Abstract: A ballast circuit for a gas discharge lamp comprises a resonant load circuit including the lamp. A d.c.-to-a.c. converter circuit induces 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 a reference conductor, and being connected together at a common node through which the a.c. load current flows. The first and second switches each comprise a reference node and a control node, the voltage between such nodes determining the conduction state of the associated switch. The respective reference nodes of the first and second switches are interconnected at the common node. The respective control nodes of the first and second switches are interconnected. An inductance is connected between the control nodes and the common node. A starting pulse-supplying capacitance is connected in series with the inductance, between the control nodes and the common node.

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 so as to induce an a.c. current in the resonant load circuit, and comprises first and second switches serially connected in the mentioned order between a bus conductor at a d.c. bus voltage and ground, and having a common switch node through which the a.c. current flows. A bridge capacitor has one end connected to ground. First and second feedback circuits regeneratively control the first and second switches, respectively, in response to a.c. current in the resonant load circuit.

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: A simulated load circuit for measuring the impedance of the arc discharge of an electrodeless discharge lamp of the type having an arc tube and an excitation coil for exciting the arc discharge in an ionizable fill contained therein includes: a secondary coil spaced apart from the excitation coil by a distance which is varied in order to vary the coupling coefficient between the secondary coil and the excitation coil; a fixed load resistance coupled to the secondary coil; and a variable matching network coupled in series or parallel with the load resistance, the impedance of the matching network being varied in order to vary the ratio of reactance to resistance of the load circuit. The distance between the secondary coil and the excitation coil is varied, and the impedance of the matching network is varied, until the input impedance of the load circuit is substantially equivalent to the operating impedance of the lamp.

Abstract: A base for an electrodeless arc discharge lamp having an elongated tubular stem extending through an outer envelope pinch or press seal includes a pair of electrically non-conductive members secured in mating relation to define an upper cavity and a lower axial bore. The lamp is mounted in the base with its pinch seal secured in the cavity and its stem extending into the bore. With the base mounted in a fixture, RF energy is coupled into the lamp to excite a starting aid in the stem via a conductive bushing in the bore.

Abstract: An auto-starting lamp system comprises an electrodeless high intensity discharge lamp of the type including an arc tube that contains an ionizable fill, an excitation coil surrounding the arc tube for exciting an arc discharge in the ionizable fill at least during steady state lamp operation, and a starter circuit for facilitating arc discharge of the ionizable fill. The system further comprises a controllable r.f. power source for powering the lamp excitation coil, and an electrical network for matching the impedance of the excitation coil to the impedance of the r.f. power source. The impedance-matching network has the same impedance-matching relation during both lamp start-up and steady state lamp operation. A system controller causes the r.f. power source, during lamp start-up, to ramp up in power to a peak level preferably substantially in excess of a steady state lamp operating power level, and then to decrease from the peak level.

Abstract: A simulated load circuit for measuring the impedance of the arc discharge of an electrodeless discharge lamp of the type having an arc tube and an excitation coil for exciting the arc discharge in an ionizable fill contained therein includes: a secondary coil spaced apart from the excitation coil by a distance which is varied in order to vary the coupling coefficient between the secondary coil and the excitation coil; a fixed load resistance coupled to the secondary coil; and a variable matching network coupled in series or parallel with the load resistance, the impedance of the matching network being varied in order to vary the ratio of reactance to resistance of the load circuit. The distance between the secondary coil and the excitation coil is varied, and the impedance of the matching network is varied, until the input impedance of the load circuit is substantially equivalent to the operating impedance of the lamp.

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.