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# What is a Snubber Circuit?

Snubber Circuit is the one used for suppressing voltage spikes. These are energy absorbing circuits. Normally, the voltage spike occurs due to the inductor present in the circuit. Most basic form of snubber circuit is the RC snubber circuit. Below shows the figure of the snubber circuit having resistor and capacitor in series.

## Designing

We take our first assumption as the circuit is having negligible impedance. The value of peak current in the circuit will be calculated using the relation

Where:

Vo= It is the value of Open circuit voltage

Rs =It is the value of Snubber Resistance

The rate of change of voltage w.r.t time is calculated as

From above two equations we can write

According to Ohm’s Law

R=Vo/I

I = switching current

Vo= open circuit voltage

The energy dissipated in the snubber circuit will be equal to the energy dissipated by the capacitor. Because of this the value of the capacitor is selected such that the resistor will dissipate half of the wattage rating of the resistor.

Where:

f= Value of switching frequency

2f= Transitions/ cycle

## Condition for snubber circuit

Firstly, the energy stored in the circuit capacitor should be greater than the energy stored in the circuit inductance.

Where:

Vo= open circuit voltage

I = Value of closed circuit current

L= Inductance

Secondly, for this circuit the time constant should be less than 10% of the ON time.

Where:

TON= shortest on-time expected

R = snubber resistance

C = snubber capacitance

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