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UC2843: Power management - INTERNAL forum

Rebecca Li
Prodigy 490 points
Part Number: UC2843

Hi Team,

Customer met a problem of UC2843 with >80degC heat during 30min, which is really close to our spec of 85degC.

The output current of the primary side is only 0.08A. I attached the schematic. Could you please give some suggestions to reduce the temperature? Thanks.

 

  • 0
    TI__Guru 73395 points

    Hi,

    What value is for C230?

    What is the power MOSFET part number and transformer specs?

    Your schematics not clear enough to read - please provide a better one for us able to read.

  • 0 in reply to Hong Huang
    TI__Prodigy 490 points

    Hi Hong,

    Just use the mouse left click on the pic to zoom in, and it is clear enough for the parameters.

    • C230 is 47pF;
    • MOSFET: AP18N20GH 200V 18A Rds=0.17ohm, -55 to 150degC
    • Transformer: MSD514-224KED

    Any comments please? Thanks.

  • 0 in reply to Rebecca Li
    TI__Guru 73395 points

    Hi,

    It look C228 = 500pF, and R294 = 6.2k, these are outside of the datasheet recommended range. This device max frequency is 500kHz, but your circuit shows frequency is much higher. So you need to reduce the switching frequency and also set up C228 within the datasheet recommended range which should not be less than 1000pF.