Bias supply for HiperLCS

Hi,

A winding on the same transformer will have no output voltage unless the HiperLCS part becomes operational and starts switching.

The part will however not start switching unless it has a bias supply.

The bias supply therefore has to be available from an alternate source or at least until the HiperLCS starts up.

Regards

PI-Sarek

Yes but thats not a reason to not use a bias winding off the transformer.......all that is needed is to supply the controller IC from a linear regulator which can be diode OR'd out by the bias winding voltage when it comes up.

Yes you can put a winding using triple insulated wire on the secondary side of the LLC transformer. However the vast majority of HiperLCS applications require a PFC and it is better to put the winding on the PFC choke. And even so you will need a HV startup circuit. By the time you build such a circuit, you end up with a better overall solution building a very small LinkSwitch based bias supply.

I agree LNKswitch is a nice solution........but really i like to have the bias winding coming off the main transformer, since if the output goes short, the bias winding drops out......
...the problem with LLC converters with integrated transformers, is how on earth could we know how well coupled the bias winding is with the primary?

I think a bias winding cannot be used with an integrated transformer for LLC?

Re-read what I wrote regarding location of said bias winding on LLC transformer.

Well i believe you suggest putting the bias coil over the secondary coil.
But i wonder if it will be well coupled with the secondary in that place....because the secondary of an integrated transformer LLC is scrunched up into the chamber of the bobbin.....-that is not a good way for the bias coil to get good coupling with the secondary.........best coupling is obtained by having a non-chambered transformer, and having the bias coil span the full length of the bobbin window, as well as the secondary occupying the full length of the bobbin window.
I think there is an issue here of coupling of the bias winding.....and that woith an integrated transformer it might not be very good.
I am not criticising powerint, rather i am criticising the use of sectioned bobbins when bias winding supplies are wanted.