IPA60R180P7 application in LLC Question

[KUOWENYUNG]

Dear IFXer,

I have IPA60R180P7 application LLC topology question.

before turn, the resonant current is negative S>D and VDS down slop to clamps VF, and the channel turn-on current is D>S, completed ZVS. Turn-off is due to the existence of the residual voltage platform and the crossover of the resonant current resulting in switch loss.

But the high side MOSFET waveform I measured, the voltage oscillates negative at turn-off, and Id_high_side downslop to zero current, the Vds_high_side rise to VBUS, resulting in no switch loss?! Is this correct?

The test conditions is below
output spec is 250W, measured under 20 load conditions.

the blue trace is VDS_high_side use differential probe

the orange trace is Id_high_side 

[Jingwei · Accepted solution]

Hi KUOWENYUNG,

Thanks for using Infineon Community. From your second screenshot, yes. There is ZCS in this condition.

But it is also weird to me, because the parasitic output capacitor of high-side mosfet needs to be charged with current Id. There must have some losses, even very small compare to the turn on losses.

Could you provide more testing results to analyze this? Is this also happen in low side mosfet?

Thanks and BR,

Steven

[Jingwei]

Hi,

Is your problem solved? Did you test at 50%Load and Full load?

BR,

Steven