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UCC28070 PROBLEM

Ravindra Nikate
Prodigy 50 points
Other Parts Discussed in Thread: UCC28070

Customer is designing 2.0 KVA Invertor,I am  following Excel sheet UCC28070 , Also following PMP4311A Design file , Observation is ‘15 V is given to  UCC 28070  and 0.8 V to Vsense and less than 0.75 V to VINAC  and observing the PWM output as get an PWM waveform of 100KHz this PWM output given to  Driver ic UCC27322D and output of this also ok  but when connected to MOSFET gate terminal PWM output get vanish and SS voltage  fluctuate between 5 volt to 1 volt continuously’ Please suggest remedy on this.

  • 0
    TI__Mastermind 34465 points
    Its difficult to understand what is happening here without a schematic but it looks like there is some fault condition being sensed on the VSENS pin that is causing the SS to cycle on/off.
    0.75V is the threshold on VSENS. Since you have an input of 0.8V I am wondering if noise on this pin is causing the UCC28070 to cycle on/off.
    How are you connecting all of the other pins? Can you please attach a schematic?
    Thanks
    John Griffin
  • 0 in reply to John Griffin1
    Prodigy 50 points
    As i refer 300 W reference design and all component are as per the 300W sch else some tolerance. As far concerned with V sense i put an jumper wire externally from output to pin no 4 of UCC28070.
  • 0 in reply to Ravindra Nikate
    TI__Mastermind 34465 points
    The UCC28070 has an external pfc disable threshold. This feature has a threshold of 0.75 v (nom) and 0.8 v (max) measured on the VSENS pin.
    It is most likely that this feature is disabling the gate drive signals