Electronic – Correctly debugging switching (DC-DC) boost converter with Oscilloscope

dc/dc converteroscilloscopevoltage-regulator

I have an LED driver (LM3410) that adjusts it's voltage based upon how many LEDs you place in series to it and I'm curious to see what voltage it is actually outputting. To test it I connected my oscilloscope probe on the v+ output and ground and after getting a little smoke I'm a little worried about trying again. I'm pretty sure I put the thing into over-drive as it tried to "power" my oscilloscope. My over-voltage protection seems to have saved it since it still seems to work (miraculously).

So my question is: what is the proper way to measure voltage output from a DC-DC boost converter that changes it's voltage based on load?

Best Answer

From the problem description, two possible hypotheses come to mind:

  1. There is a ground level mismatch: The DC-DC boost output has a ground that is different from your oscilloscope's ground
  2. The probing was done with no LED load, so the boost circuit is attempting to generate the highest voltage it can. How high this can be depends on the circuit design, of course.

With some additional detail on the boost conversion design, additional hypotheses, or a definitive answer, might be possible.