first and second thyristors, respectively; The collector and emitter of the first and second
first and second transistors connected to the p base layer and n emitter layer of the thyristor; a third pnp type transistor whose collector and emitter are connected to the bases of the first and second transistors; first and second circuit elements connected between the base and emitter of the transistor and between the base and emitter of the second transistor to form a discharge path of a third transistor; The third thyristor is connected between the n-base layers of the first and second thyristors.
A semiconductor switch circuit comprising: third and fourth circuit elements for discharging charges accumulated in the transistor to the first and second thyristors. 2. The semiconductor switch circuit according to claim 1, wherein the first, second, third and fourth circuit elements are diodes. 3. The semiconductor switch circuit according to claim 1, wherein the first and second circuit elements are diodes, and the third and fourth circuit elements are resistors.