Flyback LED Driver Signal

[jman]

Hi Guys,

anyone can pin point whats wrong with this Signal


Thanks in advance

[jman]

Thanks for the reply
yes its a DCM controller but i really want to get rid of the ringing its very high.

I have a RCD snubber across the primary
C=4.7nF
R = 33K
it seems that the ringing its not fully dumped.

Any suggestion for the transformer?
Im using EFD30 ferrite

[rbola35618]

Actually there are two ringing frequencies in the waveform. The leading edge has the higher frequency which is the resonant of the Leakage and the Cmosfet. The lower frequency happens when the transformer reset and its frequency is determined by Lprimary and the Cmosfet. You would need to separate snubbers to damp the ringing. The resistor values should be around Zdamp=Squareroot(Linductor/Cmosfet).

Here is a video that I made a while ago where I damp the higher frequency (12:20)



Hope this helps.

Robert

[jman]

thank you for your replies help allot..

[jman]

hey guys here is the new waveform after adding RC snubber and keeping the RCD

[rbola35618]

Hi Jman,

The plots show that the waveform is properly damped. This looks good.

Robert

[T3sl4co1l]

That looks well damped, but I would be concerned if the damping components are getting quite hot.

Seems like the transformer could use higher inductance (or the controller to a higher frequency), and lower leakage (to reduce the spike).

Tim