This part is a kind of semiconductor called OB2216.

Function of this product has Primary-Side Regulation PWM Power Switch.

Manufacturers : On-Bright

Image and pinout :

Some of the text within the PDF file :

OB2216 Primary-Side Regulation PWM Power Switch GENERAL DESCRIPTION OB2216 is an offline PWM Power switch for low power AC/DC charger and adaptor applications. It operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below. In CC control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. Device operates in fixed frequency mode at large load conditions, frequency reduction mode at light/medium load and ‘Extended burst mode’ at No/light load conditions. OB2216 offers power on soft start [ ... ]

OB2216 PDF Datasheet Download