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Testing a bench power supply

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diy didi

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Right, so I have just finished building my power supply. Its a 0-50V 0-4Amps bench supply.
I have an electonic DC load that can do transient tests on power supplies.
I just recently purchased this load.
How do I go about testing my power supply. I have no idea at what current rating to set the dc load and at what frequency i should set it's on/ off cycle.
What waveforms should I expect to see ?
I have done a capture of the on waveform at switch on. Looks good no overshoot.
I forgot to mention the dc load has the following parameters that can be set for transient testing.
Start current
End current
Rise tim
fall time
On time
Off time
Hope someone can give me a couple concrete steps to test my power supply
Thanx.
 
When I do load step testing I typically go from no load to full load on the load step. Since I don't have a fancy load tester, I just use power resistors and a set of contacts.
 
I would investigate a couple of things, always with a scope on the output. If the E-load has a trigger output, use it to externally trigger your scope. I would set the repetition rate at 100 Hz.
- 0 to 100% load and back; @ maximum voltage output
-10 to 90% load and back; @ maximum voltage output
Repeat for the lowest voltage output your supply can produce, or the lowest voltage the E-load is compliant to. You may have to read the manual to find out.

You'll be surprised at the difference. Then you will understand how come many precision power supplies put a pre-load resistor on the output.

Also, you should investigate:
-Startup time no load.
-Startup time resistive load.
-Startup time constant current load.

You will also be surprised that some power supply designs latch up when started under a CC load.

One question for you: which E-load did you purchase?
 
You really need to look at the start-up transient/overshoot at a variety of load conditions. I have had a radio damaged by a home-brew power supply that was reasonably well behaved in every area except turn-on overshoot...
 
I would investigate a couple of things, always with a scope on the output. If the E-load has a trigger output, use it to externally trigger your scope. I would set the repetition rate at 100 Hz.
- 0 to 100% load and back; @ maximum voltage output
-10 to 90% load and back; @ maximum voltage output
Repeat for the lowest voltage output your supply can produce, or the lowest voltage the E-load is compliant to. You may have to read the manual to find out.

You'll be surprised at the difference. Then you will understand how come many precision power supplies put a pre-load resistor on the output.

Also, you should investigate:
-Startup time no load.
-Startup time resistive load.
-Startup time constant current load.

You will also be surprised that some power supply designs latch up when started under a CC load.

One question for you: which E-load did you purchase?
Thanx for the tests. Will give them a go.
I purchased a 300W mynuo load. It's terrific!!
 
Mynuo? What is exactly Mynuo load?
I Googled it and got no hits with respect to E-loads.

Could you provide additional info?
 
sorry but no, you cannot test an SMPS with an electronic load, unless its just basic "can it ship the power or not type of testing". This is because electronic loads have an effective output capacitance, which is no good for testing smps, because the output capacitance is part of the feedback loop parametrics...so you definetely cant do transient testing for an smps with an electronic load..and definetely not stability testing either.
To do transient testing with an smps, you can only use power resistors and switchs, preferably fet switchs.
 
True that the output cap (and inductor) on a switcher output form a power pole that has to be compensated out in the loop design. If you significantly change the amount of output C, it does change the stability.
 
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