Buck Converter with isolated o/p

Could anyone help me in recognising this chip?
Its a SOT 23-6 and marked GB29


on the left of the image you can see the current sense resistors and on the right side the fet driver resistor and gate discharge diode
This is a mains input device with 310 v of dc sitting on the drain of the fet which is on the other side of the board

I have looked on most of the manufacturers web sites but cant see anything it matches in terms of pin positions.
I can post the rest of the circuit I have managed to trace.
Note the current sense resistors have cooked for some reason.
This drives a COB led 10W floodlight with what looks about 24V forward voltage on the secondary of the transformer with just a diode and cap on the o/p. Current wise this is a 330mA or thereabouts COB.
The circuit is really a feed forward buck isolator converter.


This has died after 18months which is a shame if its junk....but it might be:sad:


Thank you anyone who might know:-D

Since you already recognize most of the circuit's operation, then you might also be able to construct a substitute circuit which does the same job as the fried components.
It is possible to make a buck converter from two transistors, selected to tolerate house voltage. Control is by current regulation.

Thank you for your reply but I doubt two transistors would be emc compliant or even power factor compliant let alone isolated.
I can quite easily design another circuit using an alternative chip, etching a new board etc but finding out what chip it is and exploring its design criteria is more fun!
That's why I hoped someone would say " oh the good old gb29" that's a tabernacle made by doofanacle….well you get the idea.

Thanks for your reply though.

kr Cathoderay