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UCC28810EVM-002: clarifications on schematic of EVM

domenyko
Genius 9655 points

Part Number: UCC28810EVM-002

Hi all,

I need some clarifications on the schematic of the UCC28810EVM-002.

My customer is using the board as a reference but wants to use 2x UCC28810 (1x for PFC, 1x for _Buck).

 

the customer has asked some questions regarding the schematic of the EVM that I cannot answer:

  1. Why the bias circuitry of the PFC showed in the calculator (based on BJT) is different from the one showed in the schematic (user guide)?

  2. Benefit of boost follower configuration if any.

  3. The VOSENS_BK net label does not refer to anything in the schematic (buck stage)

  4. Why is VINS monitoring the VDD_BK ?

  5. Is there a way to configure (through any formula) the value of Current sense and feedforward resistors in the buck stage ?

 regards,

Domenyco

  • 0
    TI__Mastermind 34465 points

    Hello Domenyco,

    I have not seen this EVM or calculator before but I did look at it and I will try to answer your questions.

    1. The UCC28810EVM-002 Design Calculator is a reference to the UCC28810EVM-002.
    There are two stages a boost follower pfc and a constant current buck stage. I can find no schematic difference between the calculator and the EVM schematic.

    2. With a variable boost output voltage, the pfc can be made more efficient at lower input voltages.  The switching losses are lower.

    3. VOSENS_BK is a node marked on the schematic for reference.

    4. VINS is one input to the multiplier. As the high voltage input to the power supply increases this signal is multiplied with the current error signal.
    So the on time of the MOSFET increases.

    5.  These values are calculated in the calculations page of the calculator tool

    Regards

    John Griffin

  • 0 in reply to John Griffin1
    TI__Genius 9655 points
    Hi John,
    thanks.
    Domenico