JP3010603B2 - Overvoltage protection device for light-ignition thyristors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention occurs between a light-emitting thyristor provided with a gate electrode for electric ignition and a cathode electrode when the light-emitting thyristor is light-ignited. The present invention relates to an overvoltage protection device that suppresses overvoltage.

[0002]

2. Description of the Related Art In a light-ignition thyristor in which a thyristor is directly fired by an optical signal, its light energy is often insufficient in a light source such as a light-emitting diode. Must be several tens of times higher than that of the electric ignition type thyristor. However, an increase in the ignition sensitivity causes a steep voltage to be applied between the anode and the cathode (A / A).
K), that is, dv /
It is known that the dt resistance decreases. Also, dv / dt
If the area of the light receiving portion of the optical signal is reduced in order to improve the characteristics, there arises a problem that a withstand current when a steep rising current flows between A / K, that is, a di / dt withstand capability is reduced. Therefore, in the light-ignition thyristor, it is important to coordinate the characteristics of ignition sensitivity, dv / dt resistance, and di / dt resistance, and various improvements have been made. That is, for example, IEEJ Magazine 103, No. 1, “I
I. Thyristor. The rectifiers P3 to P6 have a structure in which the depletion layer is directly irradiated with an optical signal to increase the ignition sensitivity, a stripe is provided in the light receiving portion to effectively collect carriers and increase the ignition sensitivity, dv / dt. Structure with compensation electrode, two-stage amplification gate
A structure that increases the dv / dt resistance is introduced as an example of a structure. However, a gate for electric ignition surrounding the light receiving section is provided.
In the case of a light-emitting thyristor provided with a gate electrode and capable of being electrically fired, an overvoltage generated between the gate electrode and the cathode electrode (abbreviated as G / K) between the electric firing gate electrode and the cathode electrode during light firing. The reduction structure is not mentioned.

FIG. 7 is a cross-sectional view showing a main part of a light-firing thyristor having a two-stage amplification gate structure, and FIG. 8 is a plan view thereof. In the figure, a light-ignition thyristor 1 has a semiconductor substrate 5 of P
_E layer 5A, N _B layer 5B, P _B layer 5C, and a concentric ring-shaped N _E layer 5K, consists of 5G1,5G2, P _E layer 5
A is the side anode - cathode electrode 2A is, N _E layer concentric rings shaped electric firing together the side gate - gate electrode 7G, 2-stage auxiliary gate for amplification - gate electrode 8G, and cathode - cathode electrode 3K is provided, gate - receiving portion 9 in the center portion of the gate electrode 7G of irradiating direct light signal 10 to the P _B layer 5C is formed by etching.

[0004] The light-firing thyristor 1 thus constructed
The ignition mechanism based on the optical signal of the above is the A / K of the optical ignition thyristor.
By applying a forward voltage V _AK while forming a depletion layer at the junction of the N _B layer 5B and the P _B layer 5C between the optical signal 10 to the light receiving portion 9
The irradiated to excite carriers to P _B layer 5C, E in the depletion layer - Le and the electron multiplication between A / K by equalizing the effect becomes conductive (firing) condition, then constant for an external circuit the anode inflow current I _A which is determined by the flow.

[0005] By the way, the initial stage of ignition, that is, the optical signal
The current path immediately after irradiating No. 10 is indicated by a solid arrow in the figure.
As shown, the anode electrodes 2A, N_BLayer 5B, P_BLayer 5
C, N _ELayer 5G1, gate electrode 7G, P_BLayer 5C, N_E
Layer 5G2, auxiliary gate electrode 8G, P_BLayer 5C, N_ELayer 5
K, P which is the cathode electrode 3K_BThe path along layer 5C
And a gate electrode 7 for electric ignition which is not used during light ignition.
A potential is applied between G and the cathode electrode 3K (referred to as G / K interval).
Difference V_gkOccurs.

[0006]

FIG. 9 is a schematic waveform diagram showing an overvoltage occurrence state of a light-firing thyristor according to the prior art. The magnitude of the potential difference G _GK between G / K during light-firing is shown. It is determined depending on the steepness dv / dt of the fall of the A / K voltage V _AK . Therefore, when the fall of the voltage between the A / K is steep V _GK becomes an overvoltage, the generation loss would exceed an allowable loss between G / K, gate - gate electrode 7G and auxiliary gate - between gate electrode 8G in current is concentrated on the P _B layer 5C, P _B layer 5C of the semiconductor body 5 in this portion is at risk of developing a situation where the thermal breakdown.

On the other hand, when the light firing thyristor 1 is to be electrically fired, a positive gate pulse is applied to the gate electrode 7G.
Although firing by injecting carriers into the P _B layer 5C, this case gate - from gate electrode 7G auxiliary gate - via the gate electrode 8G cathode - current flows to the cathode electrode 3K, if the light triggered and Similarly, care must be taken to prevent the occurrence of overvoltage exceeding the gate allowable loss.

An object of the present invention is to provide an overvoltage generated between G / K in response to a sudden change in A / K voltage when a light-ignition thyristor having a gate electrode for electric ignition is light-ignited. , Without deteriorating the dynamic characteristics of the light firing thyristor,
An object of the present invention is to provide a highly reliable overvoltage protection device that can prevent thermal destruction of a semiconductor substrate.

[0009]

According to the present invention, there is provided a light receiving portion for light ignition, a gate electrode for electric ignition, and an anode electrode for passing a main current. And a cathode firing thyristor having a cathode electrode and
A clamp circuit is provided between the gate electrode and the cathode electrode for suppressing an overvoltage generated between the gate electrode and the cathode electrode at the time of light ignition to a predetermined clamp voltage. Shall be.

[0010] It is assumed that the clamp voltage of the clamp circuit is set to a voltage value lower than the generated overvoltage and equal to or less than a gate allowable loss at the time of electric ignition of the light-ignition thyristor.

The clamp circuit comprises a constant voltage diode. The constant voltage diode has a cathode terminal connected between the gate electrode and the cathode electrode of the light-emitting thyristor. Side.

A clamp circuit includes an NPN transistor having a collector connected to the gate electrode of the light-firing thyristor and an emitter connected to the cathode electrode of the light-firing thyristor, and a collector and a base. And a constant voltage diode connected with the cathode terminal facing the collector.

Further, the clamp circuit includes a field-effect transistor having a drain connected to the gate electrode of the light-ignition thyristor and a source connected to the cathode electrode of the light-ignition thyristor; And a constant voltage diode connected with the cathode terminal between the drains.

Further, the clamp circuit may be a silicon circuit.
It shall consist of a diabsorber.

[0015]

In the configuration of the present invention, the overvoltage protection device is
A clamp circuit is connected between the gate electrode and the cathode electrode of the light-firing thyristor, and an overvoltage generated between the gate electrode and the cathode electrode during light-firing is set to a predetermined clamp voltage. With the configuration to suppress, A /
By determining the clamp voltage in accordance with the steepness of the fall of the voltage between K, it is possible to prevent the destruction of the semiconductor substrate due to an overvoltage, and to determine the clamp voltage so as to be equal to or less than the gate allowable loss during electric ignition. Accordingly, it is possible to prevent the semiconductor substrate from being thermally destroyed due to an overvoltage caused by repeated light ignition.

Further, if the clamp circuit is a constant voltage diode connected between the gate electrode and the cathode electrode of the light firing thyristor with the cathode terminal being the gate electrode side. The overvoltage generated between G / K at the time of light firing of the light firing thyristor can be reduced below the Zener breakdown voltage of the constant voltage diode, and the function of protecting the semiconductor substrate from overvoltage can be obtained.

Further, an NPN transistor having a collector connected to the gate electrode of the light-firing thyristor and an emitter connected to the cathode electrode of the light-firing thyristor;
If a constant voltage diode is connected between the collector and the base with the cathode terminal connected to the collector, the overvoltage generated between G / K during the light firing of the light firing thyristor is reduced by NPN. The voltage can be suppressed below the saturation voltage of the transistor, and the semiconductor body of the light-ignition thyristor can be protected from overvoltage. Furthermore, even if the NPN transistor is replaced with a field effect transistor, the same overvoltage protection function as described above can be obtained.

Still further, the clamp circuit may include a silicon surge absorber connected between G / K of the light firing thyristor.
If it is constituted by a bar, the time required for the silicon surge absorber to become conductive in the negative resistance characteristic region is approximately equal to the time required for the light-ignition thyristor to perform electric ignition, and has excellent overvoltage response. And overvoltage
Utilizing the fact that over-voltage can be rapidly reduced by detecting the voltage, the over-voltage can be suppressed in both its magnitude and duration, so that the light-ignition thyristor has its light-ignition sensitivity, di / dt characteristics, The function to perform the overvoltage protection operation while maintaining the coordination of the dv / dt characteristics stably is obtained. Further, since the silicon surge absorber is almost in a conductive state in a region exhibiting a negative resistance characteristic, the loss generated in the silicon surge absorber is smaller than that of the constant voltage diode, and there is a risk of thermal destruction. Since the number is small, a highly reliable clamp circuit can be formed by using a small-capacity silicon surge absorber, so that a function of reducing the size of the overvoltage protection device can be obtained.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a connection diagram schematically showing an overvoltage protection device for a light-ignition thyristor according to an embodiment of the present invention by a symbol.
Is a waveform diagram showing an overvoltage protection operation of the embodiment device, and the same portions as those in the prior art are denoted by the same reference numerals, and redundant description is omitted. In the figure, a gate electrode 7 for electric firing which is not used at the time of light firing of the light firing thyristor 1 is shown.
A constant voltage diode (zener diode) 11 as a clamp circuit is connected between G and the cathode electrode 3K with its cathode terminal on the side of the gate electrode to protect the overvoltage. Configure the device.

The light-firing thyristor constructed as described above
In the overvoltage protection device, the light receiving section of the light-emitting thyristor 1
Is irradiated with a light signal 10 and light is ignited, as shown in FIG.
The voltage V between A / K of the light firing thyristor_AKFalls
As the speed dv / dt keeps decreasing, the light firing thyrist
As shown in FIG. 7, the overvoltage V_GKDeparts
And is applied to the Zener diode 11. This overvoltage
The Zener diode 11 receives the Zener breakdown voltage
Pressure V_ZAnd the overvoltage V _GKThe
Na-breakdown voltage V_ZTo suppress. Therefore, the light ignition
G / K of light firing thyristor when electrically firing the lister
Zener within the range not exceeding the gate allowable loss allowed between
-Breakdown voltage V_ZIs set to complement the gate electrode 7G.
P located between auxiliary gate electrode 8G_BLayer 5C is overcharged
Protected against pressure damage and thermal damage due to gate loss
Light firing sensitivity, dv / dt characteristics, di / dt characteristics
It is possible to obtain a light firing thyristor with stable dynamic characteristics such as
Wear.

[0021] That is, in the overvoltage protection device shown in FIG. 1, zener - constant voltage of the breakdown voltage V _Z is 27V diode -
G / K of light-firing thyristor 1 during light-firing
A result of measuring the voltage generated between, it has been demonstrated that can reduce the overvoltage V _GK there 200V case without the overvoltage protector to about 30 V. In addition, since the overvoltage protection device is configured as an external circuit of the light-ignition thyristor, a stable protection operation can be obtained without affecting the light-ignition characteristics of the light-ignition thyristor.

FIG. 3 is a connection diagram showing a different embodiment of the present invention.
And a Zener diode 22 as a constant voltage diode connected between the collector and the base with the cathode terminal on the collector side. The collector of the NPN transistor 23 is a light-emitting thyristor 1. And the emitter is connected to the cathode electrode 3K of the light firing thyristor 1, respectively.

In the overvoltage protection device configured as described above, when the light receiving portion of the light-firing thyristor 1 is irradiated with the optical signal 10 and light-firing occurs, an overvoltage occurs between G / K of the light-firing thyristor. Since the constant voltage diode 22 operates and clips the voltage V _CB between the collector and the base of the NPN transistor to the Zener breakdown voltage V _Z , the voltage V _CE between the collector and the emitter of the NPN transistor 23, In other words, the voltage V _GK between G / K of the light firing thyristor is set to N
It can be reduced to the saturation voltage of the PN transistor.

FIG. 4 is a connection diagram showing another embodiment of the present invention. The clamp circuit 31 is a field effect transistor such as an N-channel MOSFET 33, and a cathode is connected between its gate G and drain D. This embodiment differs from the above-described embodiments in that a constant voltage diode 32 is connected on the side of the IGBT. The drain of the N-channel MOSFET is connected to the gate electrode 7G of the light firing thyristor 1 and to the source. S is connected to the cathode electrode 3K of the light firing thyristor. When the light receiving section of the overvoltage protection device thus configured is irradiated with the optical signal 10 and light is fired, the N-channel MOSF
The voltage between the drain and gate of the ET is a constant voltage diode 3
Since the zener voltage is maintained at 2, the overvoltage generated between G / K of the light-firing thyristor 1 can be reduced as in the above-described embodiment using the NPN transistor.

FIG. 5 is a connection diagram showing another embodiment of the present invention, and FIG. 6 is a waveform diagram showing an overvoltage protection operation in another embodiment of the present invention. -It differs from the above embodiments in that it is constituted by a silicon surge absorber connected between the gate electrode 7G and the cathode electrode 3K. In addition, the break surge of the silicon surge absorber 41 as a clamp circuit
The voltage V _BR is preset to a voltage value that does not exceed the gate allowable loss allowed between G / K of the light firing thyristor when the light firing thyristor 1 is electrically fired. shake overvoltage V _GK that sometimes occur between G / K - Quo - by suppressing the bus voltage V _BR, configured to protect against thermal breakdown with light-triggered thyristor overvoltage breakdown, or to.

In the overvoltage protection device constructed as described above, the silicon surge absorber senses the overvoltage with its breakover voltage V _BR , exhibits a negative resistance characteristic, and is required until it becomes conductive. Since the time is 3 to 5 μs, which is almost equal to the time required for electrically firing the light-igniting thyristor, 3 μs, it has a feature that it has excellent responsiveness to overvoltage. Accordingly, when the light-ignition thyristor is light-ignited, the voltage _VAK between A / K of the light-ignition thyristor falls as shown in FIG. between thyristor G / K definitive Similarly, if an overvoltage V _GK is generated in FIG. 9, Shirikonsa - Jiabuso - Bas 4
1, the silicon surge absorber follows the rise of the overvoltage V _GK without delay, reaches the breakover voltage V _BR and exhibits a negative resistance characteristic, and the resistance becomes almost zero. Because of the near conduction state, the overvoltage between G / K drops rapidly with V _BR at the top. That is, by configuring the clamp circuit with the silicon surge absorber 41,
Since inhibition in both over-voltage V _GK the magnitude and duration of the voltage, the constant voltage diode in the embodiment described above - not be obtained by de superior protective effect can be obtained. as a result,
Gate electrode 7G and auxiliary gate electrode 8 of the light firing thyristor
P _B layer 5C located between the G, the over-voltage breakdown and gate - not only is protected from thermal destruction by preparative loss, since it enables characteristic improvement of dv / dt capability of the light triggered thyristor, light It is also possible to contribute to providing a light-ignition thyristor having light-ignition performance in which the firing sensitivity sensitivity and the di / dt resistance and the dv / dt resistance are coordinated.

On the other hand, since the silicon surge absorber is almost conductive in a region exhibiting a negative resistance characteristic, the loss generated in the silicon surge absorber is smaller than that of a clamp circuit using a constant voltage diode, for example. Therefore, there is obtained an advantage that a highly reliable and miniaturized clamp circuit can be economically and advantageously provided by using a small-capacity silicon surge absorber. When the discharge current decreases below a certain level, the silicon surge absorber is turned off, and the standby state of the next protection operation is restored, so that a self-recovering clamp circuit can be obtained.

[0028]

As described above, according to the present invention, the overvoltage protection device is a clamp circuit connected between the gate electrode and the cathode electrode of the light-firing thyristor, and the gate is activated when the light is fired. An overvoltage generated between the electrode and the cathode electrode is suppressed to a predetermined clamp voltage. As a result, by determining the clamp voltage in accordance with the steepness of the fall of the A / K voltage at the time of light ignition, it is possible to prevent the destruction of the semiconductor substrate due to overvoltage, which is a problem in the prior art, and to reduce the gate voltage. By determining the clamp voltage so as to be equal to or less than the allowable loss, thermal destruction of the semiconductor substrate caused by repetition of light ignition can be prevented, and therefore, a light-ignition thyristor with stable operation characteristics can be provided. .

Further, the clamp circuit may be replaced by a constant voltage diode connected between the gate electrode and the cathode electrode of the light firing thyristor with its cathode terminal on the side of the gate electrode. For example, an overvoltage, for example, 200 V generated between G / K at the time of light firing of a conventional light firing thyristor is suppressed to, for example, about 30 V near a Zener breakdown voltage of a constant voltage diode, thereby preventing the destruction of the semiconductor substrate due to the overvoltage. It can protect the light-firing thyristor by simply adding a simple clamp circuit that connects only one constant voltage diode between G / K of the light-firing thyristor as an external circuit of the light-firing thyristor. Since it can be applied to various light-ignition thyristors having a gate electrode for electric ignition, especially to a high-voltage and large-capacity light-ignition thyristor, the reliability and economic efficiency are greatly improved. Obtained.

Further, if the clamp circuit is constituted by an NPN transistor and a constant voltage diode connected between the collector and the base, the voltage is generated between G / K at the time of light firing of the light firing thyristor. A light-firing thyristor including an overvoltage protection device that suppresses an overvoltage to be equal to or lower than the saturation voltage of the NPN transistor and protects the light-firing thyristor from overvoltage is obtained. Furthermore, even if the NPN transistor is replaced with a field-effect transistor, a light-ignition thyristor having the same overvoltage protection function as described above and having stable operation characteristics can be provided.

Further, the clamp circuit is formed of a silicon
If it is composed of a diabsorber, the overvoltage responsiveness and the negative resistance characteristic of the silicon surge absorber are utilized to achieve G
/ K overvoltage can be suppressed in terms of both its magnitude and duration, so that the light-ignition thyristor has its light-ignition sensitivity, di
It is possible to provide an optical firing thyristor including an overvoltage protection device having a function of performing an overvoltage protection operation while maintaining dynamic characteristics such as a / dt characteristic and a dv / dt characteristic stably. Further, since the silicon surge absorber is almost in a conductive state in a region where the silicon surge absorber exhibits a negative resistance characteristic, the loss generated in the silicon surge absorber is small. Therefore, the size is reduced by using a small capacity silicon surge absorber. An overvoltage protection device having a fixed clamping circuit can be provided economically and advantageously.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an overvoltage protection device for a light-ignition thyristor according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing an overvoltage protection operation of the embodiment device.

FIG. 3 is a connection diagram showing a different embodiment of the present invention.

FIG. 4 is a connection diagram showing another embodiment of the present invention.

FIG. 5 is a connection diagram showing another embodiment of the present invention.

FIG. 6 is a waveform diagram showing an overvoltage protection operation in another embodiment of the present invention.

FIG. 7 is a sectional view showing a main part of a light-ignition thyristor having a two-stage amplification gate structure.

FIG. 8 is a plan view showing a main part of a light-firing thyristor having a two-stage amplification gate structure.

FIG. 9 is a waveform diagram showing an overvoltage occurrence state of a light-ignition thyristor according to the related art.

[Explanation of symbols]

1 light triggered thyristor 2A anode - cathode electrode 3K cathode - cathode electrode 5 semiconductor body 5A P _E layer 5B N _B layer 5C P _B layer 5K N _E layer 5 _G1 N _E layer 5 _G2 N _E layer 7G gate - gate electrode ( 8G Auxiliary gate electrode 9 Light receiving unit 10 Optical signal 11 Clamp circuit (constant voltage diode) 21 Clamp circuit 22 Constant voltage diode 23 NPN transistor 31 Clamp circuit 32 Constant voltage diode 33 Electric field Effect transistor 41 Clamp circuit (silicon surge absorber) V _GK overvoltage V _Z clamp voltage (zener breakdown voltage) V _BR clamp voltage (breakover voltage) C Collector D Drain E Emitter G Gate S Source S

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/332 H01L 29/74-29/749 H03K 17/00-17/98

Claims (6)

(57) [Claims] 1. A light receiving section for light ignition and a gate for electric ignition.
In a light-starting thyristor having a gate electrode, an anode electrode and a cathode electrode through which a main current passes, an overvoltage generated between the gate electrode and the cathode electrode at the time of light firing is reduced to a predetermined value. An overvoltage protection device for a light-firing thyristor, comprising a clamp circuit for suppressing a clamp voltage between the gate electrode and a cathode electrode. 2. The clamp voltage of the clamp circuit is lower than the overvoltage generated between the gate electrode and the cathode electrode of the light-ignition thyristor, and is equal to or less than the gate allowable loss at the time of electric ignition of the light-ignition thyristor. 2. The overvoltage protection device for a light-ignition thyristor according to claim 1, wherein the overvoltage protection device is set to the following voltage value. 3. A clamp circuit comprising a constant voltage diode, said constant voltage diode having a cathode terminal between a gate electrode and a cathode electrode of a light firing thyristor. 2. The overvoltage protection device for a light-firing thyristor according to claim 1, wherein the overvoltage protection device is connected to the electrode side. 4. A clamp circuit comprising: an NPN transistor having a collector connected to the gate electrode of a light-igniting thyristor and an emitter connected to a cathode electrode of the light-ignition thyristor; and a collector and a base. 2. The overvoltage protection device for a light-ignition thyristor according to claim 1, further comprising a constant voltage diode connected with a cathode terminal connected to said collector. 5. A clamp circuit comprising: a field-effect transistor having a drain connected to the gate electrode of the light-ignition thyristor and a source connected to the cathode electrode of the light-ignition thyristor; 2. An overvoltage protection device for a light-ignition thyristor according to claim 1, further comprising a constant voltage diode connected between said gate and said cathode terminal with said drain side. 6. The overvoltage protection device for a light-ignition thyristor according to claim 1, wherein the clamp circuit comprises a silicon surge absorber.