JP3605269B2 - Inverter protection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a protection device for preventing breakdown of an insulated gate bipolar transistor (IGBT) constituting an inverter.
[0002]
[Prior art]
FIG. 4 shows an apparatus for protecting constituent elements of a conventional inverter disclosed in, for example, JP-A-4-308420. In FIG. 4, reference numeral 1 denotes an inverter control device for controlling an inverter, 2 denotes an insulated gate bipolar transistor driving circuit which receives a signal from the inverter control device 1 and drives an insulated gate bipolar transistor 3, and 4 denotes a collector of the insulated gate bipolar transistor 3 ( C) A collector-emitter voltage detection circuit for detecting a voltage (VCE) between the emitter (E) and 6 determines whether or not the duration of the detected voltage has exceeded the insulated gate bipolar transistor overcurrent determination time. This is an overcurrent determination circuit. When the overcurrent determination circuit 6 is activated, the insulated gate bipolar transistor drive stop circuit 5 stops driving the insulated gate bipolar transistor.
[0003]
Next, the operation of the conventional inverter protection device will be described. The insulated gate bipolar transistor 3 constituting the inverter shown in FIG. 4 is a switching element, and the voltage between the collector and the emitter of the insulated gate bipolar transistor 3 is such that the current flowing between the collector (C) and the emitter (E) ( Collector current: increases substantially in proportion to Ic). For this reason, in a normal switching operation, when the insulated gate bipolar transistor 3 is turned on, the voltage between the collector and the emitter is almost 0 V, but when a large current is generated due to a short circuit or the like, the voltage between the collector and the emitter is extremely high Value.
[0004]
The above-described conventional inverter protection device utilizes this operation to detect the collector-emitter voltage of the insulated gate bipolar transistor 3 only when the insulated gate bipolar transistor drive circuit 2 turns on the insulated gate bipolar transistor 3. Then, the collector-emitter voltage detection circuit 4 operates. The collector-emitter voltage detection circuit 4 determines whether the voltage is equal to or higher than a predetermined fixed level. If the collector-emitter voltage detection circuit 4 determines that the overcurrent level is reached, the overcurrent continuation time is determined within the ON period of the insulated gate bipolar transistor 3 by the CR time constant circuit in the overcurrent determination circuit 6 to determine the overcurrent. When the CR time constant in the circuit 6 is exceeded, it is determined that an overcurrent has occurred, and the insulated gate bipolar transistor drive circuit 2 is stopped by the insulated gate bipolar transistor drive stop circuit 5.
[0005]
[Problems to be solved by the invention]
Since the conventional inverter protection device is configured as described above, the CR time constant in the overcurrent determination circuit 6 for determining overcurrent is always constant. As shown in FIG. 3, the allowable overcurrent time of the insulated gate bipolar transistor 3 is generally longer at lower temperatures and shorter at higher temperatures. On the other hand, the switching time of the insulated gate bipolar transistor 3 has a characteristic that it becomes slower as the temperature becomes lower and becomes faster as the temperature becomes higher. Therefore, when the time for detecting the overcurrent, that is, when the CR time constant in the overcurrent determination circuit 6 is fixed, there is almost no margin for the fluctuation of the use environment temperature of the apparatus. There is a problem that a malfunction of the current judging circuit 6 and a breakdown of the insulated gate bipolar transistor 3 are caused.
[0006]
The present invention has been made to solve such a problem, and has an inexpensive configuration over a wide temperature range (generally in the range of -30 ° C. to 80 ° C.). It is an object of the present invention to obtain a highly reliable inverter protection device capable of protecting a transistor.
[0007]
[Means for Solving the Problems]
In order to reliably protect the insulated gate bipolar transistor even in a wide temperature range according to the present invention, a temperature correction circuit in which an overcurrent determination circuit for detecting an overcurrent of the insulated gate bipolar transistor and a temperature sensor for detecting an ambient temperature is added. By combining them, temperature correction is performed on the CR time constant for determining overcurrent.
[0008]
Specifically, the protection device for an inverter according to the first aspect of the present invention uses an insulated gate bipolar transistor as a component of the inverter, detects a collector-emitter voltage of the insulated gate bipolar transistor, and performs overcurrent protection. In the inverter protection device to be performed , an insulated gate bipolar transistor drive circuit for enabling detection of a collector-emitter voltage only when the insulated gate bipolar transistor is on, and a detection circuit for detecting a collector-emitter voltage of the insulated gate bipolar transistor An overcurrent judging circuit for judging a time during which the collector-emitter voltage of the insulated gate bipolar transistor continues to exceed an insulated gate bipolar transistor overcurrent voltage, and an atmosphere around the insulated gate bipolar transistor. Temperature and the temperature sensor, the temperature the overcurrent detection time from the value of the sensor, the insulated gate bipolar transistor smaller than the over-current threshold time varies with temperature, is corrected to be larger than the switching time of detecting the temperature A correction circuit; and an insulated gate bipolar transistor drive stop circuit that protects the insulated gate bipolar transistor when the insulated gate bipolar transistor overcurrent is detected.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an inverter control device for controlling an inverter, 2 denotes an insulated gate bipolar transistor driving circuit that receives a signal from the inverter control device 1 and drives an insulated gate bipolar transistor 3, and 4 denotes a collector of the insulated gate bipolar transistor 3 (C) -Emitter (E) voltage (collector-emitter voltage) detector for detecting a collector-emitter voltage, wherein the duration of the detected voltage exceeds a predetermined insulated gate bipolar transistor overcurrent determination time This is an overcurrent determination circuit for determining whether or not the operation has been performed. The functions of these elements 1 to 6 are basically the same as those of the conventional example shown in FIG.
[0013]
Reference numeral 7 denotes a temperature correction circuit for adding a temperature correction characteristic to the overcurrent determination circuit 6. Reference numeral 8 denotes a temperature sensor incorporated in the device for performing temperature correction and detecting an ambient temperature around the insulated gate bipolar transistor. It is.
[0014]
Next, the operation of the inverter control device will be described. In FIG. 1, the circuit operation until an overcurrent occurs in the insulated gate bipolar transistor 3 when the inverter is driven and the overcurrent level is detected by the collector-emitter voltage detection circuit 4 is basically the same as that in FIG. Is the same as the above conventional example.
[0015]
In the present invention, the overcurrent determination circuit 6 has a built-in temperature sensor 8 for detecting the ambient temperature, such as a thermistor element, the resistance value of which changes depending on the temperature. By combining with the configured temperature correction circuit 7, as shown in FIG. 2, the overcurrent detection time has a temperature characteristic.
[0016]
It should be noted that the CR time constant of the temperature correction circuit 7 is adjusted to an optimum value from the data of the allowable overcurrent time and the switching time of the insulated gate bipolar transistor 3 to be used in advance.
[0017]
That is, the overcurrent detection time is set so as to be shorter than the allowable overcurrent time that changes depending on the temperature of the insulated gate bipolar transistor 3 and longer than the switching time. The correction is made so as to be as short as possible and as long as the temperature becomes low.
[0018]
【The invention's effect】
As described above, according to the present invention, the overcurrent detection time that matches the temperature characteristics of the insulated gate bipolar transistor can be set. As a protective device, high reliability can be obtained.
[0019]
The temperature correction circuit according to the present invention incorporates a temperature sensor for detecting an ambient temperature into a CR time constant, and sets an appropriate constant from an overcurrent allowable time and a switching time of an insulated gate bipolar transistor to be used in advance. Even under an environment of a wide temperature range, the inverter can be protected by reliably detecting the overcurrent of the insulated gate bipolar transistor.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a protection device for an inverter according to the present invention.
FIG. 2 is a characteristic diagram of an inverter protection device according to the present invention.
FIG. 3 is a characteristic diagram of a conventional inverter protection device.
FIG. 4 is a configuration diagram of a conventional inverter protection device.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 inverter control device, 2 insulated gate bipolar transistor (IGBT) drive circuit, 3 insulated gate bipolar transistor (IGBT), 4 collector-emitter voltage (VCE) detection circuit, 5 insulated gate bipolar transistor (IGBT) drive stop circuit, 6 Overcurrent judgment circuit, 7 temperature correction circuit, 8 temperature sensor.

Claims (1)

In an inverter protection device that uses an insulated gate bipolar transistor as a component element of an inverter and detects overvoltage between a collector and an emitter of the insulated gate bipolar transistor to perform overcurrent protection,
An insulated gate bipolar transistor drive circuit that enables collector-emitter voltage detection only when the insulated gate bipolar transistor is on;
A detection circuit for detecting a collector-emitter voltage of the insulated gate bipolar transistor;
An overcurrent determination circuit that determines a time during which the collector-emitter voltage of the insulated gate bipolar transistor continues the overcurrent voltage of the insulated gate bipolar transistor larger than a predetermined value;
A temperature sensor for detecting an ambient temperature around the insulated gate bipolar transistor;
A temperature correction circuit for correcting the overcurrent detection time from the value of the temperature sensor to be smaller than an overcurrent permissible time that changes depending on the temperature of the insulated gate bipolar transistor and larger than a switching time ;
Upon detecting the insulated gate bipolar transistor overcurrent, an insulated gate bipolar transistor drive stop circuit that protects the insulated gate bipolar transistor,
A protection device for an inverter, comprising:

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