Abstract: To provide a discharge lamp ignition device to light high-intensity discharge lamps in which, during alternating current ignition, the fluctuation of luminous flux on the reversal of polarity of the voltage impressed on the lamp is minimized and in which steady lighting characteristics of the discharge at startup are secured, a discharge lamp ignition device has a capacitor Ch connected to a transformer Th and an intermittent voltage impression arrangement Uj to drive voltage impression on the primary winding Ph, with the secondary winding Sh of the transformer Th constituted so that the voltage generated in the secondary winding Sh can be impressed overlapping the output voltage of an inverter Ui between the electrodes of the discharge lamp Ld by interposing it in the path connecting the output of the inverter Ui and the electrode for the main discharge of the discharge lamp Ld.

Abstract: A driving device for driving a light source module (32) includes a switch circuit (30), a transformer circuit (31), a voltage sensing circuit (34), a current sensing circuit (35), and a PWM controller (33). The switch circuit converts a received direct current (DC) power signal to an alternating current (AC) signal. The transformer circuit converts the AC signal to an appropriate signal to drive the light source module. The voltage sensing circuit receives the DC power signal and senses a voltage level of the DC power signal. The current sensing circuit receives the DC power signal and senses a current level of the DC power signal. The PWM controller controls the AC signal output from the switch circuit according to the sensed voltage and current levels.

Abstract: A lamp current balancing device comprises an electronic power switch, a transformer, a current transformer and a pulse width modulation (PWM) IC; the transformer having a primary side connected to the electronic power switch and both ends of a secondary side connected to one end of each one of two lamps respectively, with another end of each one of the two lamps connecting to one end of a primary side of the current transformer respectively, the PWM IC being coupled between a secondary side of the current transformer and the electronic power switch; since the two lamps being cascaded in series with a same current flowing through them, thus providing current balancing capability, furthermore, the current transformer being used to detect an operating current of the lamps and to feed back the operating current to the PWM IC, the PWM IC receiving and processing the operating current to obtain a control signal, then outputting the control signal to the electronic power switch to control a pulse width outputted by

Abstract: A method of matching the brightness of a plurality of lamps driven by an AC drive current may comprise the steps of: selecting a first one of said lamps having a lowest brightness; and reducing the AC drive current in a second lamp periodically so as to reduce the brightness of the second lamp to match that of the first lamp. According to another embodiment, a reference brightness may be selected, or optionally a reference AC current level, and the method may reduce the drive current periodically so as to set the lamp brightness in relation to the reference brightness or optionally the reference AC current level. A circuit for driving a lamp with controllable brightness may comprise: a drive circuit for supplying an AC drive current to the lamp; and a reducing circuit, advantageously comprised in an IC, for reducing the AC drive current in the lamp periodically to set the AC drive current in the lamp to match a reference.

Abstract: The invention describes a multiple lamp balance transformer and a drive circuit. The multiple lamp balance transformer has two magnetic cores with a closed magnetic flux path and two coils wound around the closed magnetic flux path. The two coils have the same number of windings. The impedance property of the coil and Lenz's Law are used to balance the operating current of the lamps connected to the coils. The drive circuit has a multiple lamp balance transformer connected to several lamps, and a boost transformer uses a controller to supply the current and voltage to the lamps. A current detect/protect circuit connected to the coils and the controller detects the current passing through the coils and converts the operating current of the lamp into a voltage to be sent to the controller, so that the controller controls and provides sufficient power to the lamps.

Abstract: A discharge lamp driving circuit includes an inverter, a ballast capacitor, a discharge lamp, and a lamp current detecting circuit. The inverter converts a DC voltage into an AC voltage with high frequency to output the AC voltage to an output port based on a pulse width modulation control signal. The lamp current detecting circuit outputs a first voltage signal and a second voltage signal according to a voltage across the ballast capacitor to generate a lamp current sensing voltage that is proportional to a lamp current flowing through the discharge lamp. The pulse width modulation control signal has a width varying with amplitude of the lamp current so that the lamp current may be accurately detected.

Abstract: A driving device for driving a light source module (32) includes a first power stage circuit (30) and a first transformer circuit (31). The first transformer circuit is connected to the first power stage circuit, including a first transformer (T31), a second transformer (T32), a third transformer (T33), and a fourth transformer (T34). First inputs of primary windings of the first transformer and the fourth transformer, second inputs of primary windings of the second transformer and the third transformer are jointly connected to a positive output of the first power stage circuit, and second inputs of primary windings of the first transformer and the fourth transformer, first inputs of primary windings of the second transformer and the third transformer are jointly connected to a negative output of the first power stage circuit.

Abstract: An electronic ballast for a gas discharge lamp includes an adjustable constant current source circuit adapted to convert a direct current input to provide an initial start current and a variably controlled constant current. A coupling transformer circuit is connected to the adjustable constant current source and adapted to couple the initial start current to the gas discharge lamp to provide a corresponding start voltage approximately equal to a strike voltage of the gas discharge lamp and to convert the variably controlled constant current to a square wave current to power the gas discharge lamp thereafter. A current sense circuit is adapted to sense an operating current at the coupling transformer and to provide corresponding current sense information to the adjustable constant current source, wherein said current sense information is used to vary the variably controlled constant current.

Abstract: A method for stabilizing brightness of a cold cathode fluorescent lamp includes receiving currents from two ends of the cold cathode fluorescent lamp and providing a current for the cold cathode fluorescent lamp according to a lower current of the currents received from the two ends of the cold cathode fluorescent lamp.

Abstract: A circuit for operating high-pressure discharge lamps, wherein a voltage transformer for power supply to a loading circuit includes a connection for the high-pressure discharge lamp (La) and for the secondary winding (L1b) of an ignition transformer (T1) for an impulse ignition system for igniting a gaseous discharge in the high-pressure discharge lamp. The loading circuit includes at least one capacitor (C1) serially arranged with the secondary winding (L1b) of the ignition transformer (T1) when the impulse ignition system is reconnected, the capacity of the capacitor (C1) being selected in such away that the capacitor (C1) substantially forms a bridging for ignition impulses generated by the impulse ignition device in such a way that after ignition of the gaseous discharge in the high-pressure discharge lamp (La), at least one partial compensation of the ignition transformer (T1) is produced when the lamp current passes through the secondary winding (L1b).

Abstract: A ballast (100) for powering at least one gas discharge lamp (30) at two selectable light levels includes a sensing transformer (120) and a detector circuit (200). Detector circuit (200) provides an output voltage that is dependent on the states of two on-off switches (S1,S2) interposed between the ballast (100) and a conventional AC source (20). The output voltage of the detector circuit (200) is used to control the illumination level of the lamp (30).

Abstract: In a discharge lamp lighting apparatus to light two discharge lamps, one terminal of the secondary side of a step-up transformer is connected, via each of two variable inductance elements, to one terminal of each of the two discharge lamps, the other terminal of each of the two discharge lamp is connected to one lamp current detecting unit connected to a lamp current control circuit, a switch is provided at the previous step of the lamp current control circuit, an output signal from one phase adjusting circuit is connected, via the switch, to the connection portion of the lamp current detecting unit and the lamp current control circuit, and the inductance of each variable inductance element is varied by an output signal which is sent from the lamp current control circuit, and which has a phase shifted from others, whereby the lamp current flowing through each discharge lamp is controlled.

Abstract: An electronic ballast for a lamp (16) having an input circuit (10) having a connection to a voltage supply, an output circuit (14) having a connection for the lamp (16), and a voltage converter apparatus (12), which is arranged between the input and the output circuit (10, 14), the voltage converter apparatus including an input capacitor (C1) and an output capacitor (C2), between which a switching apparatus (T1) and a freewheeling diode (D1) as well as at least one damping element (L2), at least one trapezoidal capacitor (C3) and an inductance (L1) are arranged, the voltage converter apparatus (12) being designed to carry out commutation, in each case a main circuit being defined by the current flow prior to and following commutation, at least one damping element (L2) and at least one trapezoidal capacitor (L2) being connected in series, and such a series circuit being arranged in a secondary circuit.

Abstract: An apparatus and method for driving a lamp are provided. In one embodiment, an inverter having four switching elements is split into two inverter arms that are deployed at separate terminals of a floating lamp structure to achieve even light output. A controller drives both inverter arms such that power switching lines do not cross the floating lamp structure. In one embodiment, the controller adjusts the brightness of the lamp structure by adjusting the phase difference between outputs of a first inverter arm relative to a second inverter arm. In one embodiment, the controller adjusts the brightness by symmetrically pulse width modulating the outputs of the first inverter arm and the second inverter arm.

Abstract: An efficient and flexible current-mode driver delivers power to one or more light sources in a backlight system. In one application, the current-mode driver is configured as an inverter with an input current regulator, a non-resonant polarity-switching network, and a closely-coupled output transformer. The input current regulator can output a regulated current source in a variety of programmable wave shapes. The current-mode driver may further include a rectifier circuit and a second polarity-switching network between the closely-coupled output transformer and a lamp load. In another application, the current-mode driver delivers power to a plurality of light sources in substantially one polarity by providing a regulated current to a network of time-sharing semiconductor switches coupled in series with different light sources coupled across each semiconductor switch.

Abstract: Switching elements S1, S2 connected in series are provided on the secondary side of a pulse transformer T to which an input voltage is supplied from a DC power supply E. On the primary side of the pulse transformer T, switching element S3, S4 are provided, and a regenerating unit RG including a current limiting inductor L1 and a regenerating inductor L2 is connected to the DC power supply E and the primary side of the pulse transformer T. A current is limited by the inductor L1 during an on time of the element S3 or S4, whilst a current is regeneratively supplied to the DC power supply E by using the inductor L2 during the off time of the elements S3, S4.

Abstract: The present invention discloses a push-pull inverter circuit comprising a transformer with a power output end coupled to a load and two power input ends, and a power driver unit is connected between the two power output ends and a power supply unit, and the power driver unit receives a power signal and outputs two sets of drive signals having same frequency and opposite phase to the two power input ends as to constitute an inverter circuit that adopts a push-pull voltage drive signal to drive the transformer to operate and improve the output power of the transformer.

Abstract: The invention relates to a converter circuit with coupled inductances L1 and L2 which have a core K having an air gap S which is asymmetrical with respect to the inductances.

Abstract: A ballast for at least one lamp at least two switches arranged in series; a control circuit for alternately opening and closing the two switches; a connection for applying a supply voltage to the two switches; a resonant starting circuit coupled on the input side to the junction point between the two switches and on the output side to a first connection for the lamp, the resonant starting circuit having a resonant inductance arranged in series with the junction point between the two switches (S1, S2) and the first connection for the lamp, and a resonant capacitance arranged for alternating current purposes in parallel with the first and second connections for the lamp, a first braking inductance which, for alternating current purposes, is firstly arranged in series with the first of the two connections for the lamp and secondly in parallel with the resonant capacitance.

Abstract: An electronic ballast (10) for powering a lamp load comprising an even number of gas discharge lamps (30,32, . . . ,34,36) includes an inverter (300), an output circuit (400), and a protection circuit (500). During operation, protection circuit (500) disables the inverter (300) in response to an end-of-lamp-life condition that is characterized by a predetermined imbalance in the operating current provided to each of the even number of lamps. Preferably, the output circuit (400) includes a current-sensing transformer (480) for detecting the predetermined imbalance, and the protection circuit (500) includes a silicon-controlled rectifier (530) for disabling the inverter (300).

Abstract: The present invention provides a high frequency electronic ballast with rail voltage switching which adjusts the DC rail voltage output (208) to account for different voltages of mains power (210), improving efficiency. The rail voltage switching comprises a mains power supply (200) providing mains power (210) and a mains voltage signal (212); a ballast microcontroller (206) responsive to the mains voltage signal (212) and generating a power factor correction (PFC) voltage signal (214); and a converter (204) operably connected to the mains power supply (200) and responsive to the PFC voltage signal (214) to generate a DC rail voltage output (208). For an embodiment using power factor control, the converter (204) comprises a coil (218), power factor correction (224), a switch (220), and a rectifier (222).

Abstract: A resonant circuit includes a clamped feedback signal for providing a load current signal envelope that substantially tracks an input signal. With this arrangement, circuit efficiency is enhanced by the linear operation of the circuit.

Abstract: The invention relates to an electronic ballast for a dielectrically impeded discharge lamp (L), which ballast has an inductor (W1, W2, W3) with a winding (W2) that can be short-circuited.

Abstract: A lamp lighting apparatus has a discharge drive circuit for supplying discharge current to the lamp, a voltage conversion circuit for boosting voltage from DC power and supplying the boosted voltage to the discharge drive circuit, and an arc discharge detecting circuit for detecting that a state of discharge of the lamp changes to arc discharge, and outputting an arc discharge transition signal to the voltage conversion circuit, wherein when the voltage conversion circuit receives the arc discharge transition signal which shows that the transition to the arc discharge does not take place, the voltage conversion circuit supplies a first voltage or higher to the discharge drive circuit, and when the voltage conversion circuit receives the arc discharge transition signal which shows that the transition to the arc discharge takes place, the voltage conversion circuit supplies a second voltage lower than the first voltage to the discharge drive circuit.

Abstract: A ballast circuit includes an output isolation transformer having a primary winding and first and second secondary terminals coupled to opposing ballast lamp terminals for additively applying potentials on the primary winding and the first and second secondary winding potentials across the lamp and limiting ground fault voltages. The circuit can include a closed loop feedback path from a load to a feedback rectifier for promoting linear operation of an input rectifier.

Abstract: An ideal filament preheat technique in flourescence lamp is supplied by an adjusting circuit, an output circuit and a control circuit. At the filament preheating stage, an adequate preheating voltage is provided for the filament of the lamp tube, and the voltage cross over both ends of the lamp tube is reduced, thereby preventing glow current in preheating. When the preheating stage is finished and starting stage begins, the voltage between both ends of the lamp tube increases simultaneously, and then reaches a break-down voltage of the lamp tube, then the lamp tube is lit to enter a normal operation stage, the preheating voltage of the filament is cutoff under the control circuit, so as to save the filament power consumption. Therefore, the efficiency of the electronic ballast is improved, and the operation life of the flourescent lamp tube is extended.

Abstract: The invention relates to a switching arrangement for operating at least one LED, which switching arrangement is provided with input terminals (1, 2) for connecting a supply source, —output terminals (3, 4) for connecting the LED to be operated, —a first series circuit (I) between one of the input terminals (1) and one of the output terminals (3), including at least a self-inductance (L), a capacitor (C) and a diode (D), —a second series circuit (II) between the input terminals, including at least the self-inductance (L) and a switching element (S) which is alternately switched to a conducting state and a non-conducting state at a high frequency, —a third series circuit (III) between the output terminals, including the diode and an inductive winding (SW). According to the invention, the inductive winding forms a first winding (SW1) of a transformer (T) which has a second winding (SW2) that forms part of the first series circuit and which also has a connection point with the first winding.

Abstract: The invention concerns a method for powering a discharge lamp with a switching power supply. Said method is characterised in that it consists in: applying a voltage firing the lamp, then after the lamp has been energized, applying a lower service voltage to the firing voltage. The firing and service voltages can be generated by using a resonant circuit at the terminals of which a chopped voltage is applied with different frequencies. The invention also concerns a light source comprising a discharge lamp and a switching power supply. Said light source can be equipped with devices for measuring several parameters, such as power, light intensity or the amplitude of vibrations. The invention is useful for producing public lighting.

Abstract: A piezoelectric ceramic light starter, which includes a power switch, a piezoelectric transformer, and a frequency tracking unit, is disclosed. The power switch connected to a pulse width modulated (PWM) harmonic signal output terminal closes when the PWM harmonic signal is in its positive period, and opens when which signal is in negative period. The piezoelectric transformer has the input terminal of its first-level coil connected to the power switch. The output terminal of the first-level coil generates a high-frequency AC signal to drive a cold cathode fluorescent light (CCFL). The frequency tracking unit is coupled to the output terminal of the CCFL. When the light starter starts, a first frequency is obtained when the CCFL is lighted and a second frequency is obtained when the CCFL is turned off. The PWM harmonic signal uses the average of the first frequency and the second frequency as the basis for output.

Abstract: An energy-saving light marking device with low power consumption including a head transformer (10) where the primary winding (12) is powered by an alternating current source and several marking lamps in series (14-1 to 14-3) connected to the terminals of the secondary winding (13) of the head transformer, each of the marking lamps being a fluorescent lamp (16-1 to 16-3) powered by the secondary winding of a second transformer (18-1 to 18-3), the primary windings of all the secondary transformers of the marking lamps being connected in series between the terminals of the head transformer's secondary winding (13). The starting of each of the fluorescent lamps (16-1 to 16-3) is provided by the voltage surge generated at the terminals of the secondary winding of the secondary transformers (18-1 to 18-3) when the primary winding of the secondary transformers is powered while the lamps are not yet started.

Abstract: In a circuit arrangement and a method for generating a high voltage for example for the operation of a plasma, comprising an impedance converter and a transformer including a primary coil and a secondary coil, by which the high voltage is provided, bridging switch members are arranged in the circuit and one of the primary and the secondary coil is short-circuited when a discharge occurs until the discharge is completed.

Abstract: A constant-current regulator for high-powered airport lighting loops combined a ferroresonant transformer and a digital programmable logic device to provide a versatile, software-modifiable current control for power transfer throughout a range of about 30 kW to 50 kW with uniformly good power factor and low harmonics without switching winding taps, and without requiring oil cooling.

Abstract: A ballast for at least one electric incandescent lamp, having at least two switching elements (T1, T2) that are coupled to one another with the formation of a first tie point (VP1), a drive circuit (10) with at least one output for driving the switching elements (T1, T2) with the aid of a drive signal that has a pulse duty factor (d) and an operating frequency (fs), and with an input for a dimming signal (Ud), and a power transformer (Ü) whose primary side (L1) is coupled to the first tie point (VP1), it being possible to connect the electric incandescent lamp (LA1; LA2) to the secondary side (L2) thereof, the drive circuit (10) being designed to vary the pulse duty factor (d) and the operating frequency (fs) of the drive signal as a function of the dimming signal (Ud).

Abstract: A reliable and efficient circuit for lighting a discharge lamp is described. An inverter accepts a direct current supply voltage and outputs an alternating current lamp voltage to drive the discharge lamp at a relatively high frequency. In one embodiment, the inverter includes semiconductor switches in a full-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. In one embodiment, the inverter includes semiconductor switches in a half-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. The inverter can drive multiple discharge lamps in a parallel configuration. A bypass circuit can also be coupled across a cathode of the discharge lamp to extend the life of the discharge lamp. The bypass circuit activates when a lamp cathode wears out.

Abstract: A multi-lamp system for driving a lamp set having a first lamp and a second lamp comprises a driving circuit for converting a DC signal to an AC signal, a transformer having a primary side coupled to the driving circuit and a secondary side for outputting the AC power, and a current balance circuit coupled to the low voltage terminal of the lamp set for balancing the current values flowing through the first lamp and the second lamp. The current balance circuit comprises a magnetic core, a first winding coupled to the first lamp and a second winding coupled to the second lamp. The first winding and the second winding are wound on the magnetic core and have the same coil number.

Abstract: The invention relates to a ballast for operating at least one low-pressure discharge lamp, preferably a three- or four-lamp ballast. In order for all parallel- or series-connected low-pressure discharge lamps (L40-L43) to shine equally bright even in the case of strong dimming, the ballast according to the invention has a transformer (Tr40) for balancing the currents in the lamp branch circuits and a transformer (Tr41) for compensating the losses owing to parasitic capacitances.

Abstract: A discharge lamp lighting circuit includes an open-circuit protection means to protect a driving means when a discharge lamp is not lighted. The open-circuit protection means is adapted to send out to a control means a signal for limiting a current flowing in the driving means to or below a predetermined value when the tube current is equal to or lower than a first value predetermined, and a signal for sequentially increasing a current flowing in the driving means up to a rated current when the tube current is higher than the first value and also is equal to or lower than a second value predetermined, and to stop a driving signal sent from the control means when a tube current flowing in the discharge lamp has a value equal to or lower than the first value after a predetermined time.

Abstract: A method for activating an illuminator and an illuminating device. The invention uses pins on an application specific integrated circuit (ASIC) in a scanner to output pulses of different frequencies. The illuminator has different efficiencies at different frequencies, so the heat generated by the illuminator at the frequencies of inferior efficiency is used to achieve fast warm-up, and the voltage output frequency of the highest light efficiency is provided to the illuminator after warm-up. The illumination device can be designed according to the activation method. It comprises an illuminator, a pulse output unit, a driving unit and a power supply unit. The power supply unit outputs the frequency needed for the warm-up period and the frequency needed for the working period. The driving unit activates the pulse output of the pulse output unit.

Abstract: This invention relates to a power supply that integrates a rectifier/filter's circuitry and a converter's circuitry with an inverter to reduce space occupied and increase power efficiency. The power supply includes: a rectifier/filter, a DC-DC converter and a DC-AC inverter. The rectifier/filter, connected to an alternating current (AC) input terminal, converts the input AC into a direct current (DC). The DC-DC converter and the DC-AC inverter are parallel to each other with one end concurrently connected to the rectifier/filter's output and the other end respectively outputting the desired powers. As such, DC-DC converter reduces the converted DC voltage to lower DC voltages to power all circuits except for the lamp and DC-AC inverter converts the converted DC voltage into higher AC voltage output to drive the lamp.

Abstract: A lamp lighting apparatus including a voltage control section for supplying a pulse voltage whose peak value rises stepwise, and a power conversion section for converting an output of the voltage control section into a high voltage and applying the high voltage to a lamp to light the lamp and for supplying, after the lamp is lit once, a self-sustaining discharge current to the lamp.

Abstract: An ignitor disabling apparatus is provided to reliably and automatically disable a universal sodium ignitor with hot re-strike capability, or a 120 Hz pulse capability. The ignitor is configured to disable the ignitor portion of a HID lamp if the lamp fails to start. Timing operation of the disabling circuit is achieved using a power supply that ramps to a steady state to provide triggering of a timer circuit. A normally closed, solid state gating device is used for disabling the ignitor to minimize sparks. The disabling apparatus can be retrofit into an existing universal sodium ignitor.

Abstract: A constant-current regulator for high-powered airport lighting loops combined a ferroresonant transformer and a digital programmable logic device to provide a versatile, software-modifiable current control for power transfer throughout a range of about 30 kW to 50 kW with uniformly good power factor and low harmonics without switching winding taps, and without requiring oil cooling.

Abstract: A control gear for a fluorescent lamp, comprising a voltage source and an ignition and supply circuit comprising an inductive component and a capacitance. The control gear also comprises a transformer whose primary coil is connected parallel to the capacitance, and a switching element which is connected to the secondary coil of a transformer for short-circuiting it.

Abstract: A discharge-lamp illumination circuit has a DC power supply circuit, a DC-AC conversion circuit, and a control circuit for controlling a voltage from the DC power supply circuit. The DC power supply circuit has a transformer and a first switching element connected in series with a primary coil of the transformer. The activation/deactivation of the first switching element is controlled by the control signal from the control circuit. The transformer is equipped with secondary coils equal in number with the discharge lamps. Each secondary coil is equipped with a second switching element whose activation or deactivation is controlled by a signal from the control circuit. The secondary coils provide different voltages by means of control of the second switching elements.

Abstract: One of the objectives of the present invention are to provide smaller, lighter and less expensive structure in a starting device for discharge lamp for car use so as to prevent breakage due to vibrations etc . . . And another objective is to attain simultaneous electrical and structural connections between a high voltage electrode and a coil of a starting transformer. The device having the following constitution realizes the above-mentioned objectives. A starting device for a discharge lamp comprises a socket equipped with a high voltage electrode and a grounding electrode, a bobbin with a core-less structure, a starting transformer comprising a primary coil and a secondary coil wound around the bobbin. A screw electrode is arranged at the center of the end face of the bobbin. One end of the screw electrode is connected to an output terminal of the high voltage side of the secondary coil on the starting transformer.

Abstract: An electronic ballast for a low-pressure discharge lamp (LA) contains an inverter that is fed with direct voltage (UBUS) and the output of which is connected to a load circuit containing terminal contacts for the lamp (LA), a heating transformer that has a primary winding (Tp), which is connected to the output of the inverter, and a respective secondary winding (Ts1, Ts2), which is located in a heating circuit with a coil (W1, W2), for heating each of the two electrodes of the lamp (LA), and a series circuit arrangement that is connected in parallel with the load circuit and which contains the primary winding (Tp) of the heating transformer and an electronic switch arrangement (S3, S4). For the purpose of identifying the type of lamp and the state of the lamp, the currents in one of the two heating circuits and in the primary winding (Tp) of the heating transformer are measured and evaluated.

Abstract: This invention relates to dimmable electronic ballasts for particular use with fluorescent lamps.

Abstract: Abnormal states in a high-voltage cable connected to a backlight of a liquid crystal display are detected. This invention includes: a secondary winding of a transformer; a discharge tube connected to the secondary winding of the transformer; means connected to the discharge tube for detecting a tube current; means connected to the secondary winding of the transformer for detecting a transformer current; and abnormal-state detection means for comparing a value of the tube current detected by the tube current detection means with a value of the transformer current detected by the transformer current detection means and interrupting a power supply if a difference greater than a predetermined value is detected. Thus, a case of lighting delayed due to the darkness effect can also be dealt with.

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 circuit arrangement for operating a discharge lamp includes a DC-AC converter provided with a branch A having at least one switching element alternately conductive and non-conductive for generating a current of alternating polarity at a frequency f. A load branch B is coupled to the branch A and is provided with lamp connection terminals and with inductive means. A drive circuit E renders the switching element conducting and non-conducting at a frequency f. The drive circuit is provided with a branch D which includes a series circuit of further inductive means and capacitive means, and with a branch C including a variable impedance. The drive circuit is coupled to the inductive means in the load branch B, the branch D is coupled to the switching element in branch A, and the branch C is coupled to the further inductive means in branch D. Branch C also includes inductive means and the variable impedance is a variable resistor. The lamp thus can be dimmed over a wide range by a simple and inexpensive circuit.