This part is a kind of semiconductor called AT3263.

Function of this product has Current Mode PWM Controller.

Manufacturers : ATC

Image and pinout :

Some of the text within the PDF file :

T E C H N O L O G Y AT3263 Current Mode PWM Controller Description AT3263 is highly integrated current mode PWM control IC optimized for high performance low standby power offline fly back converter applications. To meet the international power conservation requirements, optimized green mode is integrated to improve the efficiency at light or no load conditions with no audible noise. Slope compensation is integrated to ensure the stability at high load. Lead edge blanking is integrated to prevent the false trigger at the transition of the switch. Soft switching control at the gate drive can improve the EMI performance of the power supply. The Gate-drive output is clamped at 18V to protect the power MOS. AT3263 offers many protection functions with auto self-recovery feature, inc [ ... ]

AT3263 PDF Datasheet Download