Abstract: A neon discharging lamp lighting apparatus comprises a high frequency inverter of which an asymmetrical ratio of an output voltage waveform thereof is designated from 10 to 60% and a low pressure type neon discharging lamp connected to the high frequency inverter. Since the high frequency inverter circuit applies to the low pressure type neon discharging lamp a voltage having a waveform with an asymmetrical ratio for allowing rays of light free from luminance irregularity to be emitted, fringes can be prevented from taking place in rays of light emitted by the low pressure type neon discharging lamp. Thus, the low pressure type neon discharging lamp can operate as a high quality light source.

Abstract: A ballast for a discharge lamp comprises a smoothing capacitor, an inverter circuit including at least one switching device connected in parallel to the smoothing capacitor, a driving circuit for driving the inverter circuit, an activating circuit for activating the driving circuit, a resonance circuit including first and second capacitors and an inductor connected to output terminals of the inverter circuit, a discharge lamp connected to output terminals of the resonance circuit, a third capacitor connected in parallel to the discharge lamp. A fourth capacitor and first and second rectifying elements connected in series are connected in parallel to the smoothing capacitor. Between both terminals of the fourth capacitor and terminals for connection to an AC power source, a filter and a rectifier are inserted. A terminal of the first capacitor other than that connected to the inverter circuit is connected to a junction of the first and second rectifying elements.

Abstract: A ballast circuit for a gas discharge lamp with high speed gate drive circuitry comprises a resonant load circuit including a resonant inductance, a resonant capacitance, and circuitry for connecting to a gas discharge lamp. A d.c.-to-a.c. converter circuit induces a.c. current in the load circuit, 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 determining the conduction state of the associated switch. The reference nodes of the switches are connected together at a common node through which the a.c. current flows, and the control nodes of the switches are connected together. 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 an inductor in the load circuit for sensing current in the circuit.

Abstract: A series resonant ballast safety control circuit for controlling the operation of a ballast when a lamp is removed from a lamp fixture. The safety control circuit senses a diode clamp current and activates a transistor to ground one of the terminals of a dimming control circuit. The dimming control circuit reduces the duty cycle of one of the inverter transistors to decrease the available output voltage and reduce the through-lamp leakage current to safe levels. Once the lamp is replaced in the lamp fixture, the safety control circuit no longer controls the dimming control circuit and the ballast returns to normal operation. In another embodiment, the safety control circuit is used with a boost power factor correction circuit in a non-dimming ballast system to reduce the current provided to the lamp load.

Abstract: In an externally controlled electronic ballast, a driving circuit which requires a dedicated supply voltage is provided for the purpose of driving an inventor half bridge. The driving circuit is constructed such that the inventor half bridge blocks when the supply voltage V.sub.cc falls below a threshold value UVLO. Via a self-holding controllable electronic switch and a Z diode DZ2, a voltage monitoring circuit draws the supply voltage V.sub.cc below the threshold value UVLO when an excessively high lamp voltage is detected. The ballast is thereby inactive. A current sensing path which leads via at least one filament of the low-pressure gas discharge lamp serves to detect a change of lamp. The current sensing path controls a further electronic switch, which is likewise connected to the supply voltage V.sub.cc of the driving circuit and can, when it conducts, draw said voltage further to frame than the first switch.

Abstract: A power supply or inverter circuit is provided for regulating power to electroluminescent lamps over a range of lamp sizes. The power supply may have an AC and/or DC input and includes at least one switch having a power input to be coupled to an electrical power source, a control input, and an output to be coupled to an electroluminescent lamp for being switched on and off to generate a drive signal to the lamp having a predetermined constant frequency and current level that is selectable over a range of frequency and current levels. A constant current mode controller has a control output coupled to the control input of the switch for turning the switch on and off so as to maintain a constant current level and frequency of the drive signal to the electroluminescent lamp substantially over its operating life. The voltage applied to the lamp is allowed to increase to a predetermined voltage limiting value in order to provide compensation due to aging of the lamp.

Abstract: A lighting circuit for a discharge lamp comprises a DC power supply circuit having a coil and a capacitor at its input stage, a DC-AC converter for converting the output voltage of the DC power supply circuit to an AC voltage and supplying the AC voltage to a discharge lamp, ignition means for generating an ignition pulse to the discharge lamp, and control means for performing variable control on the output voltage of the DC power supply circuit 3. The control means 6 performs such a boosting operation as to boost the output voltage of the DC power supply circuit 3 to a predetermined voltage under a loadless condition while the ignition pulse generated by the ignition means 5 is supplied to the discharge lamp 11 to thereby light the discharge lamp 11. During the boosting operation, the ignition means 5 applies the ignition pulse to the discharge lamp 11, lighting the discharge lamp.

Abstract: A lighting circuit for a discharge lamp capable of improving the lighting performance of a discharge lamp with a simple circuit structure to thereby prevent a lighting failure at the end of the lifetime of the discharge lamp. The lighting circuit 1 comprises a DC power supply circuit 2, DC-AC conversion means 3 for converting a DC voltage output from the DC power supply circuit 2 to an AC voltage and supplying the AC voltage to the discharge lamp 5, a circuit element 6 (a switch element or a current limiting element) for blocking or limiting a current counter-flowing to the DC power supply circuit 2 from the DC-AC conversion means 3, and an inductive load 4 connected in series to the discharge lamp 5. A series circuit of a Zener diode 7 and a passive element 8 (a capacitor or a resistor) is provided in parallel to the circuit element 6, so that when the Zener diode 7 conducts, a rise in an auxiliary voltage for reignition is suppressed.

Abstract: A fluorescent lighting system connected to an AC voltage source providing a first AC voltage is disclosed. A converter circuit connected to the AC voltage source converts the first AC voltage to a DC voltage. An oscillator circuit receives the DC voltage and produces a second AC voltage. The oscillator circuit includes a series resonant circuit and a removable installed fluorescent lamp. The series resonant circuit includes a resonant capacitor and a resonant conductor in series. The lamp has first and second elements and is connected in parallel with the resonant capacitor of the series resonant circuit such that lighting current runs between the first and second elements. The second element is connected in series with the resonant capacitor and the resonant inductor and acts as a switching element. When the lamp is removed from the system, the absence of the switching element creates an open circuit between the resonant capacitor and the resonant inductor such that the oscillator circuit does not operate.

Abstract: An electronic ballast circuit includes an input section which rectifies, power factor corrects and filters an AC input voltage to provide a rectified signal. The electronic ballast circuit also includes an inverter section which receives the rectified voltage and switches the rectified voltage to provide an AC signal to a resonant load circuit. The input section includes a resonant tank circuit which provides a high frequency current to the inverter to soft switch the switches within the inverter. In the input section, an inductor is placed on the AC side of a diode bridge rectifier advantageously allowing the removal of several prior art ballast circuit components since placing this portion of the power factor correction (PFC) circuit within the input circuit on the AC side of the diode bridge rectifier allows the bridge rectifier to perform both the rectification and current blocking functions.

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: 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: 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 AC driving signal of a frequency in the vicinity of the resonance frequency of a piezoelectric transformer is generated by a variable oscillation circuit and the waveform of the output signal of the variable oscillation circuit is shaped so as to be substantially sinusoidal by a waveform shaping circuit and the output of the waveform shaping circuit is subjected by a driving circuit to current amplification or voltage amplification so as to be amplified to a level sufficient for driving the piezoelectric transformer and the output of the driving circuit is subjected to current limitation, and then input to the piezoelectric transformer and the output signal of the transformer is applied to a cold cathode fluorescent lamp so that the cold cathode fluorescent lamp is lit and even if the impedance of the cold cathode fluorescent lamp decreases, the piezoelectric transformer cannot supply a large current.

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: A circuit arrangement for igniting and operating at least two discharge lamps. the circuit is provided with input terminals (K1,K2) for connection to a supply voltage source and a circuit I (SC, S1, S2) coupled to the input terminals for generating a high-frequency voltage from a supply voltage delivered by the supply voltage source. A load branch B is coupled to the circuit I and comprising a first branch A including first terminals (K3,K3') for accommodating a discharge lamp and a first inductive element L1, and a second branch C shunting the first branch A and comprising further terminals (K4,K4') for accommodating a discharge lamp and a second inductive element L2 which is magnetically coupled to the first inductive element L1. A circuit II limits the voltage across branch A and branch C to a first value during the ignition of the discharge lamps.

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: A novel monolithic electronic ballast controller IC for driving two MOS gated power semiconductors, such as power MOSFETs or IGBTs, connected in a totem pole or half-bridge arrangement. Advantageously, the present invention provides programmable preheat time and current, programmable end-of-life protection, lamp fault protection, over-temperature protection. The first embodiment of the invention is a closed-loop ballast controller IC intended for multiple lamp configurations, with three current-sensing inputs and programmable lamp power. Closed-loop control is accomplished through phase control, or, more specifically, a phase-locked loop (PLL) around a resonant type output stage driving a fluorescent lamp. The second embodiment of the present invention has a similar architecture to that of the first embodiment, with some modifications which allow dimming down to low light levels.

Abstract: A protection circuit prevents, from a short load, excessive current flow through a field effect transistor that delivers current to a daytime running light on a vehicle. The present invention uses commonly available devices, such as resistors and transistors, and a low number of such devices for low cost. Furthermore, the present invention includes a latching circuit for maintaining the switching transistor to be turned off once the current level through the switching transistor reaches an excessive level to prevent the daytime running light from flashing on and off. A voltage, which develops across a resistor that is coupled to the field effect transistor, is an indication of the current level through the field effect transistor. This voltage turns on a first transistor which couples the gate of the field effect transistor to a ground node when the current level through the field effect transistor is greater than a predetermined level.

Abstract: A discharge lamp lighting controller that detects the voltage applied to a discharge lamp used by a vehicle, for example, and stops power supply to the discharge lamp if the voltage goes out of an estimated rated voltage range in a design stage. Circuit components are protected from possible impairment due to excessive current that may flow depending on the state of the discharge lamp under the constant power control of the discharge lamp.

Abstract: A clocked power supply circuit having an at least intermittently active load that is independent of a consumer, in particular for supplying power to gas-discharge lamps as consumers, contains a dc/dc converter comprising a transformer. Switching elements connect the converter to a dc voltage source in the timing of a control arrangement which makes available switching signals for the switching elements as a function of the prevailing output-side load state. The transformer of the dc/dc converter is designed so that two voltages (U+, U-) of differing polarity and magnitude, are able to be tapped off from the output side. At least one of these voltages is regulated and provided for supplying power during operation of the consumer. The at least intermittently active load can be switched to the regulated voltage.

Abstract: A method and apparatus for operating a high pressure discharge lamp is disclosed. Oscillation in the discharge arc periphery, a problem that occurs with high frequency operation, is eliminated. A high pressure discharge lamp is operated by applying thereto a dc or rectangular wave current to which is superposed an ac component shaped by a high frequency ripple signal that has been amplitude modulated by a modulation signal for inducing instantaneous fluctuations in the power supply input to both ends of the arc gap. The ripple level is thereby temporally varied, and stable operating is possible even when exceeding the ripple level at which oscillation in the arc periphery begins.

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 dead time circuitry which prevents simultaneous conduction in both MOS gated devices. The duration of the dead time is controlled in response to a feedback signal that is sensed from the output supplied to the load or the lamp. A dimming function is attained by controlling the voltage of the feedback signal.

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: 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: 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: A triac dimmable compact fluorescent lamp including a power feedback circuit. The power feedback circuit helps to maintain the level of current drawn from the triac to at least the level of the triac holding current especially during low dim levels. In one preferred embodiment, the feedback circuit is fed into a junction joining together a pair of fast recovery diodes for converting the high frequency square wave signal into a unidirectional signal supplied to an inverter. Overboost voltages across a buffer capacitor are minimized during low dim levels.

Abstract: A light source power supply circuit includes a DC power source and an energy accumulating capacitor connected in parallel through a charging switching element to the DC power source. A polarity inverting circuit is connected across the energy accumulating capacitor for applying the capacitor voltage across a light source with the polarity alternately inverted. A starting high voltage generating circuit applies a high voltage to the light source a high voltage for starting the light source. A control circuit controls a polarity inverting circuit so that the inverting frequency is above a critical fusion frequency for the light source.

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: The present invention relates to an integrated circuit adapted to perform the function of a diode of the DIAC type, the circuit having an input terminal and an output terminal. The circuit includes a first input transistor having a first terminal connected to a fixed voltage reference, a second terminal, and a control terminal coupled to the input terminal of the circuit. The circuit further includes second and third transistors in a current mirror configuration, each having a first terminal for coupling to the input terminal of the circuit, and a second terminal, and associated control terminals connected together and coupled to the second terminal of the first input transistor, the second terminal of the second transistor being connected to the control terminal of the first transistor.

Abstract: A control apparatus for an ac-powered lamp unit includes a charging circuit for generating a constant current output from an ac power source, a storage battery charged by the constant current output and supplying a dc voltage output, a first high-voltage oscillator circuit for converting the dc voltage output of the storage battery into a first high-voltage oscillating signal, a second high-voltage oscillator circuit for generating a dc voltage signal from the ac power source and for converting the dc voltage signal into a second high-voltage oscillating signal, a switch circuit connected to the first and second high-voltage oscillator circuits, and a switch control circuit for controlling the switch circuit to provide the second high-voltage oscillating signal from the second high-voltage oscillator circuit to an ac-powered lamp unit when the ac power source is available, and to provide the first high-voltage oscillating signal from the first high-voltage oscillator circuit to the ac-powered lamp unit in cas

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: An improved ballast circuit for use with a compact fluorescent lamp includes an EMI filter, a rectifier and a voltage amplification stage, an active resonant circuit, a dimming circuit, and a power factor correction stage which is connected in parallel to a lamp load. In one embodiment, the ballast circuit operates in cooperation with a three way switch to adjust the light output of the lamp to three discrete levels corresponding to each setting of the three way switch. In another embodiment 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. In still another embodiment, the ballast circuit is configured to accept input from a triac or a SCR device. In all of the embodiments, the dimming circuit works with the active resonant circuit to vary the amount of power that is supplied to the lamp load.

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: 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 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: Subject electronic ballast draws power from the power line with a power factor higher than 90%. The ballast consists of a power-factor-correcting rectifier circuit and an inverter circuit that provides a high-frequency squarewave voltage across a series-resonant L-C circuit to which a fluorescent lamp is connected.

Abstract: An electronic ballast for a gas discharge lamp includes an AC to DC converter for changing alternating current at power line voltage to direct current and an inverter powered by the converter and having a series resonant, direct coupled output coupled to the lamp. The inverter includes an AC switch having a diode bridge defining an AC diagonal and a DC diagonal and a transistor connected across the DC diagonal. The primary winding of a filament transformer is connected across the AC diagonal of the bridge and the transistor is coupled to the microprocessor for controlling current through the primary winding. The microprocessor is programmed to close the AC switch while the lamp is starting and to open the switch after the lamp is started, thereby cutting off the filaments from a source of power and reducing the power consumed by the ballast during normal operation. A resistor in series with the transistor is used to detect filament resistance and provide an indication of lamp type.

Abstract: A light source including a ballast characterized by a resonant frequency and including a reference bus and a transformer having a secondary winding. The fluorescent lamp is partially covered by a shield, connected to the reference bus and coupled to the secondary winding. The ballast further includes a current sensor connected between the secondary winding and reference bus for sensing current flow through at least the lamp including that portion of lamp current attributable to parasitic capacitances affecting the resonant frequency.

Abstract: A discontinuous conduction mode (DCM) electronic ballast topology is presented which drives the lamp with line frequency voltage and current, just like a magnetic ballast. However, compared to magnetic ballast, its weight is substantially reduced due to operation at high switching frequency (40 kHz in the experimental prototype). The topology also ensures unity power factor at the input and stable lamp operation at the output.

Abstract: An arrangement for detecting the ignition of a high-pressure gas discharge lamp, in particular for use with a motor vehicle headlamp, comprising a circuit for supplying the high-pressure gas discharge lamp with burning energy, a control circuit and an ignition circuit. The ignition circuit is provided with an auxiliary voltage for the ignition. The control circuit is configured such that it detects the ignition of the high-pressure gas discharge lamp immediately via the behavior or the status of the auxiliary voltage (U.sub.H). The control circuit can be provided with a microcontroller (20). The auxiliary voltage supplied during the ignition is connected to the microcontroller in such a way that the microcontroller detects the ignition without delay. For this, the auxiliary voltage is supplied via a voltage divider (22, 23, 24) with logic potential to the external interrupt input (21) of the microcontroller.

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 symmetry control circuit for a ballast driving a gas discharge lamp. The circuit controls the pre-heat time of a gas discharge lamp with heatable filaments by holding off the full striking voltage until the lamp has had sufficient time to pre-heat. The circuit is designed to work with electronic ballasts and especially electronic ballasts without boost power factor correction to properly pre-heat the lamp. A control circuit reduces the duty cycle in an inverter transistor, thereby keeping the voltage across the lamp low while allowing filament heating to occur. The control circuit is disabled after a time interval of about 500 ms, allowing the transistor duty cycle to increase to 50 percent, the lamp voltage to rise, and the properly pre-heated lamp to ignite.

Abstract: A discharge lamp lighting device according to the present invention includes: a discharge lamp including an electrode; and a lighting circuit for lighting the discharge lamp, the lighting circuit being connected to the discharge lamp, wherein the discharge lamp includes a conductor at least partially surrounding the electrode, and the lighting circuit provides a potential for the conductor that is higher than an average potential of the electrode.

Abstract: An electronic ballast (300) for powering at least one gas discharge lamp (10) includes an inverter (400), an output circuit (700), a lamp fault detection circuit (800), and an inverter control circuit (500). Ballast (300) operates according to an inverter control method (100) that includes repeating a filament preheating step and a frequency shifting step up to a predetermined number of times in order to facilitate lamp ignition under low-temperature conditions and to verify the legitimacy of a lamp fault. Inverter control circuit (500) is well-suited for implementation as a custom integrated circuit. Ballast (300) optionally includes an overcurrent detection circuit (820') with an adjustable lamp fault detection threshold that provides decreased sensitivity during lamp starting and enhanced protection after lamp ignition.

Abstract: A power control of an AC-operated, high-pressure gas discharge lamp, particularly in a motor vehicle, including a bridge circuit in which two controlled switching transistors are disposed in at least one branch, and in which the high-pressure gas discharge lamp is supplied with ignition and/or burning energy by way of the bridge branch provides that the switching transistors switch the current in the form of pulse packets, with the individual pulse packets respectively containing a certain number of high-frequency pulses; switching is effected with as little loss as possible in the zero crossings of the current; and regulation for maintaining a certain power of the high-pressure gas discharge lamp is effected through continuous averaging over a predetermined interval (44, 45) of the supplied power packets.

Abstract: A ballast for powering a high intensity discharge lamp including an ignitor and a resonant circuit. Ignition pulses produced by the ignitor are added to a boosted low frequency voltage produced by the circuit operating near its resonant frequency during start up of the lamp. The circuit is disabled after a predetermined period of time has elapsed following ignition of the lamp. Application of the signal precedes application of the ignitor pulses to the lamp. Disablement of the circuit can render the ignitor inoperable.

Abstract: A ballast for a high intensity discharge lamp which detects the onset of acoustic resonance instability by detecting an asymmetry in a signal which is otherwise symmetric in the absence of such instability. The AC supply ripple voltage, which is normally present in the lamp current, exhibits symmetry in the absence of acoustic resonance, and becomes substantially asymmetric at the onset of acoustic resonance. By measuring the duration of each half cycle in the ripple voltage, an asymmetry in the ripple voltage can be easily and rapidly detected, and the operating frequency of the lamp current is changed before the resonance produces visually apparent flicker.

Abstract: A microprocessor controlled, electronic ballast operates a lamp at nominal settings and shifts the operation of the ballast away from nominal settings to reduce interference. The shift is randomized by a test--flip--?shift! routine that prevents all ballasts from attempting the same correction at the same time. On DC input voltage, the frequency of the boost controller is varied to reduce EMI. The ballast operates in bands according to the input voltage. Some bands correspond to full brightness, some to a fixed amount of dimming, and some to a variable amount of dimming. In the event of an abrupt change in load, the microprocessor changes the frequency of the inverter, thereby reducing output power and gradually unloading the boost circuit and maintaining power to the microprocessor.