This part is a kind of semiconductor called LD7537.

Function of this product has Green-Mode PWM Controller.

Manufacturers : Leadtrend

Image and pinout :

Some of the text within the PDF file :

LD7537 12/15/2011 Green-Mode PWM Controller with Frequency Swapping and Integrated Protections Rev. 01a General Description The LD7537 is built-in with several functions, protection and EMI-improved solution in a tiny package. It takes less components counts or circuit space, especially ideal for those total solutions of low cost. The implemented functions include low startup current, green-mode compensation. power-saving operation, leading-edge blanking of the current sensing and internal slope It also features more protections like OLP (Over Load Protection) and OVP (Over Voltage Protection) to prevent circuit damage occurred under abnormal conditions. Furthermore, the Frequency Swapping function is to reduce the noise level and thus helps the power circuit designers to easily deal wit [ ... ]

LD7537 PDF Datasheet Download