I’ve been doing a lot of power supply testing lately, using both switching a linear supplies. Since it’s not something I’ve had to do often in the past (I’m an apps person, not so much a test engineer) … I thought it was worthwhile to spend a bit of time digging around for app notes on accurately characterising linear and switching supplies. Long story short: AN 372-1 from Agilent was one of the more useful ones I found (though I’m sure there are dozens out there). Short story long: read on …
I recently picked up a programmable load to make the measurements a bit less tedious (a B&K precision 8540 if you’re curious), which is an expensive tool for what’s in the box and perfectly doable for $50 as a DIY project, but a wide-ranging professionally built unit becomes your bench-top BFF when testing power supplies with it’s convenient constant voltage modes, etc., and direct visual feedback on supply voltages.
Armed with a good 6 1/2 DMM (an Agilent 34410A courtesy the ever generous Adafruit Elves last Christmas!), the B&K 8540, my trusty oscilloscope (Agilent MSO-X 2024A), and a DC power supply (Rigol DP1308A) I was able to quickly measure the efficiency of switching mode supplies across a variety of loads and with varying input voltages.
I’d actually like to put a quick tutorial together of getting basic measurements with a linear or switching supply, but if (like me a month or so back) you were wondering about the best setup to accurately measure certain characteristics of your power supply, the app note above from Agilent is worth the time, and include clears explanations of the benefits of different types of test equipment (depending on your budget), and what tests are available to you with the equipment you have.
I’ll try to flesh this out a bit more in the future, and take a couple photos of the setup I’ve been using (gear pr0n), but if anyone has any other suggestions on related app notes or white papers, feel free to post the in the comments section below!
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I’m working through some of this myself right now, and I’ll be very interested to see your setup. Is that diagram showing 2 probes used instead of a differential probe?
I’m working through some of this myself right now, and I’ll be very interested to see your setup. Is that diagram showing 2 probes used instead of a differential probe?