EP2249620A1 - Circuit de ballast pour circuit d'éclairage, et circuit d'éclairage incluant un circuit de ballast - Google Patents

Circuit de ballast pour circuit d'éclairage, et circuit d'éclairage incluant un circuit de ballast Download PDF

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Publication number
EP2249620A1
EP2249620A1 EP09100267A EP09100267A EP2249620A1 EP 2249620 A1 EP2249620 A1 EP 2249620A1 EP 09100267 A EP09100267 A EP 09100267A EP 09100267 A EP09100267 A EP 09100267A EP 2249620 A1 EP2249620 A1 EP 2249620A1
Authority
EP
European Patent Office
Prior art keywords
circuit
ballast
lighting
converter
ballast circuit
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP09100267A
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German (de)
English (en)
Inventor
M. Schmid
J. B. D. Kuebrich
T. A. Duerbaum
M. Weiland
G. Hoogzaad
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NXP BV
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NXP BV
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Filing date
Publication date
Application filed by NXP BV filed Critical NXP BV
Priority to EP09100267A priority Critical patent/EP2249620A1/fr
Publication of EP2249620A1 publication Critical patent/EP2249620A1/fr
Withdrawn legal-status Critical Current

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    • 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]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/385—Switched mode power supply [SMPS] using flyback topology

Definitions

  • This invention relates to ballast circuits for lighting circuits, which lighting circuits are adapted to be directly driven from mains or similar power sources. It further relates to lighting circuits including such ballast circuits.
  • LED lighting is starting to become a realistic possibility for general illumination purposes such as domestic and commercial lighting. LED lighting will become increasingly more important to an energy-conscious society, since in comparison with traditional incandescent light-bulbs which typically achieve a luminous efficiency of around 10 to 20 Im/W, LEDs already achieve efficiencies of approximately 50 to 100 Im/W. Furthermore, LEDs offer the prospect of long lifetimes, when compared with conventional lighting devices.
  • LEDs operate at a voltage of between 1.5 and 5 V, depending on their colour, type, temperature and operational conditions. Furthermore, LEDs have a very small dynamic resistance; thus directly connecting an LED to a voltage source can result in large current values. It is therefore generally not practicable to drive LEDs directly from a mains supply: protective circuitry is necessary, to prevent damage to the LEDs in the case of fluctuations of the voltage in the mains supply.
  • the simplest way of providing a protective circuit is by means of a resistor connected in series with the LEDs. However, this method is associated with high losses and is thus not desirable. As a consequence a ballast may be used in front of the LEDs.
  • An example of such a ballast is a switched mode power supply (SMPS).
  • SMPS switched mode power supply
  • SMPSs operate by supplying a rapidly chopped or pulsed output current.
  • the chopping is typically in frequency range between several kHz and several MHz.
  • SMPSs include a large electrolytic capacitor on either the input or the output side to smooth the pulsed current.
  • Such an electrolytic capacitor adds to the cost and the volume of SMPSs, and renders them non-ideal for use as a ballast for mains-driven LED circuits.
  • an electrolytic capacitor may be limiting to the lifetime of the ballast.
  • a ballast circuit for a mains-driven lighting circuit comprising a switched mode power supply, characterised in that the switched mode power supply is adapted for operation as a current generator, and the switched mode power supply does not comprise an electrolytic capacitor.
  • Reduced costs, and an extension of the lifetime of the lighting circuit may thereby be achieved.
  • the limitation of lifetime of the circuit which could otherwise result from heat-induced failure of the electrolytic capacitor due to proximity of with the LEDs can thereby be avoided.
  • the circuit has an inductance of less than 10mH and more preferably less than 0.1mH.
  • the switched mode power supply comprises a flyback converter comprising a primary inductor coupled to a secondary inductor and a freewheeling diode.
  • a flyback converter is a particularly inexpensive and convenient type of SMPS.
  • the flyback converter further comprises an input capacitor having capacitance less than 1 ⁇ F, or preferably less than 0.22 ⁇ F.
  • an input capacitor having capacitance less than 1 ⁇ F, or preferably less than 0.22 ⁇ F.
  • Such a small input capacitor can provide a useful smoothing function, and facilitate compliance with putative or existing regulations regarding on mains supplies. It is noteworthy that such a capacitor has only a smoothing function for the high frequency oscillations of the SMPS, and is thus useful for EMC reasons: it has no mains frequency capability.
  • the limiting (maximum) allowable value of the capacitance is dependant on the power of the device: for example the appropriate value of an EMI-filter (Electro Magnetic Interference) capacitor depends on the power to be transferred. This capacitor could be larger than 220nF with increasing power but even if it was larger it is still only used for EMI-filtering purposes. Higher power levels need larger capacitances for EMI-filtering.
  • EMI-filter Electro Magnetic Interference
  • the ballast circuit further comprises a controller adapted to control a primary current through the primary inductor, in dependence on an input voltage.
  • a controller adapted to control a primary current through the primary inductor, in dependence on an input voltage.
  • the ballast circuit further comprises an output capacitor with a capacitance which is less than 10 ⁇ F or more preferably less than 1 ⁇ F.
  • an output capacitor with a capacitance which is less than 10 ⁇ F or more preferably less than 1 ⁇ F.
  • Such a small output capacitor may be useful in order to improve the operation and/or the efficiency of the lighting circuit.
  • the switched mode power supply is a resonant converter.
  • the switched mode power supply is one of a Sepic-, Zeta- or Cuk- converter.
  • the switched mode power supply is one of a buck-derived forward-converter, half-bridge converter or full-bridge converter.
  • a power factor correction circuit for a lighting circuit which is adapted to be directly mains-driven, the power factor correction circuit comprising a ballast circuit as described above and which does not comprise an electrolytic capacitor
  • a lighting circuit adapted to be directly mains-driven, which comprises a ballast circuit as described above and which does not comprise an electrolytic capacitor.
  • the lighting circuit may comprise an LED circuit or an OLED circuit.
  • An SMPS driven in accordance with embodiments of the invention may be arranged to provide a nearly unity power factor.
  • the SMPS works as a power factor correction circuit such that the lighting circuit will draw a current from the mains (or other) line input which can comply with present or future national or international regulations regarding power factors for mains-connected loads.
  • FIG. 1 shows a ballast circuit in a lighting circuit according to a first embodiment of the present invention.
  • the lighting circuit 10 is driven from a mains power source 20 which supplies an AC voltage V AC , which is rectified by rectifier 30 to rectified voltage
  • the ballast circuit 50 takes as input V in the rectified AC voltage
  • the ballast circuit 50 operates as a switched mode power supply without any output smoothing.
  • the ballast circuit 50 provides a pulsating output current to drive the LEDs 40.
  • the light emitting diodes are supplied with a rectified current, whose average value pulsates with a frequency corresponding to twice that of the mains input frequency.
  • the LEDs are supplied with a current whose average value pulsates at 100 Hz.
  • superposed on the twice-mains frequency pulsations is the triangular waveform of the instantaneous current, which varies with a frequency in this case of 2kHz (for clarity), and typically between 20kHz and several MHz.
  • Figure 2 shows schematically the current which is supplied to the string of LEDs 40. Over the time interval of 0.01 seconds shown in the figure, the average LED current 210 goes through a single pulse corresponding to a pulsation frequency of 100 Hz and a mains input frequency of 50 Hz. Also shown in the figure is the LED instantaneous current 220. The peaks of the instantaneous current 220 follow the shape of the pulse in the average current. However, as the LED current 220 corresponds to the output of the SMPS and is absent any smoothing at all, the chopping frequency of the SMPS (in this case 2 kHz) is evident in the generally triangular high frequency waveform, or ripple.
  • the chopping frequency of the SMPS in this case 2 kHz
  • a chopping frequency of the SMPS is normally set to a higher value than the 2 kHz value shown in figure 2 which was chosen primarily for illustrative purposes. It will be appreciated that, in other embodiments wherein a small value (less than 10 ⁇ F and typically less than 1 ⁇ F) non-electrolytic output capacitor is included, the capacitor has the effect of smoothing the high frequency chopping or ripple 220, but has no impact on the twice-mains frequency average current pulsation 210.
  • FIG. 3 shows a schematic circuit of a lighting circuit incorporating a fly-back converter.
  • a fly-back converter has been chosen as a non-limiting example of a type of SMPS to which the invention applies.
  • the lighting circuit 300 is supplied with alternating input voltage V AC 310, which is rectified by rectifier 320 to provide an input
  • Flyback converter 350 supplies output current I out to a string of diodes 340 comprising diodes D 1 to D n .
  • the flyback converter 350 comprises coupled chokes or inductors Lp and L s , a switch S and a freewheeling diode D on the output side.
  • the freewheeling diode D is included despite the existing string of LEDs 340, in order to absorb the reverse voltage in case of a conducting switch S.
  • a bulky electrolytic capacitor is utilised on neither the input side nor the output side of flyback converter 350.
  • a smaller filter capacitor C F is placed across the input of the SMPS, and filter inductors L F1 and L F2 are included on both the live and neutral rails of the mains input 310. These components are included in order to filter out any high frequency parts of the line current. It is emphasised that they do not provide any smoothing function in the fundamental frequency range of the mains input.
  • the filter capacitor C F is small enough so that effectively it is always charged to the actual value of the rectified input voltage.
  • the timing of the switching of switch S is under control of controller 352.
  • a conventional controller IC may be used; however, since a feedback controller loop is not desirable, an alternative controller mechanism may be employed, which avoids the complexity of a feedback loop such as is often employed and involving expensive opto-couplers: instead of measuring the output voltage, the corresponding pin on the controller is used to control the maximum primary current in dependence on the value of the input voltage.
  • the switch S is switched off when the given, or pre-determined, maximum primary current is reached.
  • this embodiment provides a open-loop feed-forward control; however, it will readily be appreciated that the invention is not limited thereto, and is equally applicably to other closed loop control, such as feed-back control, and that, furthermore, standard power-factor correction control schemes like CCM/DCM-operation (Continuous Conduction Mode/Discontinuous Conduction Mode) or BCM-operation (Boundary Conduction Mode) can be implemented without departing from the invention.
  • CCM/DCM-operation Continuous Conduction Mode/Discontinuous Conduction Mode
  • BCM-operation Boundary Conduction Mode
  • Figure 4 shows the input current 420 and the input voltage 430, for a demonstrator lighting circuit including a fly-back converter SMPS as described above with reference to figure 3 .
  • the converter is driven in boundary conduction mode.
  • the input current 420 broadly follows the cycling of the input mains voltage 430, and thus can be anticipated to satisfy any future EMC regulations which may limit the harmonics of mains currents.
  • FIG. 5 shows a lighting circuit 510 which is broadly similar to that of figure 1 : corresponding components are referenced by corresponding numerals, and will not be further described.
  • this embodiment includes a filter 560 on the output side of the SMPS.
  • the easiest filter implementation is the usage of a small capacitor (ceramic or film capacitor) but also a higher order filter such as a C-L-C-filter is usable.
  • the value of the output capacitor is typically less than 10 ⁇ F, and in a preferred embodiments it is less than 1 ⁇ F.
  • this output filter does not correspond to the conventional electrolytic capacitor placed on the output of an SMPS, so no mains-frequency or 50Hz filter is employed; instead of a large electrolytic output capacitor, a small capacitor is placed in parallel to the LEDs.
  • the low frequency 100Hz-ripple will still exist - since there is no large electrolytic capacitor to provide the smoothing function for this ripple - but the high frequency ripple caused by the switching actions can be reduced or even eliminated.
  • this embodiment involves higher costs than that described above, since the capacitor is relatively small, the increase in costs and volume is minor and inclusion of such a high frequency smoothing can result in a considerably higher luminous efficiency, as the LEDs can thereby be arranged to operate close to their optimum operating point for a larger part of the time.
  • flyback topology to convert a rectified input voltage to a pulsating current delivered to the LEDs.
  • the invention is not limited to flyback topology, but other topologies such as Sepic-, Zeta- or Cuk-converter, the buck-derived Forward-converter, Half- and Full-bridges as well as resonant converters are all is suitable for use with the present invention.
  • the invention is not limited to flyback converter but is applicable to SMPS in general including buck and forward converters.
  • FIG. 6 shows a schematic of a lighting circuit 600 incorporating a forward converter, including a small output filter 660, according to an embodiment of the invention.
  • Forward converter 650 is provided with mains input 610 which has been fully rectified by rectifier 620, to provide rectified input
  • Forward converter 650 may comprise a small input filter C F1 , and has a control switch S in series with primary coil Lp of transformer 654 and operable under control of controller 652.
  • the output from the secondary coil Ls of the transformer 654 is rectified by diode D 1 ; a freewheeling diode D 2 is also included.
  • the forward converter 650 further comprises an inductor L on the secondary side circuit. The skilled person will immediately appreciate that this inductor is integral to the operation of the forward converter, and does not form a smoothing function equivalent to an output filter.
  • Figure 6 does not show any necessary reset winding or mechanism: the skilled person will appreciate that the invention is not thereby constrained, and may be used with any suitable reset mechanism.
  • capacitor C F2 which functions as a high frequency output filter.
  • capacitor C F2 is not a large electrolytic, and has no capability for storage or smoothing the 100Hz or twice-mains-frequency pulsation. However, it can smooth the high-frequency chopping or ripple caused by the forward converter itself.
  • the invention has been described above primarily with reference to LED lighting applications. However, it will be immediately apparent to the skilled person that that's the invention is applicable to other forms of lighting. In particular the invention embraces organic LED lighting (OLED), electroluminescent lighting (EL), and cathodo-luminescent lighting (CL).
  • OLED organic LED lighting
  • EL electroluminescent lighting
  • CL cathodo-luminescent lighting
  • embodiments of the invention described above are associated with a mains input supply such as that supplied through a grid. It will be immediately apparent to the skilled person that the invention is not limited to mains input voltages but is equally applicable to other AC voltages which may be for instance generated off-grid.
  • An example of such an off-grid generated AC input voltage is that produced by a local generator, such as a petrol-driven generator, for example on board a ship or in a remote environment.
  • ballast circuits for lighting circuits, such as LED circuits, which can be directly driven from a mains voltage or other, off-grid, AC voltage sources.
  • the ballast circuit comprises a SMPS without any electrolytic capacitor.
  • the SMPS can operate to provide an unregulated voltage. By not including an electrolytic capacitor, the cost, bulk, and life-time limitations associated with such a capacitor are avoided.

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  • Circuit Arrangement For Electric Light Sources In General (AREA)
EP09100267A 2009-05-05 2009-05-05 Circuit de ballast pour circuit d'éclairage, et circuit d'éclairage incluant un circuit de ballast Withdrawn EP2249620A1 (fr)

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Application Number Priority Date Filing Date Title
EP09100267A EP2249620A1 (fr) 2009-05-05 2009-05-05 Circuit de ballast pour circuit d'éclairage, et circuit d'éclairage incluant un circuit de ballast

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EP09100267A EP2249620A1 (fr) 2009-05-05 2009-05-05 Circuit de ballast pour circuit d'éclairage, et circuit d'éclairage incluant un circuit de ballast

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2273849A3 (fr) * 2009-07-09 2012-05-30 Siteco Beleuchtungstechnik GmbH Commande à DEL
EP2458722A1 (fr) * 2010-11-24 2012-05-30 Samsung LED Co., Ltd. Appareil de commande à DEL
CN103270812A (zh) * 2010-12-15 2013-08-28 皇家飞利浦电子股份有限公司 用于减少的感知到的光闪烁的线性驱动器
CN108449831A (zh) * 2018-03-14 2018-08-24 福州大学 一种高功率因数长寿命led驱动电源及控制方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040079953A1 (en) * 2002-08-17 2004-04-29 Alexander Mednik AC/DC cascaded power converters having high DC conversion ratio and improved AC line harmonics
US20070182338A1 (en) * 2006-01-20 2007-08-09 Exclara Inc. Current regulator for modulating brightness levels of solid state lighting
WO2008068705A1 (fr) * 2006-12-06 2008-06-12 Nxp B.V. Source de tension commandée pour commandes de led
WO2008112820A2 (fr) * 2007-03-12 2008-09-18 Cirrus Logic, Inc. Système de commande de puissance pour des sources de lumière régulées en courant
WO2009013676A2 (fr) * 2007-07-23 2009-01-29 Nxp B.V. Disposition de del avec circuit de dérivation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040079953A1 (en) * 2002-08-17 2004-04-29 Alexander Mednik AC/DC cascaded power converters having high DC conversion ratio and improved AC line harmonics
US20070182338A1 (en) * 2006-01-20 2007-08-09 Exclara Inc. Current regulator for modulating brightness levels of solid state lighting
WO2008068705A1 (fr) * 2006-12-06 2008-06-12 Nxp B.V. Source de tension commandée pour commandes de led
WO2008112820A2 (fr) * 2007-03-12 2008-09-18 Cirrus Logic, Inc. Système de commande de puissance pour des sources de lumière régulées en courant
WO2009013676A2 (fr) * 2007-07-23 2009-01-29 Nxp B.V. Disposition de del avec circuit de dérivation

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"HV9931 Unity Power Factor LED Lamp Driver, Initial realease", SUPERTEXT INC. HV 9931 - INITIAL RELEASE, SUPERTEX INC, SUNNYVALE, CA, USA, no. HV9931, 1 January 2005 (2005-01-01), pages 1 - 8, XP002486609 *
AN-H52 APPLICATION NOTE: "HV9931 Unity Power Factor LED Lamp Driver", 7 March 2007, SUPERTEXT INC.- AN-H52 - APPLICATION NOTE, SUPERTEX INC, SUNNYVALE, CA, USA, PAGE(S) 1 - 20, XP002486610 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2273849A3 (fr) * 2009-07-09 2012-05-30 Siteco Beleuchtungstechnik GmbH Commande à DEL
EP2458722A1 (fr) * 2010-11-24 2012-05-30 Samsung LED Co., Ltd. Appareil de commande à DEL
CN102480828A (zh) * 2010-11-24 2012-05-30 三星Led株式会社 Led驱动装置
US8581508B2 (en) 2010-11-24 2013-11-12 Samsung Electronics Co., Ltd. LED driving apparatus
CN102480828B (zh) * 2010-11-24 2015-09-30 三星电子株式会社 Led驱动装置
CN103270812A (zh) * 2010-12-15 2013-08-28 皇家飞利浦电子股份有限公司 用于减少的感知到的光闪烁的线性驱动器
CN103270812B (zh) * 2010-12-15 2016-08-10 皇家飞利浦电子股份有限公司 用于减少的感知到的光闪烁的线性驱动器
CN108449831A (zh) * 2018-03-14 2018-08-24 福州大学 一种高功率因数长寿命led驱动电源及控制方法

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