JPH04248373A - Voltage type inverter device - Google Patents

Abstract

PURPOSE:To prevent severe troubles such as burning by using a detecting means, which detects the overload of the output of a driving circuit for driving a voltage driving type power switching element, and an breaking means, which stops the output of the driving circuit based on the output of the detection means. CONSTITUTION:A differential amplifier 14 detects the voltages across a gate resistor 12 and an integrating circuit 215 integrates the output. Hereupon, if the input terminal of the voltage driving type power switching element 13 shorts, the output of the integrating circuit 15 becomes large. And when the output of the integrating circuit 15 becomes larger than a specified value after a specified time, a comparison circuit 16 outputs an EN signal to a driving control circuit 8a so as to make the drive output voltage high impedance and stops the gate current.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-type inverter device using voltage-driven power switching elements.

0002

2. Description of the Related Art FIG. 4 shows an example of the configuration of a three-phase voltage source inverter device. Reference numeral 1 denotes an input AC power source, which is converted into a DC power source by a converter circuit 2. 3 is an inverter circuit, which converts the DC power converted by the converter circuit 2,
This is a circuit that reconverts it into a variable voltage, variable frequency AC power supply. 4 is a drive motor serving as a load of the inverter circuit; 5
is the circuit that drives and controls the inverter circuit. FIG. 3 shows one drive circuit for a conventional voltage-driven power switching element. 6 and 7 are positive and negative drive power supplies, 8 is a drive control circuit, and 9 and 10 are drive circuit final stage transistors. Reference numeral 11 denotes a collector resistor of the positive end stage transistor 9 of the drive circuit, which limits the collector current and at the same time prevents a power supply short-circuit mode due to instantaneous simultaneous on of the transistors 9 and 10. This is a gate resistance that limits the instantaneous current when the gate output changes. 13 is a voltage-driven power switching element.

[0003] Voltage-driven power switching elements are
As shown in FIG. 2(b), it only flows during turn-on and turn-off, and its drive control can be easily performed with low power consumption, so a circuit with small power capacity is required and the device can be made compact. For this reason, it matches the recent needs for smaller size and lighter weight, and is becoming more and more commonly used. However, for this reason, the drive circuit has a heat dissipation design and a power capacity design for low power use, so if an accident such as a short circuit occurs in the drive input terminal of the power switching element, the drive current will flow continuously and the low power The drive circuit for the machine could burn out, resulting in a serious accident. To avoid this, if you design the power to withstand short circuits, it will be no different from a large-scale drive circuit for current-driven power switching elements such as conventional power transistors, which is an advantage of using voltage-driven elements. will be gone.

0004

[Problems to be Solved by the Invention] As mentioned above, inverters using conventional voltage-driven power devices fail in the short-circuit mode between the gate and emitter (in the case of IGBT, in the case of MOSFET: between gate and source). There was a problem with the drive circuit burning out. To avoid this, the power capacity can be designed to withstand short circuits, but
In this case, there will be no difference from a conventional current-driven drive circuit, and the advantage of using a voltage-driven element will be lost.

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks, and is intended to prevent a serious failure even when the input terminal of a voltage-driven power element fails in short-circuit mode. [Structure of the invention]

[0006]

Means for Solving the Problems In order to achieve the above object, the present invention provides a main circuit comprising a voltage-driven power switching element, a drive circuit for driving the power switching element, and a drive circuit for driving the power switching element. A voltage source inverter device comprising a detection means for detecting an output overload, and a cutoff means for cutting off the output of the drive circuit based on the output of the detection means, and a converter section for converting AC power into DC power. In an inverter device that has an inverter section that reconverts DC power into AC power, and operates a motor connected to the inverter section at variable speed under operating conditions set by a speed setting device, it is composed of a voltage-driven power switching element. a main circuit, a drive circuit for driving the power switching element, a detection means for detecting an overload of the output of the drive circuit, and a limiting means for limiting the output current of the drive circuit based on the output of the detection means. A voltage source inverter device is provided.

[0007]

[Operation] By providing the above-mentioned detection means and cutoff means, or detection means and restriction means, the current can be cut off so that the gate current does not continue to flow for more than a predetermined time or a predetermined current value even if a failure occurs in short circuit mode. A thermal fuse is inserted in series with the gate resistor to limit the current and open the gate circuit by detecting a temperature rise in the gate resistor.

[0008]

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. Note that the same reference numerals as in FIG. 3 have the same contents, so a description thereof will be omitted here.

Reference numeral 8a denotes a drive control circuit, and the EN input terminal is a terminal for turning off both output stage transistors 9 and 10, that is, for making the output high impedance. The drive control circuit 8a includes drive output transistors 9, 10,
A main circuit power element 13 is driven through a gate resistor 12. 14 is a differential amplifier, which detects the voltage across the gate resistor 12 and outputs it. In other words, it outputs a voltage proportional to the gate current. Reference numeral 15 denotes an integrating circuit that integrates the output of the differential amplifier 14. A comparator 16 outputs a low potential when the output of the integrating circuit 15 is VINT>+VR or VINT<-VR. The output of the comparator 16 is sent to the drive control circuit 8a.
is connected to the EN terminal of

In this embodiment configured as described above, when a switching waveform as shown in FIG. Since it is an input capacitor, the gate current that flows is a pulse-like current that flows only when the signal changes, as shown in FIG. 2(b). If the main circuit power element is normal, the
), and only instantaneous pulse current flows, so the integrating circuit output voltage VINT is +VR>V
The range is INT>-VR, the comparator 12 does not operate, and the EN terminal of the drive control circuit 9 also remains non-active, so switching drive is performed normally.

On the other hand, if the input terminal of the main circuit power element is short-circuited, a continuous current flows, which is determined by the gate power supply voltage and the gate resistance value, as shown in FIG. 2(c). At this time, if the drive is continued in this state, the gate resistance will burn out. FIG. 2(e) shows the integrating circuit 11 at this time.
This shows the output waveform of VINT, which naturally has a continuous current flowing, so the integrator circuit output VINT has a large value.
After a certain time VINT >+VR or V INT
<-VR, the comparator circuit 16 outputs an EN signal to the drive control circuit 8a, sets the drive output voltage to high impedance, and cuts off the gate current. Figure 2 (f
) shows an example in which the gate voltage is switched continuously, but in actual operation, the gate current becomes zero when the impedance becomes high, and the integrated output voltage is maintained, so the control power supply is switched off. The gate block state will be maintained unless dropped.

As described above, according to this embodiment, an abnormality in the gate current is detected and the drive circuit is cut off, so even if the input terminal of the main circuit power element fails in short-circuit mode, the abnormality can be detected. Since it can be detected and shut off, it prevents serious failures such as burnout, and at the same time achieves the original purpose of voltage-driven power devices, which is miniaturization.

In another embodiment of the present invention, a thermal fuse is inserted in series with the gate resistor of the drive circuit, and the thermal fuse is attached so that the heat generated by the resistor is transmitted. By doing this, the input terminal of the main circuit power element is short-circuited, and current flows continuously through the gate resistor.
Even if the temperature of the gate resistor becomes high, the thermal fuse can detect the temperature rise of the gate resistor and at the same time cut off the gate current.

Furthermore, as another embodiment, it is also possible to use a temperature-nonlinear resistor instead of a normal resistor as the gate resistance of the drive circuit. By using a temperature-nonlinear resistor whose resistance value increases with temperature rise for the gate resistor, the input terminal of the main circuit power element may be short-circuited, current flows continuously through the gate resistor, and the temperature of the gate resistor increases. Even if the temperature rises, the gate resistance value itself increases due to the temperature rise of the gate resistance, limiting the gate current, which has the effect of suppressing the temperature rise.

[0015] In addition to the above, it is the same as long as some kind of temperature detection sensor is provided, and it goes without saying that all processes such as integration and comparison can be performed by digital circuits in the electronic circuit.

[0016]

[Effects of the Invention] According to the present invention, even if the input terminal of the main circuit power element fails in short-circuit mode, the abnormality can be detected and shut off, thereby preventing serious failures such as burnout, and At the same time, the original purpose of voltage-driven power devices, which is miniaturization, can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram explaining the operation of the circuit in FIG. 1;

FIG. 3 is a diagram showing an example of a conventional drive circuit.

FIG. 4 is a schematic configuration diagram of a three-phase inverter device.

[Explanation of symbols]

1 Input AC power supply 2 Converter circuit 3 Inverter circuit 4 Drive motor 5 Inverter circuit drive control circuit 6, 7 Positive/negative drive power supply 8a Drive control circuit 9, 10 Drive circuit final stage transistor 11 Collector resistor 12 Gate resistor 13 For voltage-driven power switching element 14
Differential amplifier 15 Integrating circuit 16 Comparator

Claims (2)

[Claims] Claim 1: The motor has a converter section that converts AC power to DC power and an inverter section that reconverts DC power to AC power, and the motor connected to the inverter section is operated at variable speed under operating conditions set by a speed setting device. An inverter device comprising: a main circuit comprising a voltage-driven power switching element; a drive circuit for driving the power switching element; a detection means for detecting overload of the output of the drive circuit; and an output of the detection means. A voltage source inverter device comprising a cutoff means for cutting off the output of the drive circuit based on. Claim 2: The motor has a converter section that converts AC power to DC power and an inverter section that reconverts DC power to AC power, and the motor connected to the inverter section is operated at variable speed under operating conditions set by a speed setting device. An inverter device comprising: a main circuit comprising a voltage-driven power switching element; a drive circuit for driving the power switching element; a detection means for detecting overload of the output of the drive circuit; and an output of the detection means. and limiting means for limiting the output current of the drive circuit based on.