I have a 48V 50A SMPS driving a fairly erratic load. The load varies wildly between 1 and 10A and can suddenly drop from full load to low load. I don't have an oscilloscope at hand, so these are estimates.
The load is very tolerant and won't care much about voltage variations in either direction. The problem is that the over-voltage protection on the power supply is fairly aggressively tuned at around 54…56V. It trips pretty often. I believe this is because the output regulation can't quite keep up with the sudden drops in the load.
What can I do to remedy this issue? I have considered the following:
- Add a resistive dummy load in parallel to help the regulation in case it struggles at low loads. How should I size it? 10A? 480W is a heck of a lot of power to dissipate in a resistor.
- Add a capacitor across the power supply output. I have no idea what size it should be to have an effect, but my guess is huge.
- Add a TVS diode across the power supply output. This was suggested here and indeed it seems ideal for filtering inductive spikes. But I'm not sure how well it plays in this case. Conveniently, there is a 51V part available though.
Is my diagnosis correct? What would you suggest to solve the problem?