This part is a kind of semiconductor called AX3051.

Function of this product has Wide-Input Sensorless CC/CV Step-Down DC/DC Converter.

Manufacturers : AXElite

Image and pinout :

Some of the text within the PDF file :

AX3051/A 2.8A,Wide-Input Sensorless CC/CV Step-Down DC/DC Converter  GENERAL DESCRIPTION AX3051/A is a wide input voltage, high efficiency Active CC step-down DC/DC converter that operates in either CV (Constant Output Voltage) mode or CC (Constant Output Current) mode. AX3051/A consists of step-down switching regulator with PWM control. The device includes a reference voltage source, oscillation circuit, error amplifier and etc. AX3051/A provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to the duty ratio linearly forms 0 up to 90%. An over current protection and short circuit protection functions are built outside that it can set by a resistance. An external compensation is easily to system stable; the low ESR output c [ ... ]

AX3051 PDF Datasheet Download