/diy/ - Do It Yourself

>measuring open-circuit ripple voltage on cheap AC-DC SMPS modules
>getting ripple frequencies on the order of 30-600Hz
>pic related
I imagine this is just occasional switchings in some sort of intermittent mode, while the actual switching frequency under load will be far higher. Are common wall-warts fixed duty-cycle? I'd have thought that more sophisticated ones would vary the duty-cycle, causing their no-load ripple to be the same frequency as their normal operation, and the resultant ripple to be similar if not smaller than when under load.

Note that I have only tested shitty cheap SMPS modules, I'll check more expensive ones tomorrow. Guess I need to also test them under a variety of load currents, for which I may need some sort of variable load. By which I mean a length of nichrome in a bucket of water.