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UCC28221: Reference voltage problem

Subin thekkan
Prodigy 30 points
Part Number: UCC28221

Hi,

i have been working on dcdc converter(design is similar to one present in your paper ''200-W Interleaved Forward Converter Design Review Using TI s UCC28221 PWM Controller'' ) while testing IC alone i get every value as mentioned in datasheet, once i connected entire circuit my output is zero because gate is not switching. Problem i found is Vref is zero.

In normal DC input condition, Vref should be 3.3V right? i'm getting value of 1.5V then instantly reduce to zero.

im attaching the schemaic of converter3WDCDC_VER0_SEPT2019_2.pdf

  • 0
    TI__Genius 13660 points

    Hi Subin,

    Please check the charge resister (Pin 10) and discharge resister (Pin 9) again, they are much different with EVM's.

    Regards,

    Teng 

  • 0 in reply to Teng Feng
    Prodigy 30 points

    Hi Teng,

    thank you for reply,

    i already interchanged resistors before proceeding for testing as i found this mistake in schematic.

    once the gate driver IC UCC27324D is connected, UCC28221 outputs are zero or in other words vcc and vin is short.  (gate) output of UCC27324D was left open(entire circuit shown in schematic is not connected while checking output of UCC28221). 

    Regards 

    Subin T

  • 0 in reply to Subin thekkan
    TI__Genius 13660 points

    Hi Subin,

    I didn't find any issues with UCC28221 and UCC27324D in the schematic.

    May I know the spec of conveter, and Vin?  Could you capture the waveform of VIN and VDD?

    And try to use an external DC source for VDD power supply.

    Regards,

    Teng

  • 0 in reply to Teng Feng
    Prodigy 30 points

    48V input

    12V output ,160W

    i connected tertiary winding of transformer to primary winding creating path for current during negative cycle, but still huge current is drawn by circuit causing mosfet failure  or heating within 2-5secs from power supply turning on.

    will check the circuit after connecting eternal dc supply for vdd and let you know the situation.

    thank you