Electronics > Beginners

Power supply ripple

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Simon:
Silly suggestion, have you checked your math function settings on your scope? just make sure it does not have a probe divider set that does not correspond to your probes. Else it may be a differential probe.

JuanGg:

--- Quote ---.  You should put a small fan pulling hot air out of your case as the case is likely to impede airflow through both the original power supply's ventilation holes and the DC-DC converter's heatsink somewhat.

Those DC-DC converters likely need every bit of heat sinking they have got to work. I would also put some vent holes on the bottom, and 'feet' on the case so air can flow upward through the fins, not just from the sides up.   
--- End quote ---

As mentioned above, the 24 V switching PSU I was using gave up. I got hold of a 22 Vac transformer and I will use that to make a raw PSU for the module. I'll add a small fan to it and make some more vent holes.


--- Quote ---Silly suggestion, have you checked your math function settings on your scope? just make sure it does not have a probe divider set that does not correspond to your probes. Else it may be a differential probe. 
--- End quote ---

I am pretty sure I did. I'll check it again anyway. Setup has changed as I am no longer using the initial switching PSU measurements above were made with.

    Juan


JuanGg:
I have changed the wall-wart with a linear power supply inside the case. Now I have the full 30 V out and more power available. I have added a -rather noisy- 12 V fan. I may make it temperature controlled.
    Juan

Jwillis:
It looks like one of those cheaper SMPS .
That "ping" is typical of SMPSs.It's the power MOSFET switching on and off.The weird looking sine wave is also typical for that grade of SMPS .I suspect that the incorrect material is used in the transformer.I get the same results testing various ferrite cores at various frequencies .At the correct frequencies for the core material used the sine wave smooths out and looks correct on the scope.At different frequencies I get the same type of distortion to the sine wave.
I've got a few of these cheap SMPS and they all do the same thing.Better quality ones don't exhibit that kind of noise as bad.

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