LNK6775K problem/solution

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Hello everyone on the forum.
I have one problem, and it would be good if there was a solution to this.
I did a design where I use the LNK6775K and everything works fine in the 85Vac to 265Vac range.
Specifically, I have now received a request from a customer that they need to go down with an input voltage of up to 40Vac.
Is there a solution for the same chip, or do I have to change the whole design?
Thanks in advance, Aleksandar

Hi Aleksandar,

The output power and voltage was not specified. The minimum voltage required on the drain at start-up is 50V to charge the BP capacitor. You need to re-design the transformer (Lmag) and bias winding turns to deliver the required power at minimum input voltage. Please monitor thermals due to additional loss.

Hi and thanks for your reply.
I don't have any information about the transformer from the manufacturer.
It was specifically designed for this chip and this schematic.
With best regards, Aleksandar.

LN6775K.pdf996.65 KB


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