This part is a kind of semiconductor called SD4843.
Function of this product has (SD4840 - SD4844) Current Mode PWM Controller.
Manufacturers : Silan Microelectronics
Image and pinout :
Some of the text within the PDF file :
SD4840/4841/4842/4843/4844 CURRENT MODE PWM CONTROLLER WITH BUILT-IN HIGH VOLTAGE MOSFET DESCRIPTION SD4840/4841/4842/4843/4844 is a current mode PWM controller with low standby power and low start current for power switch. In standby mode, the circuit enters burst mode to reduce the standby power dissipation. The switch frequency is 67KHz with ±2.5 KHz jitter frequency for low EMI. The stress on transformer during power on is reduced by the builtin 15ms soft start circuit to avoid the saturation of transformer. SD4840/4841/4842/4843/4844 includes under voltage lock-out, over voltage protection, leading edge blanking, over current protection and the temperature protection. The circuit will restart automatically until the system is normal after the protection is active. FEATURES * Lower s [ ... ]