Abstract: In a drive circuit for driving an electroluminescent device having an electroluminescent lamp, a battery, and a frequency divider circuit for generating a plurality of signals, including a first signal, the improved voltage-boosting circuit comprising first and second inductors electrically connected to the battery; a digital logic gate electrically connected to the frequency divider circuit; a first transitive switch electrically connected to the frequency divider circuit for receiving the first signal, and electrically connected to the first inductor for providing the first signal to the first inductor; and, a second transitive switch electrically connected to receive an output signal from the digital logic gate and electrically connected to the second inductor for providing the output signal to the second inductor, wherein the first and second inductors are caused to alternately provide high voltage pulses for driving the electroluminescent lamp.

Abstract: An efficient ballast for Mini-fluorescent lamps, includes an inductor, in communication with a power source and constructed as transformer with only primary winding, a fluorescent lamp in series with the inductor, and a capacitor in series with the fluorescent lamp, and optionally may include a resistor in parallel with the coil, and a switch interposed between the capacitor and power source. The value of the capacitance may change based upon the degree of change in the supply voltage.

Abstract: An inductive load driver is constructed with a driving means (205), responsive to a control input (211). The driving means (205) provides energy to an inductive load (203) and then prevents the providing of energy to the inductive load (203). The inductive load (203) reflects the previously provided energy to the driving means (205) when the driving means (205) is preventing the providing of energy. A control means adjusts the energy to the inductive load (203) responsive to the reflected energy provided by the inductive load (203).

Abstract: A starting circuit is used in combination with a high intensity discharge lamp having electrodes. An inductor is in series with the electrodes of the lamp, and a first switching transistor is arranged in series with a diode and a load resistor. The first switching transistor, diode, and resistor are arranged in shunt with the electrodes of the lamp and in series with the inductor for charging the inductor when the first switching transistor is switched ON. The energy stored in the inductor is discharged as a voltage pulse across the lamp when the first switching transistor is switched OFF. A first bias circuit turns the first switching transistor ON at a first voltage level from an AC power source. A second switching transistor turns the first transistor OFF at a second voltage level. A second bias circuit turns the second switching transistor ON at the second voltage.

Abstract: An inverter for powering an electroluminescent lamp has a direct current supply terminal, a ground terminal, and a single output terminal. A high frequency pumping circuit stores electrical energy in an inductor having a first terminal and a second terminal. A switching circuit alternately connects the first and second terminals of the inductor to the output terminal at a low frequency. The output from the inverter is a high voltage, low frequency, alternating current.

Abstract: An arc stabilization arrangement for a discharge lamp having a light transmissive arc tube containing a fill of gas excitable to a discharge state upon introduction thereto of a drive signal having a predetermined frequency associated therewith, includes a modulating arrangement effective for providing a modulating signal which is imposed onto the drive signal. The modulating signal has a frequency associated therewith which approximates the acoustic resonance of the gases within the fill, such modulating signal frequency being less than the frequency of the drive signal. In one embodiment of the invention the modulating arrangement is an amplitude modulating scheme effective such that a modulating amplitude of greater than about 5% of the amplitude of the drive signal is achieved. In yet a further implementation of the present invention, the frequency of the modulating signal is swept about a range of frequencies so that a varying acoustic resonance frequency can be encompassed by the modulating signal.

Abstract: An improved arc discharge ballast is disclosed which comprises harmonic resonators, simple switching means and a drive circuit. The harmonic resonators, switching means and drive circuit are coupled to the lamp to provide squaring of the current waveform and provide even light output. By adding odd harmonic current elements to a lamp driven by a conventional ballast, advantages of even light output or power saving is obtained.

Abstract: A lamp assembly (10) for use with equipment such as construction vehicles and heavy trucks that are subjected to prolonged, intense vibrations. The lamp assembly of this invention includes a socket (14) formed by a shell (42). A sealed enclosure, in the form of a lamp housing (12), is releasably secured in the shell. The light source, such as a gas-discharge tube (16) or a set of LEDs (72) is located inside the lamp housing. A transformer primary winding (20), which is attached to a power source (56), is attached to the outside of the shell. A transformer secondary winding (22) connected across the light source is located inside the lamp housing. The secondary winding is located so that the lamp housing is seated in the socket, adjacent the primary winding. When a voltage is applied across the primary winding, an inductive voltage develops across the secondary winding.

Abstract: A starting circuit for a discharge lamp includes a tapped ballast transformer connected at one end to an AC supply and at the other end to a discharge lamp. A capacitor and charging resistor are connected in series across the lamp. A breakdown switch device and a current-limiting resistor are connected in series with each other between the transformer tap and the junction between the capacitor and charging resistor. When the capacitor charges to the breakdown value, it discharges through the breakdown device, current-limiting resistor and transformer, producing an output pulse to start the lamp. The value of the current-limiting resistor is selected to limit and shape the peak of the output pulse.

Abstract: A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Abstract: An apparatus for operating discharge lamp. The apparatus includes a source of electrical power, switching devices for switching the electrical power, a control circuit for controlling the switching devices, a transformer having a primary winding for receiving the electrical power switched by the switching devices and a secondary winding for supplying power to the lighting apparatus, a resonant circuit including an inductor and a capacitor for regulating the frequency of the electrical power and a circuit for powering the control circuit, the powering circuit including a secondary winding on the inductor and an additional winding on the transformer connected in a differential manner.

Abstract: A power supply circuit for a magnetron adapted to supply microwave energy to an electrodeless discharge bulb is disclosed. The circuit includes a rectifier coupled across a commerical AC voltage source, a filter for smoothing the output of the rectifier, an inverter for converting the DC voltage supplied from the filter into a high frequency AC voltage, a step-up transformer for stepping up the high frequency AC voltage outputted from the inverter, and a rectifier which rectifies the high voltage AC output of the transformer into a unidirectional voltage which is supplied to the magnetron. The inverter switching is controlled by a pulse width modulation control circuit to maintain the magnetron output power at a predetermined level.

Abstract: A driver for a electroluminous lamp includes a bridge switching circuit comprising four MOSFETS, the lamp and a series connected inductance being connected as the load on the bridge circuit. The switching of the transistors of the bridge circuit is controlled by logic circuitry which generates a two-phase, non-overlapping gating control signal which causes the MOSFETS to be switched in pairs whereby current will flow in alternate directions through the lamp.

Abstract: In an inverter-type fluorescent lamp ballast adapted to be powered from a DC supply voltage consisting of a substantially non-filtered full-wave-rectified 60 Hz power line voltage, the inverter's output is a 120 Hz magnitude-modulated squarewave voltage of frequency controllable about 30 kHz. The magnitude-modulated squarewave voltage is applied across a series-connected high-Q L-C circuit. The fluorescent lamp is connected in parallel with the tank capacitor of this L-C circuit. The magnitude of the current drawn by the fluorescent lamp is a sensitive function of the frequency of the squarewave voltage and is controlled by correspondingly controlling the frequency of this squarewave voltage.

Abstract: A power supply circuit for a magnetron adapted to supply microwave energy to an electrodeless discharge bulb is disclosed. The circuit includes a rectifier coupled across a commercial AC voltage source, a filter for smoothing the output of the rectifier, an inverter for converting the DC voltage supplied from the filter into a high frequency AC voltage, a step-up transformer for stepping up the high frequency AC voltage outputted from the inverter, and a rectifier which rectifies the high voltage AC output of the transformer into a unidirectional voltage which is supplied to the magnetron. The inverter switching is controlled by a pulse width modulation control circuit to maintain the magnetron output power at a predetermined level.

Abstract: In accordance with the present invention, a control device for energizing a lamp circuit including gaseous discharge lamps includes a power source having a variable amplitude varying in time. A control circuit is provided for producing a variable pulse width control signal. A switch is responsive to the variable pulse width control signal for providing a switched output from the power source. The switched output has a pulse width proportional to the variable pulse width control signal for supplying power to the lamp circuit. An inductor is interconnected between the switch and the lamp circuit. The inductor includes a first winding with a center tap for receiving the switched output from the switch for balancing the voltage and current applied to the lamps within the lamp circuit. The inductor further includes a second winding connected to the lamp circuit for providing constant lamp brightness regardless of amplitude variations in the source voltage.

Abstract: An inverter-type electronic fluorescent lamp ballast powers a fluorescent lamp with a sinusoidal current that is modified by insertion of a measured amount of properly phased third harmonic current, thereby attaining a lamp current crest factor that is substantially better than the 1.4 crest factor associated with a purely sinusoidally-shaped current.

Abstract: In a power-line-operated electronic ballast for a gas discharge lamp, an inverter converts a DC supply voltage to a high frequency current-limited operating voltage for a fluorescent lamp. The DC voltage is obtained, at least in part, by forward inductive-discharge conversion of full-wave-rectified unfiltered power line voltage; which forward conversion is accomplished by high frequency switching of an energy-storing inductor; the switching being done by the very same inverter that provides the high frequency lamp operating voltage. As an overall result, power is drawn from the power line with a power factor higher than 98% and with a total harmonic distortion under 10%.

Abstract: An inverter is made up of a parallel circuit as a voltage resonance circuit, and a first diode, which are connected in series between both ends of a power source. The parallel resonance circuit includes the primary winding of an output transformer of the leakage type, and a resonance capacitor. The first diode is connected at the cathode to the primary winding of the output transformer. The secondary winding of the output transformer is coupled with a load such as a discharge lamp. The cathode and anode of the first diode are respectively connected to the collector and emitter of a transistor. A series circuit of a second diode and capacitor is connected across the collector-emitter path of the transistor. The second diode is forwardly arranged with respect to the transistor. A voltage detector comprises the capacitor and two resistors which are connected in series, and connected across the capacitor. The output voltage is derived from the node of those resistors.

Abstract: A power supply circuit for a magnetron adapted to supply microwave energy to an electrodeless discharge bulb is disclosed. The circuit comprises a rectifier coupled across a commercial AC voltage source, a filter for smoothing the output of the rectifier, an inverter for converting the DC voltage supplied from the filter into a high frequency AC voltage, a step-up transformer for stepping up the high frequency AC voltage outputted from the inverter, and a rectifier which rectifies the high voltage AC output of the transformer into a unidirectional voltage which is supplied to the magnetron. The inverter switching is controlled by a pulse width modulation control circuit to maintain the magnetron output power at a predetermined level.

Abstract: In a power-line-operated electronic ballast, an inverter converts a DC voltage to a high frequency current-limited operating voltage for a fluorescent lamp. The DC voltage is obtained, at least in part, by forward conversion of full-wave-rectified unfiltered power line voltage; which forward conversion is accomplished by high frequency switching of an energy-storing inductor, the switching being done by the very same inverter that provides the high frequency lamp operating voltage. As an overall result, power is drawn from the power line with a power factor higher than 98% and with a total harmonic distortion well under 20%.

Abstract: An oscillator circuit for supplying a gas discharge path. A self-oscillating oscillator is controlled by pulses whose width, amplitude, and/or frequency are regulated as necessary to stabilize the oscillator output power, energy, and/or voltage.

Abstract: This ballast system for a gaseous discharge lamp comprises a reactor coil and core structure forming a magnetic circuit for flux developed by power-frequency current through the coil during lamp operation. The core comprises a leg surrounded by the reactor coil, two yokes at opposite ends of the leg, and flux-return structure connected between the two yokes radially outside the coil. For developing a high-voltage, high-frequency pulse for initiating lamp operation, there is provided an ignitor coil surrounding the flux-return structure and the reactor coil and inductively coupled to the reactor coil with respect to high-frequency pulse components.

Abstract: The invention is directed to a transformer having notch gaps extending partially across the flux path of the transformer core and having a total gap volume which stores sufficient magnetic energy to substantially eliminate inductive voltage spikes in a clipped sinusoidal waveform applied to the primary of the transformer. As used in a low voltage lighting system in which the intensity of a filament lamp is regulated by a dimmer control which selectively clips the voltage applied to the transformer primary winding by an ac source, the invention substantially eliminates filament ringing.

Abstract: A circuit arrangement for A.C. operation of gas discharge lamps comprises a full-wave rectifier (1) connected to an alternating voltage source. The direct voltage is supplied to a combinatorial circuit part (3 to 8) in the form of a direct voltage converter, to which is connected a bridge circuit (9) which comprises four thyristors. The transverse branch of the bridge circuit includes the lamp (5). The full-wave rectifier (1) is followed by a smoothing capacitor (2) and an electronic switching element (14) is connected parallel to the bridge circuit (9). The switching element is switched to the conducting state in the vicinity of the zero passages of the input alternating voltage. As a result shortcircuits in the bridge circuit are avoided.

Abstract: A DC-AC converter for igniting and supplying a low-pressure discharge lamp, e.g. an electrodeless low-pressure gas discharge lamp. The converter has two input terminals (9, 10) for connection to a d.c. voltage source. The input terminals are connected to a series arrangement controlled semiconductor switching element (12), a first coil (14) and a parallel circuit having the discharge lamp 15 in one of its branches. The control electrode and a main electrode of the controlled semiconductor switching element are connected together by means of a secondary winding (21) of a transformer (17) having a primary winding (16) that forms a part of the parallel circuit. The converter includes a starter circuit comprising a resistor (28) connected between a main electrode and the control electrode of the semiconductor switching element and a capacitor (29) coupled between the control electrode and one end of the secondary winding (21) of the transformer.

Abstract: A circuit supplied with direct voltage serves for generation of voltages and/or currents of differing curve shape and differing frequency and/or differing polarity. A load L with ohmic, inductive, capacitive or complex resistance behavior is switched in series with a choke D. Furthermore, at least two controlled semiconductor switches T.sub.1 and T.sub.2 are provided, which are each, respectively in series, as far as the load L and the choke D are connected, but which, however, lie in current paths 1 and 2 which are connected at different potentials of the supply voltage. In operational use, the one switch T.sub.2 is held open while the other switch T.sub.1 is opened and closed in alternating sequence, and after termination of an adjustable and controllable time period, the switch T.sub.1, which has been hitherto operated in alternating sequence, is now kept open, while the switch T.sub.

Abstract: A direct-current power supply circuit for gas discharge lamps includes a rectifier-capacitor bridge having a pair of input terminals and a pair of output terminals. A series input inductor is connected to one of the input terminals of the rectifier-capacitor bridge, and a pair of feedback diodes is connected to the output terminals of the rectifier bridge to provide a feedback signal to the series input inductor to control ripple of d-c output from said bridge and power factor of the a-c input to said bridge.

Abstract: A circuit containing a ballast for one or more fluorescent lamps. The circuit includes a first inductor in series with a voltage input terminal and a first capacitor to form a series resonant circuit to provide a starting voltage to the lamps. A second, shunt inductors coupled between the first inductor and the capacitor and another input terminal of the circuit to eliminate the high Q of the series resonant circuit and prevent the first inductor from saturating. The inductors are mounted on the legs of an H-shaped core to provide inductive coupling between the inductors and allow a maximum winding area for the first inductor to reduce the series resistance of the lamp current path. The core also allows the shunt inductor to adjust power line power factor independently of lamp power factor. Improvements in system efficiency of up to 15% can be achieved over conventional core/coil type ballasts.

Abstract: An object recognition system for detecting visible light of a predetermined wavelength emitted by a fluorescent material illuminated with modulated ultraviolet light produced by a self-modulated high pressure mercury vapor lamp. The lamp forms part of a resonant LC circuit which produces oscillations in the lamp intensity at a frequency higher than line frequency. The resulting visible light is detected, demodulated, and compared with a predetermined threshold to sense when the fluorescent material is present. Self-modulation of the UV lamp source eliminates external triggering, excitation or switching of the lamp power supply.

Abstract: A ballast and control circuit for use with fluorescent lights. The circuit aids energy efficiency by removing heater current flow once the lamp has ignited. The circuit also uses time delayed inductive storage to allow delivery to the lamps of increased operating current without a concurrent increase in power utilization.

Abstract: A magnetic ballast circuit for a fluorescent lamp providing improved power factor, reduced harmonic content and increased efficiency. A ballast circuit with three inductances connected at a junction, preferably with the first and second inductances comprising a tapped autotransformer, with the third inductance connected between a line terminal and the tap, with the first inductance connected in series with a capacitance to the other line terminal, and with the second inductance connected to the load. The first inductance may be provided totally as part of the autotransformer, or may be supplemented with a second inductance in series. In an alternative embodiment, separate inductances may be utilized. Alternative lamp filament power sources and alternative functionally equivalent core and winding configurations are disclosed.

Abstract: A lamp circuit having a push pull oscillator including an inductance in the D.C. supply, non-resonant coupling circuit to the lamp and cycle-by-cycle frequency control of the oscillator regulated by a lamp current sensor.

Abstract: A current fed high frequency oscillator-inverter ballast circuit includes a parallel resonant tank circuit for driving a pair of series connected discharge lamps via a series ballast capacitor. A regenerative power supply switches on when a fluctuating main DC supply voltage drops below a given level thereby providing a constant level auxiliary DC supply voltage to the oscillator inverter to maintain oscillation and lamp operation. When the main DC supply voltage exceeds said given level, the regenerative power supply switches out. The oscillation frequency is f.sub.2 during operation of the main supply and automatically switches to a frequency f.sub.1 when the regenerative power supply takes over. The frequency shift is automatic during each half cycle of a 60 Hz AC supply and is in a direction so as to maintain lamp current relatively constant.

Abstract: An arrangement for starting and supplying a discharge lamp (14) equipped with preheatable electrodes (15, 16). An electric coil (13) is arranged in series with the lamp and a capacitor (17) is arranged in parallel with the lamp. A voltage of a high frequency is first applied between the ends (A, B) of the series arrangement formed by the coil (13) and the lamp (14) whereafter approximately 1 second later said frequency is reduced until a series resonant condition is obtained and thereafter still further reduced to the operating frequency of the lamp. This starts the lamp (14) with the electrodes preheated to a sufficient extent.

Abstract: Starting and operating method and apparatus for discharge lamps comprises a current-limiting and rectifying means which provides at its output a low-ripple current-limited direct current. To effect lamp starting, a series-connected inductor and capacitor form a high "Q" resonant circuit with the capacitor connected across the lamp to be operated. This starting circuit connects through a blocking capacitor and charging resistor across the low-ripple source of DC. A pair of transistors which comprise an oscillator are connected emitter-to-collector across the source of DC, with the common-connected emitter and collector connected to the blocking capacitor. A drive air-core transformer has separate feedback windings in the starting and operating circuits and drive windings are associated with the transistors. A trigger diode is used to initially pulse one of the transistors which initially oscillate to generate square waves having a frequency corresponding to the resonant frequency of the starting circuit.

Abstract: Disclosed is a discharge lamp lighting device which comprises a series closed-loop circuit including an AC power supply, a ballast having an inductance, and a discharge lamp, and a switch circuit in parallel to the discharge lamp. The switch circuit is turned on when the voltage across the discharge lamp is reduced to zero, and then turned off when the current flowing in the switch reaches a predetermined value. The switch circuit thus repeats its on-off operation every half cycle of the voltage across the discharge lamp. The electromagnetic energy is stored in the inductance of the ballast when the switch circuit is on, and the stored electromagnetic energy is superimposed on the source voltage and applied to the discharge lamp when the switch circuit is turned off, thus reigniting the discharge lamp every half cycle. This makes it possible to light directly a discharge lamp having a lamp voltage approximate to the source voltage.

Abstract: Improved programming and control device for modified lead ballast for HID lamp. The basic ballast comprises a high reactive transformer and capacitor connected intermediate the transformer and lamp. An additional inductor and AC switch connect in parallel with the capacitor and the switch is opened and closed to vary the lamp current to control lamp output. The improved device comprises a parameter measuring means which measures a lamp operating parameter and converts same into output electrical signals. These signals are compared to a reference signal to generate error signals. The error signals are integrated by a capacitor and a potential which is indicative of the integrated signals is slowly developed at one capacitor terminal. A ramp capacitor is charged each half cycle of energizing potential. When the ramp capacitor potential crosses over the potential displayed at the one terminal of the integrating capacitor, a comparator means generates an output signal.

Abstract: An improved gas laser is disclosed. The laser has a support tube to support and to maintain the alignment of the optical resonator structure. The gas lasing medium is used within the support tube to maintain the tube at a substantially constant temperature above the ambient. Furthermore, an active temperature controller is disclosed. The temperature controller maintains the gas lasing medium in the support tube at a substantially constant temperature. An active pressure controller is also disclosed. The active pressure controller uses a pressure sensor, an electronic processor, and a motor-driven needle valve to maintain the pressure of the gas lasing medium in the laser within the desired operating pressure range. The laser can also be switched in operation from a continuous mode to a pulsing mode. An active power control system is disclosed wherein the power output of the laser, through an active feedback loop is maintained at the desired level.

Abstract: A device is disclosed for converting fluorescent lighting fixtures, having a conventional series-type ballast with at least two lamps, to effect illumination of only one of the two lamps at a time, but automatically effecting illumination of the other lamp upon that one becoming disabled. The device includes an induction coil to increase the starting boost available to one of the two lamps and also has a varistor. The varistor may be connected across a secondary coil of the ballast which is then arranged to idle. With fixtures having two pairs of instant-start lamps, the varistor is instead connected to an electrode of one lamp of each pair. The device preferably has a series circuit comprising the varistor, the inductive coil, a capacitor and a resistor. Preferably four electrical connections, two across the varistor and two across the inductive coil, are provided to connect the device into the circuitry of the ballast and lamps.

Abstract: A circuit arrangement for operating a high-pressure gas discharge lamp (14) with high frequency current in which a direct voltage is supplied to a transistor bridge (5 to 8) having a transverse branch in which is arranged a choke coil (13). The clock (switching) frequency of the transistor bridge is varied within each period of the AC mains alternating voltage in dependence upon the current derived from the AC mains voltage.

Abstract: A ballast circuit for direct current gaseous electrical discharge devices includes a rectifying bridge, and an inductive ballast for storing excess energy. The rectifying bridge uses a pair of thyristors which must be gated on for the bridge to supply rectified voltage to the inductor and device. Gating is delayed at the beginning of each half-cycle to allow the inductor to discharge most of its stored energy.

Abstract: An electric device comprising at least one low-pressure mercury vapor discharge tube intended to be connected to an AC voltage source at a frequency of 50 to 60 Hz. The discharge tube is of a type which produces a comparatively large current distortion and has a proportionally low required reignition voltage. The electric device produces relatively small electric losses. The discharge tube remains operative even for small deviations of the nominal AC supply voltage.

Abstract: A low pressure metal vapor discharge lamp has a double-tube type discharge vessel consisting of a fully closed outer glass bulb and an inner glass tube substantially coaxially disposed in the outer glass bulb, the inner glass tube being closed at its fixed end and opened at its free end. The space within the discharge vessel is filled with a small amount of a metal and a rare gas of a low pressure. A single cathode is disposed within the space inside the inner glass tube, while a plurality of anodes are disposed in the annular space between the inner glass tube and the outer glass bulb. According to the invention, a number of discharge channels corresponding to that of the anodes are formed between the single cathode and respective anodes, via the opening end brim of the inner glass tube. In operation, anode oscillations take place alternately in respective anodes to cause a self-excitation switching operation, so that a plurality of plasmas are formed.

Abstract: To operate at least one, and preferably a plurality of fluorescent lamps, a elf-oscillating transistor push-pull switching oscillator, using two similar transistors (T1, T2), is connected to respective lamps (3, 3', 3"), with an oscillatory circuit (4, 4', 4") to operate at audio, supersonic or low high frequency, for example in the 20 kHz range. Each lamp operating circuit has an individual series resonance circuit (4, 4', 4") which includes a ballast inductance (L1, L1', L1") and a capacitor (C1, C1', C1"). For multiple operation, the respective lamp operating circuits are connected in parallel. A special starting circuit (10) and a control circuit (9a, 9b; L2, L2', L2"; L3, L3', L3") for the switching transistors insures low-loss operation.

Abstract: A frequency converter for supplying an electrodeless discharge lamp comprises a VMOS controlled semiconductor switching element and a parallel circuit including an electric coil coupled to a discharge path of the lamp. A control circuit of the switching element includes a transformer which, in combination with two Zener diodes, results in a low-loss control circuit for the VMOS and, hence, an increased system efficiency.

Abstract: A dual voltage power supply, for example operable from 120 and 240 volts a-c and having three voltage input terminals, is provided with an input filter having three windings on a core and inductively coupled together, the three windings being connected respectively to the three input terminals. Filter capacitors are connected to the windings.

Abstract: A method for starting and operating a preheat type fluorescent lamp includes a source of alternating current, a fluorescent lamp having a low impedance starting mode wherein current passes through one or more starting filaments and a high impedance operating mode wherein current passes through the length of the lamp, a starting switch directing current through the starting filaments in the lamp starting mode, and an inductor ballast having a magnetically permeable core operating in a saturated condition when the lamp is in the low impedance starting mode and in a non-saturated condition when the lamp is in the high impedance operating mode.

Abstract: A converter circuit for addition to the existing lamp operating circuitry of a high pressure mercury lamp consisting of an existing series ballast inductor and a power factor connecting capacitor connected across the input terminals of the existing lamp operating circuit includes inductance arranged to be connected to the ballast inductor so as to adjust the resultant series inductance to a value suitable for a sodium lamp, and an igniter portion coupled to the converter inductance. The igniter portion operates to apply ignition voltage to the sodium lamp during at least part of the time that the converter circuit is supplied with power. Protective circuitry is coupled to the converter inductance to block or limit high frequency voltage pulses which could otherwise reach the ballast inductor.

Abstract: A two-wire ballast arrangement is disclosed for fluorescent tubes having first and second terminals for supplying variable power to dim the fluorescent tube, a choke coil connected between the first terminal and the fluorescent tube and a filament transformer having a primary connected between the second terminal and a tap on the choke coil, the tap being selected to supply substantially constant voltage to the primary winding, the transformer having secondary windings to supply filament voltage to the fluorescent tube.