How to size a snubber capacitor for your power supply – Charged EVs

Sponsored by Knowles Precision Devices.

It’s becoming more common to see power supply circuits with wide-bandgap semiconductors rather than traditional silicon insulated-gate bipolar transistors (IGBTs). There are clear performance benefits to this switch, and with costs coming down, silicon carbide (SiC) and gallium nitride (GaN) semiconductors are more accessible than ever before.

While the fundamental circuit design process doesn’t change, substituting a component as vital as a semiconductor causes a domino effect in the component selection process. With the shift towards wide-bandgap semiconductors, engineers need to step back and take a fresh look at factors like voltage rating, capacitance value, equivalent series resistance (ESR) and equivalent series inductance (ESL) in the design process.

In this white paper, we’ll cover basic snubber derivation for a simple switching circuit. While snubber circuits are much more complex in practice, this exercise is useful for understanding how these switches impact snubber capacitor sizing.