I have a simple MOSFET PWM circuit switching a 12v/8A load at a rate of 500Hz. This is being powered by a 120w switch mode power supply.
The power supply is buzzing loudly and generally unhappy with this arrangement. From my reading it appears that I need to smooth the load ripple created by the PWM circuit, by strapping a low ESR capacitor across the +/- input to the PWM circuit.
Is this correct, and if so, how do I calculate the correct value for the capacitor given the load characteristics?
Edit: PWM and PSU are commercial off the shelf units - I can't modify them. I'm after a relatively simple ad-hoc solution to go between the two units.