What is a snubber circuit?

A snubber is an RC network placed in parallel with a switching device or diode. When the device turns off, the inductor's stored energy charges the capacitor instead of spiking across the switch. The resistor damps oscillations and dissipates energy, preventing resonant ringing.

How is the snubber capacitor value calculated?

The standard formula is C = (I_peak / (2 * V_overshoot)) * sqrt(L / C), which simplifies to C = (I_peak² * L) / V_overshoot². Here L is the stray inductance, I_peak is the turn-off current, and V_overshoot is the allowed extra voltage above supply.

How is the snubber resistor chosen?

The resistor is chosen to critically damp the LC circuit: R = sqrt(L / C). A value between 0.5 * sqrt(L/C) and 2 * sqrt(L/C) works well in practice. Too low causes ringing; too high means slow energy absorption.

What power rating should the snubber resistor have?

Snubber power dissipation equals P = 0.5 * C * V_supply² * f_sw, where f_sw is the switching frequency. Use a resistor rated at least 2× this value to allow thermal headroom.

Can I use the snubber across a diode?

Yes. Diode snubbers are common in flyback converters to absorb reverse-recovery spikes. Use the same RC approach, substituting the diode reverse-recovery current for I_peak and the diode leakage inductance for L.

What is dv/dt protection for thyristors?

Thyristors can false-trigger if the voltage rises too fast (dv/dt). The snubber capacitor limits dv/dt to dV/dt = I_charge / C. Use the dv/dt mode in this calculator to size C for a given maximum rate-of-rise.

Snubber Circuit Calculator

Name: Snubber Circuit Calculator
Availability: InStock
Author: Nham Vu

Enter your switching device parameters to calculate the RC snubber resistor and capacitor values needed to suppress voltage transients.

Circuit Parameters

Calculation Mode

Stray / Load Inductance (µH)

Leakage or stray inductance causing the spike

Peak Turn-Off Current (A)

Current through the switch just before turn-off

Allowable Voltage Overshoot (V)

Maximum extra voltage above supply rail

Supply Voltage (V)

DC bus or supply rail voltage

Switching Frequency (kHz)

Used to estimate snubber power loss

Enter your circuit parameters

Click "Calculate" to get snubber component values.

Summary

Enter your switching device parameters to calculate the RC snubber resistor and capacitor values needed to suppress voltage transients.

How it works

Enter the load inductance (or stray/leakage inductance) in your circuit.
Provide the peak switch-off current (the current flowing just before the device turns off).
Enter the supply voltage and maximum allowable voltage overshoot.
Optionally specify the switching frequency to optimize snubber power dissipation.
The calculator outputs the snubber capacitor value, resistor value, and estimated power loss.

Use cases

Protecting MOSFET or IGBT transistors in DC-DC converters from voltage spikes.
Suppressing turn-off transients in thyristor (SCR) and TRIAC circuits.
Reducing EMI in switching power supplies by damping high-frequency ringing.
Protecting relay contacts from inductive kickback in motor control circuits.
Designing snubbers for flyback converters and boost converter diodes.
Meeting dv/dt rating requirements for thyristors in industrial drives.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu