SMPS - Why there is ringing on secondary ?

[MacIntoshCZ]

Hello,
Can someone explain why there is ringing on secondary side (before caps)? Its loaded with aprox. 30R Halogen lamps  on 100V at the moment. Its fullbridge converter 100V/40A. I even tried to simulate this and its also in simulations, RC snubbers removed high frequency ringing but this 1,1Mhz remains.
Also it rings only when voltage is rising. Qp1 probe is marked as 1 in schematic, QP2 probe is marked as 2.
Switching frequency is aprox 50Khz, tl494 driver. I think it should look like that, i just dont understand why.
Thanks for help

[boB]

From first glance, looks pretty much normal for a discontinuous mode inductor.

Usually from parasitic L-C  and not enough load.  Parasitics here are really small values except for the inductor.

Typically, just some ringing that doesn't over-voltage any components are fine and don't need to be dealt with.

Bring that 100K load R  down to where it is always drawing some current and the ringing should delay or go away.

boB

[radiolistener]

it happens due to impedance mismatch between secondary coil and load on high frequency.

[MacIntoshCZ]

Usually from parasitic L-C  and not enough load. 

Yes, i forgot to mention that this ringing goes away with higher loads.

it happens due to impedance mismatch between secondary coil and load on high frequency.

Ok  , I had readen in somo books that when medium has different characteristic impedance, than wave reflections happens. But how exactly this works right there i dont know