How to design a snubber circuit?

In this article, you will learn what is snubber circuit? Why we need to use snubber circuit with power electronics circuits across semiconductor switches ? What types of snubber circuits are used in power electronics circuits. Let’s start with basic definition of snubber circuit.

What is snubber circuit?

Snubber is basically a RC circuit which is used to minimize back emf voltage or dv/dt with in a limit of semiconductor diode. It is connected across semiconductor devices. It is very important part of power electronics circuits. It provide protection to semiconductor devices used in power electronics circuits. Power electronics devices protected from reverse voltage through snubber circuit.

Types of Snubber circuits :

 Three type of snubber circuits are used in power electronics circuits. Name of  three of them is given below:

  1. Forward polarized.
  2. Reverse polarized.
  3. Unpolarized Snubber circuit.

Forward polarized snubber:

It is more appropriate for when a diode is connected anti parallel to transistor or thyristor. Circuit diagram of Forward polarized snubber is shown below:

polarized snubber circuits
polarized snubber circuits

Resistor R1 is used to limit dv/dt voltage across semiconductor device. Resistor R2 control the discharging current of capacitor C1 during the turn on time of semiconductor device.

Reverse polarized snubber :

Circuit diagram of reverse polarized snubber is shown below. Resistor R1 limit the reverse voltage dv/dt. R2 discharge the capacitor. Advantage of reverse polarized snubber circuit is that capacitor doesn’t discharge through semi conductor device. Due to which losses are reduced.

reversed polarized snubber circuits
reversed polarized snubber circuits

Unpolarized snubber :

Unpolarized snubber circuits are used when two semiconductor devices are connected anti parallel to each other. Just like shown in figure below. In this circuit snubber should work in both directions. That is why unpolarized snubber is used in such situation. Circuit diagram of unpolarized snubber circuit is shown below:

unpolarized snubber circuit
unpolarized snubber circuit

To design a snubber circuit you should know about following things of snubber circuit:

  • reverse recovery time of semi conductor device
  • Current rating of semi conductor device
  • Circuit total inductance
  • Input voltage to circuit
  • Optimum value of current factor (It can be found from data sheet of semi conductor device)
  • Optimum damping factor

If you know above things you can calcualte vales of capacitor and  resistors using following formula’s :

 C = L [ Ir / dVs ]²

R = 2δ√LC

4 thoughts on “How to design a snubber circuit?”

  1. hi…. i am doing my third year in ece….i am doing my mini project. my topic is GSM BASED VEHICLE THEFT INTIMATION USING PIC MICROCONTROLLER(16F877A). i have pic board with max232 and a RESET button. with the help of this rest button the PIC microcontroller should identify the UNAUTHORISEDD UESR. I am not clear with the program to be done in PIC microcontroller with the reset button…can anyone pls help to solve this problem

  2. salut à touts,
    je fais ma projet PFE et Je suis en train de faire mon simulation et la réalisation de circuit (clac). mon sujet est étude et modélisation d’un circuit d’aide à la commutation à base éléments non linéaires . l’élément non linéaire qui en utilise ici c’est cendansateur céramique BaTiO3 elle à une caractiréstique de minimisé des perts dues à la commutation pour limiter dv/dt. dans ma projet en utilise un bras hacheur … j’ai besion état de l’art de circuit simulation avec PSIM et quelque documentation
    merci

  3. salut
    je fais mon projet PFEet Je suis en train de faire simulisaton et la réalisation de projet. mon sujet est : étude et modélisation d’un circuit d’aide à la commutation à base élement non léniaire. l’élément non linéaire ici cendansateur céramique BaTiO3 en utilise cette circuit “snubber” pour limiter les perts (dv/dt) dans mon projet en utilise un bras hacheur ….j’ai besion état l’art de mon simulation sur POWERSIM et les documentation cencernant le sujet
    merci

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