Abstract: Apparatus and method are provided for electronic ballasts control and dimming of gas discharge lamps such as fluorescent lamps. Conventional wiring is used, thereby permitting ready retrofit of existing installations. Circuits are provided in the electronic ballasts (typically in the lamp) and in a conventionally operated dimmer switch (typically installed on a wall). A user adjusts the dimmer switch in a conventional manner to achieve the desired level of dimming of the lamp. Such adjustments apply a corresponding control voltage in the dimmer switch circuit, causing a small notch to appear in the output voltage from the dimmer switch. The notch is demodulated by the circuitry in the ballast, and is used to control the brightness of the lamp or lamps.

Abstract: An improved switch-mode power supply having a direct current power source, a transformer, first and second switching transistors in series with the primary winding of the transformer, and drive means for generating signals to switch on the switching transistors. In the improved circuit, a connection is provided through a diode to complete a circuit through the first switching transistor and part of the primary winding on activation of the drive means, drawing energy from a junction between two reservoir capacitors in series. The current from this circuit generates a field in the core of the transformer which is sensed by an auxiliary winding and switches on the second switching transistor, allowing a circuit to be completed through both switching transistors and the entire primary winding of the transformer.