Power Switches -What is a Snubber Circuit?

Snubbers are voltage suppressing circuits used to suppress voltage spikes caused by a circuit’s inductance when a switch (typically a transistor, but can be mechanical type) opens. Among many different kinds of snubbers, the resistor-capacitor (RC) snubber is most popular, where a capacitor and resistor connected in series is across the switch, or transistor.

Power switches are the heart of every power converter. Their operation will directly determine the reliability and efficiency of the product. To enhance the performance of the switching circuit of power converters, snubbers are placed across the power switches to suppress voltage spikes and damp the ringing caused by circuit inductance when a switch opens.

Proper design of the snubber can result in higher reliability, higher efficiency and lower EMI. The article below explains why a snubber is needed for power switches. Some practical tips for an optimum snubber design are provided as well.

Ceramic capacitors that undergo high dv/dt swings often prove to be audibly noisy and tend to be found in clamp and snubber circuits, as well as in the output stages. To test whether they are the noise source, they can be replaced by capacitors with alternative dielectrics such as (metal) film, or the series resistance could be increased (Figure 5). Should the audible noise be reduced, a permanent change in component should be evaluated.


To suppress the peak voltage, a typical RC snubber is applied across the switch as shown in Figure 4. The value of the resistor must be close to the impedance of the parasitic resonance which it is intended to damp. The snubber capacitance must be larger than the resonant circuit capacitance, but must be small enough in order to keep the power dissipation of the resistor to a minimum.

Reference Document:

Digi-Key Reference:
Resistor-Capacitor (RC) Snubber Design for Power Switches

Digi-Key Snubber Capacitor Selection:
-Please note there may be additional capacitors not listed under “snubber”