A Methodical Approach To Snubber Design
by Gregory Mirsky, Continental Automotive Systems, Deer Park, Ill., How2Power Today, Jun 17 2019
Focus:
Even in a correctly designed switching power supply, stray capacitance and inductance
in the traces and leads can cause oscillation in switching currents at turn-off due to
the energy stored in these parasitic components. Properly designed snubbers may absorb
the energy stored in the stray components and make the switching process smooth and
oscillation-free. Unfortunately, many designers overlook the physical processes in
switching circuits and just pick values for snubber components using trial and error,
leading to poor results. This article explains the underlying process that leads to
oscillation in switching power supplies and derives the equations for accurately
calculating the R and C values that will effectively dampen the oscillation. An RC
snubber design example is presented and the performance of a properly design snubber
is contrasted with that of a snubber whose R and C values are arbitrarily chosen.
What you’ll learn:
- How to design RC snubbers for switching power supply circuits
- How to accurately calculate the resistor and capacitor values for an RC snubber
- How to understand the operation of an RC snubber at switch turn-off
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