ringing in power circuits

[Radha Sree]

Hello,

I am experiencing the ringing phenomenon in my circuit due to parasitics. I have tried using RC snubbers to alleviate the effect. But they dont seem to be helping... What else could be done to mitigate this phenomenon.... The frequency of ringing is about 500kHz. The major problem is that the amplitude of the oscillation is almost same as that of the voltage levels in the circuit....

 

[FvM]

Reducing parasitic inductances by better circuit layout is the basic method. Unwanted component behaviour, e.g. reverse recovery of slow diodes can be also causing the oscillations, in this case changing the components is mandatory. Slowing down switching speed (e.g. by increasing gate reistors) can help, but usually increases losses.

Snubbers must be tuned to the circuit impedance to be effective.

 

[Radha Sree]

Thank You. ... Besides RC snubbers will any other type of snubber circuits help???

 

[mtwieg]

Make sure that the parasitic inductance of the RC snubber is extremely low, otherwise it will be useless. If a properly designed RC snubber doesn't work, then other snubber circuits probably won't either. Are you sure you followed proper procedure for determining the RC values?

 

[avtoeleksys]

Try to put the RC snubber accross the freewheeling diode, usually it is there that oscillations originate.