App note: Diode turn-on time induced failures in switching regulators

A video from the comments on our post about fast diodes for switching regulators:

Recently, switching regulator clock rate and transition time have become faster, making diode turn-on time a critical issue. A potential difficulty due to diode turn-on time is that the resultant transitory “overshoot” voltage across the diode, even when restricted to nanoseconds, can induce overvoltage stress, causing switching regulator IC failure. This video provides a testing methology enabling proper diode selection for switching regulators.

Thanks Niklas!

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  1. Well, now I finally know which diode should Iuse for my SMPS designs. It’s LT’s Nr.1 type! I do not have 1GHz bandwidth oscilloscope nor 300ps rise time pulse generator, but it does not matter now. Thaks to Dr. Williams i know that Nr.1 schottky diode from LT saves the day. I will better order a bunch of them right now before they are out of stock after other guys sees this video.

  2. Lolz @ solipso
    Interesting video. I’ve built a couple of boards with cheap (old and slow) LM2576 (50kHz) and LM2596 (150kHz) regulators. I didn’t know the diode was that important, I just used the easiest to find schottky diodes. My boards work, peak to peak voltage on the output of the regulators is about 200mV (measured with my Rigol scope).

    1. I think that part of @solipso’s point is that you perhaps can’t see the true Vp-p on your (not high-enough bandwidth) Rigol. In lieu of that, rigging-up a hardware peak detector may be the way to go if you really want to know what your peak voltage is.

      Thanks for pointing out this post, OP.

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