Why large voltage drop across IRGPF40F IGBT

[Van12]

Hello,

I am designing a circuit in MultiSim in which I have a 600V DC source connected to the collector of an IGBT and a 1k ohm load connected to the emitter. When the IGBT is turned on, there is a voltage drop of 593V across the IGBT. What in the circuit would make this occur? What am I overlooking here? Any help is much appreciated.

[johnsold]

What is connected to the gate? That controls the conduction of the device.

Why did you choose that device for a circuit like this? The data sheet curves do not go down to collector-emitter curretns less than 1 A.

Lynn

[Van12]

The gate is being driven by the output of a LM393 comparator. I now see what you are saying about collector-emitter currents less than 1A.

I am attempting to design a short circuit protection scheme for the output of a DC/DC converter. The scheme is based on monitoring the IGBT collector-emitter voltage for an over current event.

[johnsold · Accepted solution]

Assuming that the power supply for the comparator is ground referenced, you will never be able to drive the emitter much higher than what you have now. The gate-to-emitter voltage is around 5 V at turn on and 12-13 V at rated current. If you operate with a single power supply of 32 V, you might get the emitter voltage up to about 25 V.

The LM393 would not be my first choice for driving an IGBT because the turn on time will be controlled by the pull-up resistor and the gate capacitance.

Have you considered Hall effect current sensors rather than shunt resistors? They have very low voltage drops and probably have larger output voltages than a resistor which can handle the overcurrent.

Lynn

[Van12]

Thanks for your insight and suggestions. I will look into Hall Sensors.

[johnsold]

I have used the ACS758 family of devices from Allegro MicroSystems in a solenoid driver circuit.

Lynn