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UCC28720: UCC28720 and current sense resistor damaged

Part Number: UCC28720


We are using UCC28720 as per attached image below.

In few of the power supplies, we found  Parts  R91, R92 ( Current Sense resistors), U1 ( Switcher) , T1 ( Transistor connected to the switcher drive) and R2 ( Transistor Base drive ) are damaged.

The  damage is happening in  few  power supplies(<2%).

The Powers supply is subjected to first power on at 230V, does not turn on and subsequently found that the parts are damaged.

Our specifications are as below.

Lp:330uH, Vinmin=44V, Vinmax=277V, Vout1=6.5V, Iout=0.1A, Vout2=5V, Iout2=0.35A.

What can be the possible causes of this damage? Please suggest.



  • Hello Sateesh,

    I am working with Prahlad on this issue.  He has forwarded me your schematic, transformer data sheet and BOM.

    I believe this might be electrical over-stress.  I am reviewing the materiel and Prahlad will be in email contact with you shortly.

    I am closing this issue out on the e2e.  However, I just want to let you know it is not closed and we are working on it off line.