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UCC28070: 7.3.17 ZERO-POWER DETECTION

Eddie Loy
Intellectual 850 points
Part Number: UCC28070

I HAVE BUILT THE PFC USS28070 SYSTEM  ACCORDING TO FIGURE 24 TYPICAL APPLICATION DIAGRAM.  I AM OLD SCHOOL AND LIKE TO SEE THE OUTPUT SIGNAL FROM GDA & GDB BEFORE I SEND HV POWER TO THE PFC SWITCHES.  I HAVE USED ALL COMPONENTS LISTED IN THE UCC28070 EXCEL SPREADSHEET, NO DEVIATIONS.


PROBLEM IS I CAN NOT SEEM TO GET PAST 7.3.17 ZERO-POWER DETECTION.

OR AM I NOT UNDERSTADING SECTION 7.3.17 ZERO-POWER DETECTION.

PLEASE EXPLAIN SECTION 7.3.17.

PLEASE EXPLAIN HOW I CAN VIEW OUTPUT SIGNALS GDA & GDB BEFORE I SEND HV THRU THE PFC SWITCHES

  • 0
    TI__Mastermind 34465 points

    Hello Eddie,

    In order to view a GDA or GDB signal you will need VSENSE> 0.75V and VINAC>0.7V

    This will cause the error amplifier output to go to its maximum value and the multiplier to go to one of its quantized levels.

    With VSENSE< 0.7V the controller shuts down due to an open loop protection error and with VINAC<0.7V the multiplier output is reset to zero.

    You will also need VCC> V_UVLO = 10.2V

    The effect you are seeing right now is not really due to a zero power detection.

    Regards

    John

  • 0 in reply to John Griffin1
    Intellectual 850 points

    UCC28070: NO SIGNAL OUTPUT FROM GDA & GDB

     

    Thank you for your fast response, much appreciated.

    I have rechecked the voltages on pin #4 & pin #5 and they have been adjusted to 1.00 volt. But still no output signal on GDA or GDB.

     

    What other pin(s), if any, contribute to being able to actually get a output signal from GDA and GDB (Pin #14 & Pin#17)?

    THANK YOU.

  • 0 in reply to Eddie Loy
    TI__Mastermind 34465 points

    What  bias voltage do you have ?

    If you still do not have an output signal then either there is something miswired in your circuit ,the ic is damaged.

  • 0 in reply to John Griffin1
    Intellectual 850 points

    Vcc is 12V .

    Help me out here.

    You being the support engineer of this  IC should be able to direct me to certain pins which could possibly be my problem area.  My Vvao never gets above .230V.

    DS Section 7.3.17  states pin #3 is required to ride back into the linear range of the multiplier (Vvao ™{>=) 0.9V.

    I don't understand how you can make a blanket statement with out asking for more information on other IC pins which would be associated with acheiving an out put signal.

    I don't mean to be condescending, but I was expecting was question, replies, comments, answers etc that one would expect from an "engineer".

    Either  reply that your are not an engineer and cannot help me or let us both communicate with each other as engineer to engineer.