JPH01235413A - Abnormality detection circuit for electrostatic induction thyristor circuit - Google Patents

Abstract

PURPOSE:To easily and securely detect the abnormality of an off gate circuit and the fault of a thyristor circuit itself at low cost and to operate a protection circuit by providing an exclusive OR circuit of an off gate command signal and the output signal of a voltage detection circuit. CONSTITUTION:The voltage detection circuit 12 which detects that a voltage between the gate G of the electrostatic induction thyristor 1 and a cathode K is below a reference voltage is provided, the exclusive OR circuit 18 takes the exclusive OR of a voltage detection signal (b) being the output of the voltage detection circuit 12 and an off pulse signal (a), and the output is set to a fault signal (d), whereby the protection circuit 20 executes an appropriate protection action when the fault signal (d) shows '1'. Thus, the bias voltage monitor of the electrostatic induction thyristor 1 and the fault of the thyristor itself can be realized by the simple circuit and at low cost, and the protection circuit 20 can be operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an abnormality detection circuit for an electric induction thyristor circuit.

(Prior art) In general, electrostatic induction thyristors (hereinafter referred to as SI thyristors) are normally-on elements, so 81 thyristors
In order to keep rC in the off state, it is necessary to apply a PIE reverse bias voltage to the cathode and r- of the SI thyristor.

If the value of this reverse bias voltage is not sufficient, the SI thyristor will not be able to maintain the off state, so in equipment using 81 thyristors, the main circuit will become short-circuited and the operation will not be able to continue. There is a possibility that a large amount of damage will be caused to other main circuit components. In such a case, S! The bias voltage applied to the gate and cathode of the thyristor is monitored, and if an abnormality is detected, excessive protection is applied! It is necessary to discuss one method.

TFC, in circuits used on such semiconductor switching elements, it is often desired to detect failures of the semiconductor switching element, that is, the SI thyristor itself. Therefore, in such cases, the peripheral circuit of the 81 thyristor It is necessary to transmit two types of signals from the (h potential circuit section) to the protection circuit in the low potential circuit section: the 81 thyristor dart and cathode bias voltage monitor signals, and the SI thyristor's own failure signal.

(Problem to be solved by the invention) High-voltage power conversion used for DC power transmission, etc.? ctrt.

In the case of No. 13 transmission between the high potential circuit and the low potential (b) foot part, a light guide is used for insulation and the signal is transmitted as the original signal. Since the light guide is at market price, S
In the case of a high voltage-force converter using an 1 thyristor, two types of signals are sent from the high-potential circuit to the 10 low-potential circuits: a bias voltage monitor signal between the dirt and cathode of the 81 thyristor, and a failure signal for the 81 thyristor itself. Transmission increases costs and requires two types of signals. Because of the handling, the disadvantage is that the circuit is complicated.

An object of the present invention is to take note of the above-mentioned drawbacks, and to realize a bias voltage monitor between the gate and cathode of an Sl thyristor and a failure of the Sl thyristor with a simple circuit and at low cost.
An object of the present invention is to provide an abnormality detection circuit capable of detecting both an abnormality in an off-gate circuit of a thyristor and a failure of an Sl thyristor and operating a protection circuit.

[Structure of the invention] (Means for solving problems) The non-invention will be explained in detail using FIG.

In FIG. 1, reference numeral 1 indicates a series-connected Sl thyristor, and 4 indicates an off-pulse control circuit for controlling an off-pulse sent to the Sl thyristor. 3 is offno J? In response to the off-line pulse (B number a) from the pulse control circuit 4, the Sl thyristor 1
This is the off-gate voltage that provides the off-gate. 12 is S
The voltage detection circuit detects the voltage between the dart and cathode of the thyristor.

The exclusive OR of the voltage detection signal +9b, which is the output of the voltage detection circuit 12, and the OFF signal a is performed by the algorithmic logic sum circuit 18, and the output thereof is designated as the failure number d. The protection circuit 20 performs an appropriate locking operation when the failure signal d becomes 1''.

Here, if the detection level of the voltage detection circuit 12 is VDET, and if the cathode potential is the reference and the nine-date relaxation voltage is EGK, then if the following conditions are met, the voltage detection circuit 12 is set to 1.
”.

VDET≧EGK (VDET I EGW value is negative) (1) Furthermore, the maximum f gate-to-cathode voltage required for Sl thyristor 1 to turn off is V
, 1 (81 The lowest voltage between the dart and the cathode that thyristor 1 can withstand is 1 V. Let L be the off-gate voltage between the dart and the cathode when the Sl thyristor is off during normal operation.
If NOM, % ■GHl ■Gl, I VGNO
The relationship between MIVDET is set as follows.

0>vll, H≧VDET>VGNOM>”O
L (2) (Operation) Next, the operation of the present invention will be explained.

First, normal operation will be explained. During the on-period of the Sl thyristor, the off-pulse signal a output from the off-pulse control circuit 4 is 0# and off'! Since the "-) circuit 3 does not output an off gate, EOK is sufficiently larger than v(,H. Therefore, the output voltage detection signal of the voltage detection circuit 12 is 0".

Therefore, during the ON period of the Sl thyristor, both the off-pulse signal a and the voltage detection signal are "0#", so the failure signal d, which is the output of the exclusive OR circuit 18, is "0". S1
During the off-period of the thyristor 1, the off-pulse signal a, which is the output of the off-pulse control circuit 4, becomes 1", the off-gate circuit 3 operates, and EGK becomes equal to NOM. Therefore, equation (1) holds true, so the voltage The voltage detection signal S, which is the output of the detection circuit 12, is l'. Therefore, the off-north signal a and the 1! pressure detection signal S are both 1#, so
The fault signal d, which is the output of the exclusive OR circuit 18, is MO”
It is. As a result, during normal operation, the fault signal d is always '0'), and the ia circuit 20μ does not operate.

Next, we will explain #h, in which an abnormality occurs in the off-gate circuit 3 due to some reason, and the off-gate is no longer able to supply a sufficient reverse bias voltage between the dart and cathode of the Sl thyristor 1. 81 During the on period of thyristor 1, each off-pulse a'4b' IL pressure detection signal sum are both "0" as in the normal state, and the fault signal d which is the output of the exclusive OR circuit 18 is O. be. During the off-period of the Sl thyristor 1, the off-pulse signal a, which is the output of the off-pulse control circuit 4, becomes 1'. However, there is an abnormality in the off-gate circuit 3, and sufficient reverse electric current cannot be applied between the dirt and the cathode of the Sl thyristor 1, so equation (1) does not hold, and the voltage detection signal output from the voltage detection circuit 12 is the 02 maho.

Therefore, since the input signals of the exclusive OR circuit 18 are 0" and 1#, the fault signal d which is its output becomes '1",
The protection circuit 20 will be activated.

Next, consider a case where the Sl thyristor 1 fails.

Normally, most failures of semiconductor switching elements are short-circuit failures. Further, in an FC device in which a plurality of semiconductor switch systems are connected in series, as in the case of a DC power transmission converter, an open failure will eventually lead to a short circuit failure. In most cases, when a short circuit failure occurs, a short circuit occurs between the dart and the cathode. Therefore, when the Sl thyristor 1 fails, it is best to consider the case where the r-) of the Sl thyristor 1 and the cathode are short-circuited.

During the ON period of the Sl thyristor 1, the failure signal d, which is the output of the exclusive OR circuit 18, becomes 0 in the same way as when the Sl thyristor 1 and the OFF r-) circuit 3 are normal. During the off-period of the Sl thyristor 1, the off-pulse signal 1, which is the output of the off-pulse control circuit 4, becomes 1'.

The off-gate circuit 3 tries to apply a welcoming bias between the dart and the cathode of the 81 thyristor 1, but since the date and the cathode are short-circuited, a sufficient reverse bias voltage is not applied between the dart and the cathode, so equation (1) is Therefore, the voltage detection signal S obtained from the output of the voltage detection circuit 12 is 0''. Therefore, since the signal a and the signal S do not match, the fault signal d, which is the output of the exclusive-rational sum circuit 18, is 1'', the protection circuit 20 is operated, and an appropriate protection operation is performed.

(Example) An embodiment of the present invention will be described with reference to FIG.

1 is an SI thyristor. 2trl, 6D, is an ON r-) circuit for turning on the SI thyristor, and is driven by a control circuit not shown. 3 is an off-gate circuit. 4 is an off-pulse control circuit, a is an off-pulse signal, and 5 is an air-to-optical conversion circuit '1 for converting the off-pulse signal into an optical signal. 6 is a light guide that transmits the original off-pulse signal.

The off-gate circuit 3 includes a photoelectric signal conversion circuit 7 and an amplifier 8.
, Transistor 9 that decays off-gate switching,
Off-gate power supply 10. It consists of a power supply impedance of 1. Reference numeral 12 denotes a voltage detection circuit, which includes a resistor 13, a Zener diode 14, and a light emitting diode J5. 16 is a light guide for transmitting a photovoltage detection signal, 17 is a photo-electrical signal conversion circuit, 18 is an exclusive OR circuit, 19 is a low-pass filter for preventing malfunction, and 20 is a light guide for detecting abnormalities. This is a protection circuit to protect the system when detected. The Zener diode 14 and the resistor 13 are selected so that the voltage detection circuit 12 satisfies the equation (2J).

FIG. 3 is a timing chart showing the operation of one implementation of the present invention. An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

First, normal operation will be explained. During the on-period of the SI thyristor, the off-pulse signal a tri"0" is the output of the off-pulse control circuit 4, so the transistor 9 remains off and fc, and the SI thyristor 1
No reverse bias is applied between the dirt and the cathode.In most cases, during this period, the on-gate circuit 2
- A forward bias is applied between the gate and the cathode. Therefore.

(Equation 1 is not satisfied, the light emitting diode 15 of the voltage detection circuit 12 does not emit light, and the voltage detection signal S which is the output of the optical-electrical signal conversion circuit 17 is 10#. Therefore, the exclusive OR circuit 18 The output signal C becomes 0'', and the fault signal d, which is the output of the low-pass filter 19, also becomes 0''.

Therefore, the protection circuit 20 does not operate. During the off period of the SI thyristor, the off pulse signal 1 is 1"91
The light signal is converted into a light signal by the light-to-electric signal conversion circuit 5, transmitted to the light guide 61, converted to a light signal by the light-to-electric signal conversion circuit 7, and output to the amplifier 8, which turns on the transistor 9. When transistor 9 is turned on, the voltage of offgut power supply IQ reverse biases between the dart and cathode of SI thyristor l through power supply impedance 1, and (1
) satisfies the expression. Therefore, a current flows through the resistor 13 and Zener diode 14 to the light emitting diode 15,
The light emitting diode 15 is caused to emit light, and the original signal is transmitted to the optical-to-electrical conversion circuit 17 through the light guide 16, and converted into an electric signal by the optical-to-electrical conversion circuit 17, and the voltage detection number 4M becomes 1''. Therefore, f pulse signal a,
Since both voltage detection signals become '1', the output signal C of the exclusive OR circuit 18 is 0', and the fault signal d output from the low-pass filter 19 is also 0', and the protection circuit 2
0 does not work.

Note that when the off-pulse signal a changes from 0" to 1" or from "1" to 101, the voltage detection signal changes with a delay compared to the off-pulse signal a due to the transmission delay, so the output of the exclusive OR circuit C A short pulse-like signal is generated, but the short pulse-like signal cannot pass through the low-pass filter 19t.The fault signal d, which is the output of the low-pass filter, remains "0". Protection circuit 20 does not operate.

Next, after time t0, due to some reason, the off-gate power supply 1
Either an abnormality has occurred in 0 or SI thyristor 1 has failed and SI
Assume that there is a short circuit between e-) and the cathode of thyristor 1.

The ON period of the SI thyristor 1 is the same as in the normal state, and the failure signal d remains at '0' and the 69 protection circuit 20 does not operate.

However, the SI thyristor's off period i\1jid off i
If the pulse signal a becomes '11' and the transistor 9 is turned on, but the output of the off-gate power supply 10 is insufficient or there is a short circuit between the dirt and the cathode of the SI thyristor 1, the voltage between the gate f and the cathode becomes (1 ) cannot be satisfied and the light emitting diode 15 cannot emit light, so the voltage detection signal S becomes '0'.

Therefore, since the off-pulse signal nose is @1# and the voltage detection signal is @'θ', the output signal of the exclusive OR circuit 19 is Crl1''1#. In this state, the off-pulse signal a becomes 0''. Since this continues for a relatively long period of time, the fault signal d, which is the output of the low-pass filter 19, becomes "1" and the protection circuit 20 can be operated.

Although all of the explanations so far have been based on the off-gate, the same effect can be obtained by changing the off-gate signal to the on-gate signal and the off-gate voltage detection to the on-gate voltage detection. The protection circuit 20 can be operated by detecting an abnormality.

〔Effect of the invention〕

As described above, according to the present invention, an electrostatic induction thyristor circuit that can easily and reliably detect an abnormality in the off-gate circuit of an SI thyristor and a failure of the SI thyristor itself at low cost and operate a protection circuit. Can provide an abnormality detection circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a detailed diagram of FIG. 1, and FIG. 3 is a time chart of each signal in two embodiments for explaining the present invention in detail. 1... SI thyristor, 2... On-gate circuit, 3
...Off gate circuit, 4...Off pulse control Tsukuda circuit,
5... Electrical-optical signal conversion circuit, 6... Light guide, 7... Optical-electrical signal conversion circuit, 8... Amplifier, 9
...Transistor, 10... Off-gate power supply, 11
...power supply impedance, 12...voltage detection circuit,
13...Resistor, 14...Zener diode, 15
...Light emitting diode, 16...Light guide, 17
... Optical-electrical signal conversion circuit, 18 ... Exclusive OR circuit, 19 ... Low pass filter 20 ... Protection circuit. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] In a circuit using an electrostatic induction thyristor, a voltage detection circuit detects that a voltage between a gate and a cathode of the electrostatic induction thyristor is equal to or lower than a predetermined reference voltage, an off-gate command signal to the electrostatic induction thyristor, and the An abnormality detection circuit for an electrostatic induction thyristor circuit, comprising an exclusive OR circuit to which an output signal of a voltage detection circuit is applied, and using the output signal of the exclusive OR circuit as an abnormality detection signal.