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
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/40—Details of LED load circuits
  • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
• • 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
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/30—Driver circuits
  • H05B45/37—Converter circuits
• • 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
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/30—Driver circuits
  • H05B45/37—Converter circuits
  • H05B45/3725—Switched mode power supply [SMPS]
• • 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
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/60—Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• • 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
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/30—Driver circuits
  • H05B45/37—Converter circuits
  • H05B45/3725—Switched mode power supply [SMPS]
  • H05B45/39—Circuits containing inverter bridges
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
  • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Definitions

• the invention relates to an interface circuit for operating a light source by making use of a high frequency fluorescent lamp driver, and a corresponding method of operating a light source by making use of a high frequency fluorescent lamp driver.
• Fluorescent lamps are highly efficient light sources that have been in use for many years.
• the efficiency and lifetime of fluorescent lamps are particularly high when they are driven by an electronic lamp driver that supplies a high frequency lamp current with a frequency in the order of 10 kHz.
• luminaires comprising such a high frequency fluorescent lamp driver are present in homes and offices all over the world.
• alternative electrically powered light sources in the form of LEDs and OLEDs or high pressure discharge lamps have become available that have an efficiency and a lifetime that is even higher than that of a fluorescent lamp.
• the interface circuit and the light source together must emulate a fluorescent lamp, when the interface circuit and the light source are jointly connected to the lamp connection terminals and the high frequency fiuorescent lamp driver goes through the lamp operating stages: preheat, ignition and stationary operation. Furthermore, the interface circuit must convert the high frequency AC voltage supplied by the high frequency lamp driver into a DC-current that supplies the light source.
• the invention aims to provide an interface circuit and a corresponding method that is capable of emulating a fiuorescent lamp in a simple and effective way.
• an interface circuit for operating a light source is provided, equipped with
• a third string interconnecting a first terminal of the first string and a second terminal of the second string and comprising a rectifier, output terminals of said rectifier being coupled, during operation, to the light source, and a first switching element for controlling the conductive state of the third string,
• a fourth string coupled to the third string and comprising a sensor circuit, having an output terminal coupled to a control electrode of the first switching element, for sensing the amplitude of a high frequency AC voltage between the first and the second terminal and for rendering the first switching element conductive when the amplitude of the high frequency AC voltage reaches a predetermined value.
• the high frequency fluorescent lamp driver In the case that a fluorescent lamp is connected to a high frequency fluorescent lamp driver, the high frequency fluorescent lamp driver generates a high frequency voltage with a comparatively high amplitude across the fluorescent lamp during the ignition phase. When the fluorescent lamp ignites, the voltage across the lamp decreases strongly and the lamp carries a current. In reaction to the ignition (detected by the voltage drop or the presence of a lamp current), the high frequency fluorescent lamp driver changes its operation state from ignition to stationary operation by changing its frequency of operation and supplies a high frequency AC current to the lamp. In the case of an interface circuit according to the invention being connected to the high frequency fluorescent lamp driver, the sensor circuit detects the ignition voltage that has an amplitude higher than the predetermined value and renders the first switching element comprised in the third string conductive.
• the first switching element controls the conductive state of the third string.
• the voltage between the first and second terminal drops and the light source starts carrying current.
• the high frequency fluorescent lamp driver is thereby triggered to change its operating state from ignition to stationary operation and supplies a high frequency current to the third string, that is rectified by the rectifier and subsequently supplied to the light source.
• the ignition of the lamp is emulated in a simple and effective manner.
• the interface circuit comprises a DC-DC-converter coupled, during operation, between output terminals of the rectifier and the light source.
• the DC-DC-converter can for instance be an up-converter, a down converter or a fly-back converter. Such converters are well known in the art and need not be further discussed.
• the DC-DC- converter converts the voltage across the third string, that approximately equals the voltage across a burning fluorescent lamp, into a voltage that matches the voltage across the light source when it carries current.
• the light source need not be constructed such that, in operation, the voltage across it exactly matches the voltage across a burning fluorescent lamp.
• the light source is a high pressure discharge lamp
• a commutator such as a full bridge between the DC-DC-converter and the light source to commutate the DC-current supplied by the DC-DC-converter.
• the interface circuit needs to be equipped with, for instance, a separate igniter.
• Full bridge commutator circuits and igniter circuits are well known in the art and need not be further discussed.
• the interface circuit comprises a capacitor that, during operation, shunts the light source.
• the capacitor By virtue of the capacitor, the amplitude of the current through the light source changes less during a period of the high frequency current generated by the high frequency fluorescent lamp driver, so that the same is true for the light output of the light source.
• the interface circuit according to the invention is equipped with a fifth string connected in parallel to the third string and comprising an impedance and a further switching element having its control electrode coupled to an output terminal of the sensor circuit.
• the interface circuit may be equipped with a fifth string comprising an impedance and a further switching element and being coupled between output terminals of the rectifier comprised in the third string. Also in this case, a control electrode of the further switching element is coupled to an output terminal of the sensor circuit.
• the interface circuit may be equipped with a fifth string coupled between input terminals of the rectifier comprised in the first string and comprising an impedance.
• the impedance will carry current during operation of the light source. Since the high frequency fluorescent lamp driver acts as a current source, the impedance lowers the current through the light source and thereby also the amount of power consumed by the light source. A proper choice of the impedance value thus enables a proper match to be achieved between the power that the LED-array is designed to consume and the power that the high frequency fluorescent lamp driver is designed to supply. Instabilities are thereby avoided.
• the impedance may be a resistor. However, a reactive element, more in particular a capacitor, is preferred to minimize power dissipation.
• a method of operating a light source making use of an electronic fluorescent lamp driver comprising the steps of
• the method further comprises the steps of
• the light source is preferably one of the group formed by LED, OLED and high pressure discharge lamp.
• FIG. 1-6 show embodiments of an interface circuit according to the invention with a light source connected thereto.
• the terminals 1 are terminals comprised in a high frequency fluorescent lamp driver.
• Cr and Lr are a DC-blocking capacitor and a resonant choke, respectively, that are part of the high frequency fluorescent lamp driver.
• Reference numerals 7a and 7b are a first pair of input terminals and a second pair of input terminals, respectively, of the interface circuit, that are connected to lamp connection terminals of the high frequency fluorescent lamp driver.
• Reference numeral 5 a is a first string interconnecting the first pair of input terminals 7a.
• Reference numeral 5b is a second string interconnecting the second pair of input terminals. Both strings comprise a series arrangement of two resistors, each having a resistance equal to half the resistance (Rf/2) of a filament of a fluorescent lamp.
• Capacitor Cp connects an input terminal of the first pair to an input terminal of the second pair. Capacitor Cp is also part of the high frequency fluorescent lamp driver.
• a common terminal of the resistors comprised in the first string forms a first terminal Tl of the first string and a common terminal of the resistors comprised in the second string forms a second terminal T2.
• the first and the second terminal are interconnected by a third string comprising a first switching element 11 and a circuit part 9 that comprises a rectifier.
• Circuit part 9 is coupled to light source 10.
• Light source 10 may be an array of LEDs or OLEDs or a high pressure discharge lamp.
• circuit part 9 may comprise additional circuitry such as a DC-DC-converter that, during operation, is coupled between the rectifier and the light source 10.
• the first terminal Tl and the second terminal T2 are also interconnected by means of a fourth string comprising a sensor circuit 8, having an output terminal coupled to a control electrode of the first switching element 11 , for sensing the amplitude of the high frequency AC voltage between the first and second terminal and for rendering the first switching element conductive when the amplitude of the high frequency AC voltage reaches a predetermined value.
• Input terminals 7a and 7b, first string 5a, second string 5b, first switching element 11, circuit part 9 and sensor circuit 8 together form an interface circuit 6 for operating a light source.
• the lamp driver When the high frequency fluorescent lamp driver is switched on, the lamp driver enters a first operational state, normally referred to as "preheat", during which a preheat current is generated that flows through the filaments of a connected fluorescent lamp to preheat the electrodes. During this preheat state, the voltage across the lamp is maintained at a comparatively low value to prevent ignition of the lamp. Both the lamp voltage and the preheat current are determined by the operating frequency of the high frequency fluorescent lamp driver. In the case that not a fluorescent lamp but the interface circuit shown in Fig. 1 is connected to the lamp connection terminals, the preheat current flows through the first string, capacitor Cp and the second string. The first and second string thus emulate the filaments of a fluorescent lamp.
• a second operational state "ignition” is entered.
• the operating frequency is adjusted to a value such that an ignition voltage with a comparatively high amplitude is present across the lamp. In the case that the lamp ignites under the influence of this ignition voltage, the voltage across the lamp drops and the lamp starts carrying current.
• a third operational stage “stationary operation” is entered. During this stage, the operating frequency is adjusted such that the lamp is supplied with a current that substantially equals the nominal lamp current. In the case that not a fluorescent lamp but the interface circuit shown in Fig.
• the detector circuit detects that the voltage across the lamp is higher than the predetermined value and renders the first switching element conductive. As a consequence, the voltage across the third string drops and the third string starts carrying current. This is detected by the control circuitry of the high frequency fluorescent lamp driver and the third operational stage "stationary operation" is entered. During this operational stage, a current substantially equal to the nominal lamp current flows through the third string. This current is rectified by the rectifier and supplied directly or via a DC-DC-converter to the light source.
• the embodiment in Fig. 1 comprises a fifth string connected in parallel with the third string and comprising an impedance 22 and a further switching element 21.
• the further switching element is rendered conductive at the same time as the first switching element, so that not only the third string but also the fifth string start carrying current.
• the impedance 22 is dimensioned such that the sum of the current through the third string and the current through the fifth string approximately equals the current through the fluorescent lamp that the high frequency fluorescent lamp driver is designed for. In this way, the interface circuit provides a good emulation of the fluorescent lamp also during stationary operation. As a consequence, the light source operation is stable.
• the embodiment shown in Fig. 3 also comprises a fifth string.
• the fifth string comprises an impedance 22 and is connected between input terminals of the rectifier.
• both the light source 10 and the impedance 22 carry current.
• the impedance 22 is dimensioned such that the sum of the current through the third string and the current through the fifth string approximately equals the current through the fluorescent lamp that the high frequency fluorescent lamp driver is designed for. It is remarked that in the embodiment shown in Fig. 3, sensor circuit 8 can also be connected in parallel with the first switching element 11.
• the impedance 22 carries an AC-current during operation.
• impedance 22 is preferably a capacitor.
• first switching element 11 in the embodiments shown in Fig. 1 to Fig. 3 is a bidirectional switch.
• the further switching element in the embodiment shown in Fig. 2 is also a bidirectional switch.
• the first and further switching elements comprised in the embodiments shown in Fig. 4 to Fig. 6 are unidirectional switching elements.
• Reference numeral 31 is a rectifier in the form of a diode bridge.
• a LED array 10 is shunted by a capacitor CI and connected in series with a first switching element 11 between output terminals of the diode bridge 31.
• the output terminals of the diode bridge are also interconnected by means of a fourth string comprising a sensor circuit 8, of which an output is coupled to a control electrode of the first switching element 11.
• the fifth string comprises a rectifier 41 and a series arrangement of an impedance 22 and a further switching element 21, connected to output terminals of rectifier 41.
• a control electrode of further switching element 21 is connected to the output of sensor circuit 8.
• sensor circuit 8 senses a voltage amplitude higher than the predetermined value, it renders the first switch 11 and the further switch 21 conductive.
• LED-array 10, impedance 22 and both switching elements 11 and 21 carry current.
• Impedance 22 is dimensioned such that the sum of the currents through the third and fifth string match the lamp current of the fluorescent lamp that the high frequency fluorescent lamp driver is designed for.
• impedance 22 carries a DC-current and can be implemented as an ohmic resistor.
• the embodiment shown in Fig. 5 differs from that shown in Fig. 4 in that the rectifier 41 is dispensed with and the series arrangement of impedance 22 and further switching element 21 forms a fifth string that interconnects the output terminals of the rectifier 31.
• the control electrode of the further switching element 21 is connected to an output terminal of sensor circuit 8.
• sensor circuit 8 senses a voltage amplitude higher than the predetermined value, it renders the first switch 11 and the further switch 21 conductive.
• LED-array 10, impedance 22 and both switching elements 11 and 21 carry current.
• Impedance 22 is dimensioned such that the sum of the currents through the third and the fifth string match the lamp current of the fluorescent lamp that the high frequency fluorescent lamp driver is designed for. Also in the embodiment shown in Fig. 5, impedance 22 carries a DC-current and can thus be implemented as a resistor.
• the embodiment shown in Fig. 6 differs from that shown in Fig. 4 in that the impedance 22 is connected between first terminal Tl and the rectifier 41.
• the output terminals of the rectifier are connected by means of the further switching element 21.
• the operation of the embodiment shown in Fig. 6 is very similar to that shown in Fig. 4 and that shown in Fig. 5.
• the only important difference is that impedance 22 carries an AC- current instead of a DC-current during operation.
• the impedance 22 is preferably implemented as a capacitor.

Landscapes

• Circuit Arrangement For Electric Light Sources In General (AREA)
• Circuit Arrangements For Discharge Lamps (AREA)
• Electroluminescent Light Sources (AREA)
• Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (5)

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Citations (7)

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• 2012
  • 2012-03-27 EP EP19209235.1A patent/EP3641502B1/en active Active
  • 2012-03-27 US US14/008,580 patent/US9301354B2/en active Active
  • 2012-03-27 JP JP2014501761A patent/JP5952892B2/ja active Active
  • 2012-03-27 CN CN201280016137.5A patent/CN103477710B/zh active Active
  • 2012-03-27 ES ES19209235T patent/ES2985531T3/es active Active
  • 2012-03-27 WO PCT/IB2012/051446 patent/WO2012131573A1/en not_active Ceased
  • 2012-03-27 BR BR112013024724A patent/BR112013024724A2/pt not_active Application Discontinuation
  • 2012-03-27 RU RU2013148126/07A patent/RU2604636C2/ru active
  • 2012-03-27 EP EP12715184.3A patent/EP2692208B1/en active Active

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