Abstract: A ballast (100) for powering at least one gas discharge lamp (30) at two selectable light levels includes a sensing transformer (120) and a detector circuit (200). Detector circuit (200) provides an output voltage that is dependent on the states of two on-off switches (S1,S2) interposed between the ballast (100) and a conventional AC source (20). The output voltage of the detector circuit (200) is used to control the illumination level of the lamp (30).

Abstract: A ballast (100) for powering at least one gas discharge lamp (30) at two selectable light levels includes a sensing transformer (120) and a detector circuit (200). Detector circuit (200) provides an output voltage that is dependent on the states of two on-off switches (S1,S2) interposed between the ballast (100) and a conventional AC source (20). The output voltage of the detector circuit (200) is used to control the illumination level of the lamp (30).

Abstract: An electronic ballast (100) for powering at least one gas discharge lamp (30) at two light levels includes a full-wave rectifier circuit (120) and a detector circuit (200). Detector circuit (200) provides an output voltage that is dependent on the states of two on-off switches (S1,S2), but that is substantially unaffected by typical X capacitances that are present between the hot and neutral input connections of the ballast.

Abstract: A ballast (10) for powering at least one gas discharge lamp (20) having lamp filaments (22,24) comprises an inverter (200), an output circuit (300), a filament heating control circuit (400), and a dimming control circuit (500). Filament heating control circuit (400) is coupled to the dimming control circuit and at least one of the inverter and the output circuit. During operation, filament heating control circuit (400) controls the inverter and output circuit such that heating of the lamp filaments is provided during a preheat mode that occurs prior to ignition of the lamp, and during a dimming mode that optionally occurs after ignition of the lamp and that includes operating the lamp at a current level that is substantially less than a rated normal operating current of the lamp.

Abstract: An electronic ballast (100) for powering at least one gas discharge lamp (30) at two light levels includes a full-wave rectifier circuit (120) and a detector circuit (200). Detector circuit (200) provides an output voltage that is dependent on the states of two on-off switches (S1,S2), but that is substantially unaffected by typical X capacitances that are present between the hot and neutral input connections of the ballast.