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PMP40328: Unable to start up when connected to power

Chiao Fu
Prodigy 60 points
Part Number: PMP40328
Other Parts Discussed in Thread: UCC28780

Hello,

       Recently we have been working on module PMP40328, and we followed the BOM and PCB board on the web site (without changing any subjects). We faced some problems about the module. PMP40328 seems to be locked as we power it with Vac input = 100V at no-load and with load. The module seems to be locked out and we didn't know the reason. The Pin PWML and PWMH didn't output signals from UCC28780.

The signals below are some test results of our PMP40328 at Vac=100V input.

1. VDD (Triangle wave ranging from 10-17.5V)

2. VREF (REF output of UCC28780, which will drop to 0 )

3. Vgs of the Q7 (BSS126 H69006, ranging around -2V to -1.6V)

When problems appear in PMP40328, where should us check first?

We have measured the passive components and it seems OK. There is no voltage and current on the secondary side.

Thank you for answering the questions! 

Sincerely,

Chiao

  • 0
    TI__Intellectual 995 points

    Hi, Chiao,

    Firstly, thank for your selecting TI UCC28780 soluton for ACF.

    From the VDD and VREF waveform, UCC28780 is equipped the right power startup. However, there is no PWML signal. Could you please check the whether there is short-circuit or open on HVG, RDM, and RTZ pin?  In the UCC28780 datasheet page 35, it shows related protection and action.

    Thanks.

  • 0 in reply to David Ji
    Prodigy 60 points
    Dear David:

    Thank you for your reply.

    We checked the pin HVG, RDM, and RTZ pin mentioned above and found short-circuit on RDM and RTZ pin. Also, we replaced the resistor with higher precision and soldered it again. PMP40328 did work sucessfully !

    Thank you so much for your help !

    Sincerely,
    Chiao