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Original question:

LMR38020: LMR38020 surge test failed

LMR38020: Why does the output becomes higher when the input higher?

dang xiaofeng
Prodigy 200 points
Part Number: LMR38020

Tool/software:

when this IC used in  flybuck circuit ( One isolated output) ,why Viso voltage  (isolated output) becmes higher when the input higher? 

(Light load mode）
输入电压/V 15 30 45 55
Vpri/V 11.96 11.96 11.96 11.96
Viso/V 11.8 12.14 12.39 12.6
  • +1
    TI__Mastermind 31315 points

    Hi,

    Can you provide a picture of your schematic, waveforms, and also verify if there is a resistor at the output? If there is no resistor at the output during light-load, the output voltage will rise since the energy delivered to the output is more than what is used. 

    Thanks,

    Richard