Abstract: A lamp dimming module includes a lamp receptacle in series with a triac across the AC line, and a power supply for a processing unit, the processing unit supplying firing signals for the triac to control the dimming. The module plugs into the AC line. The power supply is connected in series with the lamp receptacle and in parallel with the triac, and includes cascaded transistors coupled to the AC line for providing charging current to a capacitor. Drive current is provided at the base of one of the transistors through a current-limiting resistor to drive the transistors into saturation for passing maximum current to the capacitor when the triac is open-circuited. A Zener diode is connected to the transistor base and breaks down when the capacitor is fully charged to provide a gating current to an SCR which drains the base drive from the transistor, shutting it off.