A Methodical Approach To Snubber Design

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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Author & Publication:

Gregory Mirsky, Continental Automotive Systems, Deer Park, Ill., How2Power Today, Jun 17 2019

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