There is a cbb capacitor in the led bulb, and four diodes (should be a rectifier bridge), and a resistor (buck?)?

This is a simple power supply circuit, the diode turns AC into DC for led, cbb capacitor is used to limit the current, and a resistor above it is used to discharge, to ensure that the cbb capacitor is not charged after power failure, and the other capacitor is used to filter out the remaining AC components of the direct current after rectification.