Quite a bugger, only 6 pins and half clearly known.
I'd say that get a new charger and leave this to rainy day modding project, if it's not already.
1 GND
2 GATE
3 SENSE
4 FB1
5 FB2
6 Vcc
FB seems to have at least CC, CV and zero crossing.
SENSE is not very straight forward.
Other version has through hole C1, it also have few underside traces.
Few guesses.
There underside C7 GND connects to C1, here the hole.
There Vcc and pin 3 goes to other side of the board, here 0R and C2 holes to R17 and R18 holes.
Maybe SENSE is also indicating an AC present.
TI should have all kind of oldies available, if the used chip is a copy it's probably from something older.
But all I found was one SOT23-6 secondary side PWM, UCC82742.
Maybe the chip is not in its primary use.