August 2015 Updates

Electric Skateboard Half-Bridge Mach 4 Almost Working

I finished building and started testing half-bridge mach 4 this weekend. To my surprise, it’s working much better than the previous 3! For one, no MOSFET’s blew up within the first few seconds of connecting it up to the motor. I have a feeling it’s to do with the higher Vds (100V) of these MOSFET’s over the previous ones (75V). This gives the drain-source TVS diodes plenty of play-room to kick in and absorb transients before the MOSFET gets damaged.

The schematic the prototype board was made from.

Tentatively testing the half-bridge with a lightbulb before hooking it up to a motor.

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Testing it with a motor. I was able to stand on it for short times! (last time the MOSFET’s blew).

However, the MOSFET’s and the bulk capacitor were getting unusually hot. I hooked a scope up to the gates of the MOSFET’s and noticed ringing on the low-side FET when the high-side FET switched on. I think this is causing momentary shoot-through. This would explain hot FET’s, and, if the voltage rail was sagging, hot bulk capacitors.