Abstract: A ballast is disclosed which can operate at an effective level of output with a number of different input voltage levels. A ballast is also disclosed that uses a ceramic as a heat sink for switching transistors. A ballast is further disclosed which uses a start signal for a power factor circuit to boost voltage after the load for the ballast has already had a current applied to it. Furthermore, a ballast is disclosed which has a transformer having a permeability which varies somewhat inversely with temperature over a given temperature range.

Abstract: An air gapped inductance and a capacitance form a series resonance that is itself in series with a flourescent tube. The resulting series resonant network is permanently connected to one (+) side of the DC supply, while the other end is switched between that (+) side of the DC supply and the other (-) side of the DC supply. Switching occurs in synchronism with the different polarities of the half-cycles for the current circulating in the resonant circuit. In series with the current in the resonant circuit is the primary of a phase splitter driver transformer having separate secondaries phased to control FET switches to do the aforementioned switching, and whose turns ratios are selected to determine the duty cycles with which the resonant circuit is switched. The switched end is connected to the one (+) end of the DC supply for its entire associated half cycle.

Abstract: An electronic ballast for a fluorescent lamp which includes a frequency sweep circuit for driving a ballast controller IC at different operating frequencies depending on the operating mode of the fluorescent lamp. The sweep circuit monitors the operating mode of the lamp (e.g., preheat, ignite, running, shutdown) and automatically generates an appropriate variable voltage offset for controlling the lamp. The offset is added to a constant voltage supplied to an input of the ballast controller IC, resulting in a corresponding change in the frequency output by the ballast controller IC (and thus the lamp power). The electronic ballast also includes fault protection logic which monitors signals from the lamp resonant circuit and shuts down the ballast in the event of a fault condition. The fault protection logic also resets the frequency sweep circuit so that the lamp can restart automatically when the fault is corrected.

Abstract: A circuit arrangement for igniting and operating a high intensity discharge lamp including a Buck converter. The Buck converter includes a switch, a rectifier and an inductor having primary and secondary windings. The secondary winding is part of an integrator for controlling the non-conductive state of the switch. A detector responsive to the flow of current through the rectifier produces a signal supplied to the integrator output during the non-conductive state of the switch. The integrator output remains proportional to the flow of current through the inductor regardless of the state of the switch. Consequently, the time duration that the switch is in its non-conductive state can be limited while maintaining the circuit arrangement in a reliable non-self oscillatory mode of operation.

Abstract: An ballast includes a variable frequency boost circuit and a driven half-bridge inverter having a series resonant, direct coupled, parallel output. A control circuit includes a variable frequency driver section, a multivibrator section, and a sensing section. The variable frequency driver changes frequency smoothly, i.e. without discontinuities. The multivibrator section acts as a switch that is enabled or disabled by the sensing section for controlling the frequency of the inverter. Lamp current is required for continued operation of the control circuit. The multivibrator section controls starting by causing the inverter to produce an output signal having a trapezoidal envelope. In the event of an arc, the control circuit quenches the arc and the multivibrator periodically pulses the lamp to attempt to re-start the lamp.

Abstract: A circuit for driving a load. In one embodiment, the load is driven by an inverter circuit having a full bridge circuit divided by inductive elements to provide cross conduction protection. In another embodiment, first and second converter circuits are coupled to the inverter circuit with the inverter and converter circuits having common circuit elements. In a further embodiment, a common mode inductor is inductively coupled to a power circuit for detecting a common mode signal generated by a load current return path disruption. The common mode inductor is coupled to a control circuit for limiting current to the load.

Abstract: A circuit arrangement and control thereof for igniting a high intensity discharge (HID) lamp, for reducing the high frequency ripple superimposed on the low frequency rectangular waveform lamp current after ignition, and for increased circuit efficiency. The high frequency ignition voltage is only applied to the lamp during ignition phase and is mainly generated by the second stage of the low pass (LP) filter. The first stage of the LP filter whose resonant frequency is below the second stage further attenuates the high frequency ripple current through the lamp in normal operation. The resulting lamp current is a low frequency rectangular wave with less than 10% high frequency ripple. Acoustic resonance is avoided. The inductor in the first stage of LP filter is operated in discontinuous current mode. Doing so, the active switches are in zero current switching (ZCS) to maximize the circuit efficiency.

Abstract: A ballast circuit for a gas discharge lamp includes a rectifier coupled to convert current from an a.c. source to d.c. current provided on bus and reference conductors. A smoothing capacitance, coupled between the bus and reference conductors, smooths current supplied by the rectifier. A resonant load circuit includes a resonant inductance, a resonant capacitance, and means to connect to the lamp. A d.c.-to-a.c. converter circuit, coupled to the resonant load circuit, induces an a.c. current in the resonant load circuit. The converter circuit comprises first and second switches serially connected between the bus and reference conductors, and being connected together at a common node through which the a.c. load current flows. The 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 switches are interconnected at the common node.

Abstract: The present invention provides an improved power factor and lower harmonic distortion in the power supply circuit of a high frequency discharge lamp. An "extra" circuit path is provided so that the driving power to the lamp will "see" a load that significantly reduces the harmonic distortion and tends to cause the power factor to approach "1". In a preferred embodiment of the invention this is accomplished by providing a third capacitor with which the load circuit forms an in-series resonance circuit with the discharge lamp and its associated current-limiting inductance. The new circuit arrangement provides a high frequency current passage not provided in known lighting circuits of this type that raises the power factor and lowers harmonic distortion.

Abstract: A ballast including an inverter and a circuit having a resonant frequency coupled to the output of the inverter. In one embodiment of the invention, the only discrete type of element substantially affecting the resonant frequency is substantially inductive in electrical character. In this embodiment of the invention, there is also no discrete ballasting element in series with the lamp load. The reduction in discrete elements reduces both power consumption and costs associated with the ballast.

Abstract: An arrangement for igniting and operating a high-pressure discharge lamp provided with a Buck converter for supplying the lamp through periodic switching of a switching device which is held alternately in a conducting state for a period t.sub.on and in a non-conducting state for a period t.sub.off. The arrangement further includes circuitry which produces fixed minimum and maximum time limits for the time duration t.sub.off.

Abstract: An integrated circuit control device for driving a half bridge type of inverter. The IC control inverter powers a load including a lamp. The device includes at least one pin, which during the preheat cycle of the lamp is at a high logic level resulting in the coupling of an additional capacitor to an unloaded resonant tank circuit. The overall resonant frequency of the unloaded circuit is reduced making it less likely that a high voltage will be applied to the lamp during preheat. Once the lamp filaments have been preheated the pin is at a low logic level. The low logic level at the pin causes the additional capacitor to be decoupled from the tank circuit. The pin when at the low logic level also receives a signal representing the voltage condition across the lamp.

Abstract: A single-switch ac-to-ac converters for driving ac loads which are particularly suitable for gas discharge lamp ballast applications based upon integration of automatic current shapers and converters that resemble a class-E converter, both parts sharing a single active switch. The first part comprises a high power factor (HPF) converter having automatic input current-shaping means and internal energy storage means operated by the single active switch driven at a constant frequency and duty ratio, and the second part comprises a resonant converter means operated by the aforesaid single active switch as it is being driven. Integration of the HPF converter having automatic current shaping means and the resonant converter through the single active switch operation brings advantages from both parts into the whole circuit, such as soft-switching characteristics so that the combined circuit can shape the input current without switching losses in a compact structure.

Abstract: Proposed for the purpose of starting a high-pressure discharge lamp is a cuit which in the conventional way comprises a starting transformer (12) whose secondary side is connected to the lamp to be started and whose primary side is connected to a circuit triggering the starting pulse, the circuit triggering the starting pulse generating starting pulses with a pulse duration of less than 0.5 .mu.s and a repetition frequency of at least 2 kHz. An IGBT (Insulated Gate Bipolar Transistor) (14) is preferably used as switching element.

Abstract: A circuit arrangement for igniting and operating a discharge lamp is provided with input terminals for connecting a supply source and a commutator having output terminals for connecting a lamp to be operated, the commutator including at least two switches which are alternately in a conducting and a non-conducting state. The commutator is suitable for pulse width modulation (PWM) operation of the switches. The switches and an output terminal are connected to one another by coupled inductors for this purpose.

Abstract: An electronic flash device includes a first DC--DC converter circuit of separately-excited type, a second DC--DC converter circuit of separately-excited type, a capacitor to be charged by the first DC--DC converter circuit and the second DC--DC converter circuit, and a discharge tube which converts charging energy charged to the capacitor into light energy. The first DC--DC converter circuit includes a first switching element having a first control electrode, and an a first oscillation transformer to which energization is controlled by the first switching element. A first control pulse signal is supplied to the first control electrode. The second DC--DC converter circuit includes a second switching element having a second control electrode, and an a second oscillation transformer to which energization is controlled by the second switching element. A second control pulse signal is supplied to the second control electrode.

Abstract: A MOS gate drive (MGD) integrated circuit drives a pair of MOS gated power semiconductor devices such as are used in a half bridge circuit to drive a load in a resonant power supply circuit or to drive a gas discharge lamp in a ballast circuit. The gate drive circuit includes a protection circuit which protects against damage to the components of the driver circuit when a lamp fails or is removed by disabling both of the driver outputs. When the lamp is replaced, the gate drive circuit restarts the lamp driver circuit without cycling the lamp power switch. The protection circuit disables the driver outputs when a low logic level signal falls below a threshold voltage. The lamp driver circuit is restarted when the low logic level signal exceeds the threshold voltage.

Abstract: In an electronic ballast, a half-bridge inverter is powered from a DC voltage and provides an AC output voltage having a waveform with trapezoidally shaped half-cycles. The DC voltage is obtained by way of a pre-converter with a control input operative to permit control of the magnitude of the DC voltage. The AC voltage is applied across the primary winding of a leakage transformer, whose loosely coupled secondary winding is connected across a gas discharge lamp. The internal inductive reactance of the secondary winding constitutes a lamp ballasting means by way of limiting the magnitude of the resulting lamp current to a desired level. Prior to the flow of lamp current, the magnitude of the DC voltage is controlled by negative feedback to the control input so as to remain at a maximum level. After lamp current has started to flow, by negative feedback derived from the lamp current itself, the magnitude of the DC voltage is reduced so as to bring the magnitude of the lamp current down to the desired level.

Abstract: A lighting circuit for a discharge lamp which reliably detects short-circuiting of, or current leakage from, a discharge. A lighting circuit 1 has DC-AC conversion means 3 for converting a DC voltage from the DC power supply 2 to an AC voltage and supplying the AC voltage to the discharge lamp 9. The lighting circuit further comprises sampling means 4 for sampling a lamp voltage or a lamp current of the discharge lamp 9 in synchronism with a drive signal Sp sent to the DC-AC conversion means 3 to generate an AC wave, and abnormality determining means 5 for determining short-circuiting of, or current leakage from, the discharge lamp 9 based on a detection signal from the sampling means 4. When an abnormality is detected, power supply to the discharge lamp 9 is stopped.

Abstract: A high pressure gas discharge lamp system includes a high pressure discharge lamp selected to have a lowest lamp resonant frequency above the audible, on a current basis above about 19 kHz and on a power basis of above about 38 kHz. The ballast circuit energizes the discharge device so as to have a fundamental frequency below the lowest lamp resonant frequency and above the audible, while keeping the magnitude of any harmonics above the lowest lamp resonant frequency sufficiently small so as to avoid acoustic resonance. By operating below the lowest lamp resonant frequency, greatly simplifying ballast construction and cost. According to one embodiment, the discharge vessel encloses a discharge space which is circular cylindrical and having a L:ID ratio of about 1:1 to maximize the lowest lamp resonant frequency.

Abstract: A lighting system for a suspended ceiling comprises a plurality of power conditioning units permanently wired-in with the 120 Volt/60 Hz power line and mounted in various suitable locations on the permanent ceiling above the suspended ceiling. Each power conditioning unit conditionally provides a voltage at each of several multi-connector power output ports. Each power output port is operable: (i) to connect with a special lighting fixture by way of a light-weight flexible disconnectable connect cord; and (ii) on receipt of a special signal from the lighting fixture, to power the lamp(s) therein. Plural such special lighting fixtures are mounted in the suspended ceiling, with each lighting fixture being connected with and powered from one of the power output ports of a power conditioning unit mounted somewhere nearby on the permanent ceiling above.

Abstract: An electronic ballast (10) for fluorescent lamps includes a rectifier circuit (100), a boost converter (200), and an inverter (500). The boost converter (200) includes a boost control circuit (400) and a shifting circuit (300). The shifting circuit (300) provides filament preheating by maintaining the boost output voltage at a first level for a predetermined delay period following startup of the boost converter, and then increasing the boost voltage to a second level upon completion of the delay period in order to ignite and operate the lamps. In a preferred embodiment, shifting circuit (300) comprises a shunt circuit (320) and a time delay circuit (360), and inverter (400) is a series resonant half-bridge inverter.

Abstract: An "exit" sign lighting system comprising, in combination a housing having the word EXIT formed in an opening wall thereof, a translucent member in said opening, a gas discharge device, such as a fluorescent tube is driven from a source of a low-voltage, high-frequency square wave voltage having a pair of output terminals and an LC free circuit connecting the low-voltage, high-frequency square wave voltage to the gas discharge device to non-thermionically excite and illuminate the gas discharge device, and thereby illuminate the translucent member and the word EXIT. The low voltage is from about 2 volts to about 90 volts and the frequency is from about 75 kHz to about 3.5 MHz.

Abstract: An electronic ballast (10) for powering at least one gas discharge lamp (30) includes a rectifier circuit (100), a line blocking rectifier (220), a bulk capacitor (240), an inverter (300), an output circuit (400), and a charging circuit (500). Charging circuit (500) is coupled between the output circuit (400) and the bulk capacitor (240) and provides operating current to the bulk capacitor (240). Charging circuit (500) also protects lamp life by preventing excessive flow of DC current in the lamp (30) following application of AC power to the ballast (10). In a preferred embodiment, charging circuit (500) includes a DC blocking capacitor (510), a lamp current blocking rectifier (530), and a charging rectifier (540).

Abstract: An arrangement for igniting and operating a high intensity discharge lamp including a Buck converter. The Buck converter includes a switch, a rectifier and an inductor. The converter is connected to input terminals for connection to a supply source and output terminals for supplying the lamp with a current through periodic swithing of the switch alternately into a conducting and a non-conducting state. The Buck converter operates in a self-oscillatory mode during stable lamp opertion. The arrangement further includes circuitry for causing the Buck converter to operate in a forced oscillatory mode in dependence on the lamp condition.

Abstract: Disclosed is an integrated circuit for use in a ballast circuit for supplying a.c. current to a resonant load circuit incorporating a gas discharge lamp and a resonant inductance and capacitance. The integrated circuit comprises a d.c.-to-a.c. converter circuit comprising first and second switches serially connected between a bus pin, for connection to a bus conductor at a d.c. voltage, and a reference pin, for connection to a reference conductor. The switches are connected together at a node connected to a common pin through which the a.c. current flows, have respective control nodes connected to a control pin, and have respective reference nodes. The voltage between the control pin and an associated reference node determines the conduction state of the associated switch. A first embodiment also includes first and second resistors serially connected between the bus and reference pins, with their intermediate node connected to an intermediate pin.

Abstract: The invention relates to a circuit arrangement for operating a discharge lamp with a high frequency current comprising a power feedback circuit and an electrode preheater. The circuit arrangement comprises an antiboost switch for disabling the power feedback circuit before the lamp has ignited and enabling the power feedback circuit after the lamp has ignited. In accordance with the invention the antiboost switch is also used to enable the electrode preheater before the lamp has ignited and to disable the electrode preheater after the lamp has ignited.

Abstract: The object of the invention in to provide a drive circuit in which a high efficiency can be achieved and with which the voltage spikes reacting on the supply network are virtually zero. For this purpose, the discharge lamp (FL) is connected by its first electrode (E1), by means of a connecting line (VL), to the junction (H) between the emitter resistor (R3) of the first transistor (T1) and the collector of the second transistor (T2) of the high-frequency resonant circuit. The discharge lap (FL) in connected by its second electrode (E2) to the neutral conductor (0). As a result, the supply current with the superimposed control frequency flows via the load. Consequently, voltage spikes are compensated for and the efficiency in considerably increased.

Abstract: A driving apparatus according to the invention turns on a capacitive light emitting device having a first electrode and a second electrode in accordance with a light-on instruction. The apparatus has: a voltage accumulating unit, for example, a capacitor for holding a voltage energy corresponding to the contents of the light-on instruction; a circuit for applying the voltage energy held in the voltage accumulating unit to a portion across electrodes (A and B) in one direction in response to a first control signal and for applying the voltage energy held in the voltage accumulating unit to the portion across the electrodes in the other direction in response to a second control signal; and a circuit for alternately generating the first and second control signals. The invention can cope with a deterioration due to an aging change or the like, prevent a reduction of a light emission intensity due to the deterioration or the like, and contribute to a simplification of the construction and a decrease in costs.

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: An energy conversion device has a self-oscillating transistorized L-C series-resonant half-bridge inverter circuit having alternating resonant inductor current and adapted to deliver a high frequency signal to an effective load coupled effectively in parallel with the capacitor. The device includes a DC voltage supply able to provide DC voltage between the DC terminals; an artificial load arrangement connected to the DC terminals and operable to effectively couple itself in parallel with the capacitor; a load-coupling transformer; and a saturable feedback transformer operable to sense the alternating resonant inductor current and to control and adjust the frequency of the oscillation in proportion to the effective load applied effectively in parallel with the capacitor.

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: 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 ballast circuit for a fluorescent lamp for starting the fluorescent lamp and a compact fluorescent lamp is provided. The ballast circuit adopts a bypass capacitor which bypasses a high frequency and high harmonics to a smoothing portion for compensating a recovery characteristic of a rectification diode which causes a problem by feeding back high frequency currents (most of them are I.sub.L) which flow during the ignition of a lamp to a power source input, and including a high frequency component much included in a rectifying and smoothing operation. Thus, a power factor increases 95% or more.

Abstract: An electronic power supply (10) comprising a rectifier circuit (100) and a voltage converter circuit (200). Voltage converter circuit (200) comprises a first inductor (220), a second inductor (230), an electronic switch (240), a control circuit (300), a first rectifier (250), a second rectifier (260), a first capacitor (270), and a second capacitor (280). First inductor (220) and second inductor (230) may be implemented either as separate inductors or as coupled inductors. Power supply (10) efficiently provides a high output voltage with greater efficiency than conventional boost converters.

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: There is provided an inverter circuit for a discharge tube which does not degrade a lighting brightness of a discharge tube even if a driving frequency is increased in order to miniaturize a step-up transformer and so forth, or which does not degrade a lighting brightness of a discharge tube, this is because a voltage applying to a discharge tube is decreased even if peripheral parasitic capacitance of the discharge tube is increased. The inverter circuit for the discharge tube comprises a high frequency oscillating circuit OS and a step-up transformer for boosting an output of the OS, and the discharge tube DT is connected to a secondary side thereof.

Abstract: An electric power source device includes a power converting circuit and a load circuit (LD) for receiving an output from the power converting circuit. The power converting circuit includes a rectifier element (DB) for rectifying an input from an alternating current source (AC), a smoothing capacitor (Ce) for smoothing an output from the rectifier element (DB) with a direct current, and switching elements (Q1, Q2) for generating high frequency voltage and current in response to receipt of a voltage of the smoothing capacitor (Ce).

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. A voltage-breakover (VBO) device is effectively connected between the common node and a second node. A network is provided for setting the voltage of the second node with respect to the common node at less than the breakover voltage of the VBO device when the lamp is operating at steady state. A polarity-determining impedance is connected between the common node and one of the bus conductor and the reference conductor, to set the initial polarity of pulse to be generated upon the firing of the VBO device.

Abstract: An arrangement for switchably operating one or more gas discharge lamps, such a compact or circline fluorescent lamps, with a single ballast commonly used with a linear fluorescent lamp. One or more capacitors is either in parallel or in series with the gas discharge lamp. When engaged by a switch, the capacitor either shunts or reduces the current to the gas discharge lamp in a manner which allows appropriate starting voltage, appropriate operating current and a plurality of illumination levels of the gas discharge lamp.

Abstract: A gas discharge lamp is provided having a ballast control element and suppressible igniter. The igniter is chosen to superimpose an ignition pulse onto the initial AC ballast cycle or cycles provided to the lamp. The secondary coil of the igniter transformer is initially shorted until sufficient voltage is applied to the igniter. This causes a switch arranged across the secondary coil to open. A voltage detector coupled to a primary winding of the igniter transformer senses the amount of voltage applied from the ballast. Once that amount has been detected, the secondary winding is no longer shorted and the igniter can initially ignite the lamp during a peak of the initial cycle or cycles from the ballast. After the lamp has been initially ionized/discharged, or after a pre-defined set of discharges, the switch remains closed for the duration of each and every ballast cycle. Thus, the igniter is suppressed from the ballast output, and the ballast alone provides lamp discharge.

Abstract: A discharge lamp lighting device include an inverter circuit section supplying a square wave AC power from a DC power source to a discharge lamp, and a high voltage pulse generating unit applying, upon starting, a high voltage pulse to the discharge lamp to have it started, with an arrangement for lighting the discharge lamp by the square wave AC power made to be lower in the square wave frequency upon non-loading than that upon lighting, and controlling the square wave frequency to remain as that upon the non-loading for a fixed period immediately after detection of the start of discharge of the lamp.

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: A power supply circuit for powering a load circuit comprises a load circuit and includes a converter circuit for inducing current in the load circuit. The converter circuit comprises first and second converter switches serially connected in the foregoing order between a bus conductor at a d.c. voltage and a reference conductor, and connected together at a common node through which the load current flows. The first and second converter switches each comprise respective interconnected control nodes and references connected together at the common node. The voltage between a control node and associated reference node determines the conduction state of the associated switch. A first node is coupled to the bus conductor, and a second node is coupled to the reference conductor. A bridge network is connected between the first and second nodes and has first and second input nodes on which respective first and second input signals are applied.

Abstract: A method and apparatus for dimming a lamp in a backlight system of a display device, e.g., liquid crystal display ("LCD"), with a brightness dimming ratio of 10,000:1, which is a factor of 10 better than conventional dimming devices. A switch is provided in an inverter circuit, which has reactive components, that drives the lamp. The is positioned in the inverter circuit such that, when it is closed, the energy stored within the reactive components of the inverter circuit is discharged to ground. In one embodiment, the signals from the power supply are pulse width modulated.

Abstract: A circuit is proposed for the AC voltage operation of a discharge lamp by ans of a coupling capacitor (C3) with a safety disconnection device, connected in series with the lamp for DC current separation, which is characterized by the fact that the safety disconnection device responds to a DC voltage (UC3) at coupling capacitor (C3) by means of a DC current component flowing through the lamp.

Abstract: A discharge lamp lighting device for turning on a discharge lamp, including: a power system which generates a high voltage, the power system having a grounding line; a control system having an analog circuit which has a grounding line, and a digital circuit which has a ground wire, the control system for controlling the power system; and a power source system for generating voltages to drive the power system and the control system, wherein the grounding line of the power system, the grounding line of the analog circuit in the control system and the grounding line of the digital circuit in the control system are provided independently of each other.

Abstract: A discharge lamp driving circuit includes DC voltage input connections, lamp driving connections, bridge circuitry, and control circuitry. The bridge circuitry is connected to the DC voltage input connections and to the lamp driving connections and includes circuit elements which in one mode of operation deliver a higher frequency AC voltage to the lamp driving connections and in another mode of operation deliver a lower frequency AC voltage to the lamp driving connections. The control circuitry is connected to control the bridge circuitry selectively as either a half-bridge to deliver the higher frequency AC voltage to the lamp driving connections during starting or a full-bridge to deliver only the lower frequency AC operating voltage to the lamp while the lamp is operating normally after starting. A low frequency driver and a high frequency driver are connected to drive the bridge circuitry.