Abstract: A ballast circuit for a gas discharge lamp of the type including resistively heated cathodes includes a resonant load circuit incorporating a gas discharge lamp and including first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. Further included is a d.c.-to-a.c. converter circuit coupled to the resonant load circuit so as to induce an a.c. current in the resonant load circuit. The converter includes first and second switches serially connected between a bus conductor at a d.c. voltage and ground, and has a common node through which the a.c. load current flows. A feedback circuit provides a feedback signal indicating the level of current in the resonant load circuit.

Abstract: A ballast circuit for a gas discharge lamp includes a resonant load circuit incorporating a gas discharge lamp and including first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. Further included is a d.c.-to-a.c. converter circuit coupled to the resonant load circuit so as to induce an a.c. current in the resonant load circuit. The converter includes first and second switches serially connected between a bus conductor at a d.c. voltage and ground, and has a common node through which the a.c. load current flows. A feedback circuit provides a feedback signal indicating the level of current in the resonant load circuit.

Abstract: A ballast circuit for a gas discharge lamp comprises a resonant load circuit incorporating a gas discharge lamp and including first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. A d.c.-to-a.c. converter circuit is coupled to the resonant load circuit to induce an a.c. current in the resonant load circuit. It comprises first and second switches serially connected between a bus conductor at a d.c. voltage and ground, with a common node through which the bidirectional load current flows. An arrangement allows a user to select a setpoint signal during lamp operation that determines the amount of light output by the lamp. A feedback arrangement regeneratively controls the first and second switches; it includes a circuit for sensing a.c. current in the resonant load circuit and producing an a.c. feedback signal in proportion to the a.c. current; a circuit for producing a d.c.

Abstract: Disclosed is a ballast circuit for a gas discharge lamp, including a resonant load circuit with a gas discharge lamp and first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. The ballast circuit further includes a d.c.-to-a.c. converter circuit coupled to the resonant load circuit so as to induce an a.c. current in the resonant load circuit. The converter circuit comprises first and second switches serially connected between a bus conductor at a d.c. voltage and ground, and has a common node through which the bidirectional load current flows. A feedback arrangement regeneratively controls the first and second switches, and includes a circuit for sensing a.c. current in the resonant load circuit and producing a feedback signal in proportion to the a.c. current.

Abstract: Disclosed is a power-level selection circuit in combination with a lamp circuit including a fluorescent lamp having first and second cathodes with resistive-heating filaments each spaced at a respective end of a lamp tube; first and second power leads for respectively connecting the cathodes to an a.c. power source whose power can be selectively enabled and interrupted by a main power switch; and a ballast inductor in serial circuit with one of the power leads and including a plurality of filament-heating windings for supplying power to the cathodes. The power-level selection circuit is interposed between a first cathode and a filament-heating winding, and includes a power-receiving circuit coupled to the filament-heating winding to receive power therefrom. Further included is a filament-supply circuit for continuously supplying available power to the first cathode.

Abstract: A ballast circuit for a gas discharge lamp, of the type having a pair of resistively heated cathodes that are resistively heated both during a cathode pre-heat period prior to lamp turn-on, and during steady state lamp operation, is disclosed. The ballast circuit includes circuitry for providing, on a bus conductor, a d.c. bus voltage with respect to a ground, and a converter, responsive to the d.c. bus voltage, for supplying bidirectional current to a resonant load circuit. The resonant load circuit includes the gas discharge lamp, a resonant capacitor coupled between the lamp cathodes such that its voltage varies with lamp voltage, and a resonant inductor serially coupled to the resonant capacitor and cooperating therewith to set a magnitude, and resonant frequency, of the bidirectional lamp current. Circuitry is provided for powering the resistively heated lamp cathodes, to thereby heat the cathodes.

Abstract: An impedance matching circuit for a self-oscillating electrodeless fluorescent lamp ballast of the type having an inductor connected in series with the parallel combination of a capacitor and the lamp's drive coil includes an additional capacitor connected in series with the drive coil. The capacitance value chosen for the additional capacitor is dependent on: stresses on the parallel capacitor; matching the impedance of the ballast; and the impact of the capacitor on the loaded coil phase angle. The additional capacitor reduces the phase angle presented to the ballast, thereby lowering the sensitivity of the ballast to component and lamp variations. In addition, the overall impedance of the network is reduced, such that the required inductance of the series inductor is reduced; hence, the inductor can have fewer turns and lower conduction losses.

Abstract: A power supply circuit for powering a load with bi-directional current comprises means for supplying d.c. power from an a.c. voltage, a series half-bridge converter, and a boost converter. The series half-bridge converter alternately impresses a d.c. bus voltage from a bus conductor across a load circuit first with one polarity and then with the opposite polarity. The series half-bridge converter includes a first switch interposed between the bus conductor and a bridge-switch end of the load circuit; a second switch interposed between ground and the bridge-switch end of the load circuit; and a switching control circuit for alternately switching on the first and second switches. The boost converter comprises a boost capacitor connected between the bus conductor and ground and whose level of charge determines the bus voltage on the bus conductor; a boost inductor for storing energy from the means for supplying d.c.

Abstract: In accordance with the invention, there is provided a ballast circuit for a gas discharge lamp. The circuit comprises means for providing a d.c. bus voltage on a bus conductor with respect to ground. The circuit includes a resonant load circuit incorporating a gas discharge lamp and including first and second resonant impedances whose values determine the operating frequency of the resonant load circuit. Further included is a converter circuit coupled to the resonant load circuit so as to impress a bidirectional voltage thereacross and thereby induce a bidirectional current in the resonant load circuit. The converter comprises first and second switches serially connected between the bus conductor and ground, and having a common node coupled to a first end of the resonant load circuit and through which the bidirectional load current flows. A current-sensing winding senses at least a portion of the current flowing in the resonant load circuit.

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.

Abstract: A power supply circuit for a gas discharge lamp is disclosed. The power supply circuit includes a circuit for providing a d.c. bus voltage on a bus conductor, and a resonant lamp circuit. The resonant lamp circuit includes a gas discharge lamp, a first resonant impedance in series with the gas discharge lamp, and a second resonant impedance substantially in parallel with the gas discharge lamp. The resonant load circuit operates at a resonant frequency determined by the values of the first and second resonant impedances. Further included is a series half-bridge converter for impressing across the resonant load circuit a bidirectional voltage, and thereby inducing a bidirectional current in the resonant load circuit.

Abstract: An electronic ballast can be connected between either a DC power supply or an AC power supply and a gas discharge lamp, such as a metal halide lamp and control the electrical power supplied thereto. An inverter receives a DC power and generates a periodic waveform at a controlled frequency. A resonant circuit is connected to the inverter and tuned to resonate at a predetermined frequency and generate an output voltage. A coupling capacitor is connected between the resonant circuit and the discharge lamp and supplies the output voltage of the resonant circuit thereto. A controller sets the frequency of operation of the inverter near the resonant frequency of the resonant circuit. The controller is responsive to at least a predetermined set point control voltage and to the output voltage of the resonant circuit. The resonant circuit is tuned to increase the voltage from the inverter means to a level sufficient to cause the discharge lamp to enter a glow mode of operation.

Abstract: The present invention is directed to a control circuit for providing a substantially constant current to a high-pressure sodium lamp. The control circuit preferably comprises a circuit for providing a rectified voltage signal, and a ballast having first and second contacts to operatively connect the lamp therebetween. The ballast generates and controls a peak current through the lamp based on the value of a controlled voltage. The control circuit further comprises a current sensor to sense the amount of current through the lamp, and a buck-boost voltage control circuit to control the value of the controlled voltage in order to provide a substantially constant peak current through the lamp based on the amount of current sensed by the current sensor. By controlling the amount of voltage seen by the lamp, the buck-boost voltage control circuit controls the amount of current through the lamp, thereby providing constant color temperature regardless of the fluctuations in lamp impedance.

Abstract: Circuits, and methods of using same, are disclosed for pulse operating a sodium vapor lamp and, in response to gating pulses applied to a resonant ballast, the lamp ignites to develop a quasi-resonant bidirectional current waveform through the lamp, the shape of which is controlled to suppress the excitation of acoustic resonant nodes in the lamp. The quasi-resonant bidirectional current waveform oscillates at a prescribed frequency and contains a first group of harmonics, the harmonic content of which is outside any acoustic frequency region associated with the lamp, and further contains a second group of harmonics having a harmonic content which coincides with such acoustic frequency region. The current waveform is caused to decay substantially at the time of ignition of the lamp to quickly reduce the magnitude of the second group of harmonics to thereby suppress excitation of the acoustic frequency region and prevent arc instability in the lamp.

Abstract: A circuit and method for powering a high intensity discharge lamp, such as a high pressure sodium lamp (HPSL) are disclosed. Feedback control is used to achieve a nearly constant amplitude of lamp current so as to attain nearly constant lamp color in a HPSL, and further accommodates considerable variations in a.c. line voltage. The circuit, which shares some features with the method, includes a circuit to supply a d.c. bus voltage and first and second feedback-controlled circuits. The first feedback controlled circuit regulates the bus voltage in response to a first error signal which is derived as a function of peak lamp current and a set point signal for such peak current. The second feedback controlled circuit regulates lamp power in response to a second error signal which is derived as a function of average bus current and a set point proportional to the difference between regulated bus voltage and lamp power.

Abstract: A compact fluorescent lamp having an electronic ballast circuit arrangement which exhibits improved thermal management characteristics includes an input conditioning circuit which performs rectification and optionally, power factor correction of a standard power line current. The output of the conditioning circuit is coupled to a high frequency switching circuit which includes a pair of power MOSFET switching devices operated alternately between an on and an off condition in response to a control signal presented to the respective gate terminals thereof. The gate control signal is developed by sampling the load current and generating a speed-up pulse which, by being transformer coupled to the gate terminals, functions as the gate control signal.

Abstract: A method and a ballast circuit are disclosed for operating a metal halide lamp particularly suited for horizontal applications that provides signals capable of being varied so as to control the power applied to the metal halide lamp while still providing a uniform arc. The ballast circuit has a filter which passes a selected band of frequencies for the operating signals of the metal halide lamp.

Abstract: An improved tapped-inductor boost converter for operating a gas discharge lamp is disclosed. The converter includes a pair of input terminals connected to a power source supplying an input voltage, a pair of output terminals for providing an output voltage greater than or equal to the input voltage to the lamp, or other load, a tapped-inductor having first and second windings, an active switch for controlling current flow through the first winding for variably controlling the output voltage, a passive switch for controlling current flow through the second winding, and a first capacitor. The converter further includes an arrangement for varying the clamping voltage at the active switch in response to variations in the output voltage and also includes a clamping capacitor for transferring energy stored in the leakage inductance of the tapped-inductor to the load for improved efficiency.

Abstract: A ballast circuit for operating a metal halide lamp by applying DC excitation during its start, glow and run modes is disclosed. 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 that is easily adapted to present a high power factor to the AC power source 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: Circuits, and methods of using the same, are disclosed for controlling the power supplied to a discharge lamp of the type having a closed inductive loop, such as the resonant ballast circuit for a fluorescent lamp or the inductive ballast loop of a high pressure sodium lamp, wherein the closed inductive loop is operated by an electrical power supply having a d-c input stage and an output power controlled by the switching frequency of a switch means within the power supply itself whereby current flows to the closed inductive loop when the switch means is conductive and no current flows from the power supply to the closed loop when the switch means is non-conductive.