LLC with full bridge output is better?

[cupoftea]

Hi,

Doing LLC with Vin = 390VDC and Vout = +/-180Vdc at 4kW.
The simple 2 diode output rectifier suffers high ringing voltage on the output diodes when the respective diode switches off.
However, the full bridge LLC suffers none of this, and as such, lower voltage diodes can be used. Would you agree that overall, the full bridge approach is best?
(apart from different cases when Vout is low and Iout is very high, granted)
Attached shows the LLC with full bridge and simple 2 diode bridge in LTspice and jpeg

The Full Bridge output LLC suffers absolutely no output overvoltage ringing at all.

 

[Easy peasy]

different diodes with different capacitance ...

 

[cupoftea]

Thanks, the diodes used in either case are the same. Its noteable that when the 2-diode output LLC has a diode turn off, then there's nowhere for the leakage inductor current to go.........whereas with the full bridge LLC, there is actually a path for the leakage inductor current after a diode turns off......this is i believe what eradicates any ringing in the full wave output LLC?

 

[Easy peasy]

CT output has to have good coupling between sec wdgs - they are usualy bifilar and twisted to allow energy from one to commute to the other for this reason ...

 

[cupoftea]

Thanks very much, i see your point, i keep forgetting about coupling between secondaries....i was thinking too much of pri to sec coupling.