Speed Val Kit Double Pulse Test Current Measurement

Kenny

Dear Wolfspeed Team,

I am finding it challenging to get an accurate current measurement on the SpeedVal Kit Evaluation Board.

For my setup, My load inductor value is 53uH, DC Bus Voltage is 200V and my switching period is 3uS i.e 333KHZ with a duty cycle of 0.6% i.e T_on (1.8uS). From the mathematical calculation the Id value should be about 6.84Amps at the falling edge of the first pulse (Isw = (Vds*T_on1) / L).

However, my current value is about 213mA. As can be seen from the attached images, I use a simple BNC-to-BNC cable. At first I noticed that the current waveform was inverted by default, I had to use the scope invert function to invert the current waveform.

Please is there anything that I am not doing right? I need your valued suggestion. I purchased the SpeedVal Kit with three different Wolfspeed Daughter cards for my analysis including the surface mount discrete products.

Kind regards,

Forum_Moderator

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AAnders

Hello Kenny,

Which MOSFET power daughter card are you using? The power daughter cards come with a low shunt resistance by default in order to support continuous power operation. For DPT, the shunt resistors should be replaced with 1 ohm resistors as shown in the user guide. The higher resistance provides a more accurate measurement. Did you make this change? If so, what scaling are you applying on the scope to convert from voltage to current?

Thanks,

Adam

Kenny

Hi Adam,

I am using the MOD-PWR-MM-C3M0075120J and MOD-PWR-MM-C3M0045065K Daughter Cards.

I did not change the shunt resistors on the daughter cards.

I will follow your instructions.

Regards,

Fredrick

TBhatia

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