I could find nothing matching those markings and numbers.
But it looks very close to On-Bright
OB2262 same pinout. Original might be made by them as a guess "OB2259" which it could be? But no data. Sometimes they make crap IC's and erase them from the Internet lol.
Normally I would expect something else to have died in the charger, like the capacitors or mosfet etc.
Another sub is
SG6848TZ in SOT23-6, or Chip Rail CR6848S. Both are 70kHz as well.
This website is maybe OK to ID SMPS IC's, it does need an update though.
https://remont-aud.net/ic_power/