ringing in flyback SMPS

[jagspaul]

One question, the ringing tendency is less in case of flyback continuous mode rather than discontinuous mode. Please tell me whether it is correct or not.

Regards
jagspaul

 

[FvM]

ringing tendency is less in case of flyback continuous mode

I think it isn't generally. There are however different kinds of ringing. In discontinuous mode, the transformer main inductance is disconnected after the output current reaches zero. You have a rather high impedance resonance circuit then, that can show a low frequency ringing, but it's meaningless, because the oscillation energy is very low. You have the same phenomenon with a discontinously operated buck converter, by the way.

The more problematic ringing is a resonance of transformer leak inductance at considerably higher frequency, involving more energy. It occurs at commutation from primary to secondary current, but also at commutation back to primary in continous mode. In the latter case, the rectifier's reverse recovery causes high di/dt values and possibly stronger high frequent interferences. On the other hand, continuous mode with low current ripple brings lower peak currents and thus less ringing.

 

[jagspaul]

Hello FvM,
Thank you for your reply.
I have made a 12V 2A discontinuous mode flyback SMPS. Which is working fine but some ringing is there in output rail. see this links . for this reason I want to make the same PSU in continuous mode to see whether the ringing is removed or not.

One more think I would like to request that I don’t have any design spreadsheet for flyback continuous mode. If possible please sent me the same.

Regards
Jags