Author Topic: Proper oscilloscope specs for SMPS design  (Read 857 times)

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Offline codonumTopic starter

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Proper oscilloscope specs for SMPS design
« on: June 23, 2020, 01:10:58 am »
I plan to buy an oscilloscope for use in my power electronics MBA course. I will use it mainly to design SMPS's, not professionally for now, but with professional quality.

If I were to choose between 12-bit resolution 20 MHz bandwidth and 8-bit 100 MHz, which one would be more appropriate for this application?

Is 8-bit resolution enough to clearly see mains filtering ripple?

Is 20 MHz bandwidth enough to detect most problems in a switcher operating in the kHz range?
 

Offline james_s

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Re: Proper oscilloscope specs for SMPS design
« Reply #1 on: June 23, 2020, 05:15:11 am »
I would definitely go with at least 100MHz, there's rarely a reason to look at anything less anymore, unless it's one of the scopes that can be hacked to 100MHz. 8 bits of resolution is pretty standard, I've done plenty of power supply work with mine and never found it to be limiting. You'll probably want at least one HV differential probe too assuming these are off-line power supplies you plan on developing.
 

Offline capacitor_explosion

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Re: Proper oscilloscope specs for SMPS design
« Reply #2 on: June 23, 2020, 06:09:55 am »
If it was only power supplies i would search for one with the smallest Vertical setting aka  less than 10mV per devision . 4 channels , and a (HV)differential probe . Also it will be a good idea to buy a Power supply with galvanic isolated outputs (and by PS i mean beefy transformer 1:1 ) .
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Offline tggzzz

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Re: Proper oscilloscope specs for SMPS design
« Reply #3 on: June 23, 2020, 06:59:46 am »
The answer may be different for a DC-DC SMPS (e.g. 12V->5V) or an off-line SMPS (e.g. 240V->5V) or an inverting SMPS or a high-power SMPS.

However, the scope will be less important than type of probe and whether you use the probes safely (i.e. in a way that does not endanger you, your scope, the SMPS).

FFI on probes, read learn and understand the safety/praxis references here: https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/
« Last Edit: June 23, 2020, 07:02:32 am by tggzzz »
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Online tautech

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Re: Proper oscilloscope specs for SMPS design
« Reply #4 on: June 23, 2020, 07:58:41 am »
I plan to buy an oscilloscope for use in my power electronics MBA course. I will use it mainly to design SMPS's, not professionally for now, but with professional quality.

If I were to choose between 12-bit resolution 20 MHz bandwidth and 8-bit 100 MHz, which one would be more appropriate for this application?

Is 8-bit resolution enough to clearly see mains filtering ripple?

Is 20 MHz bandwidth enough to detect most problems in a switcher operating in the kHz range?
Bit tricky without an indication of budget but if this was to be for later pro use certainly a scope with a Power Analysis option that has all the tools to properly characterize SMPS parameters would be worth considering.
Good sensitivity and reasonable FFT might also be useful for basic examination of EMI however a spectrum analyser is the correct tool for that job.

The SDS2000X Plus series of DSO's could be an affordable solution for immediate and future needs.
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