Abstract: A device for operating a low-pressure sodium vapor discharge lamp without a ballast. The electrode voltage drop near a main electrode of the sodium lamp is influenced by a change in the pre-heating current of that electrode and/or a change in the effective area of the electrode. The changed electrode voltage drop thus obtained provides a mechanism whereby any changes in the lamp current are opposed so as to produce ballast-free lamp operation.

Abstract: A ballast for a rapid start fluorescent lamp with heated filaments has a secondary winding supplying lamp current, tertiary windings for supplying heater current to the filaments, and solid state switching circuits in secondary circuits through the filaments. Each switching circuit, which may be integrated with the ballast circuit or connected to a filament within the lamp envelope, comprises two voltage divider resistors having a common junction coupled to the gate of a triac whose primary electrodes are connected in parallel with the voltage divider. The triac is in series with the filament and supplies heating current to the filaments prior to lamp starting. When the lamp starts and conducts rated operating current the voltage divider reduces the voltage at its junction and at the triac gate below triac breakdown level thereby substantially eliminating heater current.

Abstract: A fluorescent lamp installation for very high intensity illumination uses standard rapid start filament type lamps with standard ballast remote from the lamp pairs to reduce cooling requirements. The heavy wiring harnesses previously required of six leads between each ballast and a lamp pair are reduced to one with a common lead for all the lamp pairs.

Abstract: A ballast especially useful in forming symmetrical half cycles of lamp current during dim light level operation, and thus in overcomming a type of lamp flicker. The light level of the lamp is controlled by an intensity selector circuit which controls an auxiliary circuit that, in turn, controls the ballast circuit. The intensity selector circuit comprises an oscillator which produces timing pulses at a frequency controlled by a potentiometer. The oscillator operates a control switch in the auxiliary circuit and the control switch supplies gate current for a power switch. The power switch controls the ballast circuit which turns on the lamp during a portion of each current half cycle; the light level being determined by the length of the conduction portion of that half cycle. The ballast circuit comprises primary, secondary, and heating windings mounted on a common core. The primary winding is connected to ground through a resistor.