We call this the little switcher part that COULD, in a TO-220 package.
TOP224YN by Power Integrations.
AC/DC Converter 45W 85-265 VAC 75W100/115/230 VAC
It is a three-terminal off-line PWM switch.
Very low AC/DC losses.
Built-in auto-restart and current limiting.
Latching thermal shutdown for system level protection.
75W single voltage input(100/115/230Vac), or 45W(85 to 265Vac universal input).
Ya wanna know what is inside? Download the data sheet.