Abstract: For driving one or more gas discharge lamps (2) to conduct or to block at any time and at the same time, a rectangular high voltage is generated from a high DC voltage, an alternating voltage with respect to a reference voltage (V?) is generated from the rectangular voltage, the alternating voltage is supplied to first electrodes (4) of the lamps, second electrodes (6) of the lamps are selectively connected to the reference voltage, a current flowing through each lamp is stabilized (26), the alternating voltage is filtered to provide a filtered voltage, a property of the filtered voltage is measured to provide a control signal, the control signal is used to control the frequency of the rectangular voltage, and the filtering has a response characteristic which is substantially identical to a response characteristic provided by a lamp when conducting and means for said stabilizing of current flowing through the lamp.

Abstract: A drive circuit for driving a fluorescent tube lamp comprises a variable frequency oscillator generating a lamp drive frequency, a resonant drive circuit driving the lamp with the lamp drive frequency, and a control unit for driving the variable frequency of the latter under control of a synchronization signal. When a pre-heating frequency is generated by the variable frequency oscillator, the lamp is pre-heated while when an illumination drive frequency is generated, the lamp ignites and operates in its illuminated state. The control unit comprises a transition controller for at an ignition of the lamp limiting the drive frequency to an ultimate ignition frequency, and only enabling transition from the ultimate ignition frequency to the illumination drive frequency after an ignition delay time.

Abstract: The invention provides a current balancing circuit for powering a first load with a negative dynamic resistance and a second load with an essentially different negative dynamic resistance, and a transformer with such turns ratio that at least at an operating frequency impedances of the first and second windings complement the resistances of the first and the second loads, respectively, to a common value.

Abstract: The present invention provides a method and circuit for accurately controlling heating of an electrode of a discharge lamp. According to the present invention a feedback voltage is generated. The feedback voltage is representative of an electrode voltage, in particular an electrode voltage when the discharge lamp is in a non-burning state, the electrode voltage then representing a heating voltage. The feedback voltage is compared to a predetermined reference voltage, which represents a desired heating voltage. The comparator generates and outputs an error signal representing a difference between the actual feedback voltage and the reference voltage. The error signal is supplied to a power supply circuit. The power supply circuit generates the alternating supply current corresponding to the error signal such that the electrode voltage is adjusted towards the desired heating voltage.

Abstract: A gas discharge lamp driver circuit, comprising an inverter (10) of a bridge type, which has first and second input terminals connected to DC power lines (6, 8) for receiving a DC power voltage and output terminals (18) for providing a substantial rectangular power voltage, a ballast (20), which is connected to the output terminals of the inverter and to one or more lamp circuits (30), each having a gas discharge lamp (32) connected in series with a current control circuit having a high frequency semiconductor switch element (34), which receives an individual selection signal (S1, S2) from a selection circuit (36), such that an individual lamp (32) can be selected to operate. If deselected, the switch element conducts such that current is diverted to a selected switch element to thereby only ignite and operate a lamp connected to a selected switch element.

Abstract: A drive circuit for driving a fluorescent tube lamp comprises a variable frequency oscillator generating a lamp drive frequency, a resonant drive circuit driving the lamp with the lamp drive frequency, and a control unit for driving the variable frequency of the latter under control of a synchronization signal. When a pre-heating frequency is generated by the variable frequency oscillator, the lamp is pre-heated while when an illumination drive frequency is generated, the lamp ignites and operates in its illuminated state. The control unit comprises a transition controller for at an ignition of the lamp limiting the drive frequency to an ultimate ignition frequency, and only enabling transition from the ultimate ignition frequency to the illumination drive frequency after an ignition delay time.

Abstract: A back light emitter (4) of a display apparatus is supplied with alternating current (AC) bursts. An emitted light representing signal is generated from the AC bursts as supplied to the light emitter (4). The emitted light representing signal is compared with a reference signal REF to provide an error signal. A duration of the AC bursts is adjusted dependent on the error signal, such as to minimize the error signal.

Abstract: The present invention deals with a lighting control system suitable for small system configurations such as in offices and conference rooms. One or more luminaires are communicatively connected in an addressable digital bus system as well as to a unit including a processing means. In connection with installation of the device, the processing means is programmed to automatically assign a digital address to each luminaire and further to automatically identify a spatial position of each luminaire by use of light measuring cells. A relationship between the digital address and the spatial position of each luminaire is thereby provided. Furthermore, the device supports the functionality of installing pre-programmed lighting scenes suitable for the determined configuration of the luminaires as well as other factors such as the position of a window.

Abstract: For driving one or more gas discharge lamps (2) to conduct or to block at any time and at the same time, a rectangular high voltage is generated from a high DC voltage, an alternating voltage with respect to a reference voltage (V?) is generated from the rectangular voltage, the alternating voltage is supplied to first electrodes (4) of the lamps, second electrodes (6) of the lamps are selectively connected to the reference voltage, a current flowing through each lamp is stabilized (26), the alternating voltage is filtered to provide a filtered voltage, a property of the filtered voltage is measured to provide a control signal, the control signal is used to control the frequency of the rectangular voltage, and the filtering has a response characteristic which is substantially identical to a response characteristic provided by a lamp when conducting and means for said stabilizing of current flowing through the lamp.

Abstract: In an electronic ballast circuit equipped with lamp presence detection means that generate a current flowing through one of the lamp electrodes the detection means are periodically switched off. The power dissipated by the lamp presence detection means is thereby reduced.

Abstract: The present invention relates to a power control device for controlling the output power supplied to a discharge lamp operated by an electrical power supply, comprising power level determining means for determining the actual lamp power level, error determining means for determining the error between the determined lamp power level and a specified reference power level, and output power determining means for maintaining the output power level supplied by the electrical power supply to the lamp if the error falls within a specified window and for adjusting the output power level supplied by the electrical power supply to the lamp towards said reference power level if the error falls outside the specified window.

Abstract: The invention concerns a circuit arrangement for igniting and operating an electrodeless gas discharge lamp by means of a high operating frequency drive voltage, comprising a half-bridge commutator having two switching elements each having an emitter electrode and a control electrode. The said switching elements are alternately switched to a conducting state by means of a resonant control circuit, which is coupled to an oscillator via a transformer. The said resonant control circuit comprises capacitor means forming part of said oscillator and a driver stage driven by an oscillator, the driver being of the class-E type. A DC supply voltage is supplied to the driver via a current-limiting circuit. The amplitude of the high frequency drive voltage is substantially constant in a chosen frequency range.

Abstract: A ballast (1) for feeding a fluorescent lamp (9), comprising power supply means (2) for supplying a stabilised power to the lamp (9), dimming means (3) for adjusting said power, a voltmeter (5) which is capable of measuring the voltage across the lamp (9), comparator means (6) which are capable of comparing the measured voltage with a threshold value, contact breaker means (7) which are capable of interrupting the power supply to the lamp (9) when the measured voltage is higher than the threshold value for a predetermined period of time, as well as adjusting means (4) which are capable of adjusting the magnitude of the threshold value in dependence on the power.

Abstract: The present invention relates to a power control device for controlling the output power supplied to a discharge lamp operated by an electrical power supply, comprising power level determining means for determining the actual lamp power level, error determining means for determining the error between the determined lamp power level and a specified reference power level, and output power determining means for maintaining the output power level supplied by the electrical power supply to the lamp if the error falls within a specified window and for adjusting the output power level supplied by the electrical power supply to the lamp towards said reference power level if the error falls outside the specified window.

Abstract: An electronic ballast for supplying a lamp comprises a control loop for controlling the rms value of an operational parameter so as to be constant. In the control loop, the actual rms value of the parameter is generated as a linear combination of its average value and its peak value.

Abstract: In an inverter for operating a discharge lamp by means of an AC current comprising two switching elements, the effect of hard switching is counteracted by means of a snubber comprising two inductive elements and at least two diodes.

Abstract: A method of feeding a fluorescent lamp, wherein the actual power through the lamp is measured, an actual power value is determined by means of a moving weighted average of a series of most recently measured actual power values, wherein a measured actual power value is substituted with an alternative value if said measured value exceeds a predetermined maximum difference with respect to said average value, and wherein said measured actual power value is compared with a target value, and the power through the lamp is adjusted in the case of a significant difference.

Abstract: A ballast for feeding a fluorescent lamp, comprising a power supply unit controlled by an input variable, dimming means for adjusting the desired power through the lamp, and a control circuit for adapting the input variable from a starting value to a final value, the actual value through the lamp being at least substantially equal to the adjusted power value, said control circuit additionally comprising processor means capable of determining the starting value in dependence upon the adjusted power value.

Abstract: A ballast (1) for feeding a fluorescent lamp (9), comprising power supply means (2) for supplying a stabilised power to the lamp (9), dimming means (3) for adjusting said power, a voltmeter (5) which is capable of measuring the voltage across the lamp (9), comparator means (6) which are capable of comparing the measured voltage with a threshold value, contact breaker means (7) which are capable of interrupting the power supply to the lamp (9) when the measured voltage is higher than the threshold value for a predetermined period of time, as well as adjusting means (4) which are capable of adjusting the magnitude of the threshold value in dependence on the power.

Abstract: A ballast circuit for operating a discharge lamp is equipped with a timer for measuring the service life of the lamps, and with means for increasing the power supplied to the lamp as the number of burning hours increase. The decrease in efficiency associated with the increase in burning hours is compensated thereby.