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UCC28722: Could you tell me about "How to design of UCC28722's external circuit"？

Pokkun
Genius 4695 points
Part Number: UCC28722

Hi, team.

My customers are considering UCC28722 for a smart meter.

I am considering referring to the following documents.

www.ti.com/.../TIDA-00628

www.ti.com/.../tidrh29.pdf

However, since customers do not want to use auxiliary windings, I would like to regulate the secondary side to 5 V without using auxiliary windings.

※Challenging the proposal by adding DC/DC to the 15V regulation circuit, but it is said that there is no cost merit.

＜Reason not want to use auxiliary winding wire＞

・Circuit cost is occupied by transformer, because there is price difference of more than twice with and without auxiliary winding.

・There was also a circumstance that was connected to a trouble trying to use a transformer of the auxiliary winding type before.

And, considering a circuit to return to VDD from the secondary side, the secondary side voltage must be higher than UVLO.

For this reason, we consider a discrete charge pump circuit using the switching operation of the following part and think whether it can return to the power supply of the primary side.

※I would like to sell TI's charge pump ICs originally, but I'm thinking of having a desire to reduce the cost to the limit and building it with a discrete configuration.


＜Question＞

Combine the charge pump circuit with discrete configuration and can return to the power supply of the primary side?

Best regards,

Pokkun

  • 0
    TI__Expert 7080 points
    Hi Pokkun,

    Thanks for the interest in TI here.

    The auxiliary winding have 6 functions for the UCC28722 , as show in below:

    1. Provide power supply of VDD.

    VS pin was connected to auxiliary winding through a resistor divider. VS pin's function：

    2. Regulate output voltage through sample feedback voltage at every switching cycle.
    3. Senses bulk capacitor voltage to provide for AC-input run and stop thresholds
    4. Compensate the current-sense threshold across the AC-input range.
    5. Utilizes valley switching to reduce switching losses.
    6. Output voltage protection.

    I guess the charge pump can only utilizes function 1 above mentioned ---Provide power supply of VDD
    * If I was wrong , please correct me .

    And I have a little doubt about " there is price difference of more than twice with and without auxiliary winding"

    Attached DS of UCC28722.
    Hope can help you .

    Thanks.