40 W, Low-Parts-Count, Multi-Output, Galvanically Isolated DC/DC?

johny radio

Expert 1280 points

Other Parts Discussed in Thread: UCC2803

How to make a lowest-parts-count, small-footprint, 40 W, galvanically isolated, DC/DC converter?

Input: 12 V to 24 V

Output: 4 V to 9 V @ 10 W x 4

the outputs should be isolated from each other.

I'm assuming a device or topology that outputs 40 watts of non-isolated, unrectified power, and then a separate transformer+rectifier for each output.

over 3 years ago

0 Teng Feng over 3 years ago

TI__Genius 13660 points

Hi Johny,

I suggest flyback topology with UCC2803 controller.

and maybe a shut regulator or LDO is required for high output precision and load regulator.

Regards,

Teng

0 johny radio over 3 years ago in reply to Teng Feng

Expert 1280 points

Thanks, Teng!

It seems the UCC2803 requires more external parts than we'd like. What components are optional?

Could it be as simple as this?

(from datasheet)

Could the following be simplified for a 40W, positive-only step-down?

(from Design Note DN-56A, Single Switch Flyback Circuit Converts + 5 VDC to +/- 12 VDC for RS-232 and RS-422 Applications)

Best,

John

0 Teng Feng over 3 years ago in reply to johny radio

TI__Genius 13660 points

Hi John,

I think you want a PSR flyback, but I don't find a PSR flyback which UVLO on is low as 12V.

for the provided specs, i suggest flyback UCC2803 or pushpull UCC2808 with SSR.

you also can try to find the better controller in below two page by yourself.

https://webench.ti.com/power-designer/switching-regulator/select

https://www.ti.com/power-management/acdc-isolated-dcdc-switching-regulators/flyback-controllers/overview.html

Thanks,

Teng

0 johny radio over 3 years ago in reply to Teng Feng

Expert 1280 points

Teng Feng said:
pushpull UCC2808 with SSR.

How can i use SSR with multiple trafos?

Are my proposed simplifications possible?

0 Teng Feng over 3 years ago in reply to johny radio

TI__Genius 13660 points

Hi John,

for multiple outputs, one main rail is controlled by accurate secondary feedback, the voltage of other rails are determined by the turns ratio with main rail.

Yes, you can use primary side controlled flyback without opto-coupler, but below circuit is no isolated.

0 johny radio over 3 years ago in reply to Teng Feng

Expert 1280 points

Teng Feng said:
Yes, you can use primary side controlled flyback without opto-coupler, but below circuit is no isolated.

But your image looks like SSR, not PSR.

0 Teng Feng over 3 years ago in reply to johny radio

TI__Genius 13660 points

Yes, I was replying your question, this picture your provided is non-isolated.

If you don't want use optocoupler, PSR flyback is best, but I didn't find it.

Thanks.

Power management

Power management forum

40 W, Low-Parts-Count, Multi-Output, Galvanically Isolated DC/DC?