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UCC28180 can not over current protect?

Other Parts Discussed in Thread: UCC28180

When the AC power off, the bus is under pressure, the duty cycle increases to 98%, suddenly power on, can not over current protection, explosion, why can not flow protection?

  • Hi,

    I will ask one of my colleagues to look at this issue for you.

    Regards

    Peter
  •   

    Hi Peter,

    thank you very much.

    I set the protection threshold is 4A,but From the oscilloscope waveform,can find The current exceeds 10A for 700us to turn off, and I use the RC parameter for 220R and 1NF less than 1us.

    Regards

    Charles

  • Hi ,
    Can you please explain what signals are shown in the scope plots?
    What was the conditions of the test?
    Thanks
    John Griffin
  • Hi John,
    red: mosfet current
    yellow:driver signal
    Regards
  • Hi John,
    red: mosfet current
    yellow:driver signal

    t1-t2: turn off the AC grid,but ucc28180 still working(use the extra DC source),the bus cap voltage is reduce,so the D increase to the max,see the yellow signal.

    t2-t3:     suddenly,turn on the AC grid ,there will be a large spike current throuth the extra diode i draw and the Risense(because  test the mosfet curren ,there is no spike current in the scope),so the chip check the over current and turn off the driver immediatly.       

    t4:   the chip begin wave, two cycle,the current reach 15A.until the fifth cycle,turn off the driver(pic 3).

  • Hi Charles,
    If I understand you correctly, the red trace represents the current measured on the source of the MOSFET.
    If this is the case, it should be a switching waveform every time the gate (the yellow trace) switches.
    Every time the MOSFET turns off, the red trace should go to zero because the only path for the inductor current is through the boost diode.
    But this is not happening so I don't understand what the red trace is.
    Can you measure the inductor current with the voltage on the DC side of the rectifier.
    This will give a better understanding of what is happening.

    Also can you attach the schematic and do you have a design specification?
    Regards,
    John