PMP22951: some dammage issue

Hi Jimmy,

Could you confirm which reference design your customer is using? There is no net named "BBSW" in the PMP22951 schematic. Is your customer possibly using PMP23069 or PMP23338?

Best Regards,

Ben Lough

Hi Benjamin,

The BBSW is pin42 of XMG3522R050QRQSTQ1. Component on the GaN Half Bridge Daughter Card.

Hi Jimmy,

Thanks for the clarification. Is the BBSW getting shorted on all 4x GaN of the primary side in the PSFB? Or only certain ones? Is there any change to the layout of the GaN compared to PMP22951 or did they use the GaN duaghter cards as-is?

Best Regards,

Ben Lough

Hi Benjamin,

Customer reply the GaN in the low side arm is more likely to be damaged. and layout same  the GaN duaghter cards.

Which key waveform is needed? thanks 

Hi Jimmy,

Is it only one of the low side GaN getting damaged or both low sides?

Best Regards,

Ben Lough

Hi Benjamin,

It's random, but mostly on the low side of damage.

But I got PWM and VDS, and the Transformer waveform from the customer side. 

Red: Transformer waveform ( different probe to measure both ends of the transformer

Blue: VDS

Green: PWM

400V to 200V (Condition is low load 20W)(

When low load(20W) GaN temp around 60 to 70C. Is normal? 

Can you provide an email address? I can show you the schematic and layout. thanks )

Hi Jimmy,

It is expected for a PSFB to lose ZVS on one side of the bridge at lighter load because there is not enough circulating current to achieve ZVS. 

My email address is ben.lough@ti.com.

Best Regards,

Ben Lough