Abstract: A dimmable fluorescent lamp system comprises a fluorescent lamp with filaments at each end that are continuously heated by a transformer. A resonating capacitor is connected in series with a resonating inductor and a pair of DC blocking capacitors are connected from each end of the fluorescent lamp to put it in parallel with the resonating capacitor. A control logic drives the resonating inductor with a pulse-width modulated square wave that is controlled by a feedback voltage derived from a pair of rectifiers and a dropping resistor in series with one of the DC blocking capacitors. An error amplifier with two gain settings, e.g., one for a range of 0-20% of maximum light dimming and the other for 20%-100% dimming, compares the feedback voltage to a setpoint. A threshold comparator establishes the switchover point between the two error gain ranges.

Abstract: A circuit arrangement for high-frequency operation of a low-pressure discge lamp (18) includes a mains rectifier (10), a radio interference suppression filter (12) connected to the mains rectifier (10), an RF inverter (14), connected to the direct current output of the mains rectifier (10) and having two alternatingly switching transistors (T.sub.1, T.sub.2) along with an inductance (L.sub.K), a trigger circuit and a center tap (M), which is between the two transistors (T.sub.1, T.sub.2). A filter capacitor (C.sub.S) is connected parallel to the switching paths of the two transistors (T.sub.1, T.sub.2) of the RF inverter (14). A series resonant circuit (16) is assigned to the low-pressure discharge lamp (18), and comprises a resonant inductance (L.sub.3), a coupling capacitor (C.sub.3), and a resonant capacitance parallel to the lamp. The connection lines for the low-pressure discharge lamp (18) lead on the one hand from a first electrode (E.sub.1) via the resonant inductance (L.sub.

Abstract: A circuit for driving a gas discharge lamp load and including an EMI and transient supply filter coupled to an input source, a rectifier coupled to the filter, a power inverter coupled to the rectifier, a load including a transformer coupled to the power inverter, and a control circuit coupled to the power inverter and the load. A feedback circuit couples the load transformer to the AC side of the rectifier to create a path for transferring a feedback voltage over the rectifier to cause the rectifier to conduct current over a substantive portion of each cycle of the AC input voltage.

Abstract: In a fluorescent lamp ballast, a source of high-frequency voltage is applied directly across a series-resonant L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means is operative to prevent the series-resonant L-C circuit from overloading the voltage source during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the series-resonant L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp.

Abstract: A circuit arrangement for operating a high pressure discharge lamp includes input terminals for connection to a supply voltage source and an apparatus coupled to the input terminals for supplying an alternating lamp current to the high pressure discharge lamp. A device (III) is provided for generating a current pulse in each half period of the lamp current. This current pulse has the same polarity as the lamp current and is superimposed on the lamp current in the latter part of a predetermined fraction of the half periods of the lamp current. The circuit substantially suppresses flickering of the discharge arc during lamp operation.

Abstract: A circuit for operating a lamp includes supply input terminals for connection to a supply voltage source and a transformer provided with a primary winding L1 and a secondary winding L2. A first branch has terminals (N1,N2) for holding the lamp and connects a first end of the secondary winding L2 to a second end thereof. A second branch comprising a series circuit of a switching element (Q1) and the primary winding L1 interconnects the supply input terminals. A control circuit (SC1) is coupled to a control electrode of the switching element for generating a control signal for rendering the switching element conducting and non-conducting, and thus generating a first current in the primary winding L1 and a second current in the secondary winding L2. The second branch comprises a series arrangement of the primary winding, the switching element (Q1), and the terminals (N1,N2) for connection to the lamp. The total lamp current is controlled via the switching element which passes only a portion of the lamp current.

Abstract: In a device to control a fluorescent tube supplied from a DC source by an accumulating converter, a rectifying bridge 17 is mounted opposite to the secondary 13, between the preheating electrodes 2, 3 of the tube, and supplies an auxiliary transistor 16. An energizing synchronizer 14 supplied by the rectifying bridge 17 receives at one input 24 the control signal of the primary transistor 5 from the modulator 4, and controls the blocking of the auxiliary transistor 16 in synchronism with the blocking of the primary transistor 5.

Abstract: A control system for gas discharge lamps (5) includes a fuzzy controller (7) which, for controlling the lamp current of the gas discharge lamp, generates a setting value for an inverter (3), for setting the frequency or duty ratio of the lamp current, in dependence upon an actual value of the lamp current. Further, in accordance with the invention, fuzzy logic is employed for the purpose of recognition of the lamp type of a connected gas discharge lamp (5), in that on the basis of various detected operational parameter values, during the operation of the gas discharge lamp, the lamp type of the gas discharge lamp is determined.

Abstract: A discharging lamp lighting apparatus is provided to perform lighting control of high voltage discharging lamps such as high pressure sodium lamp or metal halide lamp. In the discharging lamp lighting apparatus, a control section determines a power control pattern balancing with stored discharging lamp stable voltage so as to perform power control of the discharging lamp according to the pattern. If no voltage is stored, the control section performs the power control according to a power control pattern balancing with the minimum rated voltage of the discharging lamp. Then, it is possible to store the voltage when the discharging lamp is stabilized. If the discharging lamp is exchanged, the control section erases contents in stable voltage storing means so as to perform the lighting control of the discharging lamp from an initial state.

Abstract: A circuit for operating a discharge lamp includes input terminals for connection to a supply voltage source and a first apparatus coupled to the input terminals for generating a low-frequency alternating current from a supply voltage delivered by the supply voltage source. A second apparatus is coupled to the input terminals for generating from the supply voltage a further current which is superimposed on the low-frequency alternating current. The polarity of the further current is the same as that of the low-frequency alternating current. As a result, instabilities do not arise in the discharge arc of a high-pressure discharge lamp operated by the circuit.

Abstract: The present invention provides a method and circuit for controlling the flow of current through a load. In a preferred embodiment, an oscillator generates a pulse signal of constant frequency. A pulse width modulator adjusts the duty cycle of the pulse signal in response to a dimming level signal input indicative of the desired level of current flow through the load. A converter receives the pulse signal as an input and converts it into an AC signal, the frequency of which follows the frequency of the pulse signal and the symmetry of which varies with the duty cycle of the pulse signal. The load is connected into a resonant circuit tuned such that a change in the symmetry of the AC signal changes the level of current flowing through the load.

Abstract: A low cost, high efficiency electronic larger DC/smaller AC ballast for fluorescent lamps and other gas discharge devices uses fast react feedback and constant power sources to power a fluorescent lamp at a stable working point and to reduce the accuracy requirements of related components. An input-side chopper regulator provides a DC supply voltage. A voltage multiplier in combination with the input-side chopper smoothly and reliably starts the lamp, providing high voltage at low current during startup, and minimal loading thereafter. A second constant power source drives the bulb via an output side chopper coupled to a storage capacitor and inductor, maintaining larger DC/smaller AC operation while reducing harmonics. The operational voltage applied to the load has a large DC component and a smaller AC component, thereby reducing electrophoresis effects. The constant power sources can be adjustable manually or automatically, for dimming control.

Abstract: A circuit for regulating the pixel current in a field emission display so as to enhance pixel-to-pixel uniformity of pixel current. The pixel current flows through a pair of diodes connected back-to-back. A transistor circuit controls the voltage across the back-to-back diode pair, so that the voltage/current transfer characteristic of the diode pair determines the pixel current.

Abstract: A lighting circuit converts the output voltage of a DC booster circuit to an AC voltage which is in turn supplied to a discharge lamp. The lighting circuit comprises a current/voltage detector for detecting signals equivalent to the current and voltage of the discharge lamp and a control circuit for controlling the output voltage of the DC booster circuit in accordance with detection signals from the current/voltage detector.

Abstract: The present invention is concerned with a power supply circuit for discharge lamps, especially those intended for vehicle headlamps. It also relates to a headlamp having a power supply circuit. The latter has a half wave bridge structure, the discharge lamp being connected to the midpoint of the bridge. A primary of a transformer works as a quasi-resonant wave generator under the switching effect of a quasi-resonant interrupter, which is controlled by a control circuit for controlling the electrical state of the discharge lamp. In addition, starting of the lamp is effected by a second transformer, the primary of which is connected to a spark gap having a suitably chosen triggering voltage.

Abstract: A lighting circuit, which is lit with a voltage with a square wave, has a DC booster circuit, a bridge type DC-AC converter and an inductor provided at the subsequent stage of the DC-AC converter. A metal halide lamp is connected in series to the inductor. Another inductor and a capacitor are provided between the DC booster circuit and the DC-AC converter. A series circuit of a resistor and a diode is connected in parallel to the second inductor. This structure generates a resonance voltage having a high peak value to compensate for a re-ignition voltage of a discharge lamp which is produced when the polarity of the square-wave voltage is switched, thereby preventing the lighting failure of the discharge lamp immediately after the lighting starts.

Abstract: An electronic ballast for hot cathode discharge lamp comprises a DC voltage source, a chopper, and an inverter. The chopper includes a switching element connected in series with an inductor across the DC voltage and driven to turn on and off for providing a periodically interrupted voltage which is smoothed by a capacitor to produce a smoothed DC voltage as a chopper output. The inverter includes at least one switching element which is coupled to the chopper output to produce therefrom a high frequency AC voltage as an inverter output to be applied to cathodes of the discharge lamp for lighting the discharge lamp. The ballast is characterized to include an inverter controller and a delay circuit. The inverter controller controls the inverter to operate selectively in a normal mode of providing the inverter output of a first level and in a limited mode of providing the inverter output of a second level which is lower than the first level and is determined to give a preheating current to the cathodes.

Abstract: A high voltage discharge lamp driving device which can be used for an outdoor high voltage discharge lamp driving device due to reduce discharge start voltage of the high voltage discharge lamp by changing a turns ratio of a last output coil. The high voltage discharge lamp driving device which can light the high voltage discharge lamp in an instant by outputting over tens of thousands volt discharge start voltage, and can raise power efficiency by generating high voltage pulse signals for driving the high voltage discharge lamp and by shortening the time the high voltage pulses are applied to the high voltage discharge lamp.

Abstract: Method for operating a ballast for discharge lamps. The ballast comprises a rectifier for rectifying and filtering an AC line voltage, with the rectified voltage being smoothed with a capacitor and fed to an inverter, wherein the inverter drives a resonant lamp circuit that includes a gas discharge lamp, with the frequency of the inverter being generated by a voltage controlled oscillator and a control circuit, so that during normal operation of the lamp, the inverter frequency is chosen according to the current value of the rectified voltage, and during start-up of the ballast, the inverter frequency is lowered from a high starting frequency, while being continuously monitored to ensure the latter does not fall below a minimum frequency, with the value of the minimum frequency depending on the value of the rectified voltage, thus decreasing the dependence of the light flux on the rectified voltage and assuring a safe start-up process.

Abstract: A ballast for operating gas discharge lamps has a voltage boost, a half-bridge inverter and a parallel resonant circuit. An inverter control inhibits operation of the inverter when power is initially applied to the ballast.

Abstract: A modulated electronic ballast for driving a gas discharge lamp includes a full wave rectifier for supplying a modulating signal to a series fed parallel resonant circuit including two transistors. Inductors are provided on both the hot and neutral alternating current power source lines for shielding the power source from electromagnetic interference and providing transient protection. A biasing circuit supplies a small direct current to the resonant circuit for retaining the resonant circuit in a continuous oscillating mode during substantially zero voltage valleys of the modulating signal. A diode is provided across the base and collectors of each transistor in the resonant circuit for preventing over saturation and co-conduction.

Abstract: A clocked power supply circuit is proposed which includes a control arrangement (20) which outputs switching signals (21) to switching means (13) as a function of a load condition present on the output side and which includes at least one inductive element (12). Provided on the output side is a load (22) which is independent of the electric consumer (18), preferably a gas discharge lamp, and is at least temporarily active. It is possible using the load (22) specifically to avoid no-load operation of the clocked power supply by means of a load, as a result of which the system-induced reaction time can be substantially shortened in the case of a short-term energy requirement of the consumer (18). The energy required in the short term can be supplied by the magnetic energy stored in the inductive element (12).

Abstract: A circuit for igniting and operating a discharge lamp includes a DC-AC converter provided with a first branch coupled to a DC voltage source and including at least one switching element for generating an alternating current at a frequency f. A load branch is coupled to the first branch and includes inductive means, capacitive means, and an inductor for coupling the lamp to the load branch. A control circuit switches the switching element at the frequency f and includes a resonant circuit of a further inductor and a further capacitor. An ignition voltage limiter includes a second branch coupled to the resonant circuit and comprising a series arrangement of a frequency-dependent impedance and a semiconductor element of variable impedance as a function of its control electrode potential. A third branch is coupled to the load branch and to the control electrode of the semiconductor element for influencing the potential of the control electrode dependent upon the lamp voltage.

Abstract: Electrical activation of an arc lamp is accomplished by a plurality of circuits, each of which has a boost topology including a capacitor and a charging circuit for charging the capacitor by a series of current pulses. One of the circuits is an igniter circuit and includes a transformer to convert voltage from a relatively low voltage supply to a relatively high voltage for striking an arc within the lamp. A second of the circuits provides for a steady flow of current to maintain the arc after completion of ignition of the arc. The second circuit is protected from the high voltage of the first circuit by a saturable reactor connected in series between the second circuit and the arc lamp.

Abstract: A monolithic MOS gate driver chip is described for driving high side and low side power MOSFETs in a gas discharge lamp ballast circuit. The chip includes a timer circuit for generating a square output at the natural frequency of resonance of the lamp ballast. Dead time circuits are provided in the chip to prevent the simultaneous conduction of both high side and low side MOSFETs. The chip may be housed in an eight pin DIP package.

Abstract: In a fluorescent lamp ballast, a source of high-frequency voltage is applied directly across a series-resonant L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means is operative to prevent the series-resonant L-C circuit from overloading the voltage source during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the series-resonant L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp.

Abstract: A power-supply and control circuit is provided for driving a fluorescent lamp from a low-voltage DC power source such as a battery. In typical lamp-driving circuits, a step-up transformer is used to apply well known magnetic techniques to achieve the low-to-high voltage conversion required by the lamp. The present invention uses a new approach, applying piezoelectric characteristics of certain ceramic materials to replace the magnetic transformer. Resonant characteristics of such ceramic materials permit them to be self-resonated. A DC-to-AC converter coupled to a switching regulator converts low DC voltage into a higher AC voltage for driving the fluorescent lamp. In one embodiment, the lamp is included in a feedback loop which includes a circuit for producing a feedback signal indicative of the magnitude of current conducted by the lamp. The feedback signal is applied to the switching regulator to produce in the lamp a regulated current and, hence, a regulated lamp intensity.

Abstract: A monolithic MOS gate driver chip is described for driving high side and low side power MOSFETs in a gas discharge lamp ballast circuit. The chip includes a timer circuit for generating a square output at the natural frequency of resonance of the lamp ballast. Dead time circuits are provided in the chip to prevent the simultaneous conduction of both high side and low side MOSFETs. The chip may be housed in a right pin DIP package.

Abstract: An electronic ballast includes a converter coupled to a variable frequency inverter and a series resonant, parallel loaded output coupled to the inverter. The frequency of the inverter increases when the supply voltage from the converter decreases. The converter includes a full wave rectifier producing a first voltage and an unregulated boost circuit producing a second voltage which is combined with the first voltage to produce the supply voltage. The amount of boost, and therefore the magnitude of the supply voltage, is varied to provide dimming. Dimming is controlled mechanically, via a potentiometer, or electrically, via a control input. Dimming also occurs in response to changes in the first voltage, i.e. from changes in the voltage on an AC power line or from changes in the voltage provided by a capacitive dimmer coupled between the ballast and an AC power line.

Abstract: A starter for a fluorescent lamp selectively conducts current from an AC power source through a ballast and cathodes of the lamp during one half cycle of conducted current from the AC power source. Thereafter and during the same on half cycle of current the starter ceases conducting current substantially instantaneously when the current is of a predetermined level. The resulting di/dt generates a starting voltage pulse from the ballast sufficient to ignite the plasma. The starting pulse occurs when the AC voltage across the cathodes exceeds an ignition voltage of the plasma. Preferably the starter employs a thyristor which has a predetermined holding current at least equal to the predetermined level to allow the inherent commutation of the thyristor to create the di/dt. The current conducted by the thyristor heats the cathodes prior to igniting the plasma.

Abstract: This generator for supplying high-frequency power to an arc lamp (12), coises:a primary circuit (1) connected up to the terminals (5, 6) of the power-supply mains and incorporating an electromagnetic inductor (L', T) connected to a resonant circuit (7);a secondary circuit (2) comprising, in series, the arc lamp (12) and an electromagnetic sensor (E.sub.1, E.sub.2) making it possible to provide magnetic coupling with the primary circuit (1) at high frequency.The secondary circuit (2) is formed by two electrical circuits (10, 11) mounted in parallel with the terminals of the lamp (12), each of the two circuits incorporating an electromagnetic sensor coupled with the electromagnetic inductor of the primary circuit (1).

Abstract: A DC power supply for a gas discharge lamp includes a high voltage starting circuit for supplying high voltage pulses to effect initial energization of a gas discharge lamp, a lower voltage running circuit for supplying a desired average lamp operating current at a substantially constant current to the gas discharge lamp, and a transformer having a primary connected in the high voltage starting circuit and a secondary connected in the lower voltage running circuit. The transformer provides an inductance which acts as a current source inductor to supply current to the gas discharge lamp.

Abstract: For triggering a discharge lamp powered by a d.c. source and having electrodes disposed in the lamp bulb, a power supply circuit is proposed having a triggering device where, after the start of heating of a cathode (which cathode is in the form of a heated cathode), the triggering device switches a triggering pulse to a discharge path of the lamp, which discharge path is formed by the two electrodes, and initiates a triggering phase, such that the triggering pulse at least partly overlaps in time with the heating phase of the cathode. In this way, reliable triggering of deuterium discharge lamps and hydrogen discharge lamps is possible, particularly in the case of a deuterium lamp having a relatively small opening, e.g. on the order of 0.3 mm.

Abstract: The load circuits for the different lamps of a 2-lamp ballast are selected to have sufficiently different resonant frequencies so that the luminous fluxes of the two are different when the ballast operating frequency is at one of the resonant frequencies. The ballast is operated at a frequency between those two resonant frequencies. The circuit may include a device for measuring the ratio between the luminous fluxes of the two lamps, and the frequency control circuit is then responsive to that ratio.

Abstract: A DC/AC convert circuit for operating a discharge lamp includes a branch A having ends suitable for connection to a DC voltage source and comprising a series circuit of two switching elements for generating a periodic voltage by being conducting and non-conducting alternately at a frequency f, each switching element being shunted by a diode. A control circuit is coupled to control electrodes of the switching elements for rendering the switching elements conducting and non-conducting alternately at the frequency f. A load branch B shunts one of the switching elements and comprises an inductor. The discharge lamp is coupled to the load branch B. The power consumed by the discharge lamp is adjusted by adjusting the value of the difference Tt-Td, in which Tt is a time interval during which one of the switching elements is conducting during a half cycle of the periodic voltage, and Td is the time interval during which a diode is conducting during the same half cycle of the periodic voltage.

Abstract: In a switching inverter where transistor switches are controlled so as to provide current through an inductor which is connected in series with the switches across a battery so as to power a capacitive load (such as an electroluminescent lamp) with higher voltage than the battery voltage, control current for the switches and particularly the emitter to base current therethrough is shared by connecting the bases of these transistors via a current limiting resistor. Using the same base current reduces the battery drain and improves the efficiency (power applied to the load versus battery power drawn) of the inverter.

Abstract: A circuit arrangement for operating a high-pressure discharge lamp provided with a ballast circuit VI for generating a current through the high-pressure discharge lamp from a supply voltage. A controller is provided for controlling the power consumed by the high-pressure discharge lamp. The run-up behavior of the high-pressure discharge lamp is governed by an apparatus III for controlling the luminous flux of the high-pressure discharge lamp and by a device IV for the automatic activation of the controller after the run-up of the high-pressure discharge lamp. As a result, the luminous flux of a high-pressure discharge lamp operated by the circuit arrangement has the same, substantially constant value during substantially the entire time duration of the run-up of the high-pressure discharge lamp as during stationary lamp operation.

Abstract: To insure high power factor for the operating circuit of a low-pressure discharge lamp, especially of miniature fluorescent lamps, a high-frequency active rectifier bridge (D1-D4) is provided which interrupts charging of a smoothing capacitor (C2), which smoothing capacitor supplies an inverter circuit (WR) in the switching rhythm of the inverter. A storage choke or inductance (L1), a negative feedback capacitor (CG) and an auxiliary capacitor (CS) are coupled to the high-frequency rectifier bridge (D1-D4) which, together with the inductance insure an approximately sinusoidal current being taken from a power network, with a power factor of 0.98 or higher. Preferably, the circuit includes voltage dividers (R8, R9, R11; R15, R16, R17) which are coupled to a voltage sensitive trigger circuit (DI, TH) to turn OFF alternate switching of transistors (T1, T2) of the inverter (WR) in case excess supply voltage or operating voltages of the lamp are sensed.

Abstract: An electronic ballast is provided with a built-in timed electric power saver and with photoelectric switching for high-pressure mercury vapor, metallic vapor and sodium vapor lamps. The electronic ballast with the built-in timed saver and photoelectric switching for high-pressure mercury vapor, metallic vapor and sodium lamps includes an electronic circuit having as a principle the obtaining of an increase in the frequency of the electric power distribution network. This increase is accomplished by means of a switching that results in a current limiting electronic device, which also is able to incorporate a timed electric power saver, the utilization of a single equipment for various lamp lower ratings, a photo-sensitive element for control of the lamp switching in accordance with the lighting level of the installation site and an ignitor for lamps requiring a voltage higher than the rated one.

Abstract: The present invention features a gas discharge lamp electronic ballast that uses a frequency-dependent control circuit. The lamps are all energized by means of a single electronic ballast, including an electronically regulated power supply, a power oscillator/driver circuit, an output coupling circuit and a feedback circuit that provides frequency-to-voltage conversion for controlling the output voltage of the power supply. In this way, constant lamp current is maintained, regardless of the number of lamps connected. Since the remaining lamps are operated at their specified, correct lamp current, lamp life is preserved. Another feature of the circuit is its ability to dim the lamp output continuously over a limited range to reduce energy usable in circumstances in which full lamp illumination is not required. Such dimming can be controlled by a suitable external control signal such as from a potentiometer, switch, light monitoring device or a motion detector.

Abstract: A two terminal pulse width modulated incandescent lamp dimmer using low frequency pulse repetition rate provides increased illuminating efficiency by compensating both for light producing inefficiency of a tungsten filament at dimmed level settings, and for internal resistance of a direct current power source. A preferred embodiment of the dimmer is designed for 3.5 to 9.0 volt operation.

Abstract: Disclosed is a lighting circuit for a discharge lamp, which employs a rectangular-wave based lighting system and is designed to prevent lighting failure from frequently occurring in the discharge lamp immediately after the lighting of the discharge lamp starts or at the end of the lamp's life. In the lighting circuit, a battery voltage is boosted by a DC booster circuit and is then converted to a rectangular-wave voltage by a DC/AC converter. This rectangular-wave voltage is then applied via an inductor of an igniter circuit to a metal halide lamp. The DC booster circuit has a chopper type structure and has a smoothing capacitor at the output stage. A resonance controller comprising a diode and a resonance capacitor is located between the DC booster circuit and the DC/AC converter. The DC/AC converter has a bridge structure having field effect transistors (FETs). The two pairs of FETs are reciprocally switched from one pair to the other by a drive controller.

Abstract: A circuit arrangement for igniting and operating a discharge lamp (La), provided withinput terminals (K1,K2) for connection to a DC voltage source,a commutator (COM) coupled to the input terminals and provided with terminals (K3,K4) for connecting the discharge lamp (La), for cornmutating a current through the discharge lamp (La),a branch A which is conducting in both directions at least for alternating current, of which branch a first end is connected to an input terminal (K2) and a further end is connected to the commutator (COM), and which branch comprises an inductive element L shunted by a branch B which comprises a unidirectional element (D),a branch C which connects a further input terminal to the commutator (COM), andan ignition circuit (S) for igniting the discharge lamp. According to the invention, the unidirectional element (D)is so included in the branch B that the branch B conducts a current at least immediately after ignition of the discharge lamp (La).

Abstract: A half-bridge inverter is powered from a constant-magnitude DC supply voltage and provides at the inverter's output a first AC output voltage that is describable as a modified squarewave voltage. This first AC voltage is applied across a series-combination of an inductor and a capacitor, the junction between which is clamped to the DC supply voltage. As a result, a second AC voltage gets established across the capacitor; which second AC voltage is also describable as being a modified squarewave voltage. However, the phasing of the second AC voltage is delayed by approximately 90 degrees with respect to the first AC voltage; which results in the voltage across the inductor being of approximately sinusoidal waveform. A fluorescent lamp is connected in series with a ballast capacitor; and the lamp-capacitor series combination is connected across the inductor, thereby resulting in a nearly sinusoidal current being provided to the fluorescent lamp.

Abstract: A transformer-less electronic ballast for a gas-discharge lighting system having a power amplifier, with an input, driving a gas-discharge lamp in combination with reactive elements to form a resonant load. The lighting system includes a resistor for sensing current flowing in the resonant load, a comparator having an output coupled to the input of the power amplifier, a non-inverting input coupled to the resistor, and an inverting input coupled to the output of a ramp generator, polarity of the ramp signal being dependent on the output of the comparator. The comparator generates a first signal that is amplified by the power amplifier and applied to the load. The ramp generator generates a ramp signal in response to the first signal. The first signal is asserted by the comparator when the sensed current flowing in the load differs from the ramp signal.

Abstract: A switchmode AC power controller for controlling the current through a load such as a large lamp array connected to an alternating current source. The controller contains an AC solid state switch, a synchro-flywheel, an output inductor and capacitor. The load current is controlled by triggering signals generated by a synchronized modulator.

Abstract: A gas discharge lamp power ballast or power supply having simplified power factor correction, simplified automatic short circuit/overload protection and output open circuit voltage regulation. The gas discharge power ballast or power supply includes self-oscillating converter circuitry to which simplified power factor correction is provided via simple passive circuitry that includes a split winding from the power transformer in conjunction with an input storage capacitor and a current limiting resistor. The short circuit/overload protection is implemented, without elaborate current sensing circuitry, by utilizing the drive winding of the power transformer. In a shorted or overloaded state, a capacitor interacting with oscillator circuitry, controls oscillator cycling to reduce current flow and protect the circuitry against the overload at the output. Output open circuit voltage regulation and power regulation are also implemented in a simplified manner without the need for significant additional circuitry.

Abstract: In a preferred embodiment, a lighting device may include a metal halide lamp and a polarity inversion step-up circuit which generates a DC voltage Va of minus value. An inverter circuit inverts the output of the polarity inversion step-up circuit to create AC voltage and supplies it to a discharge lamp. Consequently, the discharge lamp has applied a square wave AC voltage with voltage between zero and peak being nearly .vertline.Va.vertline.. Potential of a lighting tool to enclose the discharge lamp is set to ground potential. Since the discharge lamp is lit always at a mean lighting potential which is less than the potential of the lighting tool, the Na loss phenomenon is suppressed. That is, life of the discharge lamp can be lengthened. Other embodiments also operate to keep the mean lighting potential of the discharge lamp less than the potential of the lighting tool.

Abstract: DC power is converted by an inverter to high-frequency power, which is supplied to the primary winding of a neon transformer. One or more neon tubes are connected in series across the secondary winding of the neon transformer. A saturable reactor is connected across the secondary winding or the neon transformer. The saturable reactor has a characteristic that its magnetic flux is saturated when the output voltage from the secondary winding of the neon transformer increases 1.1 to 2.0 times the rated voltage.

Abstract: A power supply for driving one or more loads includes a DC voltage source, an inverter connected to the DC voltage source for providing a high frequency AC voltage at its output end, and an output transformer having a primary winding and a secondary winding. The primary winding is coupled to the output end of the inverter through a tuning inductor, while the secondary winding is coupled to the load. A tuning capacitor, which constitutes a resonant circuit in cooperation with the resonance inductance for supplying a resonance current to the load, is connected across the secondary winding of the output transformer in parallel relation to the load. The tuning capacitor is arranged in circuit on the opposite side of the secondary winding from the load such that the tuning capacitor is open-circuited when the load is disconnected from the secondary winding.