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UCC28061: I'm having the Switcher Transistors Damaged during Start Up ...!!!!

Eleazar Galvez
Prodigy 60 points
Part Number: UCC28061

Hello T.I Community...!!!

   I'm a test engineer (not design engineer) and my problem is that We are having a lot of failures on Our power supplies that use the chip UCC28061D during Start Up test. The switcher transistors are damaged. And I want to know tips or suggestions to check or looking for the root cause. I observed that at start up some cycles the phases on both transistors are the same, and after some time the chip make the correction and the driver signals are 180° out of phase. The input voltage at Start Up test is 90VAC and the Output voltage is loaded at 500W, this is in one of Our test equipment, but in the other the input voltage at start up is 120VAC and the output is loaded at 0W or Not load. Looks like We have the problem at different load condition.  Somebody can help to provide a guide or Steps to verifiy...signals..??

What is the safe time for this topology to start working properly this PFC stage  200mS, 400mS or less...?

Thanks and Regards.....

 

  • 0
    TI__Mastermind 25570 points
    Hi Eleazar

    First - the two phases of the UCC28061 always start up in phase. It takes a little time for the internal circuitry to establish the 180° phase shift between them so what you are seeing is normal.

    I'd suggest that you look at the following
    Double check the soft-start components
    Check that the VCC rail to the device is OK during start-up - perhaps supply VCC from an external source
    Check the gate drive waveform at the GDA and GDB pins - if you are using an external driver check the waveform at the MOSFET and at the controller
    Look at the Vds switching waveform of the MOSFETs, is it 'clean' or is there excessive voltage spikes or ringing on it.

    The device should be able to start up immediately into any load condition. However PFC operation won't become established until after the SS ramp is completed. The output voltage will have to be steady (385V or so) and the load condition will have to be steady.

    Let me know how you get on
    Regards
    Colin