Protection circuit for power management semiconductor devices and power converter having the protection circuit
A collector voltage of a power management semiconductor device is detected by a first comparator, and when the detected collector voltage exceeds a first reference voltage, the first comparator outputs a first detection signal. Furthermore, a gate voltage of the power management semiconductor device is detected by a second comparator, and when the detected gate voltage exceeds a second reference voltage, the second comparator outputs a second detection signal. The second reference voltage is a minimum gate voltage for feeding a rated power to the power management semiconductor device or over, and less than a line power voltage of a drive circuit of the power management semiconductor device. When both the first detection signal and second detection signal are being outputted, the gate voltage is reduced by a gate voltage reduction means so as to protect the power management semiconductor device from overcurrent and overvoltage.
1. A protection circuit for a power semiconductor device having a collector, a gate, and an emitter, the circuit comprising:
a first comparator which detects a collector voltage of said power semiconductor device to output a first detection signal when the detected collector voltage exceeds a first reference voltage;
a second comparator which detects a gate voltage of said power semiconductor device to output a second detection signal, when the detected gate signal exceeds a second reference voltage which is set, relative to the potential at the emitter of said power semiconductor device, to be lower than a line power voltage of a drive circuit for outputting a drive signal that drives said power semiconductor device and higher than a terraced voltage of the power semiconductor device;
logic means for outputting a protection start signal when both the first and second detection signals are being output; and
gate voltage reduction means for reducing said gate voltage in accordance with the protection start signal from said logic means,
said power semiconductor device being a trench type power semiconductor device.
2. The protection circuit according to claim 1 , wherein said second comparator detects said gate voltage based on a voltage obtained by dividing a gate voltage of said power semiconductor device by voltage dividing resistors.
3. The protection circuit according to claim 1 , wherein said gate voltage reduction means cuts off a drive signal of said drive circuit and reduces said gate voltage such that it sequentially decreases.
4. The protection circuit according to claim 2 , wherein said gate voltage reduction means cuts off a drive signal of said drive circuit and reduces said gate voltage such that it sequentially decreases.
5. The protection circuit according to claim 1 , wherein the first reference voltage of said comparator is set at a voltage which is higher than an On-state collector voltage and lower than a line power voltage of said drive circuit.
6. The protection circuit according to claim 2 , wherein the first reference voltage of said comparator is set at a voltage which is higher than an On-state collector voltage and lower than a line power voltage of said drive circuit.
7. The protection circuit according to claim 3 , wherein the first reference voltage of said comparator is set at a voltage which is higher than an On-state collector voltage and lower than a line power voltage of said drive circuit.
8. The protection circuit according to claim 4 , wherein the first reference voltage of said comparator is set at a voltage which is higher than an On-state collector voltage and lower than a line power voltage of said drive circuit.
9. The protection circuit according to claim 1 , wherein said first comparator, second comparator, logic means, and gate voltage reduction means are formed in semiconductor integrated circuits together with said drive circuit.
10. The protection circuit according to claim 2 , wherein said first comparator, second comparator, logic means, and gate voltage reduction means are formed in semiconductor integrated circuits together with said drive circuit.
11. An inverter for converting DC current to AC current, the inverter comprising:
a power semiconductor device for converting DC current to AC current; and
a control unit which controls a switching operation of said power semiconductor device, said control unit comprising:
a first comparator which detects a collector voltage of said power semiconductor device to output a first detection signal when the detected collector voltage exceeds a first reference voltage;
a second comparator which detects a gate voltage of said power semiconductor device to output a second detection signal, when the detected gate signal exceeds a second reference voltage which is set, relative to the potential at the emitter of said power semiconductor device, to be lower than a line power voltage of a drive circuit for outputting a drive signal that drives said power semiconductor device and higher than a terraced voltage of the power semiconductor device;
logic means for outputting a protection start signal when both the first and second detection signals are being output;
gate voltage reduction means for reducing said gate voltage in accordance with the protection start signal from said logic means; and
computer processor means for controlling the ON/OFF operation of said power semiconductor device,
said power semiconductor device being a trench type power semiconductor device.
12. A hybrid electric vehicle having an internal combustion engine, an electric motor, a transmission for transmitting power from said internal combustion engine and/or said electric motor to wheels, an inverter unit for converting DC power to AC power, and a DC power storage unit, wherein
said electric motor is an AC motor driven by AC power from said inverter unit including the inverter according to claim 11 .
13. An electric vehicle having an electric motor, a transmission for transmitting power from said electric motor to wheels, an inverter unit for converting DC power to AC power, and a DC power storage unit, wherein
said electric motor is an AC motor driven by AC power from said inverter unit including the inverter according to claim 11 .