This part is a kind of semiconductor called AP3842C.

Function of this product has (AP3842C - AP3845C) Current Mode PWM Controller.

Manufacturers : Shanghai SIM-BCD Semiconductor

Image and pinout :

Some of the text within the PDF file :

CURRENT MODE PWM CONTROLLER General Description Features Data Sheet AP384XC The AP3842C/3C/4C/5C are high performance fixed frequency current-mode PWM controller series. These integrated circuits are optimized for off-line and DC-DC converter applications with minimum external components. They feature under-voltage lockout (UVLO) circuit with low start-up current, trimmed oscillator for precise duty cycle control, current sense comparator providing maximum current limiting and a totem pole output stage for increasing output current. In addition, these ICs also feature accurate protection against over-temperature, over-current and maximal output power. The AP3842C and AP3844C have UVLO thresholds of 16V(on) and 10V(off); The corresponding thresholds for AP3843C and AP3845C are 8.4 V(on) [ ... ]

AP3842C PDF Datasheet Download