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UCC2897A: UCC2897A

SUBHAMAY MAJI
Prodigy 10 points
Part Number: UCC2897A
Other Parts Discussed in Thread: UCC2894

Hello,

I designed an 'Active clamp forward converter' by using the UCC2897A Advanced Current-Mode Active-Clamp PWM Controller. I want to start at 212Vdc input, when I was giving the 212Vdc, the converter was not started.And the waveform I captured is attached below (the pink wavefoam is Vdd voltage, and Yeollow is Lx node voltage.). Also provide the schematic pdf as well.

Note : This Lx voltage is not regular waveform

 

DC of Active clamp forward convt.pdf

https://www.ti.com/product/UCC2897A/part-details/UCC2897APWR?utm_source=google&utm_medium=cpc&utm_campaign=ocb-tistore-promo-app_opn_en-cpc-storeic-google-in&utm_content=Device&ds_k=UCC2897APWR&DCM=yes&gad_source=1&gclid=Cj0KCQjw0ruyBhDuARIsANSZ3wq6rFAc788K4_kMTsj6HKuh--O2X711s9cXD3_LSATOMq4quUpCaAAaAt7SEALw_wcB&gclsrc=aw.ds

Thanks,

Subhamay

  • 0
    Prodigy 10 points

    Additional waveforms (below) show:

      (1) Once the converter enters into this mode (Vin = 200 Vdc, UVLO set at 140 Vdc), narrow single-pulse switching (200ns) occurs (see the Yellow trace as Switch node voltage)

      (2) The SS/SD pin voltage (pink trace) goes up and down continuously. Converter is unable to move out of this state.

      (3) VDD pin voltage (Blue) looks to be normal.

      (4) No abnormality seen on UVLO pin voltage. OVLO pin was grounded.

    Please suggest the possible sources/reasons, which can cause this type of issue.

  • +1 in reply to SUBHAMAY MAJI
    TI__Mastermind 26415 points

    Can you show all the startup waveforms on a single plot (VIN, VDD/PVDD, SS/SD, CS)? Show OUT and AUX (U8-14, 15)? Also, by inverting the AUX signal, you have introduced an addition prop delay on AUX that is not apparent on OUT and this can skew the deadtime. Trace the OUT and AUX signals through the entire power stage and make sure they are as you expect. What is the purpose of R27 - can you remove it? 

    When you show waveforms, please use full horizontal/vertical scale, use cursers and labels and align each trace reference to a horizontal line (0V, 10V, 20V, etc). This makes it easier to tread your waveforms.

    For HV input and the need for a high-side N-CH MOSFET, without the internal 110V JFET startup, you might consider UCC2894 as a better option?

    Regards,

    Steve

  • 0 in reply to Steven Mappus1
    Prodigy 10 points

    Thanks Steve !!