JPH05260644A - Semiconductor switch damage detection device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive semiconductor switch damage detection device which has a low breakdown voltage by comparing a current which flows a semiconductor switch element with a temperature increase obtained by calculating a thermal loss content based on the actual temperature for judging damage of the element. CONSTITUTION:The difference between a temperature T1 of a cooling fin 2 detected by a temperature sensor 3 and a surrounding temperature T2 detected by a surrounding temperature detection sensor 8, namely an actually measured temperature increase DELTAT of a semiconductor switch element 1, is obtained by an actual temperature increase detection circuit 10. On the other hand, a current Idet of the element 1 is detected by a current level detection circuit 9, an average current lave and a voltage drop DELTAV are estimated by a current.voltage estimation circuit 11, and then a loss content DELTAV X lave is calculated by a loss content calculation circuit 12. Then, an estimation temperature increase DELTAT' at the current Idet detected by an estimation temperature increase calculation circuit 13 is obtained. Then, a comparison circuit 14 compares the temperature increases T and DELTAT' and then it is determined that the element 1 is damaged in the direction of continuity the case of DELTAT'>>DELTAT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor switch using a semiconductor switch element such as a thyristor and a GTO, and more particularly to a semiconductor switch breakage detecting device for detecting breakage in the conduction direction of the semiconductor switch element. Is.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor switch using a semiconductor switch element such as a thyristor or GTO, when the semiconductor switch element is damaged in the conduction (forward) direction, a method for detecting this is as shown in FIG. There is one that detects a voltage drop in a different conduction direction.

[0003]

However, in a semiconductor switching device such as a thyristor or GTO, the voltage between its anode and cathode terminals is several volts when it is on, whereas it is several hundred to several kilovolts when it is off. Yes, again
When it is broken in the conduction direction, the voltage is almost zero. As described above, the voltage difference between the terminals of the semiconductor switch element is very large when it is on and when it is off, whereas it is very small when it is normal and when it is abnormal (damaged).

For this reason, in the conventional abnormality (damage) detection, a high breakdown voltage detection device is required because the voltage at the time of off is high, and a highly accurate detection device is required because the voltage difference between the normal state and the abnormal state is small. There was a drawback that it was expensive and required.

[0005]

SUMMARY OF THE INVENTION The present invention is intended to eliminate the drawbacks of the prior art and to obtain a highly accurate damage detection device for a semiconductor switch. Basically, it is applied to a semiconductor switch element. The estimated temperature rise value obtained by detecting the current and the actual temperature of the semiconductor switch element and calculating the heat loss (loss) of the semiconductor switch element based on the detected amount and the actually measured temperature rise value The result of comparison is to judge whether the semiconductor switch element is normal or abnormal (damage) based on the result.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the detection circuit device of FIG. 1 which is an embodiment.

In the semiconductor switch damage detection circuit shown in FIG. 1, 1'is a semiconductor switch composed of semiconductor switch elements 1 connected in antiparallel, and 3 is a temperature sensor attached to a cooling fin 2 for detecting the temperature of the semiconductor switch element 1. ,
Reference numeral 5 is a gate circuit for applying a gate signal to each gate of the semiconductor switch element 1 by a control signal from a gate control device 6 such as a phase control circuit, and 7 is the presence or absence of current in the semiconductor switch element 1 and the presence or absence of a gate signal. Is a determination circuit for determining abnormality (damage) of the semiconductor switch element 1 by Reference numeral 9 is a current level detection circuit for detecting the current of the semiconductor switching element 1 by the current transformer 4, and 10 is the semiconductor switching element 1 by the temperature sensor 3 and the ambient temperature detection sensor 8.
Temperature rise value detection circuit that detects the temperature rise value (ΔT) of
Reference numeral 11 is a current-voltage estimation circuit that estimates the average current (Iave) and the voltage drop (ΔV) from the detection current (Idet) of the current level detection circuit 9, and 12 is the heat loss (loss) of the semiconductor switch element 1.
The loss calculation circuit for calculating the value, 13 is the estimated temperature rise value of the semiconductor switch element 1 from the loss from the loss calculation circuit 12.
An estimated temperature rise value calculation circuit for calculating (ΔT '), 14 compares the output value ΔT' from the estimated temperature rise value calculation circuit 13 with the output value ΔT (T1-T2) from the actual temperature rise value detection circuit 10. A comparison circuit for determining whether or not the semiconductor switch element 1 is damaged in its conduction direction.

The detection principle and operation of this semiconductor switch damage detection device will be described.

When a current flows through the semiconductor switch element 1,
Normally, a voltage drop of several volts (element terminal voltage) occurs between the anode and cathode terminals, the product of this voltage and the conduction current becomes a loss, heat is generated, and the temperature of the semiconductor switching element 1 rises. .. Therefore, the cooling fins 2 are usually used to cool the semiconductor switching element 1.

These relationships are expressed by the following equations.

ΔΘ = (Rfin) ΔV × Iave (1) ΔΘ: Temperature rise (heat loss) Rfin: Thermal resistance of cooling fins ΔV: Voltage drop of the semiconductor switch element 1 Iave : Average current flowing through the semiconductor switch element 1 From this equation, if the temperature rise (ΔΘ) is measured, the average current value (Iave) in the normal state can be estimated. Therefore, the estimated average current value and the actually measured current By comparing with the value, it is possible to judge whether the semiconductor switch element 1 is normal or abnormal (damaged). The present invention uses this principle to detect an abnormal (damaged) state of the semiconductor switch element 1.

Next, the operation of the detection device of FIG. 1 will be described. "When the semiconductor switch element is normal" When the current normally flows in the semiconductor switch element 1 in the conduction direction, the temperature of the semiconductor switch element 1 rises as shown in the above formula (1). The temperature rise ΔΘ is the temperature T1 of the cooling fin 2 detected by the temperature sensor 3 (semiconductor switch element 1
Temperature that is substantially equal to the temperature of the above) and the ambient temperature T2 detected by the ambient temperature detection sensor 8, that is, ΔΘ = T
1-T2, and this temperature rise ΔΘ is the temperature rise value detection circuit
It is obtained by 10 as the measured temperature rise value ΔT. on the other hand,
The current (Idet) flowing through the semiconductor switching device 1 is changed to the current transformer 4
The current level detection circuit 9 detects the average current (Iave) from the detected current value (Idet) by the current voltage estimation circuit 11 and the current of the semiconductor switch element shown in FIG.
The voltage drop (element terminal voltage) ΔV is estimated using the voltage characteristics, and the loss component (ΔV × Iav
e) is calculated by the loss calculation circuit 12. Then, the temperature rise value calculation circuit 13 multiplies the loss by the thermal resistance Rfin of the cooling fin 2 to detect the detected current value Idet.
The estimated temperature rise Δθ ′ at is obtained as the estimated temperature rise value ΔT ′.

In the comparison circuit 14, the measured temperature rise value ΔT
If the semiconductor switch element 1 is normal, the temperature rises to approximately the same temperature as ΔT = ΔT ′.

"A semiconductor switch element is abnormal (damaged)" When a current flows in a state where the semiconductor switch element 1 is damaged in the conduction (forward) direction, the voltage drop of the semiconductor switch element 1 becomes approximately zero volt. In this state, the loss of the semiconductor switch element 1 becomes substantially zero regardless of the value of the flowing current because the voltage drop ΔV is substantially zero volt, so that the temperature T1 of the cooling fin 2 becomes substantially equal to the ambient temperature T2.
Even though the current (Idet) is flowing through the semiconductor switch element 1, the actually measured temperature rise value ΔT by the temperature rise value detection circuit 10 becomes substantially zero.

On the other hand, the semiconductor switch element 1 has a current
Since (Idet) is flowing, the estimated temperature rise value ΔT ′ by the temperature rise value calculation circuit 13 becomes much larger than the actually measured temperature rise value ΔT (ΔT ′ >> ΔT), and the semiconductor switch element 1
The abnormality (damage) of can be judged.

As described above, although the voltage difference in the conduction (forward) direction of the semiconductor switch element 1 is small between the normal state and the abnormal state (damage), the voltage drop (element terminal voltage) is small. The value can be used to reliably distinguish between normal and abnormal.

Further, in the detection apparatus of FIG. 1, the semiconductor switch element 1 is normally or abnormally based on the relationship between the presence or absence of a gate signal of the semiconductor switch element 1 and the presence or absence of a current (Idet) flowing in the semiconductor switch element 1. Can be judged. That is, when the gate signal by the control signal from the control device 6 to the gate circuit is “present”, the current is “absent” and abnormal.
Also, when the gate signal is "absent", the current is "present" and abnormal (damaged)
Can be judged.

If the direction of the current flowing through the semiconductor switching element 1 is detected by the current transformer 4, it is possible to determine which of the semiconductor switching elements 1 connected in anti-parallel is abnormal. ..

[0019]

According to the present invention, an abnormal state of a semiconductor switch element can be reliably determined only by detecting a temperature rise of the semiconductor switch element and a current flowing through the semiconductor switch element. It is economically superior in that it does not require high withstand voltage and high accuracy like the damage detection device. Also, if you monitor the temperature of the cooling fins,
Abnormalities in the cooling system can also be detected at the same time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a semiconductor switch damage detection device of the present invention.

[Fig. 2] Element current of a semiconductor switching element under normal conditions
(Iave) and voltage drop in conduction direction (ΔV: Element terminal voltage)
connection of

FIG. 3 Conventional semiconductor switch damage detection device

[Explanation of symbols]

 1 ... Semiconductor switch element 2 ... Cooling fin 3 ... Temperature sensor 4 ... Current transformer (CT) 5 ... Gate circuit 6 ... Control circuit 7 ... Judgment circuit 8 ... Ambient temperature detection temperature sensor 9 ... Current level detection circuit 10 ... Actual Temperature rise value detection circuit 11 ... Current voltage estimation circuit 12 ... Loss calculation circuit 13 ... Estimated temperature rise value calculation circuit 14 ... Comparison circuit

Claims (2)

[Claims] 1. A temperature rise value detection circuit for detecting the temperature rise value of the semiconductor switch element by detecting the temperature of the semiconductor switch element attached to the cooling fin and the ambient temperature of the semiconductor switch element installation, and to the semiconductor switch element. The heat loss is calculated by detecting the flowing current, and calculating the heat loss by the voltage drop of the semiconductor switch element estimated from the current-voltage characteristic of the semiconductor switch element based on the detected current and the detected current and the thermal resistance of the cooling fin in the previous period. A temperature rise value calculation circuit for calculating an estimated temperature rise value of the element; a temperature rise value of the semiconductor switch element from the temperature rise value detection circuit; and an estimated temperature rise value of the semiconductor switch element from the temperature rise value calculation circuit. And a comparison circuit for judging whether the semiconductor switching element is normal or abnormal based on the comparison result. Semiconductor switch damage detection device. 2. A determination circuit for detecting a current flowing through a semiconductor switch element, and determining whether the semiconductor switch element is normal or abnormal based on the presence or absence of the current and the presence or absence of a gate signal to the semiconductor switch element. Semiconductor switch damage detection device.