Suitable IC for 3.3V, 3A output

Andrius Baltrusaitis

Other Parts Discussed in Thread: TL431

Hello,

I would like to choose an isolated AC/DC flyback controller IC which would be best suitable to get 3.3V, and up to 3A output. It should be low cost (<0.5$)as it will be used in mass production.

First, I was looking at UCC28702, but is it suibale for 3.3V, 3A ? The WEBENCH doesn't allow to choose output voltages lower than 5V with UCC28702.... Why?

I will be grateful if you can answer my question.

over 10 years ago

0 Ali Mansoori over 10 years ago

Intellectual 385 points

Any flyback controller can be used for 3.3v output but there are two problem.

1-Efficiency will be lower than higher output voltages because of more VF/Vout. (0.5/3.3 is almost 15%)

2-when using tl431 and opto for feed back,the voltage is lower than what you need.(2.5+1.2+resistor drop>3.3)

so you have to use low voltage comprator(=more cost) or using auxiliary winding and a diode and capacitor for generating a higher voltage for FB circuit.

0 Andrius Baltrusaitis over 10 years ago in reply to Ali Mansoori

Prodigy 30 points

Thank you for the answer! What is "Vf " that you used in calculating efficiency? why it is equal 0.5 ?

0 Ali Mansoori over 10 years ago in reply to Andrius Baltrusaitis

Intellectual 385 points

VF is the forward drop voltage of the rectifier diode and for low voltage schottky diodes is around 0.5v.

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Suitable IC for 3.3V, 3A output