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LM3481-FLYBACKEVM: Thermal in diode and MOSFET

Roy Chou1
Genius 16080 points
Part Number: LM3481-FLYBACKEVM

Hi Team,

We use the EVM to do measurement and we find that temp is too high on MOSFET and diode.

Could we use parallel MOSFET and diode for current sharing? (D1 and Q1 in schematic) http://www.ti.com/lit/ug/snvu528/snvu528.pdf?&ts=1590145951132

Do you think that parallel parts will cause the too large power loss ?

Regards,

Roy

  • 0
    TI__Guru* 78080 points

    Hi Roy,

    You can use parallel MOSFETs.  However, I would not recommend paralleling diodes. Diodes forward drop voltage have negative temperature coefficient, the one with lower VF will conduct first, then it gets heated up and reduces its VR further, leaving little chance for the other diode to conduct.  To resolve the thermal issue, you can consider to use a larger sized Schottky diode.  Also, consider to add heat-sinks to both the MOSFET and diode.

    Thanks,

    Youhao Xi, Applications Engineering