Abstract: A circuit arrangement including a DC/AC converter for operating a discharge lamp. The DC/AC converter includes input terminals for connection of the DC/AC converter to a DC voltage source, and a switching circuit connected to the input terminals and provided with at least one switching element. The switching element has a control electrode and a main electrode and a control circuit between the main electrode and the control electrode for generating a control signal for the switching element. The switching element is conductive when a voltage is present between the control electrode and the main electrode with a first polarity having a value which exceeds a threshold value. A load branch includes at least inductive means and output terminals for connection of the discharge lamp, which load branch is supplied via the switching circuit. The control circuit also generates a DC voltage component between the control electrode and the main electrode with a polarity which is opposed to the first polarity.

Abstract: An electronic ballast (100) for powering at least one gas discharge lamp (10) comprises an inverter (200) and an output circuit (300). Output circuit (300) comprises a resonant inductor (310), a resonant capacitor (330), a DC blocking capacitor (360), a first rectifier (350), and a second rectifier (370). Output circuit (300) prevents excessive current flow and power dissipation in the event of lamp removal or failure, and provides automatic ignition following lamp replacement. In an alternative embodiment, a ballast (160) for powering two lamps (10,20) includes a pair of modified output circuits (500,600) and a ground-referenced lamp return wire (504) for accommodating conventional instant-start type wiring.

Abstract: A resonance type power converter unit has, in an inverter circuit in which voltage driven type semiconductor devices each having the function not to prevent a backward current are connected in series, the respective voltage driven devices are associated with capacitors which are charged or discharged with currents flowing through the devices and voltage detectors for detecting voltages of the capacitors, and drive circuits for turning on and off the voltage driven devices in accordance with outputs of the voltage detectors. With the resonance type power converter unit, stable resonance operation synchronous with a high-frequency load current can be warranted.

Abstract: An electroluminescent lamp is driven by a driving circuit that can supply an approximately sinusoidal signal, a bi-directional sawtooth signal or a single-ended sawtooth signal. Switches selectively transfer energy from a battery to an inductor and then from the inductor to the lamp. In one embodiment, the lamp voltage is compared to a reference waveform, such as a sinusoid. The switches are activated responsive to the error between the lamp voltage and reference waveform to minimize the error. The lamp can thus be driven with a closer approximation of the reference waveform.

Abstract: A dimmable ballast circuit for a gas discharge lamp comprises a resonant load circuit with a resonant inductance, a resonant capacitance and circuitry for connecting to a gas discharge lamp. A d.c.-to-a.c. converter circuit is coupled to the resonant load circuit for inducing a.c. current therein, and comprises a pair of switches serially connected between a bus conductor at a d.c. voltage and a reference conductor. The voltage between a reference node and a control node of each switch determines the conduction state of the associated switch. The respective reference nodes of the switches are interconnected at a common node through which the a.c. current flows, and the respective control nodes of the switches are substantially directly interconnected. A gate drive arrangement for regeneratively controlling the switches comprises a driving inductor connected between the common node and the control nodes and mutually coupled to the resonant inductor for sensing current therein.

Abstract: A discharge lamp lighting device which comprises a DC power source for generating a voltage necessary for a discharge lamp from a DC power source, a control circuit for calculating a power required by the discharge lamp to perform feedback control over the DC power source, a polarity switching circuit for switching polarities of an output of the DC power source to apply the output to the discharge lamp, an ignitor for superposing a high pulse voltage to the discharge lamp at the time of starting the discharge lamp, and a capacitor which forms a closed circuit together with the ignitor, wherein, in order to suppress excessive charging and discharging currents flowing through the capacitor when the polarities of the polarity switching circuit are switched, the control circuit controls the polarity switching circuit to be operated at a low frequency and simultaneously be chopper-operated at a high frequency.

Abstract: A discharge lamp operating circuit is connected to a source of alternating current (AC) voltage, and has a discharge lamp and a semi-resonant circuit connected to the source of alternating current voltage and in series with the lamp. A starting circuit for initiating operation of said discharge lamp is also connected in the circuit. The lamp switching maintains the series semi-resonant circuit in oscillation and the series semi-resonant circuit maintains the lamp in operation after operation has been initiated by the starting circuit. Highly efficient energy transfer between inductive and capacitive components of the system result in low loss and high power factor. A variable capacitance circuit is provided to allow use of the discharge lamp operating circuit with different line voltages, and to allow dimming.

Abstract: An improved ballast circuit for use with a compact fluorescent lamp includes an EMI filter, a rectifier and voltage amplification stage, an active resonant circuit and power factor correction stage which is connected in parallel to a lamp load. The ballast circuit includes a feedback capacitor which provides a feedback path for a portion of the high frequency current to the rectifier and voltage amplification stage. The feedback capacitor of the improved ballast circuit reduces the non-linear characteristics of the diode, thus providing almost a linear load on the input power supply and therefore achieving an improved power factor, on the order of 0.95 or greater. The improved ballast circuit may also include a dimming stage which works with the active resonant circuit to vary the amount of power that is supplied to the lamp load. The dimming stage does not require the addition of parasitic active stages and thus provides a lamp with high electrical efficiency.

Abstract: The device provides a power-supply section (3) connected to an AC source (21) and an inverter section (5) for supplying power to an electrical load (9, 11) through an oscillating circuit (13, 15). Two capacitors, a filter and a smoothing capacitor (27, 29) are arranged between a rectifier bridge (25) and the controlled cutouts (33, 35) of the inverter. The power-supply section (3) has an inductor (39) with a value such that the power-supply section (3) exhibits a predominantly inductive behaviour towards the inverter section (5).

Abstract: Remote ballasting apparatus adapted for insertion between a high frequency power source and one or more gaseous discharge lamps. The ballasting apparatus includes an isolation transformer having a primary winding adapted for connection to the high frequency power source, a low capacitance power transmission line having an output end adapted for connection to the one or more gaseous discharge lamps, and current limiting means, such as an inductor or a capacitor or a series resonant circuit connected between the secondaries of the isolation transformer and the input end of the low capacitance power transmission line.

Abstract: A fluorescent lamp flashing circuit is comprised of a fluorescent lamp to which an alternating supply voltage source is connected through a series connected loading reactance device which provides current limiting. The heaters of the fluorescent lamp are independently fed. A switching device disconnects and reconnects the alternating supply voltage at a predetermined frequency rate which is determined by a control circuit which controls a switching device. When the switching device is closed, the fluorescent lamp is bypassed through a full wave rectifier bridge and the reactance device is connected in parallel with the supply voltage source and with a bleeding resistance to load the bridge and to form a resonant circuit to maintain the loading reactance device constant and permitting an energy exchange between the supply voltage source and the loading reactance device in a resonant mode thereby maintaining a sine wave form and minimizing loss.

Abstract: The invention relates to a switching device for operating a lamp by means of a high-frequency current, which switching device comprises a DC-AC converter whose oscillation frequency is determined by a timer circuit comprising a resistor and a capacitor. In accordance with the invention, the timer circuit also comprises a chain C which includes a switching element and which is used to increase the RC period of the timer circuit during ignition of the lamp, thereby increasing the amplitude of the voltage across the lamp.

Abstract: An electronic ballast for discharge lamps comprises a main resonance circuit for applying a voltage necessary for operating of a discharge lamp having filaments to both ends of the discharge lamp and a filament resonance circuit for supplying a filament current to the filaments, wherein the main resonance circuit and filament resonance circuit have resonance circuits having different resonance characteristics in an output path leading to the discharge lamp and also change their outputs depending on an operating frequency of switching elements. Thereby a filament current and a voltage across the discharge lamp can be set at suitable one of respective operational modes of the discharge lamp according to an operational state of the discharge lamp.

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: The present invention describes a method and circuitry for igniting high frequency operated, high intensity discharge lamps by means of a dual resonant circuit driven by a nonsinusoidal waveform; typically a square wave in the preferred embodiment. A capacitor in series with the lamp is selected to resonate at the fundamental frequency of the applied waveform when the lamp is in the on condition, providing thereby the high frequency power to the lamp for its normal operation. A capacitor in parallel with the lamp is chosen to resonate at a higher harmonic of the applied frequency, typically the third harmonic, when the lamp is in the off condition. Hysteresis heating causes the ignition voltage of the lamp to decrease as higher frequency power is applied, leading to ignition of the lamp at the third harmonic without applying to the lamp one or more pulses of high voltage.

Abstract: A constant light output ballast circuit capable of regulating lamp current to a substantially constant level independent of the number of fluorescent lamps on load. The circuit incorporates a power factor control circuit and an electronic ballast circuit having a secondary winding on its output transformer. The voltage on the secondary winding, which is proportional to the ballast circuit's output voltage, is fed back to the power factor control circuit to regulate the DC output voltage supplied to the electronic ballast circuit and thereby maintain a constant lamp current.

Abstract: An electronic ballast (200) includes a rectifier circuit (20), a clamp inductor (44), an electronic switch (62), a control circuit (60) for driving the electronic switch (62), an energy storage capacitor (34), a first diode (38), a second diode (50), a clamping capacitor (58), and an output circuit (80). In a preferred embodiment, the rectifier circuit (20) includes a full-wave diode bridge (22) and a high frequency filter capacitor (24), and the output circuit (80) has a resonant inductor (82), a resonant capacitor (92), and a DC blocking capacitor (98). The ballast (200) provides power factor correction, low in-rush current, and high frequency power for fluorescent lamps, but requires only a single electronic switch (62) and a single clamp inductor (44).

Abstract: An electronic ballast (100) for powering at least one gas discharge lamp (10) comprises an inverter (300), an output circuit (400), and a switching circuit (500). Output circuit (400) includes a resonant inductor (440) and a resonant capacitor (460). Switching circuit (500) is coupled between the resonant capacitor (460) and an AC ground node such as circuit ground node (60), and is operable to effectively disconnect the resonant capacitor (460) after the lamp (10) ignites, thereby eliminating circulating current and significantly enhancing ballast energy efficiency. Switching circuit preferably comprises an electronic switch (600) and a pulse circuit (700), and optionally includes a diode matrix for use in ballasts for powering two or more lamps. In one embodiment, pulse circuit (800) monitors for lamp replacement and provides automatic ignition of a replaced lamp.

Abstract: An improved ballast circuit controls the power delivered to a three-way dimmable fluorescent lamp for use in European countries and elsewhere where the input voltage is on the order of 220 volts. The ballast circuit comprises passive power factor correction to increase the overall power factor of the circuit to above 95% while also reducing the total harmonic distortion to less than 20%. Adaptations to connect a fluorescent lamp to a three-wire dimming switch are also included.

Abstract: A dimming control circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant half-bridge inverter driven by a pulse-duration-modulated voltage, for providing a high-frequency ac voltage between the lamp electrodes. A combination inductive and capacitive snubber circuit reduces switching losses in the inverter and increases the efficiency of the dimming circuit. A low-voltage transformer connected across the resonant portion of the inverter provides voltage to heat the lamp filaments. The filament voltage is substantially constant over a range of pulse-durations providing a dimming range from about 100% to 1% of full light output. A power supply circuit having a power factor of about 0.95 provides both high-voltage and low-voltage dc power to the dimming circuit with minimal losses. A shutdown circuit is provided to shut off power to the lamp if the dimming circuit is miswired or a ground fault occurs.

Abstract: A circuit arrangement for igniting and supplying a discharge lamp by means of a substantially square-wave voltage at a frequency f1. It is possible to dim the lamp by adjusting the frequency of the substantially square-wave voltage to a value f2 which is different from f1. A protection circuit prevents damage to the lamp and to the circuit arrangement if the lamp current does not flow any more at the frequency f2.

Abstract: A circuit arrangement for operating a high pressure discharge lamp having a full bridge commutator network. A capacitor across each of four commutator switches forms a tuned circuit together with a ballast coil for soft switching. To counteract the core material of the ballast coil from vibrating audibly during lamp operation about no more than 15% of the commutation cycle elapses between turning off the first of the four commutator swithes and turning on the last of the four commutator switches.

Abstract: A dimming control circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant half-bridge inverter driven by a pulse-duration-modulated voltage, for providing a high-frequency ac voltage between the lamp electrodes. A combination inductive and capacitive snubber circuit reduces switching losses in the inverter and increases the efficiency of the dimming circuit. A low-voltage transformer connected across the resonant portion of the inverter provides voltage to heat the lamp filaments. The filament voltage is substantially constant over a range of pulse-durations providing a dimming range from about 100% to 1% of full light output. A power supply circuit having a power factor of about 0.95 provides both high-voltage and low-voltage dc power to the dimming circuit with minimal losses. A shutdown circuit is provided to shut off power to the lamp if the dimming circuit is miswired or a ground fault occurs.

Abstract: An electronic ballasting circuit provides high efficiency ballasting for most common types of fluorescent lamps. The circuit consists of a half-bridge inverter providing a substantially squarewave voltage across a series-combination of an inductor and a capacitor. The fluorescent lamp is connected in parallel circuit with the capacitor in such a way that the current flowing through the capacitor also flows through the lamp cathodes, thereby providing continuous low voltage heating therefor. The values of inductance and capacitance are so chosen that the series-combination has a natural resonance frequency that is substantially equal to or lower than the lowest frequency component present in the squarewave voltage.

Abstract: The invention relates to a circuit arrangement for operating electric lamps, having a free-running half-bridge inverter (Q1, Q2). An auxiliary transistor (T1, T2) is in each case connected into the control circuits of the half-bridge inverter transistors (Q1, Q2), so that the emitter impedance of each half-bridge inverter transistor (Q1, Q2) is formed by a parallel circuit which consists of at least one resistor (R5) or (R7) and the control path, arranged in parallel therewith, of the corresponding auxiliary transistor (T1) or (T2). The control inputs of the two auxiliary transistors (T1, T2) are, furthermore, connected to the output of a common control circuit (IC).

Abstract: The circuit arrangement according to the invention has a self-oscillating inverter having at least two alternately switching transistors (Q1, Q2), a load circuit connected to the inverter output and designed as a resonant circuit (L1, C1), and terminals for at least one electric lamp (LP). According to the invention, the control junction of a transistor (T1) is arranged in the emitter line of one of the inverter transistors (Q2). Via the variable conductivity of this control junction, the effective emitter resistance of the inverter transistor (Q2) is continuously varied as a function of the voltage drop across one of the resonant circuit components (C1), and the clock frequency of the inverter (Q1, Q2) is thereby increased so far that because of the now stronger detuning with respect to the resonant frequency of the resonant circuit (C1, L1) a reduction in the no-load voltage in the load circuit is achieved.

Abstract: A discharge lamp operating circuit is connected to a source of alternating current (AC) voltage, and has a discharge lamp and a semi-resonant circuit connected to the source of alternating current voltage and in series with the lamp. A starting circuit for initiating operation of said discharge lamp is also connected in the circuit. The lamp switching maintains the series semi-resonant circuit in oscillation and the series semi-resonant circuit maintains the lamp in operation after operation has been initiated by the starting circuit. Highly efficient energy transfer between inductive and capacitive components of the system result in low loss and high power factor.

Abstract: A dimming control for a high intensity lighting system uses a single additional control wire for control of the dimming function. The lighting system operates on multi-phase power. A transmitter for transmitting a control signal over the single control wire is connected between two of the phases of the multi-phase power supply, or between one phase and neutral. The transmitter, upon the occurrence of a predetermined condition, transmits a control signal to the single control wire. The control signal is a rectified portion of the power supply. The predetermined condition is motion as sensed by a motion sensor, operation of a timer, or operation of a manual switch. A receiver connected to the control line receives the control signal and switches the light to a low light output mode. The is accomplished by changing the capacitance of the ballast circuit for the light. Each lamp of the lighting system has a receiver connected to the single control wire.

Abstract: A device for the lighting and instantaneous hot-relighting of lamps of the discharge type, including: a transformer having a first winding and a second winding; a discharge lamp, in which a first electrode is connected to the second winding; one or more capacitive means, which are series-connected to the first winding; and trigger means adapted to trigger, by means of pulses, discharge control means that are connected thereto; the discharge control means produce the discharge of the one or more capacitive means on the first winding, which induces on the second winding a high voltage for the hot-lighting of the discharge lamp.

Abstract: An electronic ballast to power a gas discharge load (FL1) operating from a low frequency AC voltage source (ACVS) equipped with a dimmer (DIM) and having variable voltage magnitude. The device comprising a primary resonant oscillator (RO1) exhibiting an inductive character of frequency dependent impedance as an auxiliary resonant inductance (La) interacting with an auxiliary resonant capacitance (Ca) coupled to a rectifier circuit (RB, VSD) which performs switching and rectifying functions developed by and synchronized with a pulsating current drawn from the rectifier circuit by the primary oscillator circuit (RO1) equipped with switching transistors (Q1, Q2) and adapted to deliver to the gas discharge load (FL1) high frequency signal to of a variable magnitude proportional to the variable magnitude of the voltage of the AC voltage source.

Abstract: An improved ballast circuit for use with a fluorescent lamp includes an EMI filter, a feedback network, a rectifier and voltage amplification stage, and an active resonant circuit which connects to the lamp load. The ballast circuit includes a magnetic feedback path which couples the resonant circuit to the feedback network. The magnetically coupled feedback network of the improved ballast circuit reduces the non-linear characteristics of the rectifier diodes, thus providing an almost linear load to the input power supply and therefore achieving an improved power factor, on the order of 0.95 or greater. The improved ballast circuit may also include a dimming stage which works with the active resonant circuit to vary the amount of power that is supplied to the lamp load. The dimming stage does not require the addition of parasitic active stages and thus provides a lamp with high electrical efficiency.

Abstract: An electronic starter for high intensity discharge devices, such as mercury vapor, high pressure sodium, and metal halide lamps. The present invention includes voltage controlled oscillator with a resonant frequency that is determined by the direct voltage applied and by a resonance circuit that includes the high intensity device as part of the resonance circuit. A higher frequency of oscillation is present upon start-up before the device is ionized of approximately 300 kilohertz. After that, the high intensity device shunts out one of the capacitance reactive elements lowering the circuit's Q and maintaining an operating frequency that oscillates between 20 and 100 kilohertz. The inductive element acts as a current limiting device and a protection circuit is provided to monitor the voltage across the lamp and to disable the oscillator if abnormal conditions are detected including removal of the lamp.

Abstract: A ballast circuit for a gas discharge lamp comprises a resonant load circuit incorporating the gas discharge lamp and including a resonant inductance and a resonant capacitance. 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 which are connected together at a common node through which the a.c. load current flows. The first and second switches each comprise a control node and a reference node, the voltage between such nodes determining the conduction state of the associated switch. The respective control nodes of the first and second switches are interconnected. The respective reference nodes of the first and second switches are connected together at the common node.

Abstract: A circuit arrangement for operating a discharge lamp with a high frequency current comprising input terminals for connection to a source of low frequency supply voltage, a rectifier bridge coupled to the input terminals for rectifying the low frequency supply voltage, and an inverter shunting a first capacitor for generating the high frequency current. The circuit arrangement incorporates two power feedback loops to feed power back to an output terminal of the rectifier bridge. As a result the circuit arrangement has a relatively simple configuration, causes only a very limited amount of harmonic distortion and can be realized with relatively cheap and simple components.

Abstract: A power-line-operated frequency-converting power supply provides a 30 kHz current-limited AC voltage at an output receptacle. An instant-start gas discharge or neon lamp is connected across the secondary winding of a gapped ferrite-type leakage transformer, the primary winding of which is connected with the output receptacle by way of a light-weight cord, thereby permitting the lamp-transformer combination to be located remotely from the power supply. The secondary winding is arranged to have a well defined inductance; which inductance is tuned to resonate at 30 Khz by way of a parallel-connected tuning capacitor. Tightly coupled with the secondary winding is a control winding with which is connected a protection circuit operative to place an auxiliary capacitor across the control winding in case the neon lamp fails to ignite within a few milli-seconds, thereby detuning the secondary winding enough to protect the power supply and the leakage transformer from sustained overload.

Abstract: A modular ballast system particularly suited for strip lighting installations has ballast modules on opposite ends of each fluorescent lamp tube, each module having lamp connectors for receiving the end pins of the fluorescent lamp, capacitance and inductance elements connected to the lamp connectors in each module, and jumper conductors interconnecting the capacitance and inductance elements of the modules to define a bridge type ballast circuit for powering the fluorescent lamp. Each ballast module can be made small and lightweight with a single inductor and capacitor forming two legs of a four leg bridge type ballast. Pairs of ballast modules can be connected back-to-back to transmit electrical power without external wiring to successive fluorescent lamps along the strip.

Abstract: A programmed electronic ballast circuit including a voltage maintenance circuit to ensure that the integrated circuit continues to oscillate and drive the half-bridge inverter until the DC bus voltage falls to a level insufficient to permit the fluorescent bulbs at the output to ignite. Additionally, the voltage maintenance circuit drives the voltage of the integrated circuit down to a level whereby proper resetting of the integrated circuit and proper preheating of the florescent bulb filaments is assured.

Abstract: Power to a self-oscillating inverter ballast is supplied from a DC voltage source through an inductor means having two separate windings on a common magnetic core--with one winding being positioned in each leg of the power supply. The inverter is loaded by way of a parallel-tuned L-C circuit connected across the inverter's output, thereby providing an output voltage thereat. The output voltage consists of sinusoidally-shaped voltage pulses of alternating polarity, with a distinct brief period of discontinuity at or near the cross-over points. A fluorescent lamp is connected by way of a current-limiting capacitor with the inverter's output.

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 voltage-boosting and current-regulating circuit delivers energy from a high voltage resonant circuit source to a fluorescent lamp. A controllable switch is connected in series with the lamp cathodes and is triggered into conduction during a predetermined conductive time interval within each half-cycle of current conducted through the plasma from the resonant circuit. A charging current which flows during the conductive time interval stores energy in the resonant circuit which is subsequently released as a boosted voltage and as increased current flow through the plasma. The boosted voltage allows higher efficiency illumination lamps to the used, and regulation of the conductive time interval achieves the optimal current conduction through the lamp.

Abstract: A fluorescent lighting system has: (A) a central power supply including: (i) a parallel-resonant self-oscillating bridge inverter operative to provide a 35 kHz sinusoidal output voltage at a pair of primary output terminals; (ii) a tank-inductor and a tank-capacitor parallel-connected across the primary output terminals; and (iii) plural pairs of secondary output terminals, each connected with the primary output terminals via its own dedicated current-limiting sub-circuit; thereby to prevent a load connected therewith from drawing more than a certain amount of power; thereby, in turn, to render each pair of secondary output terminals fire-hazard-safe and shock-hazard-safe; each pair of secondary power output terminals being connected with its own power output receptacle; and (B) a light-weight power cord plug-in-connected with one of the power output receptacles and having a pair of power conductors between which are connected a number of individually ballasted lighting units; each lighting unit having at lea

Abstract: A lamp driving circuit having a series inductor and capacitor (L-C) in which the lamp load is connected in parallel with the capacitor. During pre-ignition of the lamp load, the driving signal supplied by a half-bridge oscillator includes a fundamental frequency and higher odd harmonics including a third harmonic of the fundamental frequency. The resonant frequency of the series connected L-C circuit is at least .sqroot.5 times greater than the fundamental frequency but not equal to the higher odd harmonic frequencies, preferably less than the third harmonic of the driving signal.

Abstract: An electronic ballast is powered by power source (102) and (104). The ballast controls the electrical power supplied to a gas discharge lamp (116), providing the voltages and currents required to start, warm-up and operate the lamp (116). Line power conditioner (100) reduces interference and harmonic generation, and provides a source of DC power (103), which may be regulated. DC power (103) is applied to inverter (105), which generates a square-wave voltage at a variable frequency determined by control circuit (200). Inverter (105) output is connected to resonant circuit (600) consisting of series inductor (110), series capacitors (112) and (118), and parallel inductor (114), across which gas discharge lamp (116) is connected. Operation begins with inverter (105) running at a frequency initially near but above the unloaded series resonance frequency of resonant circuit (600). Controller (200) reduces the frequency until resonant circuit (600) gives sufficient voltage to start lamp (116).

Abstract: Apparatus for generating a stream of charged particles, for example for use in an electron beam welding device. The apparatus includes a charged particle source (5) such as a filament and a target (6). The charged particle source (5) is connected in series with a resonant electrical circuit and the target is connected in parallel with the circuit. The source and target (5,6) are relatively juxtaposed such that under working conditions, when the circuit is in resonance, electric current passing through the source (5) causes emission of first charged particles and the potential difference between the source (5) and the target (6) accelerates the first charged particles towards the target.

Abstract: A protection circuit for non-isolated ballasts that drive gas discharge lamps to prevent shock hazards. The device acts to prevent excessive leakage currents from flowing between the ballast and ground by introducing a higher common mode impedance path in the circuit. A two stage common mode filter assembly has a first common mode inductor series connected to a second common mode inductor. A first capacitor is connected across the common mode inductors. A second capacitor is connected between the junction of the first capacitor, the first inductor, the second inductor and ground. The circuit protects by reducing high frequency leakage currents.

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: 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 power supply periodically draws power from a DC soure. The power supply includes an electroluminescent lamp and an inverter used to convert the DC into a sinusoidal voltage that is applied to the lamp.

Abstract: An electronic ballast for powering at least two rapid start, parallel connected fluorescent lamps. Associated with each lamp is a serially connected choke and capacitor combination. A train of pulses of alternating polarity having a fundamental frequency, which is generated by an inverter, is applied to each serially connected combination. Each combination is characterized by a resonant frequency which is other than an odd harmonic of and at least two times and preferably .sqroot. 5 times greater than the fundamental frequency. Reduction in filament heating, following lamp ignition, is provided through the addition of voltages applied to each filament which are substantially out of phase with each other.

Abstract: A ballast filter in which the ballast can operate at a total harmonic distortion of power line current of less than 10%. Power dissipated by the filter when at a THD of less than 10% is relatively low. The input impedance of the ballast is chosen to be no greater than twice the equivalent filter impedance of a front end filter and no less than the equivalent filter impedance/1.5. The filter includes a transformer having a core which at times operates within the non-linear region of its B-H curve under nominally rated ballast load conditions.