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UCC28180: From Average current Mode to Peak current Mode Control

chee hua how
Prodigy 20 points
Part Number: UCC28180

 

UCC28180D is an average current mode controller which sensing boost inductor current (negative), existing design perform this by using low side current sense resistor.

May I know would that be alright if I feeding this current signal (ISENSE of UCC28180D) with a current from switching MOSFET (i.e. peak current mode control instead of average current mode control) as I am thinking of using a current sense transformer on switching MOSFET (using two current sense transformer is too costly for me)?

Thanks.

How

  • 0
    TI__Mastermind 31580 points
    Hi Chee

    There are two problems with this arrangement.

    1. the UCC28180 is designe to work with a negative current sense signal
    2. the current in the mosfet is only a portion of the current in the inductor and it is missing the current during the off time when the current is ramping down in the inductor.

    Why cannot you not use the standard circuit?

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Prodigy 20 points

    1. For the negative current sensing, current transformer can easily oriented to give negative current as well.

    Standard circuit,

    (a) extra losses on sensing resistor

    (b) by measurement I can found that due to the palcement at low side the sensed current come with signifiacnt spike during gate drive signal turn on and turn off. Current transformer can get rid of that by puting it at high side of the switch.

         

  • 0 in reply to chee hua how
    TI__Mastermind 31580 points
    Hi Chee,

    The UCC28180 CS voltage is designed around a maximum value 300mV to minimise the power dissipation in the CS resistor.

    The UCC28180 cannot be used with a CS transformer in series with the mosfet. The current in series with the mosfet does not represent the average current in the inductor and UCC28180 will not be able to control the PFC stage correctly.

    Regards

    Peter