Das Szenario
An AC-mains LED bulb must survive line surges and maintain a stable LED current across normal mains variation.
Was diese Zeichnung zeigt
Die dahinterstehenden Entscheidungen verstehen.
01
TVS diode after the fuse clamps line transients before the rectifier
02
Bridge rectifier plus bulk capacitor creates the DC bus
03
Discrete NPN transistor with zener reference and emitter sense resistor forms the constant-current sink
Use for small offline LED bulbs or indicator lamps that need basic surge protection and current regulation without an integrated driver IC.