Issues during turn off of SiC MOSFET C3M0120090D in Asymmetrical Half-Bridge converter

Kalpak

Hello,

I am trying to make Asymmetrical Half-bridge converter using two SiC MOSFETs(C3M0120090D) and two diodes. I am getting ambiguous waveform of drain-source voltage, load current and load voltage during turn-off period. During turn-off, load current is getting higher and then settling to zero. There is overshoot in Vds also. I am not able to understand why this kind of waveform is coming.

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TBhatia

Hello Kalpak,

Are the 2 SiC MOSFET C3M0120090D in parallel? Which topology is the converter? Which diodes are you using? What is the switching frequency? Thank you so much!

Kalpak

Yes, the 2 SiC MOSFETs are in parallel. I am using two ultra-fast Si diodes (MUR1560) and my switching frequency ranges from 5kHz to 50kHz. The above-shown results are for 5kHz switching frequency. I am using Asymmetrical Half-bridge topology as shown below.

Julius_R

Greetings Kalpak:

I am looking at the waveforms in the first image and have a question. It shows only one gate (Vgs) high at a time. Looking at your schematic, how can you get current to begin flowing without gating both switches? If there was current already flowing through the inductor, one could turn on just one gate and the current would freewheel through one of the diodes but here the current is starting from zero.

TBhatia

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