Semiconductor leakage measurement in HTRB

[arijav]

Hello,

I am trying to design a test system for HTRB of power semiconductors. The system will have a High Voltage Power Supply (f.i. 2kV) which will be connected in series to several Power Semiconductors (Devices Under Test) in parallel whose leakage needs to be measured. Each one of the Power Semiconductors will have a protection switch in series (3.3kV SiC MOSFET) and a measurement circuit (logarithmic amplifier measuring the range of 1nA to 10mA). I need a protection circuit to assure that in case of breakdown of the Devices Under Test, the measurement circuitry (AD8304 + ADC, etc...) does not see the 2kV or >10mA. A series current limiting resistor at the output of the HVPS will not do the job as the DUTs need to see the 2kV @10mA in worst case. I am not sure if I can solely rely on the protection switches as I think I will need at least 10us to switch them open.

Do you have any idea on how to limit the current in case of failure to 10mA and assure the AD8304 does not see the 2kV?

Thanks,

Javier

[Kleinstein]

It is usually quite easy to protect a current measurement part, so that it can withstant quite a bit more current. With clamping diodes the current measurement part should be ok with some 1 A and maybe also 10 A for a short pulse. The question for the current limiting is more on how to protect the power supply and DUT, so that they don't blow up.

This would normally be something as part of the power supply, so that the supply could compensate for the voltage drop on some series resistance.

[PartialDischarge]

IMO you should reevaluate the 10mA target, seems too high, do you really expect the leackage to get into the 1..10mA range?

Other than that your requirements call for a floating (battery powered) protection circuit that measures the current and switches the PSU off via fiber optic signal for example.

[MK]

Another way to measure is to set a current through the device, and measure the voltage, that way you do not exceed the limits usually

[mzzj]

IMO you should reevaluate the 10mA target, seems too high, do you really expect the leackage to get into the 1..10mA range?

Other than that your requirements call for a floating (battery powered) protection circuit that measures the current and switches the PSU off via fiber optic signal for example.

10mA sounds reasonable for large 1200v IGBT in HTRB (High Temperature Reverse Bias) test.