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Part Number: UCC28710

Hello Ulrich:

Intriguing issue: while running a module with UCC28710D, using a convenient 650v GaN device ( from Transphorm, same $), with only 10W operation- but has 2 outputs thnx to very tightly controlled transformer( lkg ~1uH)- so both outputs appear well regulated. The second output is 18V, about 300mA.

DC input never was above 180V during this testing.

the failure came out to be the controller  HV pin to GND.

Any idea how to add protection for the controller?WBDesign25_28710_6v2_350mA.pdf

I am following a Web-bench-designed circuit..

Pl see attached

  • Hi Robin,

    May I ask you some questions as in below:

    1. Does this failure can be duplicated ? if yes, could you please capture the HV pin voltage during the reproduce test.

    2. What the input connected to , a well regulated DC source or a public supply system which maybe connected with other equipment ? 

    Since the maximum allowed voltage for HV pin is 700V , it has a lot of margin for a input voltage around 180Vdc . 

    If this failure was caused by input line surge , I'd like to recommend you add a surge protect device such as TVS or varistor . shown in below 


  • Thnx Jaden. I think this failure can be reproduced. We will try to.

    Will try to capture HV pin voltage.

    We were testing using a dc source. I suspect rapid turn-off caused HV pin to source current into the HVbus cap. In a manner similar to LDO failures when LDO output cap discharges thru the reverse path. To prevent this, LDO safe design practice is to add a shunt diode . We will add a similar reverse current path blocking here as well .