Author Topic: Trouble turning on high side MOSFET in H-bridge circuit  (Read 496 times)

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Offline Capacitor_1886Topic starter

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Trouble turning on high side MOSFET in H-bridge circuit
« on: October 04, 2022, 05:44:24 am »
Hi, i am designing an h-bridge circuit to control a brushed dc motor and after trying to test this circuit out on the pcb i have failed to get the circuit to work. Only my low side MOSFETS turn on and the voltage on my high side fets remains in the mV range. I am unsure on what is happening, i have probed with a scope and traced my signals all the way to the input of my drivers and after the drivers the high side signal comes out very messy and in the mV range. I just want to understand if i did something wrong on my design or if there is something i am not understanding fundamentally. On the simulation everything comes out nicely, my high sides turn on and everything is fine, but on the pcb the high switches remain off.

For more context:

I am using an all N-MOS design, so 4 n-channel MOSFETs

The mosfets: ixfb210n30p3
The gate driver: dgd2190m

Any comments or suggestions would be greatly appreciated
 

Offline fourtytwo42

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Re: Trouble turning on high side MOSFET in H-bridge circuit
« Reply #1 on: October 04, 2022, 09:30:33 am »
Almost certainly your problem is related to frequency of operation or duty cycle being such that the boost capacitors are unable to charge, this is compounded by your static discharge of them through the 10K gate-source resistors on the high side.
If you want this circuit to work down to DC you will have to provide a separate permanent boost supply.
 


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