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About UCC28710d- no pwm output

yuvaraju sasanamu
Prodigy 10 points

hi!

We are using UCC 28710D to develop a 5V/2A AC/DC converter module. but we are unable to get any drive pulses..

By suspecting the transformer auxiliary output  We used external DC source to give VDD at 21V. We modified Vs pin resisters to give a stable input of 4.05V.

The Rcs used is 1.4ohms.

Issue: For some reason we do not see any drive pulses from the DRV pin.

output load connected at the secondery side is 

Can anyone please suggest what could be the problem?

  • 0
    TI__Expert 5900 points
    Hi Sasanamu,
    Don't put DC voltage on VS pin. And 21V is not enough to power up IC, for the electrical table you could see VDD(on) is from 19V to 23V.

    My suggestion is please attach your schematic and transformer design.

    Capture the VDD, AUX winding, Vbulk waveforms at startup.

    Provide more detail information as possbile.

    We could help you based on the information you provided.

    Br