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UCC29002: The UCC29002 in -40C startup abnormal

Rock Shao
Expert 2995 points
Part Number: UCC29002

Hi 

At present, there are 3 units of 500W connected in parallel. At a low temperature of -40 degrees C, the startup will be abnormal and the current cannot be stabilized.
The figure shows the current waveform of a unit.
Have you encountered related problems? Can you provide suggestions?

  • 0
    TI__Mastermind 40580 points

    Hello Rock, 

    Most high-power SMPS use aluminum electrolytic capacitors on their output for ripple filtering and energy storage. 
    This kind of e-cap has very poor impedance characteristics at temperatures near -40C.

    I suggest that the abnormal current sharing at -40C ambient may be due to instability in each power supply from poor output cap performance. 
    If operation at such low temperatures is a requirement, please investigate the behavior of the output capacitors and their effects on stability. 
    You may or may not need to increase Cout or choose different capacitors which are formulated to maintain stable characteristics at -40C. 

    Regards,
    Ulrich