This part is a kind of semiconductor called AP3101.

Function of this product has GREEN MODE PWM CONTROLLER.

Manufacturers : BCD Semiconductor

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Some of the text within the PDF file :

Preliminary Datasheet GREEN MODE PWM CONTROLLER General Description The AP3101 is a green PWM controller operating in current mode. It is specially designed for off-line ACDC adapter and battery charger applications where the needs for low standby power and better protection function are increasing. The AP3101 features adjustable oscillator frequency in normal operation, which is done by an external resistor. It automatically switches to skip cycle mode when output power drops below a given level. The IC also features low start-up and operation current for its BiCMOS process. The AP3101 provides comprehensive protection features including leading edge blanking, synchronized slope compensation, over-current, over-temperature and short circuit protection. The AP3101 is available in 2 package [ ... ]

AP3101 PDF Datasheet Download