Power dissipation in RCDZ clamp

Posted by: Barfly on 10/23/2015

I'm working with PI Expert Online for a design using LNK6767E and EF25 to produce 13V @ 2.5A. Trying to understand how to lower power dissipation in RCDZ clamp. Showing RC=3K3 2W, CC=2.2nF, RDB=6.2 and TVS=120V; the dissipation is 2.98W.

Compared to RDR-313 design only requires 1/4W for RC resistor. Trying to use part values close to RDR-313 is disallowed. Leakage inductance of EF25 shows lower than that in this reference design, I would expect clamp to be less demanding for EF25 design.

Any insight or suggestions would be appreciated!!

Regards,

Josh

Comments

Hi Josh,

PIExpert gives a first pass design. Once you have the working design you still need to optimize the design.

Clamp size will increase with output power and leakage inductance.

Could you please attach your PIExpert design here so that I can review.

Regards,

PI-NANO

Thanks for your reply. Look forward to input on how to proceed with design optimization. Attached is most recent design export as pdf.

Regards,

Josh

Attachment	Size
13v 2.5A v1_sm.pdf (338.77 KB)	338.77 KB

Hi Josh,

Check your drain voltage and see how much margin you have, if you have higer margin than required then you can relax the snubber design so that you can reduce the losses in the snubber. Check the snubber temperature and see if you can use a lower power rated snubber.

If you want to optimize the transformer, I would suggest you to use the PIXls and try chaning number of turns, VOR, KP etc so that you find a suitable transformer design.

Regards,

PI-NANO