I finally got around to committing my modified design to a homemade PCB. When I say modified I had to change the design to incorporate a 5V voltage source for the TC4428 Mosfet driver chip because if I used the the cars 12V (which can go higher than 13.8V) this was higher than the BUK953R5-60 Mosfet’s maxium Voltage Gate to Source VGS allowed. This is specified at 15V max for pulsed and 10V max for DC. So as you can see it would be very close when being pulsed i.e. PWM and over when at DC by a significant margin.
My original comments on the need for a pull down resistor on the PWM input turned out to be true. The TC4428 outputs were jumping all over the place if the input PWM input was left floating. I’ve now included a resistor in the circuit diagram.
Sorry if it sounds all techo, but I didn’t want it to fail on me… or anyone else also!
Anyway I’m not happy with the circuit… so since I’m trying to get my car back on the road I have gone back to plan ‘A’ i.e. using a SSR.
I have ordered two CRYDOM D1D20 SSR that are specified to work up to 3500Hz in a PWM application (less than 100uS turn on time). But boy are they expensive, well at least here in Australia.
I’ll post my findings when I get them… I should have ordered 3 though as I think I have decided to also ditch the water pump and use a Electric Water Pump (EWP) to tame the cooling further… more money needed.