UCC38C40: DCDC Flyback design without optocoupler feedback

Ronny Ståhle

Part Number: UCC38C40

Tool/software:

Hi,

I'm considering to use UCC38C40 in a DCDC flyback application where there is no need for isolation. The standard flyback circuit (when used in a off-line applicaiton) involves an opto-coupler for the feedback loop to fully isolate the output from the AC input voltage.

However, in my DCDC flyback application I dont need the isolation feature and therefore I would like to remove the whole opto-coupler circuit to save cost and board space.

Now, can I simply connect the output voltage directly to the FB pin via a resistive voltage dividerm or should the signal to the somehow FB still be biased from the VREF output of UCC38C40 ?

Ronny

29 days ago

0 Pratik Adibatla 29 days ago

TI__Expert 7473 points

Hi Ronny,

Thanks for reaching out with interesting question. Yes, you can use it without opto if isolation is not needed. You can just use the resistor divider circuitry provided the divider is scaled down version of output voltage and proper equivalent voltage is going through the divider which the opto was providing initially.

Best,

Pratik A.

0 Ronny Ståhle 26 days ago

Prodigy 40 points

Hi Pratik,

Thanks for feedback.

Ronny

+1 Pratik Adibatla 26 days ago in reply to Ronny Ståhle

TI__Expert 7473 points

Hi Ronny,

Please click on the green button if your issue is resolved.

Best,

Pratik A.

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UCC38C40: DCDC Flyback design without optocoupler feedback