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Original question:

UC2845A: UC2845A Question about ON / OFF function by using the COMP terminal.

WEBENCH® Tools/UC1845: UC1845

Vikrant Sharma77
Prodigy 20 points
Part Number: UC1845
Other Parts Discussed in Thread: LM431, TIDA-070002, UC1845

Tool/software: WEBENCH® Design Tools

Hello,

 I need to design an isolated, variable output power supply. Input voltage is 15 to 53VDC

The output voltage is 2V to 50V, the output current is up to 12A. (Maximum output wattage should be 50 W, my requirement is 5V/8A or 28V/2A) for this, I want a variable power supply so I can select my output voltage accordingly 

PWM IC is http://www.ti.com/sitesearch/docs/universalsearch.tsp?searchTerm=UC1845#q=UC1845&t=everything&linkId=1 

I am confused with the transformer selection with this design (Schematic attached)

Can you please help me with the selection of transformer for this design (Please provide me the part number)

and also let me know whether I choose the right PWM IC for this design or not?

Thank you very much

  • 0
    TI__Mastermind 28915 points

    Hey Vikrant,

    The IC you choose should work for the topology.

    I do notice in the schematic that you use LM431 which has a reference voltage of 2.5, thus you would be unable to make a 2 V output.

    I mostly deal with custom transformers for designs and if you want transformer selection you will have to contact a transformer manufacturer or distributor.

    I can help in the selection process as TIDA-070002 goes through transformer selection for a similar part.

    You will have to make sure the transformer works for all input/output conditions along with the maximum duty cycle of the UC1845 of 50%.

    Thanks,

    Daniel

  • 0 in reply to Daniel Hartung
    Prodigy 20 points
    Thank you for your quick response

    Can I use any standard transformer for design 5V/8A and 28V output
  • 0 in reply to Vikrant Sharma77
    TI__Mastermind 28915 points
    Hey Vikrant,

    Whether you can find a standard transformer will be up to what you pick for your design.
    I don't know what the standard transformers are and you are going to have to talk to a transformer manufacturer/distributor for that.

    Thanks,
    Daniel