Schematic diagram of a 12w 220V LED light bulb made by Star Light:
The heart of the circuit is a PT4554D high precision non-isolated step-down LED constant current IC. The IC has an integrated 500V power MOS and requires only a few peripheral components, which greatly saves system cost and size. It also offers comprehensive protection features such as LED short-circuit protection, over temperature drop current protection, etc.
The only active discrete components are the rectifier bridge and a diode. There are two high voltage electrolytic capacitors, one non-polarized capacitor on the AC line side, two inductors, one fusible resistor and a few surface mount resistors.
On a separate PCB connected through a connector you'll find 16 (double) LEDs connected in series, generating a bright, warm (3000K) light.