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TIDA-01622: fabricated boards not working

Art Mecina
Genius 16725 points
Part Number: TIDA-01622
Other Parts Discussed in Thread: UCC28070, UCC28780, UCC28782

Hello Guys,

Good day.

Our customer have fabricated several of TIDA-01622 boards. Only some are working. No output is observed for those that are not working. The run pin does not go high. This is despite the Vref pin toggling between 5 and 0V. VDD is the same as described in Figure 3 of slu982.

For those that are working, they run at 220Vac 50hz. But they have to insert a low-value pre-load resistor at Vo across the no-mount C7 on the Daughter card. This resistor does not appear on the TIDA-01622 schematic. Is this required? Without this resistor, they observe the power brick output continuously failing to start/regulate. 

Again, the schematic is the same as TIDA-01622 with the exception of a preload resistor across the no-mount C7 on the Daughter card.

Thanks and regards,

Art

  • 0
    TI__Intellectual 2160 points

    Hi Art

    thanks for reaching out, I am wondering if some boards works and some are not working, would you please have an sanity check on PCB soldering to see if there is any issue related,

    for the condition that required a pre load, please check if the converter fall into survive mode at open load

    To prevent the controller from getting stuck in survival mode continuously or toggling between SBP and survival
    mode at zero load, some guidelines on the auxiliary power delivery path to VDD can be considered:
    1. The normal VVDD level under regulated VO must be away from the 11-V threshold.
    2. VDD capacitor should not be over-sized, but designed just big enough to hold VVDD > VVDD(OFF) under the longest VO soft-start time.3. The current-limiting resistor (RVDD1) in series with the auxiliary rectifier diode (DAUX) should not be too large,
    so the delivery path with lower series impedance can help the VDD capacitor charge faster.
    4. Ensure good coupling between the auxiliary winding (NAUX) and the secondary winding (NS) of the
    transformer.

    Thanks

    Max

  • 0 in reply to Max Wang1
    TI__Genius 16725 points

    Thanks for looking into this Max.Below are the customer response in verbatim.

    "We are indeed reviewing the soldering process. For preventing the controller from getting stuck, in points 2 and 3 could you provide us with some values for RVDD1 and VDD capacitor? As we have fabricated the boards according to the reference design, but it does not operate at the claimed specifications."

    Thanks and regards,

    Art

  • 0 in reply to Art Mecina
    TI__Intellectual 2160 points

    Hi Art,

    the above mentioned is rule of thumb for RVDD1 and VDD selection, the actual value should be based on debug. but 1R and 2.2uF can give a start point to debug, other than that, the transformer winding design and arrangement is also important as the coupling will have critical impact on VCC voltage.  you can have magnetic design P/N 750343803 from Wurth for reference, the contact window is Hedy.He@we-online.com

    BR

    Max

  • 0 in reply to Max Wang1
    TI__Genius 16725 points

    Hi Max,

    The customer are still suffering from the issue where the power brick repeatedly fails to start up. Attached some images of the HVG and FB pin voltages. Hope these provides more insight.

    They've tried what's been suggested to reduce the VDD capacitance near to 2.2uF, but still not much improvement.

    Thanks and regards,

    Art

  • 0 in reply to Art Mecina
    TI__Intellectual 2160 points

    Hi Art,

    for this design, could you help to send us the customer PCB file(Altium PCB) and main transformer for a sanity check before we can draw a conclusion, as all this is crucial to the circuit debug. for UCC28070 detail pin operation, I may need to get UCC28070 AE Jaden involved as a back up to solve this issue.

    BR

    Max 

  • 0 in reply to Max Wang1
    TI__Expert 7080 points

    Hi Art,

    Basically, the primary low side Mosfet Vds , transformer primary winding current, VDD voltage are necessary for the start point to identify what protection have happened , here is a application note which detailed descripted all of start up issue we have faced during the past . hope this can help you to solve this issue and better understand ACF and our controller control strategy.

    Debugging UCC28780 ACF Converter Start-up Issues (ti.com)

    Thanks.

  • 0 in reply to Jaden Ning
    TI__Genius 16725 points

    Hello Guys,

    I just sent you a separate email regarding the requested design files of the customer.

    Thanks and regards,

    Art

  • 0 in reply to Art Mecina
    TI__Intellectual 2160 points

    Hi Art,

    well received, we will take a Schematic review and PCB check, and get back to you by next week! thanks!

    BR

    Max

  • 0 in reply to Max Wang1
    TI__Intellectual 2160 points

    Hi Art,

    looks like the schematic and PCB is exactly same with original design, just copy and paste, then i would like to check the transformer design to see if there is any mismatch. can you share the transformer detail design to us, also UCC28780 is old generation ACF controller, the new updated version UCC28782 has better features, simplified design. please check the latest design https://www.ti.com/tool/UCC28782EVM-030

    for more information.

     

    BR

    Max

  • 0 in reply to Max Wang1
    TI__Genius 16725 points

    Hi Max,

    Good day.

    Apologies for the late response. Customer just sent the latest update. They have the power adapters working now but the transformer produces an audible buzzing noise a no load. They have added several output capacitors to no avail. They noticed rapid switching producing large voltage spikes on the Vo line. They will provide us with an image as soon as their equipment is available.

    If you have an idea of what could be the cause, just let me know.

    Thanks and regards,

    Art

  • 0 in reply to Art Mecina
    TI__Intellectual 2160 points

    Hi Art

    for audible noise, could you please send the switching waveform when the audible noise happen, beside of switching frequency, please make sure the transformer are firmly vanished. this will help to reduce audible noise.  

    BR

    Max

  • 0 in reply to Max Wang1
    TI__Intellectual 2160 points

    Hi

    looks like we have not received feedback from you for many days, i assume you have solve this issue, i will close this ticket if no more request. 

    BR

    Max

  • 0 in reply to Max Wang1
    TI__Genius 16725 points

    Hello Max,

    I have not received any feedback from the customer too. It's okay to close for now. I'll just reach-out again referencing this thread in case they get back to us.

    Thanks and regards,

    Art