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Original question:

UCC27524A: UCC27524AD schematics review

UCC27524A: Support Required for UCC27524AD in Interleaved PFC Boost Circuit

Anand Matta
Prodigy 120 points
Part Number: UCC27524A

Tool/software:

Dear TI Team,

Please find attached the reference circuit I am using.
I am implementing the UCC27524AD as a driver in an interleaved PFC boost circuit (as per the attachment).

Currently, I am observing proper PWM signals at the INA and INB pins. However, there is no corresponding output at the OUTA and OUTB pins.

Could you please advise on possible causes or configuration checks that I might be missing?
Also, kindly confirm if any additional connections, such as enable or supply-related requirements, need to be ensured for proper output operation.

Best regards,
Anand Matta400 Watt Half Bridge LLC.pdf

  • 0
    TI__Expert 8640 points

    Hi Anand,

    Looking at your schematic, there's nothing I see that would impede OUT from working. However, I do recommend some adjustments if possible:

    1. Provide an RC filter for your IN pin. We typically recommend R = 0-10ohms (100ohms at the most typically) and C = 10-100pF (1nF at the most typically).

    2. Even though ENA/ENB is pulled up internally, we still recommend connecting them to VDD through a strong pull-up (10kohms) to increase noise immunity.

    3. Add another 0.1uF capacitor in parallel with your 2.2uF capacitor, and place the 0.1uF closer to the device than the 2.2uF. This is to ensure that any noise past the self-resonant frequency of the 2.2uF will be shunted by the 0.1uF capacitor.

    --

    Regarding your output, have you experimented by tying ENA/ENB to VDD? Can you also provide waveforms of the following signals taken at the pin of the driver with short GND probe loop:

    1. ENA and ENB

    2. INA and INB

    3. OUTA and OUTB

    4. VDD

    Thanks,
    Rubas

  • 0 in reply to Rubas Khalid
    Prodigy 120 points

    Dear Rubas,

    I had already implemented the suggested changes earlier, but unfortunately, the issue still persists.

    I am sharing the input waveforms from both input channels. However, I am not observing any corresponding output at the driver side.

    Please find the attached input waveforms for your reference. The yellow channel is the output

    Best regards,
    Anand Matta

  • 0 in reply to Anand Matta
    TI__Expert 8640 points

    Hi Anand,

    I'm sorry that you are still facing output issues. Is it possible you can decrease the timescale such that only 4 input pulses show on the scope? Can you also share pin ENA and ENB signals and VDD?

    Along with waveforms, can you share what the Idd is when the device is powered (both when inputs are switching and not switching). This is to investigate any quiescent anomalies.

    Thanks,
    Rubas