WO2008135938A2 - Procédé et circuit pour fonctionnement pulsé d'une lampe fluorescente - Google Patents

Procédé et circuit pour fonctionnement pulsé d'une lampe fluorescente Download PDF

Info

Publication number
WO2008135938A2
WO2008135938A2 PCT/IB2008/051720 IB2008051720W WO2008135938A2 WO 2008135938 A2 WO2008135938 A2 WO 2008135938A2 IB 2008051720 W IB2008051720 W IB 2008051720W WO 2008135938 A2 WO2008135938 A2 WO 2008135938A2
Authority
WO
WIPO (PCT)
Prior art keywords
lamp
frequency
power signal
current
reference source
Prior art date
Application number
PCT/IB2008/051720
Other languages
English (en)
Other versions
WO2008135938A3 (fr
Inventor
Arnold W. Buij
Marcel Beij
Alexander A. C. Van Der Zande
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2008135938A2 publication Critical patent/WO2008135938A2/fr
Publication of WO2008135938A3 publication Critical patent/WO2008135938A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/295—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously
    • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
    • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
    • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation

Definitions

  • the invention relates to a method and circuit for pulsed operation of a fluorescent lamp, a ballast comprising such circuit and an assembly of such circuit and such fluorescent lamp.
  • US 5 907 222 discloses a controller for driving a fluorescent lamp.
  • the controller comprises an arc current regulator and a filament current regulator.
  • a separate filament current regulator is provided which provides for filament current to heat the electrodes of the lamp, and a separate arc current regulator to control an arc current as well as a voltage over the lamp.
  • An object of the invention is to control heating of the fluorescent lamp electrodes as well as ignition and arc current of the lamp, by a simple control circuit.
  • the above object may be achieved by a method for pulsed operation of a fluorescent lamp, the method comprising: providing the lamp via a network having a frequency dependent transfer function, with a power signal; controlling during a heating part of a pulse repetition time period a frequency of the power signal to be in a first frequency band to provide an electrode current to the lamp to heat an electrode of the lamp; and controlling during an operating part of the pulse repetition time period the frequency of the power signal to be in a second frequency band to ignite the lamp and to provide arc current and electrode current to the lamp.
  • the above object may be achieved by a circuit for pulsed operation of a fluorescent lamp, the circuit comprising: a power signal generator for generating a power signal to power the lamp, - a network having a frequency dependent transfer function, the network being connected to the power signal generator and for providing the power signal to the lamp; and a lamp controller for driving the power signal generator, the lamp controller having a setting input for receiving a setting input signal and being arranged for controlling when the setting input is at a first level, the power signal generator to set a frequency of the power signal in a first frequency band to provide an electrode current to the lamp to heat an electrode of the lamp; and controlling when the setting input is at a second level, the power signal generator to set the frequency of the power signal in a second frequency band to ignite the lamp and to provide arc current and electrode current to the lamp.
  • the lamp driving frequency will be set to be in a first frequency band and in a second frequency band.
  • a voltage over the lamp will be relatively low, due to the frequency dependency of the resonance network.
  • an arc in the lamp will not be maintained, and therefore, the lamp will turn off.
  • Electrical current flowing via the network through the electrodes will only heat the electrodes.
  • the frequency is brought towards the second frequency band, the voltage over the lamp will increase, which will lead to an ignition of the lamp.
  • the lamp will remain on during the second time period, and will be turned out at the end of the second time period when the frequency is altered, as at that moment in time the voltage over the lamp will decrease due to a change in frequency.
  • the single drive circuit enables providing a single control circuit for control of the current in the two time periods.
  • the network may comprise a resonant network such as an inductor/capacitor resonant network, the first frequency band being chosen to be outside a resonance frequency band of the resonant network, while the second frequency band being chosen to be in the resonance frequency band.
  • the resonance a significant increase of the electrical quantity (e.g. voltage) driving the lamp may be obtained, which allows a reliable ignition of the lamp when setting the second frequency band to be in the resonance frequency band.
  • the second frequency band may be below a resonance frequency band of such resonant network.
  • the network may comprise any suitable network having one or more components which show a frequency dependency, such as one of more capacitors, one of more inductors, transformers, etc.
  • a setting input may be provided, a signal at the setting input to control the frequency of the power signal to be in the first or second frequency band.
  • a reference source is set to a first output value
  • a signal representative of an electrode current flowing through the lamp is compared with the first output value of the reference source, and wherein the frequency of the power signal is adjusted based on the comparison between the signal representative of the electrode current and the first output value of the reference source.
  • the reference source is set to a second output value
  • a signal representative of the electrode current is subtracted from a signal representing a total electrical current flowing through the lamp, a result of the subtraction being compared with the second output value of the reference source, and wherein a frequency of the power signal is adjusted based on the comparison between the result of the subtraction and the second value of the reference source.
  • electrode heating may be compensated for a variation in duty cycle of the electrode heating part of the pulse cycle, to thereby e.g. keep a desired electrode temperature.
  • the controller may be formed by a simple, cost effective circuit in that the controller comprises a pair of bipolar transistors, the respective bases of the bipolar transistors being electrically connected, the emitters of the bipolar transistors being electrically connected to the reference source and to the signal representing the total electric current flowing through the lamp respectively, a collector of one of the transistors being electrically connected to an integrator or the controller.
  • the power signal generator may comprise a controlled oscillator, a frequency of the oscillator being controllable by an electrical input quantity of the oscillator, an output of the integrator being electrically connected to the controlled oscillator for providing the electrical input quantity.
  • the controller may comprise a capacitor, one terminal of which being connected to a driving side electrode of the lamp, the capacitor for providing a current there through which provides the signal representative of the heating current: the inventors have realized that an indication of the electrode heating current which also flows through the current supply electrode, can be obtained by connecting one terminal of a capacitor to the driving side electrode (i.e. the "hot" side of the lamp where a high voltage is provided by the network tot he lamp), and keeping the other terminal of the capacitor at a low voltage similar to a voltage at the other electrode of the lamp, a current through the capacitor providing an indication of the current through the electrodes of the lamp.
  • the driving side electrode i.e. the "hot" side of the lamp where a high voltage is provided by the network tot he lamp
  • the invention further comprises a ballast for driving a fluorescent lamp, the ballast comprising a circuit according to the invention. Still further, the invention comprises an assembly of a fluorescent lamp and a circuit according to the invention.
  • Fig. 1 depicts an example of a graph of the driving of the fluorescent lamp according to an embodiment of the invention
  • Fig. 2 depicts a block schematic view of a control circuit for controlling a fluorescent lamp according to an embodiment of the invention.
  • Fig. 3 depicts a simplified circuit diagram of a control circuit according to an embodiment of the invention.
  • Fig. 1 depicts a graphical view of lamp driving frequency versus time. Along a horizontal axis, time is depicted, while along a vertical axis, a lamp drive power signal PS is depicted. As illustrated in fig. 1, the lamp is driven with an alternating current power signal, a frequency of which changes over time. It is noted that also an amplitude or a voltage over the lamp may change due to the change in frequency, e.g. due to a frequency dependency of a network via which the lamp is driven, as will be explained in more detail below. It is noted that in this example, the network comprises a resonant network, as will be outlined in more detail below. As is depicted in fig.
  • the lamp driving signal in this embodiment shows a first time period Tl wherein the lamp driving signal has a first frequency (more generally speaking: wherein the lamp driving signal is in a first frequency range or band), and a second time period T2 wherein the lamp driving signal has a second frequency (more generally speaking: wherein the lamp driving signal is in a second frequency range or band).
  • the lamp driving frequency in the first time period Tl, the lamp driving frequency is above a resonance frequency of the network, while in the second time period T2, the lamp driving frequency is in a resonance frequency band of the network.
  • a voltage over the lamp will be relatively low, due to the frequency dependency of the resonance network. As a consequence of the low voltage, an arc in the lamp will not be maintained, and therefore, the lamp will turn off.
  • Tl and T2 together form pulse repetition time period T, as indicated in fig. 1.
  • resonance frequency band is to be understood as a frequency band within which the network shows some extent of resonance, e.g. 5 % or more peaking in a suitable electrical transfer characteristic thereof. As depicted in fig.
  • the network may comprise a combination of an inductor and a capacitor.
  • the network may comprise a combination of a transformer and a capacitor. Any other network may be applied too.
  • the network comprises a bypass capacitor Cr that is connected between the electrodes at opposite sides of the lamp. Heating current flowing through the electrodes is led by the bypass capacitor from a first of the electrodes to a second of the electrodes.
  • the network in fig. 3 further comprises inductor L. Cs forms a coupling capacitor, connected in series with inductor L, to allow a single ended (i.e. single supply voltage) driving of the lamp.
  • Fig. 2 shows a block schematic view of a circuit for driving fluorescent lamp
  • Power supply 10 (e.g. a mains, a mains adapter, a battery or a rectified mains) supplies electrical energy to power supply circuit 20 which provides the power signal PS to the lamp TL via network 30.
  • Power supply circuit 20 operates on the electrical power supplied to it by the power supply 10, to generate an alternating current lamp drive current at a lamp drive frequency.
  • the power supply circuit 20 may comprise a half bridge or other suitable switching element.
  • the power supply circuit 20 may comprise an oscillator to generate the frequency of the lamp drive current.
  • the oscillator may comprise a controlled oscillator, which may be controlled by lamp controller 40.
  • the lamp controller is in this example provided with a feedback signal FB representing a current through the lamp TL.
  • Controller 40 generates a control signal to control power supply circuit 20, e.g. by providing a control signal (such as a voltage) to a controlled oscillator (such as a voltage-controlled oscillator) of the power supply circuit 20.
  • the controller is further provided with a setting input S, the controller in response to a suitable signal at the setting input S and being provided with the feedback signal FB, driving the power supply circuit 20 to form a feedback control system operating the lamp.
  • a suitable signal to the setting input By supplying a suitable signal to the setting input, a frequency of the power signal provided to the lamp, can be altered, as the feedback loop will settle to a corresponding frequency in response to a corresponding signal at the setting input S.
  • the setting input S may be provided with an analogue signal to form a set-point signal, while in other embodiments, the setting input may form a switching input, to be provided with e.g. a digital or similar signal, to set an internal reference of the controller to a suitable value under control of the input signal at the setting input.
  • a suitable value under control of the input signal at the setting input.
  • in internal reference such as a reference voltage source, may be provided, an output value of which is controlled by the input signal at the setting input S, to e.g. have the reference voltage source change between different values, to thereby make the feedback control circuit settle at different frequencies.
  • the setting input may thus be provided with a signal having a first level during the first time period and a second level during the second time period, to thereby drive the lamp with a power signal having the frequency pattern as depicted in fig. 1.
  • Fig. 3 shows a more detailed view of an embodiment of the circuit according to the invention.
  • the power supply circuit as depicted in fig. 2 comprises voltage controlled oscillator VCO and a half bridge, which has been schematically indicated by Vhb.
  • the network 30 comprises inductor L, capacitor Cr to bridge the electrodes, and coupling capacitor Cs, a function of which having been described above.
  • a feedback signal is generated by series resistor R, which provides for a feedback voltage proportional to a total lamp current, i.e.
  • the controller 40 in this example comprises a comparator formed by transistors Ql, Q2, an integrator formed by capacitor Ci and current source II.
  • the reference signal is generated by voltage source V2, which is controlled by a signal to be provided at input S.
  • a signal at S is provided having a first value, and hence the reference source V2 provides a reference voltage having a corresponding value.
  • the comparator formed by transistors Ql, Q2 now compares, the voltage of the reference source with the voltage over series resistor Rs ( or more precisely, with the peaks of the voltage alternating voltage over Rs), and outputs a current to the comparator formed by capacitor Ci and current source Ii.
  • a current provided by current source Ii equals a current sourced by transistor Ql.
  • the voltage controlled oscillator is driven by the (output voltage of) the integrator, which via the feedback effect results in a frequency of oscillation which is above the resonance frequency band of the network, and consequently in a turning-off of the lamp.
  • the voltage over the series resistor Rs is thus proportional to the heating current. Therefore, a feedback control operation is now provided which controls the heating current: the comparator formed by Ql, Q2 compares the voltage over series resistor Rs with reference voltage V2, and drives the integrator and voltage controlled oscillator VCO to obtain a heating current which results in a voltage over resistor Rs which matches the momentary value of V2.
  • the driving signal at the input S provides for a different value as compared to the first time period.
  • the driving signal at driving input S may have digital levels low and high, a signal having digital low level e.g. indicating the first time period and setting the voltage source V2 to the first reference voltage value, while a signal having a high level setting the voltage source V2 to a second reference voltage value.
  • the comparator formed by Ql, Q2 will drive the integrator and therefore the voltage controlled oscillator VCO to alter (in this example: lower) the frequency of oscillation, and hence the frequency with which the lamp is driven via the network.
  • the frequency having reached the resonance frequency band of the network voltage over the lamp will increase resulting in an ignition thereof.
  • total current through the lamp i.e. a sum of the electrode current heating the electrodes of the lamp, and the arc current
  • a single control circuit controls both electrode heating current as well as arc current of the lamp.
  • a pulse repetition frequency of the lamp may be determined by a repetition frequency of the signal provided at input S, thereby allowing for a synchronization of the lamp pulses with an external source, which may be useful in many applications, e.g. an image repetition frequency of a display which is illuminated by the lamp.
  • the second time period i.e. when the lamp is ignited and on
  • the arc current instead of the sum of the arc current and the heating current.
  • this is provided by transistor Q3, capacitor Cv and resistor R3.
  • transistor Q3 is switched to a nonconducting state by a suitable value of the signal at input S, which will provide an additional signal to the input of the comparator formed by Ql and Q2.
  • a terminal of capacitor Cv is connected to an high voltage side electrode of the lamp, a voltage across a series connection of capacitor Cv and resistor R3 will be largely correspond to a voltage across capacitor Cr which is connected between the lamp electrodes, and series resistor Rs.
  • a capacitance of capacitor Cv may be chosen to be lower than a capacitance of Cr resulting in a current through Cv which is lower than the heating current.
  • the control circuit as described with reference to fig. 3 now allows a controlling of the heating current in the first (i.e. the heating) time period and a controlling of the arc current in the second (i.e. the ignition and operation of the lamp) time period with a simple, single control system.
  • the output value e.g.
  • the output voltage) of the reference source may be made variable to enable establishing a relation between pulse width of the pulsed operation of the lamp, and electrode heating current: With lower pulse widths, the electrode heating current tends to diminish due to arc current. This can be counteracted by a corresponding change of the output value of the reference source, to increase the electrode current thereby keeping electrode temperature constant. Furthermore, when the lamp is on, the output value of the reference source may be used to set the arc current. Thereby, intensity of the lamp may thus be set by a change in a duty cycle of the heating / operating cycle, and/or a change in the reference source output value to change a desired arc current.
  • An application where arc current may be changed may include scanning backlight systems with double pulse schemes where two pulses are used with different current magnitudes.

Landscapes

  • Circuit Arrangements For Discharge Lamps (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)

Abstract

L'invention concerne un circuit permettant le fonctionnement pulsé d'une lampe fluorescente, lequel comprend : - un générateur de signal de puissance permettant de générer un signal de puissance pour alimenter la lampe, - un réseau présentant une fonction de transfert dépendant de la fréquence, le réseau étant relié au générateur de signal de puissance et étant destiné à appliquer le signal de puissance à la lampe, ainsi qu'un contrôleur de lampe permettant d'attaquer le générateur de signal de puissance. Le contrôleur de lampe comporte une entrée de réglage destinée à recevoir un signal d'entrée de réglage, et il est agencé pour -commander, lorsque l'entrée de réglage est à un premier niveau, le générateur de signal de puissance afin d'établir la fréquence du signal de puissance dans une première bande de fréquences pour appliquer un courant d'électrode à la lampe afin de chauffer l'électrode de la lampe, et commander lorsque l'entrée de réglage est à un second niveau, le générateur de signal de puissance afin d'établir la fréquence du signal de puissance dans une seconde bande de fréquences afin d'amorcer la lampe et fournir un courant d'arc et un courant d'électrode à la lampe.
PCT/IB2008/051720 2007-05-08 2008-05-05 Procédé et circuit pour fonctionnement pulsé d'une lampe fluorescente WO2008135938A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07107668 2007-05-08
EP07107668.1 2007-05-08

Publications (2)

Publication Number Publication Date
WO2008135938A2 true WO2008135938A2 (fr) 2008-11-13
WO2008135938A3 WO2008135938A3 (fr) 2009-09-03

Family

ID=39800729

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2008/051720 WO2008135938A2 (fr) 2007-05-08 2008-05-05 Procédé et circuit pour fonctionnement pulsé d'une lampe fluorescente

Country Status (2)

Country Link
TW (1) TW200948203A (fr)
WO (1) WO2008135938A2 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4123187A1 (de) * 1991-07-12 1993-01-14 Tridonic Bauelemente Vorschaltgeraet zum pulsbetrieb von gasentladungslampen
US5907222A (en) * 1993-11-03 1999-05-25 Litton Systems, Inc. High efficiency backlighting system for rear illumination of electronic display devices

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4123187A1 (de) * 1991-07-12 1993-01-14 Tridonic Bauelemente Vorschaltgeraet zum pulsbetrieb von gasentladungslampen
US5907222A (en) * 1993-11-03 1999-05-25 Litton Systems, Inc. High efficiency backlighting system for rear illumination of electronic display devices

Also Published As

Publication number Publication date
TW200948203A (en) 2009-11-16
WO2008135938A3 (fr) 2009-09-03

Similar Documents

Publication Publication Date Title
US7385360B2 (en) High intensity discharge lamp control
EP1729549B1 (fr) Appareil d"eclairage a lampe de decharge haute tension et luminaire
EP1128709B1 (fr) Control de puissance de ballast pour lampe céramique à halogénure métallique
JPH02142096A (ja) 放電ランプ用電力制御回路とその作動方法
US5243261A (en) Modulated high frequency dimmer circuit with infrared suppression
JPH07245189A (ja) 低圧放電ランプの作動回路装置
WO2002104082A1 (fr) Ballast electronique pour lampe a decharge haute intensite
US5298836A (en) Power supply circuit for gas discharge lamps operating at a resonant frequency
US7569998B2 (en) Striking and open lamp regulation for CCFL controller
US7525261B2 (en) Circuit arrangement for operating a high pressure discharge lamp
US8193719B2 (en) Using pulse density modulation for controlling dimmable electronic lighting ballasts
WO2008006024A2 (fr) Amorçage et régulation en lampe allumée pour un dispositif de commande de lampe fluorescente à cathode froide (ccfl)
US6608452B1 (en) Xenon power supply
WO2002098187A1 (fr) Dispositif de regulation de puissance et appareil et procede de regulation de la puissance fournie a une lampe a decharge
WO2008135938A2 (fr) Procédé et circuit pour fonctionnement pulsé d'une lampe fluorescente
US6686702B1 (en) Transformerless xenon power supply
US20090184645A1 (en) Method and circuit for heating an electrode of a discharge lamp
EP2192821B1 (fr) Dispositif d'éclairage par lampe à décharge et accessoire d'illumination
AU2004237249B2 (en) High intensity discharge lamp control
KR20080067358A (ko) 단일의 인버터를 이용한 가스 방전 램프 구동 방법 및 회로
JP2942272B2 (ja) 放電灯点灯装置
WO2006043144A1 (fr) Commande secteur d'une sortie de puissance de charge
MXPA99000873A (es) Inversor para una lampara de descarga de gas y frecuencias variables paso a paso

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08738078

Country of ref document: EP

Kind code of ref document: A2

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 08738078

Country of ref document: EP

Kind code of ref document: A2