LNK603 for flyback with opto coupler feedback?

Posted by: treez on 01/17/2014

Hello,

I wish to do a low power flyback with vin = 230VAC, -it is simply to provide a high side drive rail for the high side FET of a 320W two transistor forward converter.

I wish to use LNK603.

Its very low power as it just powers the high side gate driver IC, and the secondary-connected side of the digital isolator which feeds the gate drive signal from the controller to the high side.

For the flyback transformer I will just use a LPD6235 type coupled inductor....as follows..

http://www.coilcraft.com/pdfs/lpd6235.pdf

I wish to power the LNK603 directly via its drain pin (no auxiliary winding).

So is it possible to just use optocoupler feedback for this and regulate the FB pin of the LNK603 to 1.84V on the primary side?

The secondary rail (high side) will be a 12 V rail

Comments

Hi,

LNK603 is our primary side control IC. It means that it can eliminate the opto-cupler for power supply.

So you just need a bias winding on the transformer, and get the feedback from the bias winding. It is not necessary to use the opto-coupler for feedback.

Hope this is helpful

Thanks, but the optocoupler and off-the-shelf coupled inductor is cheaper than getting a custom wound transformer with a bias winding (3 windings total).........this is for a very low power smps, <1W, so we don't want the expense of a custom wound transformer

Hi,

Understand your point. In this case, the LinkSwitch-XT may be the better option for you. Please find the information in the following link:

http://www.powerint.com/en/products/linkswitch-family/linkswitch-xt

Thanks