The PL2303HX is a USB to UART TTL (Transistor-Transistor Logic) converter module that allows communication between a computer or other USB-equipped device and a UART device through a USB port.
The 2SK3515, 2SK-3515, K3515, 3515 is a 450V, 10A, 48W TO-220NIS Package MOSFET, The FUJI Electric manufacturer is a IC Chips with N CHANNEL SILICON POWER MOSFET for more details of 2SK3515 can be seen below.
The TPC8214H, TPC8214, TPC-8214, 8214 is a N-Channel MOSFET TOSHIBA Field Effect Transistor Silicon N-Channel MOS Type (Ultra-High-Speed U-MOS)-SOP-8P.
The TIP31C is a base island technology NPN power transistor in TO-220 plastic package with better performances than the industry standard TIP31C that make this device suitable for audio, power linear and switching applications. The PNP type is TIP32C.