Abstract: A ballast (10) for powering one or two gas discharge lamps (30,40) includes an inverter (100), an output circuit (200), and a control circuit (500). During a period prior to startup of inverter (100), control circuit (500) monitors a signal within output circuit (200) in order to determine the presence of lamps with intact filaments that are present at the ballast output connections (202,204, . . . ,210,212). Preferably, control circuit (500) is realized by a programmable microcontroller which implements a dual timing scheme in order to accurately determine the number of lamps with both filaments intact. The resulting determination may be used for various purposes, such providing appropriate levels of filament heating and/or for setting thresholds for accurately detecting and protecting against various lamp fault conditions.

Abstract: A ballast (10) for powering one or more gas discharge lamps (30,40) includes an inverter (100), an output circuit (200), a filament heating control circuit (300), and a control circuit (500). During a lamp filament detection period prior to startup of inverter (100), control circuit (500) monitors a signal within output circuit (200) in order to determine the number of lamps with intact filaments that are present at the ballast output connections (202, 204, . . . , 210, 212). During a lamp type detection period following startup of inverter (100), control circuit (500) monitors a current within filament heating control circuit (300) in order to determine the type of lamp(s) present at ballast output connections (202, 204, . . . , 210, 212). The determinations as to the number of lamps and the type of lamps are utilized by control circuit (500) to provide an appropriate level of heating to the lamp filaments.

Abstract: A ballast (10) for powering one or two gas discharge lamps (30,40) includes an inverter (100), an output circuit (200), and a control circuit (500). During a period prior to startup of inverter (100), control circuit (500) monitors a signal within output circuit (200) in order to determine the presence of lamps with intact filaments that are present at the ballast output connections (202,204, . . . ,210,212). Preferably, control circuit (500) is realized by a programmable microcontroller which implements a dual timing scheme in order to accurately determine the number of lamps with both filaments intact. The resulting determination may be used for various purposes, such providing appropriate levels of filament heating and/or for setting thresholds for accurately detecting and protecting against various lamp fault conditions.

Abstract: A ballast (10) for powering one or more gas discharge lamps (30,40) includes an inverter (100), an output circuit (200), a filament heating control circuit (300), and a control circuit (500). During a lamp filament detection period prior to startup of inverter (100), control circuit (500) monitors a signal within output circuit (200) in order to determine the number of lamps with intact filaments that are present at the ballast output connections (202, 204, . . . , 210, 212). During a lamp type detection period following startup of inverter (100), control circuit (500) monitors a current within filament heating control circuit (300) in order to determine the type of lamp(s) present at ballast output connections (202, 204, . . . , 210, 212). The determinations as to the number of lamps and the type of lamps are utilized by control circuit (500) to provide an appropriate level of heating to the lamp filaments.

Abstract: A method (700) for protecting a ballast from an output ground-fault condition includes the steps of applying power to the ballast (step 710), providing a startup delay period for a DC-to-DC converter (step 730), monitoring a voltage across a DC blocking capacitor (step 740), preventing startup of the DC-to-DC converter in response to the voltage across the DC blocking capacitor being greater than a threshold value during the startup delay period (step 750), and allowing startup of the DC-to-DC converter in response to the voltage across the DC blocking capacitor being less than the threshold value throughout the startup delay period (step 760). Preferably, the steps of monitoring (step 740), preventing (step 750), and allowing (step 760) are implemented by a microcontroller, and the DC-to-DC converter is preferably implemented as either a Sepic converter or a buck converter.

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 (10) for powering at least one gas discharge lamp (40) includes an EMI filter (100), a full-wave rectifier (200), a DC-to-DC converter (300), an inverter (400), an output circuit (500), and a microcontroller (600). In response to an output ground-fault condition wherein at least one output terminal (502,504,506,508) of the ballast (20) is shorted to earth ground, the microcontroller (600) directs the DC-to-DC converter (300) to remain in a non-operating mode wherein the output voltage of the DC-to-DC converter (600) is substantially zero, thereby protecting the inverter (400) from damage. Preferably, the microcontroller (600) monitors a voltage across a DC blocking capacitor (530) within the output circuit (500) prior to startup of the DC-to-DC converter (300) in order to determine if an output ground-fault condition is present.

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: 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 (40) includes an EMI filter (100), a full-wave rectifier (200), a DC-to-DC converter (300), an inverter (400), an output circuit (500), and a microcontroller (600). In response to an output ground-fault condition wherein at least one output terminal (502,504,506,508) of the ballast (20) is shorted to earth ground, the microcontroller (600) directs the DC-to-DC converter (300) to remain in a non-operating mode wherein the output voltage of the DC-to-DC converter (600) is substantially zero, thereby protecting the inverter (400) from damage. Preferably, the microcontroller (600) monitors a voltage across a DC blocking capacitor (530) within the output circuit (500) prior to startup of the DC-to-DC converter (300) in order to determine if an output ground-fault condition is present.

Abstract: A method (700) for protecting a ballast from an output ground-fault condition includes the steps of applying power to the ballast (step 710), providing a startup delay period for a DC-to-DC converter (step 730), monitoring a voltage across a DC blocking capacitor (step 740), preventing startup of the DC-to-DC converter in response to the voltage across the DC blocking capacitor being greater than a threshold value during the startup delay period (step 750), and allowing startup of the DC-to-DC converter in response to the voltage across the DC blocking capacitor being less than the threshold value throughout the startup delay period (step 760). Preferably, the steps of monitoring (step 740), preventing (step 750), and allowing (step 760) are implemented by a microcontroller, and the DC-to-DC converter is preferably implemented as either a Sepic converter or a buck converter.