This part is a kind of semiconductor called STR-A6251.

Function of this product has (STR-A6251/-A6252) Universal-Input/15 W 50 kHz Flyback Switching Regulators.

Manufacturers : Allegro MicroSystems

Image and pinout :

Some of the text within the PDF file :

g n i h tors c t i a Sw egul R STR-A6251 AND STR-A6252 Universal-Input/15 W 50 kHz Flyback Switching Regulators The STR-A6251 and STR-A6252 are 50 kHz PWM topology (with ±5% frequency jittering for minimum EMI) regulators specifically designed to satisfy the requirements for increased integration and reliability in flyback converters. They incorporate a primary control and drive circuit with avalanche-rated power MOSFETs. The STR-A6252 features higher allowable switching current and lower on-resistance. The STR-A6251 is also available for 67 kHz operation. Covering the power range from below 21 watts or 24 watts for a 230 VAC input, or to 15 or 20 watts for a universal (85 to 264 VAC) input, these devices can be used in a wide range of applications, from DVD players and VCR player/recor [ ... ]

STR-A6251 PDF Datasheet Download