WO2017202380A1 - Pilote de del intégré de type hybride - Google Patents

Pilote de del intégré de type hybride Download PDF

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Publication number
WO2017202380A1
WO2017202380A1 PCT/CN2017/086104 CN2017086104W WO2017202380A1 WO 2017202380 A1 WO2017202380 A1 WO 2017202380A1 CN 2017086104 W CN2017086104 W CN 2017086104W WO 2017202380 A1 WO2017202380 A1 WO 2017202380A1
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WO
WIPO (PCT)
Prior art keywords
led
switch
voltage
led driver
inductor
Prior art date
Application number
PCT/CN2017/086104
Other languages
English (en)
Inventor
Lisong LI
Kwok Tai Mok
Yuan Gao
Original Assignee
The Hong Kong University Of Science And Technology
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 The Hong Kong University Of Science And Technology filed Critical The Hong Kong University Of Science And Technology
Publication of WO2017202380A1 publication Critical patent/WO2017202380A1/fr

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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]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/48—Details of LED load circuits with an active control inside an LED matrix having LEDs organised in strings and incorporating parallel shunting devices
    • 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
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/17—Operational modes, e.g. switching from manual to automatic mode or prohibiting specific operations

Definitions

  • Embodiments of the present invention relate to AC-powered light-emitting diode (LED) driving systems, and more particularly, to circuitry and methodology that improve the power efficiency of an LED system.
  • LED light-emitting diode
  • LEDs light-emitting diodes
  • ⁇ H microhenries
  • E-Cap electrolytic capacitor
  • Linear LED drivers do not require power inductors.
  • the maximum power efficiency is limited by the ratio of the LED voltage to the input voltage. If there is a big difference between the LED voltage and input voltage, a lot of power will be dissipated on the pass device (e.g., the power MOSFETS depicted in FIG. 1) , resulting in low power efficiency.
  • the lifespan of an E-Cap is usually much shorter than that of an LED, the lifespan of the LED system will be seriously reduced based on inclusion of the E-Cap.
  • the LED system has a switching loss of 6.4W.
  • a buck converter LED driver can theoretically achieve 100%efficiency.
  • large switching losses occur due to the parasitic drain capacitor of the power MOSFET, especially when the switching frequency is above 1MHz.
  • the invention provides a light-emitting diode (LED) driver.
  • the LED driver includes: a plurality of switches corresponding to a plurality of LEDs; and a controller, configured to switch between operating the LED driver in a linear mode and in a switching mode such that the LED driver is operated in the linear mode when an input voltage is relatively close to an LED voltage level and the LED driver is operated in the switching mode when the input voltage is relatively farther from the LED voltage.
  • the invention provides a method for controlling a plurality of light-emitting diodes (LEDs) .
  • the method includes: operating, by the controller, an LED driver in a linear mode, wherein in the linear mode, a first switch corresponding to a first LED voltage is activated while a second switch corresponding to the second voltage is deactivated; and operating, by a controller, the LED driver in a switching mode, wherein in the switching mode, the first switch corresponding to the first LED voltage and the second switch corresponding to the second LED voltage are alternately turned on.
  • FIG. 2A is a circuit diagram of a conventional three-string linear LED driver.
  • FIG. 2B depicts the power consumption distribution of the linear LED driver.
  • FIG. 2C is a plot depicting conduction loss caused by the voltage difference between V IN and V LED , regardless of the quality of the power MOSFET, in the conventional 3-string linear LED driver in FIG. 2A.
  • FIG. 3 is a circuit diagram of a conventional single-stage switching converter-based AC LED diver and a plot showing a large switching loss due to a parasitic capacitor C D .
  • FIG. 4 is a circuit diagram depicting the structure of an integrated hybrid-type LED driver according to an exemplary embodiment of the present invention.
  • FIG. 5 is a circuit diagram depicting an exemplary implementation of the integrated hybrid-type LED driver depicted in FIG. 5A having three LEDs.
  • FIG. 6 is a plot depicting exemplary waveforms corresponding to the integrated hybrid-type LED driver depicted in FIG. 5.
  • FIGS. 7A-7C illustrate exemplary operation of the integrated hybrid-type LED driver depicted in FIG. 5.
  • FIG. 8 is a circuit diagram depicting the structure of an integrated hybrid-type LED driver according to an exemplary embodiment of the present invention.
  • FIG. 9 is a chip micrograph depicting an exemplary implementation of an integrated hybrid-type LED driver.
  • FIGS. 10A to 10D are plots showing measured waveforms for an exemplary implementation of an integrated hybrid-type LED driver resulting from a variety of voltage inputs.
  • FIG. 11 is a plot of power efficiency and power factor against input voltage for an exemplary implementation of an integrated hybrid-type LED driver.
  • Exemplary embodiments of the present invention provide an LED driving system that uses a hybrid control method which achieves very high performance and efficiency at a low cost.
  • the integrated hybrid-type LED driving system is AC powered (it will be appreciated that exemplary embodiments of the invention may be applied to any environment in which a time-varying input voltage is used, and that environments having an AC input are generally the most common) .
  • the integrated hybrid-type LED driving system ensures that the majority of power that is inputted into the system is delivered to the LEDs, and very high power efficiency and power factor can thus be achieved.
  • the integrated hybrid-type LED driving system utilizes a very small inductor and does not require an electrolytic capacitor. This allows for relatively low costs, long lifespan, and low maintenance relative to conventional LED driving systems.
  • the power MOSFETs and the controller of the integrated hybrid-type LED driving system may be implemented on-chip.
  • exemplary embodiments of the invention provide improvements with respect to size, efficiency, and reliability relative to conventional LED driving systems, while achieving outstanding performance.
  • FIG. 4 is a circuit diagram depicting the structure of an integrated hybrid-type LED driver according to an exemplary embodiment of the present invention, which efficiently utilizes input power without large switching losses or excessive current and voltage stress.
  • an inductor L is added to the power stage of a multiple-string linear LED driver. For a certain input voltage, only two adjacent MOSFETs will be fully turned on and off alternately while other power MOSFETs remains off-state. The inductor current is sensed by a resistor R S and fed back to the controller.
  • Hysteretic control is used to ensure the inductor current I L is bounded between I LOk and I HIk (I LOk and I HIk refer to the LED current boundaries in different states, with k ranging from 1 to n where n is the number of LEDs; in general I LOk and I HIk should increase with input voltage and I HIn should be smaller than the LED current rating) .
  • the integrated hybrid-type LED driver is in a Switching Mode where M 1 and M 2 are turned on and off alternately (in an example with a 110 V AC input, V LED1 may be about 60V and V LED1 +V LED2 may be about 80V) .
  • the integrated hybrid-type LED driver will enter a Linear Mode.
  • the V IN approximately matches with V LED1 +V LED2 .
  • the voltage across the inductor is 0V and there is no switching behavior.
  • the LED driver operates in the following modes of operation: (1) a linear mode with a first switch M 1 on; (2) a switching mode where the first switch M 1 and a second switch M 2 are alternately on; (3) a linear mode with the second switch M 2 on; (4) a switching mode with the second switch M 2 and a third switch M 3 alternately on; (5) a linear mode with the third switch M 3 on; and so on up to an n th switch M n corresponding to an n th LED.
  • exemplary embodiments may be configured such that V LED1 +V LED2 +...+V LEDn is larger than the maximum V IN for the system.
  • FIG. 5 is a circuit diagram depicting an exemplary implementation of the integrated hybrid-type LED driver shown in FIG. 4 having three LEDs.
  • the integrated hybrid-type LED driver depicted in FIG. 5 operates in a similar manner as discussed above with respect to FIG. 4.
  • FIG. 6 includes plots depicting exemplary waveforms corresponding to the integrated hybrid-type LED driver depicted in FIG. 5.
  • V IN is a sinusoidal wave as shown.
  • V X is the voltage of the anode of LED1. If M 1 is on, V X equals V LED1 . If M 2 is on and M 1 is off, V X equals V LED1 +V LED2 . If M 3 is on and M 1 and M 2 is off, V X equals V LED1 +V LED2 +V LED3 .
  • V X is the voltage of the LED (s) that is/are on, namely output voltage.
  • V G1 , V G2 , V G3 are the gate control voltages of M 1 , M 2 and M 3 , respectively.
  • V G1 If V G1 is high, M 1 is turned on. I L is the current that flows through the inductor. If V IN is larger than V X , I L will ramp up and if V IN is smaller than V X , I L will go down. Therefore, when V IN is between V LED1 and V LED1 +V LED2 , I L will go up and down by alternately turning on M 1 and M 2 . Alternately turning on M 1 and M 2 allows the difference between input voltage (V IN ) and output voltage (V X ) to be stored and used to drive an additional LED once enough energy is stored (when V IN is smaller than V LED1 +V LED2 , V IN alone is not enough to drive both LED1 and LED2 without the help of the energy stored in the inductor) .
  • V IN V X plot of FIG. 6, even while V IN is smaller than V LED1 +V LED2 , the two LED strings can still be driven with the energy previously stored in L until it is discharged to I LO1 again in the Switching Mode, and V IN matches with V LED1 +V LED2 in Linear Mode.
  • I L plot of FIG. 6 hysteretic control ensures that the inductor current I L is bounded between I LOk and I HIk
  • FIG. 7A illustrates the integrated hybrid-type LED driver depicted in FIG. 5 in Switching Mode under conditions where V LED1 ⁇ V IN ⁇ V LED1 + V LED2 , L is being charged, and M 1 is on while M 2 is off. Under these conditions, M 1 is fully turned on with a minimum voltage drop on M 1 , and extra energy is stored in L.
  • FIG. 7B illustrates the integrated hybrid-type LED driver depicted in FIG. 5 in Switching Mode under conditions where V LED1 ⁇ V IN ⁇ V LED1 + V LED2 , L is being discharged, and M 2 is on while M 1 is off. Under these conditions, energy previously stored in L is released to drive an additional LED, allowing the extra energy discussed above with respect to FIG. 7A to be efficiently used.
  • FIG. 7C illustrates the integrated hybrid-type LED driver depicted in FIG. 5 in Linear Mode under conditions where V IN ⁇ V LED1 + V LED2 . Under these conditions, all of the input power goes to the LEDs, allowing high efficiency to be achieved.
  • FIG. 8 is a circuit diagram depicting the structure of an integrated hybrid-type LED driver, having six LEDs in a string (i.e., six branches) , according to an exemplary embodiment of the present invention.
  • the power MOSFETs and the controller are implemented on-chip.
  • the sensed inductor current represented by a voltage V S
  • V HI and V LO the outputs of the comparators are sent into an RS latch, whose outputs are Q and NQ.
  • V Gk is connected to Q
  • V G, k+1 is connected to NQ and other power MOSFETs are off .
  • a 2 A 1 A 0 can be used to indicate V IN and select the two power MOSFETs that are suitable for the current input voltage.
  • a 2 A 1 A 0 also controls V HI and V LO to increase or decrease with V IN such that a high power factor (PF) is achieved.
  • control logic provided by the RS latch, the 3-bit bidirectional counter, the reference voltage selector, and the gate voltage selector depicted in FIG. 7 is merely exemplary, and that other implementations of control circuits, controllers, integrated circuits (ICs) , etc., whether analog or digital, may be used to implement exemplary embodiments of an integrated hybrid-type LED driver.
  • FIG. 9 is a chip micrograph depicting an exemplary implementation of an integrated hybrid-type LED driver for general lighting applications.
  • the exemplary integrated hybrid-type LED driver was fabricated with a 0.35 ⁇ m 120V high voltage CMOS process, and utilizes a 6.8 ⁇ H inductor and 9 LEDs, each of the LEDs having a voltage of about 20V.
  • additional implementations of the present invention may also be implemented in higher voltage applications—e.g. 220VAC.
  • the exemplary integrated hybrid-type LED driver depicted in FIG. 9 was demonstrated as achieving 97%power efficiency and 0.996 power factor with a 120V AC 60Hz input.
  • FIGS. 10A to 10D are plots showing measured waveforms for the exemplary integrated hybrid-type LED driver depicted in FIG. 9 resulting from a variety of voltage inputs.
  • FIG. 10A, 10B, 10C, and 10D show the measured waveforms of V IN , V X and I L under 100/110/120V AC inputs.
  • V X follows V IN , as shown on the left side of FIG. 10A.
  • Switching Mode V X switches above and below V IN , and I L ramps up and down between a hysteretic window of about 100mA, as shown on the right side of FIG. 10A.
  • FIGS. 10B and 10C show the measured waveforms under 100V AC and 120V AC input, respectively.
  • 10D shows the waveforms of I L as well as A 2 , A 1 , and A 0 under 110V AC input.
  • the inductor value was 6.8 ⁇ H (relatively small when compared to inductors used in conventional switch-mode LED drivers (e.g., 5.5mH, 470 ⁇ H, 400 ⁇ H) )
  • the maximum switching frequency was approximately 5MHz
  • the supply voltage for the controller was 5.5V.
  • I L had a similar shape to V IN , indicating that a good power factor was achieved.
  • the switching frequency depends on the voltage drop on the inductor (V IN -V X ) , namely the voltage difference between the input voltage and the LED voltage.
  • V IN -V X When V IN -V X is large, the switching frequency is high (e.g., ⁇ MHz range) and the hybrid LED driver is operating in the “switching mode. ”
  • V IN -V X As the input voltage approaches the LED voltage (e.g., V LED1 or V LED1 +V LED2 ) , V IN -V X becomes very small, resulting in slow changes with respect to the inductor current.
  • the frequency of an AC power line may be 50Hz or 60Hz, when the inductor current is going up or down in this frequency range, the foregoing “switching” behavior is no longer observed. Instead, the change of inductor current is synchronized with the change of the input voltage, and the hybrid LED driver is operating in the “linear mode. ”
  • a switching frequency in the ⁇ MHz range may correspond to a voltage drop on the inductor (V IN -V X ) being about 10 V.
  • the voltage drop on the inductor (V IN -V X ) is very small, and the input voltage is very close to the LED voltage. Since there will be some voltage difference due to the resistance of the inductor, the on-resistance of the MOSFET and the sense resistor Rs, there is not a fixed exact value for the voltage drop on the inductor (V IN -V X ) at which the hybrid LED driver changes between the switching mode and the linear mode.

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

Abstract

La présente invention concerne un pilote de diode électroluminescente (DEL) comprenant : une pluralité de commutateurs correspondant à une pluralité de DEL; et un dispositif de commande configuré pour commuter le fonctionnement du pilote de DEL entre un mode linéaire et un mode de commutation, de sorte que le pilote de DEL fonctionne en mode linéaire lorsqu'une tension d'entrée est relativement proche d'un niveau de tension de DEL et que le pilote de DEL fonctionne en mode de commutation lorsque la tension d'entrée est relativement plus éloignée de la tension de DEL.
PCT/CN2017/086104 2016-05-26 2017-05-26 Pilote de del intégré de type hybride WO2017202380A1 (fr)

Applications Claiming Priority (2)

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US201662392254P 2016-05-26 2016-05-26
US62/392,254 2016-05-26

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WO2017202380A1 true WO2017202380A1 (fr) 2017-11-30

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1914575A (zh) * 2004-02-05 2007-02-14 美国芯源系统股份有限公司 利用单一电压基准对线性和开关模式运行进行自动电流检测选择的dc/dc电压调节器
US20080018261A1 (en) * 2006-05-01 2008-01-24 Kastner Mark A LED power supply with options for dimming
CN101427606A (zh) * 2006-04-21 2009-05-06 特利多尼凯特库瑞士公司 用于发光二极管的驱动电路
CN101483951A (zh) * 2009-02-16 2009-07-15 湖南力芯电子科技有限责任公司 发光二极管驱动器和驱动发光二极管的方法
CN102668701A (zh) * 2009-12-29 2012-09-12 爱特梅尔公司 用于具有功率因数校正能力的智能发光二极管驱动器的方法及装置
CN102812780A (zh) * 2010-03-23 2012-12-05 欧司朗股份有限公司 用于运行至少一个led的线路布置和方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1914575A (zh) * 2004-02-05 2007-02-14 美国芯源系统股份有限公司 利用单一电压基准对线性和开关模式运行进行自动电流检测选择的dc/dc电压调节器
CN101427606A (zh) * 2006-04-21 2009-05-06 特利多尼凯特库瑞士公司 用于发光二极管的驱动电路
US20080018261A1 (en) * 2006-05-01 2008-01-24 Kastner Mark A LED power supply with options for dimming
CN101483951A (zh) * 2009-02-16 2009-07-15 湖南力芯电子科技有限责任公司 发光二极管驱动器和驱动发光二极管的方法
CN102668701A (zh) * 2009-12-29 2012-09-12 爱特梅尔公司 用于具有功率因数校正能力的智能发光二极管驱动器的方法及装置
CN102812780A (zh) * 2010-03-23 2012-12-05 欧司朗股份有限公司 用于运行至少一个led的线路布置和方法

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