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UCC256402: Application issues.

Reed
Expert 1910 points
Part Number: UCC256402

Tool/software:

Hi Team,

According to the parameters on the schematic, using 431 for feedback is normal and stable. But when replacing the operational amplifier feedback, the output is set to 24-36V adjustable, and the upper and lower half bridge MOS are burned when powered on, especially the lower half bridge MOS and driver. The UCC256402 control chip driver is also short circuited. Could you please help me identify the problem? thank you!

01_03_AC8020_300W-ACDC New Ver.pdf07_300W-ACDC old Ver.pdf

  • 0
    TI__Guru* 85616 points

    Hello,

    I reviewed your schematic and it looks O.K.

    Generally FETs fail due to over current, over voltage and/or over heating.  Since this is an H Bridge it is more than likely failing do to over current.   I would double check your ISNS capacitor resistor divider to make sure it is sized correctly to prevent your FETs from seeing and over current.   

    The following link will bring you to an excel design tool that you can use to check the ISNS resistor divider to make sure it is protecting your FETs from an over current.  You can use it to check your ISNS divider; as well as, double check your design. 

    https://www.ti.com/tool/download/SLUC675

    If your ISNS divider is setup correctly maybe your FETs are just over heating.  You can check this with a thermal camera.  If this is the case you may require better heat sinking or select FETs with lower Rdson that will dissipate less power.

    Regards,