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UC2846: UC2846

robin gangopadhya18
Mastermind 6326 points

Part Number: UC2846
Other Parts Discussed in Thread: UC1846, UC2843A, UC2843

Seems in a recent implementation of a 3 ph PFC with UCC2846 controller using Weinberg  converter topology, folks were seeing problem below 20% duty cycle. Any report on the duty  range ? I know it is 0 to 100% but have seen reports that showed dependence of UC1846 on  extreme temps &/or radiation. Maybe the industrial version may have that too?

appreciate any feedback on this.

thnx

robin

  • 0
    TI__Mastermind 31580 points
    Hi Robin,

    Sorry I am unaware of this three phase application and the duty cycle observation, do you have a link to the report?

    Thanks

    Peter
  • 0 in reply to Peter Meaney
    TI__Mastermind 31580 points
    Hi Robin,

    Since there has been no activity on this post for some time I am going to close it. If you have more questions please post a new thread.

    Regards

    Peter
  • 0 in reply to robin gangopadhya18
    Mastermind 6326 points

    Peter

    A possible intriguing observation :we were using UC2843A in a 270v/3kW Buck design.

    Pl see attached model.

     

    We had many tests to carry out.

    In between, something blew: and they ended up changing the chip- which happened to be UC2843 NOT A version.

    All hell broke lose.

    Most nuisance was that output was at approx. HALF THE OSCILLATOR FREQ!

    How is that possible?...unless A version higher discharge current allows higher duty cycle.

    Our input is 350V, output 270V. It is not a synchronous rectification circuit but has SiC diode.

     

    We are still looking for a valid reason & looking for the A version: we only have non A left in inventory.

    How come my account does not have sampling privileges any more do you know?

     

    Also: we see loop response to be very narrow BW while we expect it to be 10 kHz.

    Would appreciate any help in figuring out why.

    Is it possible to get a loop simulation file as it is mentioned in some app notes?

     

    Thnx

    RobinUCC2843buck270vstabilized_do_not_change2.TSC

  • 0 in reply to robin gangopadhya18
    TI__Mastermind 31580 points
    Hi Robin

    The document in the link describes the changes between the non-A and A version, www.ti.com/.../slua163.pdf

    There should be no reason why the change between the two controller should cause the power circuit to fail.

    Please check the oscillator frequency by power up the IC in circuit but with the gate drive to the mosfet disconnected and the gate of the mosfet tied to its source to prevent it from turning on.

    I am not aware of any reason why you can no longer requests TI samples.

    The expect loop BW appears to be very high at 10kHz, normally for a voltage loop the crossover frequency would be in the region of 1kHz or less.

    Can you give me the literature number for the apps note and I will see if I can find the loop simulation that it refers too.

    Regards

    Peter