Why can't I drive my MOSFET when connected to PWM?

Isolate the pulse width modulation (PWM) to see if it is working or not. If the PWM is working, it can be a MOSFET-driver problem. It is possible that the output current of the driver is not enough to drive the MOSFET. The MOSFET has a gate-source capacitance that will be charged.

There is an amount of charge necessary to switch the MOSFET. It is dependent on Vgs and is usually shown on a graph in the electrical specification of the MOSFET. If there is no graph available, there should be a rise and fall time specification (switching) at specified capacitance.

For example:
Qg =30 nC at Vgs = 10 V, PWM = 50 kHz and you want your rise time to be at 30 nS Q = I x t 30nC = 1A x t; t = 30nS; the MOSFET driver should be capable of sourcing 1 A of current.

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