JPH0664120B2 - Method for measuring dv / dt tolerance of thyristor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thyristor dv / dt tolerance measuring method for detecting malfunction of a thyristor and measuring dv / dt tolerance of the thyristor.

[Background of the Invention]

FIG. 6 is an explanatory view showing the layer structure of the thyristor, in which R _GK is a short emitter resistor. Between the anode A and the cathode K of the thyristor shown in FIG.
When a voltage _VL having a constant slope rise as shown in the figure (hereinafter referred to as a ramp voltage) is applied, a charging current of a junction capacitance indicated by a PN junction at the center of the thyristor flows through the thyristor, and the gate G and the cathode K And the voltage V _GK shown in FIG. 7 is generated. Then, when the slope of the ramp voltage V _L is changed, the peak voltage value of the voltage V _GK increases or decreases, which is the base-emitter forward voltage V _{be of the} transistor (usually about
0.7V), the thyristor fires even though the gate G is not controlled externally. The voltage change amount dv / dt of the lamp voltage V _L per unit time at this time indicates the malfunction tolerance of the thyristor, and is called the dv / dt tolerance or the forward critical voltage increase rate.

In order to measure the dv / dt withstand capability of the thyristor, it is necessary to sequentially apply ramp voltage pulses having different slopes to the thyristor to find out the slope of the lamp voltage at which the thyristor malfunctions, that is, the dv / dt value. For this reason, a means for detecting whether or not the thyristor has malfunctioned is required. As this malfunction detection means, for example, Japanese Patent Publication
As disclosed in Japanese Patent Laid-Open No. 54-3348, there is a method of detecting the time when the thyristor malfunctions from the change in the observed waveform of the voltage across the thyristor.

However, in the above-mentioned measuring method, the voltage across the thyristor is unstable before and after the malfunction, so that the accuracy is low and the stability is lacking, especially in the measurement of high voltage, and it is difficult to automate because the malfunction is detected by the waveform observation. There was a point.

[Object of the Invention]

The present invention has been made to solve the above-mentioned problems, and particularly, the dv / dt withstand capability of a thyristor at a high voltage can be measured accurately and stably, and a thyristor suitable for automation of measurement can be provided. The purpose is to provide a method for measuring dv / dt tolerance.

[Outline of Invention]

The circuit of the present invention uses an optical coupling element as the malfunction detection means, and its light receiving part is connected in series to a load resistor connected in series to the thyristor to be measured, and malfunction detection information is obtained from the light receiving part. It was done like this.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram of an embodiment for realizing the dv / dt withstanding capability measuring method of a thyristor according to the present invention, and illustrates an example in which an optical coupling transistor is used as an optical coupling element.
In FIG. 1, reference numeral 1 is a thyristor to be measured, and a load resistance R _L and a light emitting diode D ₁ which is a light emitting portion of an optical coupling element 3 are connected in series to an anode A of the thyristor 1 and are connected through them. And further lamp voltage generator 2
Are connected. Also, the gate G of the thyristor 1
A resistor R _GK is connected between the cathode and the cathode K, and the cathode K is grounded. On the other hand, the emitter of the light receiving transistor Q ₁ which is the light receiving portion of the optical coupling element 3 is grounded, and the collector is connected to the power source E ₁ via the resistor R ₁ .

In the circuit configuration of FIG. 1, the dv / dt withstand capability of the thyristor 1 is measured as follows. First, a ramp voltage pulse V ₀ is periodically generated by the ramp voltage generator 2,
Apply to thyristor 1. At this time, as shown in FIG. 2, the ramp voltage pulse V ₀ is changed from a gentle slope to a steep slope. As a result, the thyristor 1 is finally ignited, but when the thyristor 1 is ignited, the impedance rapidly decreases due to its characteristic, and an on-current flows, and the anode-cathode voltage V _AK changes as shown in FIG. Indicates. In addition, light is emitted from the light emitting diode D ₁ due to the on-current flowing through the thyristor 1, but this light turns on the light receiving transistor Q ₁ .
The output voltage V ₁ changes from E ₁ to 0V as shown in FIG.

In the present invention, the change in the output voltage V ₁ at this time is measured by the thyristor 1.
Is used as the malfunction detection information. The dv / dt withstand capability of the thyristor 1 is indicated by a voltage change amount (V _T / _tr ) per unit time indicated by the slope of the lamp voltage pulse V ₀ at the time when the malfunction is detected. Where thyristor 1
The malfunction of is also detected from the change in the voltage across V _AK, V _AK of the ignition verge not sure as detection information for a very unstable. Also, in general, thyristor dv / dt
The withstand capability depends on the maximum reaching voltage (V _T ) of the lamp voltage pulse (V ₀ ), and its voltage value is an important measurement condition. Therefore, the maximum reaching voltage (V _T ) is changed to dv /
Often measures dt tolerance. Therefore, high voltage dv / dt
In the measurement of withstand voltage, when it is considered to detect a malfunction of the thyristor 1 from the change of the voltage V _AK , it is difficult to handle the detection information as logic circuit level information because the voltage V _AK is a high voltage. However, in the present invention, the thyristor 1
Since the malfunction detection information is obtained from the ON current of the device, the handling of that information is simple and reliable, and since the above information is transmitted by optical coupling, it can be electrically connected to the measurement system regardless of the dv / dt withstand voltage. Therefore, the detection voltage at the logic circuit level can be obtained in the state of being separated. As a result, high voltage dv /
Even in the measurement of dt resistance, the measurement can be performed stably and accurately. Further, since the detection information of malfunction is obtained as a signal at the logic circuit level, it is suitable for automation of dv / dt withstand measurement.

The lamp voltage generator 2 may have various configuration examples, one example of which is shown in FIG. FIG. 3 is a circuit diagram showing an example of the ramp voltage generator 2 configured by combining a transistor and a capacitor. That is, the signal generated by the pulse generator 4 is applied between the emitter and the base of the transistor Q ₀ via the resistor R ₀ , the capacitor C ₀ is charged by the collector current of the transistor Q ₀ , and the output ramp is output to the terminal V _0. It is what gets the voltage. In this ramp voltage generator 2,
The cycle of the output ramp voltage is determined by the pulse generator 4, and the rising slope changes depending on the output pulse amplitude of the pulse generator 4, the resistance value of R ₀ and the capacitance value of C ₀ , and the maximum reaching voltage (V _T ) is It is almost equal to the power source E ₀ .
Therefore, a desired lamp voltage pulse (V ₀ ) can be generated by changing these values.

Returning to FIG. 1, the load resistance R _L is for limiting the on-current of the thyristor 1 when the thyristor 1 is ignited, and its resistance value is the maximum reaching voltage of the applied lamp voltage. (V _T ) and the current capacity of the thyristor 1 or the maximum output current of the ramp voltage generator 2.
Due to the presence of this resistance R _L , dv / dt indicated by the output voltage V ₀ of the lamp voltage generator 2 and dv actually added to the thyristor 1
There may be a difference between / dt and a measurement error. The magnitude of this error is determined by the ratio of the resistance R _L and the off-time impedance of the thyristor 1. If a measurement error occurs, the problem can be solved by connecting the capacitor C _L in parallel with the series circuit of the resistor R _L and the light emitting diode D ₁ as shown in FIG. In FIG. 4, if the value of the capacitance C _L is set to be an impedance sufficiently lower than the off-state impedance of the thyristor 1, the measurement error can be ignored and the dv / dt can be accurately measured.
There is no change in that the withstand capability can be measured and the stable malfunction detection information can be retrieved.

FIG. 5 is a circuit diagram of another embodiment for realizing the present invention, in which the anode A of the thyristor 1 is grounded and the potential of the cathode K is lowered to measure the dv / dt withstand capability. Is. The circuit configuration shown in FIG. 5 includes the positions of the lamp voltage generator 2, the load resistance R _L , and the light emitting diode D ₁ .
Although the polarity of the generated lamp voltage is different from that of the embodiment shown in FIG. 1, the procedure for measuring the dv / dt withstand capability is the same as that of the embodiment shown in FIG. In the embodiment of FIG. 5, the lamp voltage has a negative polarity unlike the case of FIG.
The voltage level of the output voltage V ₁ of the light receiving transistor Q ₁ as the malfunction detection information is the same as in the case of FIG. 1, and the dv / dt withstand capability can be measured stably and accurately.

In the above-mentioned embodiment, the case where the photo-coupled transistor is used as the photo-coupled element has been described, but the same effect as that of the above-mentioned example can be obtained even if another photo-coupled element such as a photo-coupled thyristor is used. Needless to say.

〔The invention's effect〕

As described above, according to the present invention, even in dv / dt withstanding capability measurement of a thyristor at a high voltage, since the malfunction detection information can be reliably taken out, more accurate and stable measurement can be performed. Further, the malfunction detection information can be obtained at a voltage level separated from the measurement system regardless of the maximum reaching voltage of the lamp voltage and the polarity, and thus it is suitable for automation of dv / dt withstand measurement.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment for realizing the present invention, FIG. 2 is a voltage waveform diagram of each part of the circuit shown in FIG. 1, and FIG. 3 is a circuit showing an example of a ramp voltage generator in FIG. Figures and 4 are the first
FIG. 5 is a diagram showing another example of a main circuit in the figure, FIG. 5 is a circuit diagram of another embodiment for realizing the present invention, FIG. 6 is a diagram showing a layer structure of a thyristor, and FIG. 7 is a lamp voltage and a thyristor. Gate of
It is a wave form diagram of the voltage between cathodes. 1 ...... thyristor, 2 ...... ramp voltage generator, 3 ...... optocoupler, _{D 1} ...... emitting diodes, _{Q 1} ...... phototransistor, _{R L,} R _{GK, R 1} ...... resistance, _{E 1} ...... DC power supply.

Claims (1)

[Claims] 1. A load resistor connected in series to a thyristor,
Malfunction detecting means for detecting malfunction of the thyristor,
It consists of a ramp voltage generator that periodically generates a ramp voltage of an arbitrarily set ramp voltage and applies it to a series circuit of the thyristor and a load resistor.The malfunction detection means detects a malfunction of the thyristor and detects the malfunction of the thyristor. In the method of measuring dv / dt withstand capability, the malfunction detecting means is an optical coupling element in which a light emitting section is connected in series with the load resistor,
And a capacitor connected in parallel with the series circuit of the load resistor and the light emitting element light emitting portion, the impedance of the capacitor is set to a value sufficiently lower than the off-time impedance of the thyristor dv / dt Resistance measurement method.