This part is a kind of semiconductor called MDF12N50B.
Function of this product has N-Channel MOSFET.
Manufacturers : MagnaChip
Image and pinout :

Some of the text within the PDF file :
MDP12N50B / MDF12N50B N-channel MOSFET 500V MDP12N50B / MDF12N50B N-Channel MOSFET 500V, 11.5A, 0.65Ω General Description The MDP/F12N50B uses advanced Magnachip’s MOSFET Technology, which provides low on-state resistance, high switching performance and excellent quality. MDP/F12N50B is suitable device for SMPS, high Speed switching and general purpose applications. Features VDS = 500V ID = 11.5A RDS(ON) ≤ 0.65Ω @VGS = 10V @VGS = 10V Applications Power Supply PFC Ballast Absolute Maximum Ratings (Ta = 25oC) Drain-Source Voltage Gate-Source Voltage Characteristics Continuous Drain Current Pulsed Drain Current(1) Power Dissipation Repetitive Avalanche Energy(1) Peak Diode Recovery dv/dt(3) Single Pulse Avalanche Energy(4) Junction and Storage Temperature Range ※ Id limite [ ... ]
MDF12N50B PDF Datasheet Download
