How to determine component values and switch dead-times in a fly-back passive snubber circuit

Thread Starter


Joined May 22, 2019
I have been studying the use of snubber circuits within flyback converters and other hard-switched converters, and doing some simulations to see the results. I have came across one type of snubber called a passive snubber circuit, which uses no resistor and instead some additional passive components such as capactiors and inductors, alongside diodes to snub the ringing and clamp the FET voltage. I have attached such a design. My main goal is to use this to help with transformer parasitics for a hard-switched, high voltage flyback converter or push-pull converter. Simulations are showing good results for the snubber however I believe these can be improved if I could calculate accurately the component values and dead-times. I will attach simulation results when I am able tomorrow.

My questions are as follows:
Does the inductance have to be an additional transformer winding, as shown, or can it be a discrete inductor?
How to calculate the inductance and capacitance value for the passive snubber circuit? Do these caps have to be those marketed as "snubber caps" to work, or are other capacitors suitable?
I have found through simulation that changing the dead-time between two switches using this snubber circuit in a push-pull configuration rather than fly-back changes the waveforms quite a lot. Is there a way to determine the optimum switch deadtime for a snubber in a push-pull or half bridge type configuration, for example - to allow the right amount of snubber action? May it be beneficial to provide a controls means to modify this dead-time at all?