Abstract:
A gas discharge lamp ballast with an indicator of operability of the ballast is disclosed. The ballast circuit comprises circuitry for providing a d.c. bus voltage on a bus conductor with respect to a ground, and a resonant load circuit. The resonant load circuit includes lamp terminals for connecting to a removable gas discharge lamp, a resonant inductor, and a resonant capacitor. The resonant inductor and resonant capacitor are selected to set a magnitude, and resonant frequency, of a bidirectional current in the lamp. Further included is a converter circuitry, including first and second serially connected switches coupled between the bus conductor and the ground, and providing to the resonant load circuit, at a node coupled between the first and second switches, a voltage that alternates between first and second voltage levels. Circuitry for generating first and second switch control signals for alternately switching into conduction the first and second switches, including circuitry responsive to a feedback signal representing a current in the resonant load circuit, are further included. The ballast circuit, moreover, includes overload detection circuitry for detecting if voltage applied to the lamp terminals exceeds an overload level; and circuitry for indicating, in response to such an overload condition being detected by the overload detection circuitry, probable operability of the ballast circuit.
Abstract:
A gas discharge lamp ballast (10) circuit comprises circuitry for providing a d.c. bus voltage (V B ) on a bus conductor (16) with respect to a ground, and a resonant load circuit (18). The resonant load circuit includes lamp terminals for connecting to a removable gas discharge lamp, a resonant inductor (L R ), and a resonant capacitor (C R ). The resonant inductor and resonant capacitor are selected to set a magnitude, and resonant frequency, of a bidirectional current in the lamp. Further included is a converter circuitry, including first (S 1 )and second (S 2 ) serially connected switches coupled between the bus conductor and the ground, and providing to the resonant load circuit, at a node (12) coupled between the first and second switches, a voltage that alternates between first and second voltage levels. Circuitry (24,26) for generating first and second switch control signals for alternately switching into conduction the first and second switches, including circuitry responsive to a feedback signal representing a current in the resonant load circuit, are further included. The ballast circuit includes, a starter circuit arrangement (48) coupled to the converter circuit arrangement to generate a pulse to start conduction of one of said first and second switches. The starter pulse circuit arrangement includes an electric switch coupled between the d.c. bus conductor and ground to switch into a conducting state whenever the bus conductor is initially brought to a rated bus voltage. The electrical switch is a latch-type switch that remains conducting until such time as the bus voltage falls substantially towards the potential of ground.
Abstract:
A gas discharge lamp ballast with an indicator of operability of the ballast is disclosed. The ballast circuit comprises circuitry for providing a d.c. bus voltage on a bus conductor with respect to a ground, and a resonant load circuit. The resonant load circuit includes lamp terminals for connecting to a removable gas discharge lamp, a resonant inductor, and a resonant capacitor. The resonant inductor and resonant capacitor are selected to set a magnitude, and resonant frequency, of a bidirectional current in the lamp. Further included is a converter circuitry, including first and second serially connected switches coupled between the bus conductor and the ground, and providing to the resonant load circuit, at a node coupled between the first and second switches, a voltage that alternates between first and second voltage levels. Circuitry for generating first and second switch control signals for alternately switching into conduction the first and second switches, including circuitry responsive to a feedback signal representing a current in the resonant load circuit, are further included. The ballast circuit, moreover, includes overload detection circuitry for detecting if voltage applied to the lamp terminals exceeds an overload level; and circuitry for indicating, in response to such an overload condition being detected by the overload detection circuitry, probable operability of the ballast circuit.
Abstract:
A discharge lamp having improved thermal management properties includes a housing base (12) in which the ballast circuit (26) utilized for driving the discharge lamp (20) at an appropriate operating frequency is located. The ballast circuit (26) is disposed on a circuit board (22) which is mounted in a vertical orientation within the housing base (12) relative to the discharge lamp (20) being mounted in an upright position. The space along either side of the circuit board (22) on which the components (28,32) of the ballast circuit (26) are mounted allows for the flow of thermal convection currents thereover. Additionally, the circuit board (22) extends into the lowermost portion of the housing base (12) to the point where the screw base (14) attaches and is disposed in thermal connection to the screw base (14) such that the screw base (14) acts as a heat sink for the components (28,32) disposed on the circuit board. Selective placement of the components (28,32) of the ballast circuit (26) is made such that the components capable of generating the most heat are located toward the bottom (22a) of the circuit board (22) in closer proximity to the screw base (14) than those components which generate less heat.
Abstract:
A ballast circuit (10) operates a metal halide lamp (12) by applying DC excitation during its start, glow and run modes. The type and values of the circuit components of the ballast circuit are selected to provide automatic, sequential and desired transfer functions as the impedance value of the metal halide lamp transitions from its value occurring during the start, glow and run modes of operation. The ballast circuit has an input stage (14) that is easily adapted to present a high power factor to the AC power source (20) supplying the metal halide lamp. Further, the ballast circuit generates a signal for more easily starting the lamp and having a relatively high DC level upon which are developed pulse signals.
Abstract:
A ballast circuit (10) operates a metal halide lamp (12) by applying DC excitation during its start, glow and run modes. The type and values of the circuit components of the ballast circuit are selected to provide automatic, sequential and desired transfer functions as the impedance value of the metal halide lamp transitions from its value occurring during the start, glow and run modes of operation. The ballast circuit has an input stage (14) that is easily adapted to present a high power factor to the AC power source (20) supplying the metal halide lamp. Further, the ballast circuit generates a signal for more easily starting the lamp and having a relatively high DC level upon which are developed pulse signals.