WO2011050421A1 - Procédé et appareil améliorés permettant d'atténuer la lumière d'un dispositif d'éclairage - Google Patents

Procédé et appareil améliorés permettant d'atténuer la lumière d'un dispositif d'éclairage Download PDF

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Publication number
WO2011050421A1
WO2011050421A1 PCT/AU2010/001458 AU2010001458W WO2011050421A1 WO 2011050421 A1 WO2011050421 A1 WO 2011050421A1 AU 2010001458 W AU2010001458 W AU 2010001458W WO 2011050421 A1 WO2011050421 A1 WO 2011050421A1
Authority
WO
WIPO (PCT)
Prior art keywords
light device
electrical power
accordance
converter
current
Prior art date
Application number
PCT/AU2010/001458
Other languages
English (en)
Inventor
Corby Mo-Szu Fu
Dah Chuan Dylan Lu
Original Assignee
University Of Sydney
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
Priority claimed from AU2009905347A external-priority patent/AU2009905347A0/en
Application filed by University Of Sydney filed Critical University Of Sydney
Publication of WO2011050421A1 publication Critical patent/WO2011050421A1/fr

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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]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/375—Switched mode power supply [SMPS] using buck topology
    • 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 present invention relates to a method and apparatus for controlling illumination of a light device, and, particularly, but not exclusively, to a method and apparatus for controlling dimming of a High Power
  • HP-LED Light-Emitting Diode
  • Light devices such as Light-Emitting Diodes (LEDs) and High Power Light-Emitting Diodes (HP-LEDs) have many uses.
  • HP-LEDs are particularly attractive due to their high efficacy, robustness and fast transient response. They are used in many applications, such as screen displays, signal indicators, lighting, building decoration and many other applications.
  • Display applications for example, television and computer displays, building displays (and other signage) . Dimming may also be used for domestic lighting, torches, and other applications. Control of brightness may also be important in precision applications, such as precision flash photography and other precision applications where precise luminance is required.
  • One method of applying dimming to HP-LEDs utilizes Amplitude Modulation (AM) of the current to the HP-LED.
  • AM Amplitude Modulation
  • the magnitude of the forward current to the HP-LED is changed by adjusting resistance of the circuit providing the current to the HP-LED, using a varistor, for example. This is associated with a number of problems, however, including shift of the Correlated Colour
  • CCT Temperature
  • Pulse Width Modulation (PWM) dimming is applied by pulsing current to the HP-LED.
  • the time period (T) of the pulse governs the average current delivered to the
  • PWM can be applied by a number of methods, including periodic shutting down of a converter providing current to the HP-LED, a switch placed in series with the HP-LED to periodically block conduction, or developing converters that have an ultra- fast output transient.
  • Contrast ratio is the ratio between the minimum and maximum brightness which is available.
  • the contrast ratio with. prior art PWM dimming methods for HP-LEDs is limited because the delay inherent in the prior art methods results in ripple, particularly at high PWM frequencies and therefore variations in temperature in the HP-LED and resulting limitations to contrast ratio.
  • Prior art dimming methods are not suitable for HP-LED specialized applications such as flash for high speed cameras (which may take samples at a rate of 250,000 frames per second) and other applications.
  • Parallel dimming circuits suffer from a number of problems, however.
  • the converter in the parallel dimming circuit must be kept on during dimming, which results in continued losses and inefficiency.
  • a controller with a fast response is required for controlling the system.
  • the present invention provides a method of controlling illumination of a light device, the light device being provided with electrical power for illumination from an electrical power source via an electrical energy storage arrangement, the method comprising the steps of:
  • the step of conserving electrical energy comprises the step of creating a circuit via which current circulates via the energy storage arrangement .
  • the electrical energy storage arrangement comprises a smoothing arrangement which is arranged to smooth current to the light device.
  • Creating the circuit in an embodiment, comprises the step of short circuiting the smoothing arrangement .
  • the smoothing arrangement may be an inductor. In an embodiment, short circuiting the inductor causes the inductor to drive circulating current in the short circuit.
  • the inductor does not need to be provided with power from, for example, a power source such as a converter ⁇ It still conserves electrical energy within the inductor, sufficient to reduce delays when the electrical power is again switched to the light device (and electrical power is switched to the inductor from the source) .
  • the electrical power source comprises a converter arranged to provide electrical current to the energy storage arrangement and light device.
  • the converter is a buck converter.
  • a further step is carried out of switching the converter so no electrical power is provided by the converter.
  • the light device is an HP-LED.
  • the present invention provides an apparatus for controlling
  • illumination of a light device comprising an electrical power source for providing electrical power to the light device for illumination, an energy storage arrangement, a switching arrangement for alternately switching electrical power to the light device via the energy storage • arrangement and switching electrical power away from the light device, and
  • Figure 1 is a timing diagram for PWM of an HP-LED, using prior art PWM methods
  • Figure 2 is a circuit diagram of a circuit for applying parallel dimming to an HP-LED
  • FIG. 3 is a timing diagram for the circuit of
  • Figure 4 is a further circuit diagram of a parallel dimming circuit showing equivalent circuits for some components
  • Figure 5 is a schematic circuit diagram of an embodiment of the present invention.
  • Figure 6 is a circuit diagram illustrating an embodiment of the present invention.
  • Figure 7 is a timing diagram for the circuit of Figure 6;
  • Figure 8 is a circuit diagram of a further embodiment of the present invention.
  • Figures 9a to 9f are plots illustrating operation of a prior art parallel dimming circuit, and
  • FIGS. 10a to lOf are plots illustrating operation of an embodiment of the present invention. Detailed Description of the Embodiments
  • FIG. 5 illustrates schematically a generalized circuit for implementing a method in accordance with the present invention.
  • the circuit is arranged to control illumination of a load Lo, which in this example may be an HP-LED, which provides advantages similar to the prior art parallel dimming circuit for HP-LEDs, without many of the disadvantages .
  • the circuit comprises an electrical power source Vs, a switching device Cvtr and a diode D.
  • An energy storage device E is connected between the source Vs and the load ' Lo.
  • E is an inductor for smoothing current to the load Lo.
  • a switch Swr arrangement is utilized to pulse width modulate current to the load Lo.
  • switch Swr When switch Swr is closed, the converter Cvtr is not providing power (and no power is provided to the load Lo) .
  • Energy is conserved in the inductor E, however, as the switch Swt results in a closed circuit circulating current via the inductor E.
  • the converter does not have to provide power when the load is not receiving current, this minimizes losses in the converter and provides other advantages over a conventional parallel dimming scheme. Having the switch Swr short circuit the inductor E also provides a number of other advantages not seen in parallel dimming
  • PWM dimming of light devices such as HP-LEDs
  • the entire converter providing current may be shut down; a switch may be placed in series with the HP-LED to block the path of conduction (by opening and closing the switch to pulse width modulate the HP-LED) ; a converter may be developed that has an ultra- fast output transient.
  • Contrast ratio is defined in equation (1) below.
  • Figure 3 is a timing diagram of converter using parallel dimming with a hysteresis controller.
  • hysteresis bands are denoted as VREP! and VRE F2 and output current is bounded within the two values.
  • inductor current i L (t) is flowing through HP-LED (bold line) with average value of I L .
  • DIM signal is HI, loading experienced by converter is lowered and hence iz,(t) rushes up with
  • Figure 4 is a typical buck converter parallel dimming scheme with parasitic components
  • the scheme suffers from higher power dissipation due to power loss at sense resistor as well as other losses (such as switching loss) since the converter is never turned-off completely during the dimming period. This is done deliberately to ensure that inductor current in switching regulator never falls to zero (as depicted in Figure 3) and it is ready to supply HP-LED at any time once the parallel switch Q 2 is turned-off.
  • buck converter When buck converter is working, it has losses as given in (4) -(9), where P c , Psw, PG, PDCR, PD and P R3 represent conduction loss, switching loss, gate driving loss, inductor DC Resistance (DCR) loss, freewheeling diode loss and sense resistor loss, respectively.
  • controller asserts DIM signal
  • output current is steered to Q 2 and R s and then to ground.
  • controller needs to maintain level of inductor current to facilitate fast transient, controller must keepon running in order to achieve that. This implies during DIM interval, losses due to P c , Psw, Pa, PDCR, PD and P Rg remain active and thus lower the overall efficiency of the converter.
  • n represents number of occurrence during dimming interval .
  • Figure 9(e) In a single string the reverse current was minus 180mA, and minus 300mA was measured using two strings of HP-LEDs. Moreover, this discharge Cj also means additional power losses in the area overlapped by output voltage and output current in Figure 9 (d) . The current transients may also cause electromagnetic interference and false triggering of the controller.
  • Figure 9(f) shows an example of false triggering. Note a trigger of Qi was observed while i L stays perfectly within the hysteresis bands (dashed line) .
  • photosensor are needed if the device is required to alert user automatically, or manual inspection must be performed instead which raises maintenance cost.
  • FIG. 6 illustrates one embodiment of the present invention. In this embodiment, the idea is to benefit from low on-resistance of MOSFET switch and inductor's characteristic, which is gradual change of current upon state change. Operation of converter is described with timing diagram as shown in Figure 7.
  • Proposed converter will operate as described without any consideration under ideal conditions. In non-ideal conditions there will be on-resistance, denoted as RDS ⁇ OW in Q 2 and also 23 ⁇ 4CH from inductor L which would affect the loop used to maintain inductor current. This effect is also shown in Figure 7. Notice within interval a--b, current circulating within the loop is no longer a flat horizontal line but drops slightly (dotted line) depending on the amount of parasitic resistance on the path.
  • An example circuit can be implemented by using two serially connected MOSFET and bootstrap floating drivers for driving these switches. Schematic of an example circuit is shown in Figure 8. Resistor J? B sr provides current path for the bootstrap driver to work since the connected load has a non- linear characteristic which may prevent charging of the bootstrap capacitor if total forward voltage V F of HP-LEDs is greater than voltage of bootstrap driver (*10V) .
  • Use of two MOSFETs is to ensure flow of unidirectional current when DIM signal is set. If single MOSFET is used, current will flow throughout body diode of Q 2 when Vi node drops to ground level during freewheeling stage of buck converter, or through body diode of Q 3 when DIM is LO. But this also means double of RDSIO N ) when compared with parallel dimming scheme.
  • One of the key benefits of proposed circuit is its flexibility in selection of controller.
  • the method is capable of working on a converter that uses controller such as peak current mode and hysteresis control.
  • inductor has several additional advantages. For example, the issue of reverse recovery discussed above is avoided as there is no ground referenced path for Cj to discharge. Moreover the issue of current steering is eliminated since the sum of load resistance is now clamped by R S and in most cases its resistance is greater than R D S ⁇ O N > + 3 ⁇ 4CR « Finally, unintended short circuit of load can be detected easier as controller can simply analyse information obtained from R S and if it falls below some limit (due to reverse recovery current) then it is definite that accidental output short circuit has occurred.
  • Figure 9 (d) is around 130 mA (Label a in Figure 9(a)) whereas in Figure 10 (c) this is reduced to zero.
  • Figure 9 (c) shows the use of modified COT controller to achieve better average output. However due to
  • Figure shows delay of 75 s in regulating the output to its original state after dimming signal.
  • the correct brightness and timing may be achieved for flash.
  • the apparatus and method is not limited to
  • HP-LEDs application with HP-LEDs, but may be used with other lighting devices, such as standard LEDs, for example.
  • MOSFETs are used for the switches.
  • Other types of switching technology may be used, such as bipolar junction transistors, insulated gate bipolar transistors, and other types of switches.

Landscapes

  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

La présente invention concerne un procédé et un appareil permettant de réguler l'éclairage d'un dispositif lumineux, tel qu'une diode électroluminescente à haute puissance (HP-LED). Le courant électrique alimente la HP-LED par l'intermédiaire d'un agencement de stockage de l'énergie, tel qu'une bobine d'induction, et la quitte, alternativement. L'énergie est conservée dans la bobine d'induction grâce à un court-circuit se produisant à travers ladite bobine, alors que le courant quitte la HP-LED.
PCT/AU2010/001458 2009-11-02 2010-11-02 Procédé et appareil améliorés permettant d'atténuer la lumière d'un dispositif d'éclairage WO2011050421A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2009905347A AU2009905347A0 (en) 2009-11-02 Improved method and apparatus for dimming a lighting device
AU2009905347 2009-11-02

Publications (1)

Publication Number Publication Date
WO2011050421A1 true WO2011050421A1 (fr) 2011-05-05

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013127939A (ja) * 2011-12-19 2013-06-27 Panasonic Corp 点灯装置及びそれを用いた照明器具
WO2016030382A3 (fr) * 2014-08-26 2016-04-21 Osram Oled Gmbh Procédé pour faire fonctionner un module optoélectronique et module optoélectronique
US9883565B2 (en) 2014-08-26 2018-01-30 Osram Oled Gmbh Method for operating an optoelectronic assembly and optoelectronic assembly

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060164377A1 (en) * 2005-01-25 2006-07-27 Honeywell International, Inc. Light emitting diode driving apparatus with high power and wide dimming range
US20070222399A1 (en) * 2004-12-01 2007-09-27 Montgomery Bondy Energy saving extra-low voltage dimmer lighting system
US20080018261A1 (en) * 2006-05-01 2008-01-24 Kastner Mark A LED power supply with options for dimming

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070222399A1 (en) * 2004-12-01 2007-09-27 Montgomery Bondy Energy saving extra-low voltage dimmer lighting system
US20060164377A1 (en) * 2005-01-25 2006-07-27 Honeywell International, Inc. Light emitting diode driving apparatus with high power and wide dimming range
US20080018261A1 (en) * 2006-05-01 2008-01-24 Kastner Mark A LED power supply with options for dimming

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013127939A (ja) * 2011-12-19 2013-06-27 Panasonic Corp 点灯装置及びそれを用いた照明器具
US9320110B2 (en) 2011-12-19 2016-04-19 Panasonic Intellectual Property Management Co., Ltd. Lighting device and illumination apparatus including same
WO2016030382A3 (fr) * 2014-08-26 2016-04-21 Osram Oled Gmbh Procédé pour faire fonctionner un module optoélectronique et module optoélectronique
CN106489302A (zh) * 2014-08-26 2017-03-08 欧司朗Oled股份有限公司 用于运行光电子组件的方法和光电子组件
US9883565B2 (en) 2014-08-26 2018-01-30 Osram Oled Gmbh Method for operating an optoelectronic assembly and optoelectronic assembly
CN106489302B (zh) * 2014-08-26 2018-10-09 欧司朗Oled股份有限公司 用于运行光电子组件的方法和光电子组件
US10231311B2 (en) 2014-08-26 2019-03-12 Osram Oled Gmbh Method for operating an optoelectronic assembly and optoelectronic assembly

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