Abstract: A ballast (100) includes an inverter (140,144,146) and a protection circuit that prevents excessive lamp-to-earth-ground fault current. The protection circuit includes a transformer (202,204,206,208,210) and an inverter disable circuit (300). The transformer measures a first current going out of one set of ballast output terminals (106,108) and a second current going into another set of ballast output terminals (206,208). In response to a substantial imbalance between the first current and the second current, inverter disable circuit (300) terminates inverter switching. Preferably, protection circuit further includes a restart timer circuit (400) that, following termination of inverter switching in response to a fault condition, prevents the inverter from restarting for a predetermined delay period.

Abstract: A dimming control system includes a first circuit (100) and a second circuit (400). First circuit (100) is coupled in series with the AC line source (10) and receives brighten and dim commands from a user. The brighten and dim commands are communicated to second circuit (400) by momentarily altering the AC voltage waveforms observed by second circuit (400). Second circuit (400) provides an adjustable output signal that is coupled to inverter circuitry within an electronic dimming ballast. The output signal is adjusted by the second circuit (400) in dependence on the observed AC voltage waveforms.

Abstract: A dimming control system includes a first circuit (100) and a second circuit (400). First circuit (100) is coupled in series with the AC line source (10) and receives brighten and dim commands from a user. The brighten and dim commands are communicated to second circuit (400) by momentarily altering the AC voltage waveforms observed by second circuit (400). Second circuit (400) provides an adjustable output signal that is coupled to inverter circuitry within an electronic dimming ballast. The output signal is adjusted by the second circuit (400) in dependence on the observed AC voltage waveforms.

Abstract: A ballast (100) includes an inverter (140,144,146) and a protection circuit that prevents excessive lamp-to-earth-ground fault current. The protection circuit includes a transformer (202,204,206,208,210) and an inverter disable circuit (300). The transformer measures a first current going out of one set of ballast output terminals (106,108) and a second current going into another set of ballast output terminals (206,208). In response to a substantial imbalance between the first current and the second current, inverter disable circuit (300) terminates inverter switching. Preferably, protection circuit further includes a restart timer circuit (400) that, following termination of inverter switching in response to a fault condition, prevents the inverter from restarting for a predetermined delay period.

Abstract: A ballast (10) for powering a gas discharge lamp load includes an inverter (200) and a protection circuit (400) for preventing start up of the inverter (200) in response to a ground fault condition wherein one or more of the ballast output connections (302,306) is coupled to earth ground.

Abstract: A dimming control system includes a first circuit (100) and a second circuit (200). First circuit (100) is coupled in series with the AC line source (10) and receives brighten and dim commands from a user. The brighten and dim commands are communicated to second circuit (200) by momentarily altering the AC voltage waveforms observed by second circuit (200). Second circuit (200) provides an adjustable dimming control voltage that is coupled to existing dimming control circuitry within an electronic dimming ballast. The dimming control voltage is adjusted by the second circuit (200) in dependence on the observed AC voltage waveforms.

Abstract: A ballast (10) for powering a gas discharge lamp load includes an inverter (200) and a protection circuit (400) for preventing startup of the inverter (200) in response to a ground fault condition wherein one or more of the ballast output connections (302,306) is coupled to earth ground.

Abstract: A dimming control system includes a first circuit (100) and a second circuit (200). First circuit (100) is coupled in series with the AC line source (10) and receives brighten and dim commands from a user. The brighten and dim commands are communicated to second circuit (200) by momentarily altering the AC voltage waveforms observed by second circuit (200). Second circuit (200) provides an adjustable dimming control voltage that is coupled to existing dimming control circuitry within an electronic dimming ballast. The dimming control voltage is adjusted by the second circuit (200) in dependence on the observed AC voltage waveforms.

Abstract: A dimming ballast apparatus comprises at least one power line dimming control input and at least one non-power-line dimming control input. In a preferred embodiment, the apparatus comprises a firing-angle-to-pulse-width-modulation converter responsive to the power line dimming control input, a voltage-to-pulse-width-modulation converter responsive to the non-power-line dimming control input, a low-pass filter responsive to the firing-angle-to-pulse-width-modulation converter and the voltage-to-pulse-width-modulation converter, and a dimming ballast circuit having a dim level command input responsive to the low-pass filter.

Abstract: An arrangement for protecting low-voltage control circuitry from externally applied high voltages comprises a voltage source (30) and a current-sourcing circuit (40). Current-sourcing circuit (40) provides current to an external controller (18) in a normal manner when an external source of high voltage is not applied to the output connections (42,44), protects itself (40) and the voltage source (30) from damage when an external source of high voltage is applied to the output connections (42,44), and provides current to the external controller (18) in a normal manner after the external source of high voltage is subsequently removed from the output connections (42,44). The arrangement may be employed as the dimming interface circuit (900) of an electronic dimming ballast (60) for gas discharge lamps to protect ballast circuitry from damage due to wiring errors during installation.

Abstract: An electronic ballast (10) comprising an AC-to-DC converter (100), an inverter (200), an output circuit (400), a high-voltage detection circuit (500), and a no-load detection suit (600). The inverter (200) includes an inverter control circuit (300) that monitors the lamp(s) via the high-voltage detection circuit (500) and the no-load detection circuit (600), and that terminates inverter switching in response to various lamp-fault conditions such as "diode-mode" behavior. Inverter control circuit (300) also provides for automatic ignition of a replaced lamp and may be economically implemented as a single integrated circuit.

Abstract: An electronic ballast (10) for powering at least one gas discharge lamp (20) comprising an AC-to-DC converter (100), an inverter (200), an output circuit (300), and an inverter protection circuit (400). Inverter protection circuit (400) includes a high voltage detection circuit (500), a no-load detection circuit (600), and a latch circuit (700), and is operable to turn off the inverter (200) in response to removal or failure of the gas discharge lamps. Inverter protection circuit (400) is well-suited for use in ballasts that power multiple, parallel-connected lamps and maintains operation of inverter (200) under a partially-loaded condition in which at least one operational lamp is present and each of the failed lamps has at least one open filament.

Abstract: An electronic ballast (10) for powering at least one gas discharge lamp (20) comprising an AC-to-DC converter (100), an inverter (200), an output circuit (300), a relamping circuit (400), and an inverter protection circuit (500). Protection circuit (500) shuts down the inverter (200) in response to lamp removal or lamp failure. Following replacement of a failed lamp with an operational lamp, relamping circuit (400) provides restarting of the inverter (200) and ignition of the operational lamp by momentarily disabling the inverter protection circuit (500).

Abstract: An electronic power supply circuit (12) having a rectifier circuit (18) adapted to receive a source of alternating current (10), a power factor correction driven boost converter (20), and a bulk capacitance (22). The boost converter (20) includes a boost transformer (24) having a primary winding (32) and a secondary winding (34), a boost switch (26), a boost diode (28), a zener diode (46), and a power factor correction control circuit (30) having a zero current detect input (58). The presence of the zener diode (46) effectively adds a fixed offset to the voltage provided to the zero current detect input (58), thereby allowing the boost converter (20) to operate under high input line voltage conditions. The zener diode (46) may be oriented in various ways, and may be incorporated into an integrated circuit containing other elements of the power factor correction control circuit (30). One particular embodiment of the power supply circuit (12) is for use in an electronic ballast (70) for fluorescent lamps.