JPS6348208B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in optically coupled semiconductor switch devices. When controlling a power transistor, the base control power becomes large, so various amplification means are required. This amplifying means requires an auxiliary power source, which makes it complicated to make it conduct continuously over time.

On the other hand, there is no problem if direct amplification can be performed using a photosensitive element without an auxiliary power source. Based on this idea, the system shown in FIG. 1 has been proposed. In the figure, 1 is a main transistor, 2 is an amplification element transistor (hereinafter referred to as an intermediate amplification element), 3 is a photosensitive semiconductor element such as a phototransistor or a photothyristor (hereinafter referred to as a photosensitive element), Reference numeral 4 denotes a light emitting element such as a light emitting diode that irradiates light onto the photosensitive element 3. S ₁ and S ₂ are input terminals to which input signals are applied, and C
is the main switch terminal, and E is the ground terminal. By the way, as the device shown in Fig. 1 becomes a high-voltage, large-current switch device, it is necessary to obtain a high current amplification degree to increase optical control sensitivity and to obtain a high withstand voltage, so it has a long time time. It requires the use of semiconductor wafers, which significantly slows down the switching speed. Especially when the load is light, the accumulation time is several to several.
It reaches as much as 10μsec. For this reason, even if there is no problem in the steady ON state, the semiconductor element is likely to be destroyed by the switching loss energy (the time integral value of the product of the transient voltage and the transient current during the transient period) during turn-on switching transients.

Furthermore, in this type of device, in general, in a steady conductive state, only a DC amplification factor is required, so that light from the light emitting element 4 can be used to continuously energize the device.

For example, if the switching speed is not considered, the degree of direct current amplification can be increased from several hundreds to several tens of thousands by using a Darlington connection consisting of the main transistor 1 and the intermediate amplifying element 2. Therefore, the optical coupling part consisting of the photosensitive element 3 and the light emitting element 4 has a current of several 100 μA to several
If you take out an output of 10 μA, you can turn on the main transistor of 1 A to several tens of A. Therefore, there is no problem from the viewpoint of steady-state characteristics.

However, there is a problem when turning it on. In order to obtain the above-mentioned steady-state characteristics, it is sufficient to use a semiconductor wafer with a long lifetime and to make the intricate pattern of emitters and bases narrower.
This is achieved by repurposing the manufacturing technology of high-amplification transistors (Hfe≧500 per unit). However, a new problem arises in that the turn-on time becomes extremely long and damage occurs due to loss during turn-on.

In view of the above points, the present invention has been made to solve such problems and eliminate such drawbacks.The purpose of the present invention is to increase the turn-off speed and reduce the light input during continuous ON operation by a simple configuration. It is possible to further increase the speed by reducing the storage effect by lowering the power consumption, and also to improve the turn-off switching speed and reduce the turn-off switching loss, thereby improving the power capacity that can be switched. An object of the present invention is to provide an optically coupled semiconductor switch device that can perform the following steps.

In order to achieve this purpose, this invention
A light-emitting means for emitting light; a light-sensitive semiconductor switch element having a control pole and a light-receiving surface; Initial light emission enhancing means for enhancing light emission from the light emitting means; and reverse biasing means for applying a reverse bias to the control pole of the light sensitive switch element when the light sensitive semiconductor switch means is rendered non-conductive. This is what I did.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

In FIG. 2, the same reference numerals as in FIG. Reference numeral 50 includes a pulse generator 110 and the like, and applies a reverse bias to the control pole of the light-sensitive semiconductor switch element when the light-sensitive semiconductor switch means is made non-conductive. Reference numeral 50 strengthens light emission at the initial stage of turn-on and turns on the light-emitting element 4. The light emission control means 7 and 8 are diodes for common series reverse biasing of the main transistor 1, the intermediate amplification element 2, and the photosensitive element 3. Here, as is clear from the explanation below,
The light emitting element 4 constitutes a light emitting means, and the photosensitive element 3 constitutes a photosensitive semiconductor switch means in cooperation with an inductor 203 which will be described later. This photosensitive element 3 has a control pole.

In FIG. 2, when electrical conduction is established between main switch terminals C and E, a current i ₄ is applied from the light emission control means 50 to the light emitting element 4 to cause the light emitting element 4 to emit light, and the light is irradiated onto the photosensitive element 3. The current of the photosensitive element 3 is amplified by the intermediate amplifying element 2 and applied to the control pole (base) of the main transistor 1. At this time, the photosensitive element 3
~Turn-on delay of main transistor 1 is 1μsec~
If it reaches several tens of microseconds, there is a risk that the main transistor 1 to the photosensitive element 3 will be destroyed due to the loss during this turn-on transition. . In particular, when the transient impedance of the main circuit (including the power supply 201, load 202, etc.) 200 side to which the main switch terminals CE are connected is low, it is likely to be destroyed by the main current at the initial stage of turn-on. For this reason, as shown in FIGS. 4 and 5, which will be described later, the light emission at the initial stage of turn-on is strengthened. A “turn-on initial luminescence enhancement means” is provided. Here, without using a capacitor as a snubber, the surge voltage is absorbed by the avalanche diode 5 as shown in the figure, and the terminal C--
If a means 203 (for example, a reactor or a saturable reactor) for increasing the turn-on initial impedance on the main circuit 200 side as viewed from E is provided, the problem of destruction due to the turn-on delay described above can be further improved.

In contrast, in the present invention, in order to shorten the turn-on time, reduce switching loss during turn-on, and prevent destruction due to this, a means is provided to strengthen the light emission at the initial stage of turn-on. This will be explained with reference to FIG.

A detailed embodiment of the light emission control means 50 having the above-mentioned initial light emission strengthening means 60 is shown in FIG. In the embodiment shown in FIG.
A capacitor 54 is charged to a predetermined voltage through a resistor 53. Next, when the transistor 55 is made conductive when a current i _4A is applied to the light emitting element 4, a current that is the sum of the continuous current i ₄₂ and the initial strengthening current i ₄₁ which is a discharge current from the capacitor 54 emits light at the beginning of turn-on. Flows to element 4. Therefore, the input current _i4A to the light emitting element 4 has a waveform having an initial peak as shown in FIG. 5a. In other words, a current with a high peak value flows at the beginning of turn-on, and a continuous current flows at the wave tail.
i ₄₂ flows.

In the embodiment shown in FIG. 4b, a first transistor 55a for controlling energization via a first resistor 52 connected in series with the light emitting element 4 is provided on the cathode side of the light emitting element 4; A second transistor 55b is provided to control energization through a second resistor 53 connected in series. On the other hand, the first transistor 55a is continuously controlled to be conductive in response to a signal applied to the signal input terminal Sig. On the other hand, the second transistor 55b responds to the signal applied to the terminal Sig by connecting the resistor 57, capacitor 58,
A differentiating means consisting of a diode 59 makes it conductive only at the initial stage of turn-on. As a result, the sum of the continuous current i ₄₂ through the first transistor 55a and the initial enhanced current i ₄₂ through the second transistor 55b flows, resulting in the emission of a waveform with an initial peak such as waveform i _4B shown in FIG. 5b. An input current i _4B is obtained.

As described above, the light emission at the initial stage of turn-on can be enhanced.

When trying to achieve a high amplification with a high withstand voltage of the photosensitive element 3, the response speed decreases and this causes turn-on switching transient breakdown of the element. Switching damage can also be prevented.

Furthermore, in FIGS. 2 and 3, when the auxiliary switch element 101 is used, the auxiliary switch element 101 is turned off during the period when the photosensitive element 3 is irradiated with light.
Since it is kept in the OFF state, the potential of the control electrode of the photosensitive element 3 (internal junction voltage drop of the elements 1 to 3) appears at the reverse bias control terminal RB. This voltage
When V _RB-E is used, the control interelectrode voltage waveform compared with the waveform of the light emission control input current i ₄ becomes a waveform as shown in FIG. 5C. Here, V ₁₀₀ shown by a solid line or a dotted line is an example of a voltage waveform given from the reverse bias pulse generator 110.

Furthermore, in the embodiment shown in FIG. 2, in order to improve the turn-off characteristics, the photosensitive element 3 is also provided with a control pole, and is provided with means 100 for reverse biasing the control pole.
A pulse generator 110 is provided which provides pulsed reverse bias, particularly at turn-off. As a result, a semiconductor with a long lifetime can be used for the photosensitive element (for example, a phototransistor) 3, and its withstand voltage and amplification degree (or photosensitive output current) can be increased, while its turn-off speed can also be reduced. can. As a result, loss during turn-off can be reduced, and destruction of the photosensitive element 3 due to turn-off loss can also be prevented.

Furthermore, an auxiliary switch element 101 is provided in the reverse bias means 100, and when pulse reverse bias is performed, the output voltage _V100 of the pulse generator 110 itself makes the auxiliary switch element 101 conductive via a resistor 102. On the other hand, when the photosensitive element 3 is made conductive, the output voltage V ₁₀₀ is not generated, so the auxiliary switch element 101 becomes non-conductive. Therefore, the light emitting element 4
When the photosensitive element 3 becomes conductive by being irradiated with light from
The photosensitive current flows from its control pole (base) to the terminal
The auxiliary switch element 101 can prevent leakage to the shunt RB-auxiliary switch element 101-winding 103-terminal E-. This ensures that the photosensitive current reaches the emitter of the photosensitive element 3, and high photosensitivity can be maintained. Second
As the auxiliary switch element 101 shown in the figure, in addition to a transistor, a thyristor (optical thyristor, gate turn-off thyristor), etc. can be used.

Further, the reverse bias means 100 also reverse biases the control poles of the main transistor 1 and the intermediate amplifying element 2. That is, the diodes 7 and 8 are connected in antiparallel to the control poles of each of the photosensitive element 3 and the intermediate amplification element 2, and further connected in series with the control pole of the main transistor 1 between the output terminals of the reverse bias means 100. It has been done. This shortens the turn-off time of the intermediate amplifying element 2 and the main transistor 1, and prevents destruction of these elements due to loss during turn-off.

Also, in this way, the reverse bias means 100 applies a reverse bias to the control pole of the light sensitive switch element when making the light sensitive semiconductor switch means non-conductive.
This increases the turn-off speed, lowers the optical input during continuous ON, and reduces the accumulation effect, further increasing the speed.

As described above, it is possible to increase the voltage while maintaining photosensitivity, reduce both turn-on and turn-off transient losses that occur when trying to obtain high breakdown voltage and high amplification, and reduce the effects of switching elements due to these transient losses. Destruction can be prevented. In particular, it is possible to increase the pressure while maintaining the photosensitivity of the photosensitive element itself, and to prevent switching damage. Furthermore, if the intermediate amplifying element 2 and the main transistor 1 are also reverse biased, a high-voltage, high-power switch device based on optical coupling control can be obtained as a whole.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the optical thyristor 6 is configured such that the semiconductor inversion layers of the photosensitive element 3 and the intermediate amplification element 2 have opposite structures. It was formed.

In this case, the amplification degree of the photosensitive element 3 is increased, the amplification degree of the intermediate amplification element 2 is suppressed, and
It can be made as a PNPN thyristor element. Further, the base of the photosensitive element 3 corresponds to the gate pole of the thyristor element, and can be turned off by applying a reverse bias to the base. That is,
It can be said that it is a photosensitive gate turn-off thyristor. In this embodiment, due to the positive feedback effect between the intermediate amplifying element 2 and the photosensitive element 3, a high pulse current can flow as the base current of the main transistor 1 at the initial stage of turn-on, so that turn-on breakdown is less likely to occur.

Furthermore, in Fig. 2, an inductor (reactor, saturable reactor, etc.) 2 is used as a di/dt suppressing means to reduce switching loss at turn-on and prevent damage caused by this switching loss.
03, and a constant voltage element (such as an avalanche diode) 5 that absorbs this magnetic energy and suppresses surge voltage is connected in antiparallel to the main transistor 1. As a result, the rising speed of the current between the terminals C and E of the main transistor 1 can be delayed in response to the turn-on delay of the photosensitive element 3, and the loss of the photosensitive element 3 or the main transistor 1 at turn-on can be reduced. can prevent damage caused by

As is clear from the above description, according to the present invention, the turn-off speed can be increased by providing a reverse bias means for applying a reverse bias to the control pole of the light sensitive switch element when the light sensitive semiconductor switch means is made non-conductive. This speeds up the process and reduces the light input during continuous ON to reduce the accumulation effect, further increasing the speed.In addition, the turn-on is strengthened at the beginning of the light-emitting turn-on of the light-emitting means that irradiates the control pole of the light-sensitive switch element with light. By providing the initial light emission enhancement means, it is possible to obtain an optically coupled semiconductor switch device with high withstand voltage or high sensitivity while reducing the decrease in turn-on speed, and it is possible to prevent destruction due to switching loss during turn-on in a high voltage circuit. Therefore, the practical effect is extremely large.

In addition, if the photosensitive switch means is a photothyristor with a control pole and the main transistor is controlled by this, the turn-on delay is improved, the problem of destruction of the main transistor at turn-on is improved, and the reverse bias of the control pole is If you also do this, you can turn on the control pole. Also, if you install a constant voltage element in anti-parallel to the main transistor and a reactor or saturable reactor in series with the main transistor, switching at turn on can be done. This is extremely effective in that destruction due to loss can be prevented.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing a problem to be solved by this invention, Fig. 2 is a circuit diagram showing one embodiment of this invention, and Fig. 3 is a circuit showing another embodiment of this invention. 4A and 4B are circuit diagrams showing one embodiment of the turn-on initial light emission enhancing means used in the present invention, and FIG. 5 is a waveform diagram for explaining the operation of each embodiment of the present invention. In the figure, 1 is a main transistor, 2 is an amplification element, 3 is a photosensitive semiconductor element, 4 is a light emitting element, 5 is a constant voltage element, 6 is an optical thyristor with a control pole, 50 is a light emission control means, and 60 is turn-on initial light emission. 100 is a reverse bias means, 110 is a pulse generator, 101 is an auxiliary switch element for preventing leakage of photosensitive current to the reverse bias circuit, 203 is an inductor, and 200 is a main circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A light-emitting means that emits light, a light-sensitive semiconductor switch means that is provided with a light-sensitive switch element having a control pole and a light-receiving surface, and conducts electricity upon receiving light from the light-emitting means, and this light-sensitive semiconductor switch. initial light emission enhancing means for enhancing light emission from the light emitting means at the initial stage of turn-on when the means is conductive; and a reverse bias that applies a reverse bias to the control pole of the light sensitive switch element when the light sensitive semiconductor switch means is rendered non-conductive. An optically coupled semiconductor switch device comprising: means. 2. The optical coupling according to claim 1, wherein the photosensitive semiconductor switch means comprises a photosensitive semiconductor switch element and a transistor switch means whose control input is the output from the photosensitive semiconductor switch element. Semiconductor switch device. 3. The optically coupled semiconductor switch device according to claim 1, wherein the photosensitive semiconductor switch means comprises a photosensitive semiconductor switch element and an inductor connected in series with the photosensitive semiconductor switch element. 4. The optically coupled semiconductor switch device according to claim 2, wherein the photosensitive semiconductor switch element comprises a photothyristor or a phototransistor. 5. The optically coupled semiconductor switch device according to claim 3, wherein the inductor is a saturable reactor. 6. The transistor switch means shall consist of a main transistor whose base electrode is connected to the output side of a photosensitive semiconductor switch element, and a constant voltage element connected between its collector and emitter in antiparallel to the main transistor. An optically coupled semiconductor switch device according to claim 2 or 4, characterized in that: 7 The transistor switch means includes a main transistor whose base electrode is connected to the output side of the photosensitive semiconductor switch element, a constant voltage element connected between its collector and emitter in antiparallel to the main transistor, and the main transistor. An optically coupled semiconductor switch device according to claim 2 or 4, characterized in that the device comprises an inductor connected in series with an inductor. 8. The optically coupled semiconductor switch device according to claim 7, wherein the inductor is a saturable reactor.