WO2007049911A1 - Light device using lighting emitting diodes - Google Patents

Light device using lighting emitting diodes Download PDF

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Publication number
WO2007049911A1
WO2007049911A1 PCT/KR2006/004363 KR2006004363W WO2007049911A1 WO 2007049911 A1 WO2007049911 A1 WO 2007049911A1 KR 2006004363 W KR2006004363 W KR 2006004363W WO 2007049911 A1 WO2007049911 A1 WO 2007049911A1
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WO
WIPO (PCT)
Prior art keywords
voltage
current
generator
unit
constant
Prior art date
Application number
PCT/KR2006/004363
Other languages
French (fr)
Inventor
Jung Hwan Kim
Eul Sik Kim
Original Assignee
Choi, Byong Heon
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 Choi, Byong Heon filed Critical Choi, Byong Heon
Publication of WO2007049911A1 publication Critical patent/WO2007049911A1/en

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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
    • 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
    • H05B45/395—Linear regulators
    • H05B45/397—Current mirror circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21—LIGHTING
    • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00—Light-generating elements of semiconductor light sources
    • F21Y2115/10—Light-emitting diodes [LED]
    • 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 light emitting diode (LED) lighting device, and more particularly, to an LED lighting device which can use alternating-current (AC) or direct-current (DC) voltage as an input power source, and can apply constant voltage and current to LEDs to thereby prevent damage of the LEDs and minimizes an amount of electric power supplied to the LEDs.
  • LED light emitting diode
  • AC alternating-current
  • DC direct-current
  • Filament bulbs, fluorescent lamps, neon sign lamps, and LED lamps are used as the lighting devices, respectively.
  • the LEDs have the advantages that their lives are semi-permanent, their prices are inexpensive, and their electrical energy consumption is low.
  • FIG. 1 is a configurational circuit diagram showing a conventional light emitting diode (LED) lighting device.
  • the conventional LED lighting device includes a plurality of resistors (R1-R4) and a plurality of LEDs (LED1-LED4) connected in series to the respective resistors.
  • Direct-current (DC) voltage (Vdc) is applied across both ends of a combination of the resistors (R1-R4) and the LEDs (LED1-LED4) which are connected in series, respectively.
  • the plurality of LEDs (LED1-LED4) are turned on by the supplied DC voltage Vdc.
  • the DC voltage (Vdc) which is a power supply voltage source is supplied to the LEDs in the case of the conventional LED lighting device. Accordingly, in the case that overvoltage or excess current is induced in the DC voltage (Vdc), the induced overvoltage or excess current is applied to the LEDs, and thus the LEDs may be damaged. Further, in the case that heat is generated in resistors which are connected in series with each other, the resistance values of the resistors are reduced. As a result, the voltage and current which are applied to LEDs become large, thereby cause the LEDs to be damaged. [7] Moreover, the conventional LED lighting devices are designed to use DC voltage as power supply voltage. Thus, AC voltage cannot be used in the conventional LED lighting devices as an alternating power supply source. As a result, if a user wrongly connects the polarities of the supply voltage by mistake or carelessly, LEDs are not turned on.
  • LEDs light emitting diodes
  • a lighting device using light emitting diodes (LEDs) which are turned on and emit the light comprising: a power supply unit to which direct-current (DC) or alternating-current (AC) voltage is applied in order to supply the electric power to the LEDs; a rectifier unit receiving the supply voltage supplied from the power supply unit and converting the received supply voltage into DC voltage, to then output the converted result; a constant voltage generator receiving the DC voltage which is output from the rectifier unit and generating constant voltage having a certain voltage value; and a constant current generator receiving the constant voltage which is output from the constant voltage generator and supplying constant current having a certain current value for the plurality of LEDs in the light emitting unit, wherein the constant voltage generator comprises: a switching unit which is turned on or off according to a switching control signal and outputs the DC voltage of the rectifier unit to a first node when the switching unit is turned on; a filter unit including a coil
  • the constant voltage generator further comprises: a Shottkey diode whose one end is connected to the first node, and whose other end is connected the ground voltage and which makes surge voltage or surge current generated from the first node, to the ground voltage when the switching unit is turned on or off.
  • the LED lighting device further comprises a first limit resistor which is installed between the rectifier unit and the constant voltage generator, and limits the maximum value of the current flowing through the constant voltage generator.
  • the LED lighting device further comprises a second limit resistor which is installed between the constant current generator and the light emitting unit, and limits the maximum value of the current flowing through the light emitting unit.
  • the present invention provides alight emitting device using light emitting diodes (LEDs) including a constant voltage generator and a constant current generator, to thereby supply constant voltage and current for the LEDs to thus prevent damage of the LEDs. Further, the present invention provides a light emitting device which uses not only direct-current (DC) voltage but also alternating-current (AC) voltage as a power supply voltage source, to accordingly enable the LEDs to operate normally although a user wrongly connects the polarities of the supply voltage by mistake.
  • DC direct-current
  • AC alternating-current
  • FIG. 1 is a configurational circuit diagram showing a conventional light emitting diode (LED) lighting device
  • FIG. 2 is a configurational circuit diagram showing an LED lighting device according to the present invention.
  • FIG. 3 is a configurational circuit diagram showing a constant current generator of
  • FIG. 2
  • FIG. 4 is a configurational diagram showing another preferred embodiment of the constant current generator of FlG. 2;
  • FlG. 5 is a waveform diagram for explaining operation of the constant voltage generator of FlG. 2. Best Mode for Carrying Out the Invention
  • FlG. 2 is a configurational circuit diagram showing an LED lighting device according to the present invention.
  • the LED lighting device of the present invention includes: a light emitting unit 50; a power supply unit 10; a rectifier unit 20; a constant voltage generator 30; and a constant current generator 40.
  • the light emitting unit 50 includes a plurality of LEDs (LED1-LED4) which are turned on and emit the light if current flows therethrough and a plurality of resistors (RE1-RE4) connected in series to the plurality of LEDs, respectively.
  • Direct-current (DC) or alternating-current (AC) voltage is applied to the power supply unit 10 in order to supply the electric power to the LEDs (LED1-LED4).
  • the rectifier unit 20 receives the supply voltage (Vin) supplied from the power supply unit 10 and converts the received supply voltage into DC voltage (Vdc), to then output the converted result.
  • the constant voltage generator 30 receives the DC voltage (Vdc) which is output from the rectifier unit 20 and generates constant voltage (Vcc) having a certain voltage value.
  • the constant current generator 40 receives the constant voltage (Vcc) which is output from the constant voltage generator 30 and supplies constant current (lout) having a certain current value for the plurality of LEDs (LED1-LED4) in the light emitting unit 50.
  • the constant voltage generator 30 includes: a switching unit (SW); a filter unit 37; a distribution unit 39; an offset generator 33; and a comparison unit 35.
  • the switching unit (SW) is turned on or off according to a switching control signal
  • SC and outputs the DC voltage of the rectifier unit to a first node when the switching unit is turned on.
  • the filter unit 37 includes a coil (L) whose one end is connected to the first node
  • the distribution unit 39 includes first and second resistors (Ra, Rb), in which one end of the first resistor (Ra) is connected to the output node (NO) and whose other end is connected to one end of the second resistor (Rb), to thereby output a distribution voltage (Va), and the other end of the second resistor (Rb) is connected to the ground voltage (Vss).
  • the offset generator 33 receives reference voltage (Vref) and the distribution voltage (Va) and outputs an offset signal (DL) according to an amount of variation of the distribution voltage (Va) when the distribution voltage (Va) has been varied.
  • the comparison unit 35 compares a triangle wave signal (T) output from a triangular wave generator 31 and the offset signal (DL) output from the offset generator 33, and outputs a switching control signal (SC) whose duty is different according to the offset signal (DL).
  • the constant voltage generator 30 further includes a
  • Shottkey diode (SD) whose one end is connected to the first node (Nl), and whose other end is connected the ground voltage (Vss) and which makes surge voltage or surge current generated from the first node (Nl), to the ground voltage when the switching unit (SW) is turned on or off.
  • the LED lighting device further includes a first limit resistor (RTl) which is installed between the DC voltage (Vdc) output from the rectifier unit 20 and the constant voltage generator 30, and limits the maximum value of the current flowing through the constant voltage generator 30.
  • RTl first limit resistor
  • the LED lighting device further includes a second limit resistor (RT2) which is installed between the output of the constant current generator 40 and the light emitting unit 50, and limits the maximum value of the current flowing through the light emitting unit 50.
  • RT2 second limit resistor
  • DC or AC voltage of 8V through 40V is applied to the power supply unit 10, in order to supply the power to the LEDs (LED1-LED4).
  • the rectifier 20 uses a bridge diode circuit, to thereby convert the DC or AC voltage (Vin) supplied from the power supply unit 10 into DC voltage (Vdc) to then output the DC voltage (Vdc). That is, although the supply voltage (Vin) is the DC or AC voltage, the voltage output from the bridge diode circuit is the DC voltage (Vdc). Accordingly, although a user wrongly connects the polarities of the DC supply voltage by mistake or carelessly, the voltage output from the bridge diode circuit is always the DC voltage (Vdc).
  • the LED lighting device further includes a smoothing capacitor (CS) between the DC voltage (Vdc) and the ground voltage (Vss).
  • the smoothing capacitor (CS) can prevent overvoltage or excess current generated in the DC voltage (Vdc) which is the voltage output from the rectifier unit 20, and remove a ripple component formed in the DC voltage (Vdc).
  • the offset signal (DL) of the offset generator 33 increases by an increment of the distribution voltage (Va). Accordingly, a region having a high logic value becomes smaller in the switching control signal (SC) which is the signal output from the comparison unit 35 and thus the time when the switching unit (SW) is turned on is reduced. As a result, reduced DC voltage is output as the constant voltage (Vcc).
  • the distribution voltage (Va) decreases if the voltage at the end of the constant voltage (Vcc) decreases, and the offset signal (DL) also decreases.
  • a region having the high logic value becomes large in the switching control signal (SC) and thus an on-time of the switching unit (SW) becomes long.
  • the DC voltage at the end of the constant voltage (Vcc) has an increased value. Therefore, the constant voltage generator 30 applied in the present invention varies the duty ratio of the switching control signal (SC), according to the voltage at the end of the constant voltage (Vcc), and thus controls an on-time of the switching unit (SW).
  • the switching unit (SW) can be implemented by a MOS (Metal-Oxide Semiconductor) transistor or bi-polar transistor.
  • the constant voltage (Vcc) from which the ripple component has been removed is output at the output node (NO) by the filter unit 37 including the coil (L) and the capacitor (C).
  • the Shottkey diode (SD) in the constant voltage generator 30 enables the surge voltage or surge current which is generated at the first node (Nl) according to the on- or off-operation of the switching unit (SW) to flow to the end of the ground voltage (Vss) to thereby make the constant voltage (Vcc) which is the voltage output from the constant voltage generator 30 have stabilized certain constant voltage.
  • the first limit resistor (RTl) is connected between the end of the DC voltage (Vdc) and the constant voltage generator 30 to thus limit the maximum value of the current flowing in the constant voltage generator 30.
  • the LED lighting device according to the present invention includes the constant voltage generator 30 to thereby make the voltage supplied to the light emitting unit 50 always have certain constant voltage.
  • FIG. 3 is a configurational circuit diagram showing a constant current generator 40 of FIG. 2
  • FIG. 4 is a configurational diagram showing another preferred embodiment of the constant current generator of FIG. 2.
  • the constant current generators 40 receive the constant voltage (Vcc) which is the voltage output from the constant voltage generator 30 and supply the constant current (lout) having a certain current value to a plurality of LEDs (LED1-LED4) in the light emitting unit 50.
  • the constant current generator 40 includes a constant current unit 41 and an output unit 43 using a current mirror circuit.
  • the constant current unit 41 includes first and second MOS transistors (Ml, M2) which are two N-channel MOS transistors, and third and fourth MOS transistors (M3, M4) which are two P-channel MOS transistors both of which include a generally used current mirror circuit, respectively.
  • the constant voltage (Vcc) is input to the constant current generator 40 as the supply voltage. Accordingly, the current flowing in the second MOS transistor M2 and the fourth MOS transistor M4 is determined by the current flowing in the first MOS transistor Ml and the third MOS transistor M3.
  • the current (lout) flowing in the fifth MOS transistor M5 of the output unit 43 is output as certain constant current according to the current flowing in the fourth MOS transistor M4.
  • the constant current generator 40 includes a differential amplifier (OP) and a plurality of resistors (R1-R5) in order to output the constant current (lout).
  • the constant current (lout) outputs a certain constant current value which is determined by Vcc*R2/Rl*R3, in which Rl, R2, and R3 are resistance values of the respective resistors (Rl, R2, R3).
  • the constant current generator 40 applied in the present invention can be implemented by the circuits shown in FIGS. 3 or 4, but can be implemented a general con stant current circuit which can output constant current.
  • the LED lighting device includes the constant voltage generator 30 and the constant current generator 40, and thus supplies the constant voltage (Vcc) having the certain constant voltage (Vcc) and the constant current (lout) having the certain constant current to the light emitting unit 50 including a plurality of LEDs (LED1-LED4) and a plurality of resistors (RE1-RE4) connected in series with the plurality of LEDs (LED1-LED4), respectively.
  • the resistance values of the plurality of resistors (RE1-RE4) are reduced by the heat generated in the plurality of resistors (RE1-RE4), the current value and the voltage value flowing in the plurality of LEDs (LED1-LED4) can be consistently maintained constant, to thereby prevent the LEDs from being damaged and to thus enable a user to use the LEDs semi-permanently.
  • the maximum value of the current flowing in the light emitting unit 50 can be limited by the second limit resistance (RT2) which is installed between the output of the constant current generator 40 and the light emitting unit 50.
  • RT2 second limit resistance
  • the present invention relates to a light emitting diode (LED) lighting device which can use alternating-current (AC) or direct-current (DC) voltage as an input power source, and can apply constant voltage and current to LEDs to thereby prevent damage of the LEDs and minimizes an amount of electric power supplied to the LEDs.
  • LED light emitting diode
  • the light emitting diode (LED) lighting device can be applied as lighting sources using LEDs in which the current value and the voltage value flowing in the plurality of LEDs can be consistently maintained constant, to thereby prevent the LEDs from being damaged and to thus enable a user to use the LEDs semi-permanently.

Abstract

Provided is a lighting device using light emitting diodes (LEDs), which includes: a power supply unit to which direct-current or alternating-current voltage; a rectifier unit receiving the supply voltage; a constant voltage generator receiving the DC voltage which is output from the rectifier unit and generating constant voltage having a certain voltage value; and a constant current generator receiving the constant voltage which is output from the constant voltage generator and supplying constant current having a certain current value for the plurality of LEDs in the light emitting unit.

Description

Description
LIGHT DEVICE USING LIGHTING EMITTING DIODES
Technical Field
[1] The present invention relates to a light emitting diode (LED) lighting device, and more particularly, to an LED lighting device which can use alternating-current (AC) or direct-current (DC) voltage as an input power source, and can apply constant voltage and current to LEDs to thereby prevent damage of the LEDs and minimizes an amount of electric power supplied to the LEDs. Background Art
[2] In general, various kinds of lighting devices which are installed in the indoor or outdoor advertisements or signboards are being used in order to identify images day and night.
[3] Filament bulbs, fluorescent lamps, neon sign lamps, and LED lamps are used as the lighting devices, respectively. In particular, the LEDs have the advantages that their lives are semi-permanent, their prices are inexpensive, and their electrical energy consumption is low.
[4] FIG. 1 is a configurational circuit diagram showing a conventional light emitting diode (LED) lighting device. The conventional LED lighting device includes a plurality of resistors (R1-R4) and a plurality of LEDs (LED1-LED4) connected in series to the respective resistors. Direct-current (DC) voltage (Vdc) is applied across both ends of a combination of the resistors (R1-R4) and the LEDs (LED1-LED4) which are connected in series, respectively. The plurality of LEDs (LED1-LED4) are turned on by the supplied DC voltage Vdc.
[5] When voltage or current which is applied to each LED is lower than that of reference voltage or current, the LED is not turned on. The former is greater than the latter, the light intensity of the LED is reduced or the LED is cracked to cause damage of the LED. Accordingly, a constant voltage or current should be always applied to the LEDs (LED1-LED4), respectively.
[6] However, the DC voltage (Vdc) which is a power supply voltage source is supplied to the LEDs in the case of the conventional LED lighting device. Accordingly, in the case that overvoltage or excess current is induced in the DC voltage (Vdc), the induced overvoltage or excess current is applied to the LEDs, and thus the LEDs may be damaged. Further, in the case that heat is generated in resistors which are connected in series with each other, the resistance values of the resistors are reduced. As a result, the voltage and current which are applied to LEDs become large, thereby cause the LEDs to be damaged. [7] Moreover, the conventional LED lighting devices are designed to use DC voltage as power supply voltage. Thus, AC voltage cannot be used in the conventional LED lighting devices as an alternating power supply source. As a result, if a user wrongly connects the polarities of the supply voltage by mistake or carelessly, LEDs are not turned on.
Disclosure of Invention Technical Problem
[8] To solve the above problems, it is an object of the present invention to provide a light emitting device using light emitting diodes (LEDs) including a constant voltage generator and a constant current generator, to thereby supply constant voltage and current for the LEDs to thus prevent damage of the LEDs.
[9] It is another object of the present invention to provide a light emitting device which uses not only direct-current (DC) voltage but also alternating-current (AC) voltage as a power supply voltage source, to accordingly enable the LEDs to operate normally although a user wrongly connects the polarities of the supply voltage by mistake. Technical Solution
[10] To accomplish the above object of the present invention, according to an aspect of the present invention, there is provided A lighting device using light emitting diodes (LEDs) which are turned on and emit the light, the LED lighting device comprising: a power supply unit to which direct-current (DC) or alternating-current (AC) voltage is applied in order to supply the electric power to the LEDs; a rectifier unit receiving the supply voltage supplied from the power supply unit and converting the received supply voltage into DC voltage, to then output the converted result; a constant voltage generator receiving the DC voltage which is output from the rectifier unit and generating constant voltage having a certain voltage value; and a constant current generator receiving the constant voltage which is output from the constant voltage generator and supplying constant current having a certain current value for the plurality of LEDs in the light emitting unit, wherein the constant voltage generator comprises: a switching unit which is turned on or off according to a switching control signal and outputs the DC voltage of the rectifier unit to a first node when the switching unit is turned on; a filter unit including a coil whose one end is connected to the first node and whose other end is connected to an output node and a capacitor whose one end is connected to the output node and whose other end is connected to the ground voltage, to thereby output constant voltage from which a ripple component has been removed for the output node; a distribution unit including first and second resistors, in which one end of the first resistor is connected to the output node and whose other end is connected to one end of the second resistor, to thereby output a distribution voltage, and the other end of the second resistor is connected to the ground voltage; an offset generator receiving reference voltage and the distribution voltage and outputting an offset signal according to an amount of variation of the distribution voltage when the distribution voltage has been varied; and a comparison unit comparing a triangle wave signal output from a triangular wave generator and the offset signal output from the offset generator, and outputting a switching control signal whose duty is different according to the offset signal.
[11] Preferably, the constant voltage generator further comprises: a Shottkey diode whose one end is connected to the first node, and whose other end is connected the ground voltage and which makes surge voltage or surge current generated from the first node, to the ground voltage when the switching unit is turned on or off.
[12] Preferably, the LED lighting device further comprises a first limit resistor which is installed between the rectifier unit and the constant voltage generator, and limits the maximum value of the current flowing through the constant voltage generator.
[13] Preferably, the LED lighting device further comprises a second limit resistor which is installed between the constant current generator and the light emitting unit, and limits the maximum value of the current flowing through the light emitting unit.
Advantageous Effects
[14] As described above, the present invention provides alight emitting device using light emitting diodes (LEDs) including a constant voltage generator and a constant current generator, to thereby supply constant voltage and current for the LEDs to thus prevent damage of the LEDs. Further, the present invention provides a light emitting device which uses not only direct-current (DC) voltage but also alternating-current (AC) voltage as a power supply voltage source, to accordingly enable the LEDs to operate normally although a user wrongly connects the polarities of the supply voltage by mistake. Brief Description of the Drawings
[15] The above and/or other objects and/or advantages of the present invention will become more apparent by describing the preferred embodiments thereof in detail with reference to the accompanying drawings in which:
[16] FIG. 1 is a configurational circuit diagram showing a conventional light emitting diode (LED) lighting device;
[17] FIG. 2 is a configurational circuit diagram showing an LED lighting device according to the present invention;
[18] FIG. 3 is a configurational circuit diagram showing a constant current generator of
FIG. 2;
[19] FIG. 4 is a configurational diagram showing another preferred embodiment of the constant current generator of FlG. 2; and
[20] FlG. 5 is a waveform diagram for explaining operation of the constant voltage generator of FlG. 2. Best Mode for Carrying Out the Invention
[21] Hereinbelow, an LED lighting device according to preferred embodiments of the present invention will be described with reference to the accompanying drawings. Like reference numerals and symbols denote like elements through the following embodiments.
[22] FlG. 2 is a configurational circuit diagram showing an LED lighting device according to the present invention. The LED lighting device of the present invention includes: a light emitting unit 50; a power supply unit 10; a rectifier unit 20; a constant voltage generator 30; and a constant current generator 40.
[23] The light emitting unit 50 includes a plurality of LEDs (LED1-LED4) which are turned on and emit the light if current flows therethrough and a plurality of resistors (RE1-RE4) connected in series to the plurality of LEDs, respectively.
[24] Direct-current (DC) or alternating-current (AC) voltage is applied to the power supply unit 10 in order to supply the electric power to the LEDs (LED1-LED4).
[25] The rectifier unit 20 receives the supply voltage (Vin) supplied from the power supply unit 10 and converts the received supply voltage into DC voltage (Vdc), to then output the converted result.
[26] The constant voltage generator 30 receives the DC voltage (Vdc) which is output from the rectifier unit 20 and generates constant voltage (Vcc) having a certain voltage value.
[27] The constant current generator 40 receives the constant voltage (Vcc) which is output from the constant voltage generator 30 and supplies constant current (lout) having a certain current value for the plurality of LEDs (LED1-LED4) in the light emitting unit 50.
[28] The constant voltage generator 30 includes: a switching unit (SW); a filter unit 37; a distribution unit 39; an offset generator 33; and a comparison unit 35.
[29] The switching unit (SW) is turned on or off according to a switching control signal
(SC) and outputs the DC voltage of the rectifier unit to a first node when the switching unit is turned on.
[30] The filter unit 37 includes a coil (L) whose one end is connected to the first node
(Nl) and whose other end is connected to an output node (NO) and a capacitor (C) whose one end is connected to the output node (NO) and whose other end is connected to the ground voltage (Vss), to thereby output constant voltage (Vcc) from which a ripple component has been removed for the output node (NO). [31] The distribution unit 39 includes first and second resistors (Ra, Rb), in which one end of the first resistor (Ra) is connected to the output node (NO) and whose other end is connected to one end of the second resistor (Rb), to thereby output a distribution voltage (Va), and the other end of the second resistor (Rb) is connected to the ground voltage (Vss).
[32] The offset generator 33 receives reference voltage (Vref) and the distribution voltage (Va) and outputs an offset signal (DL) according to an amount of variation of the distribution voltage (Va) when the distribution voltage (Va) has been varied.
[33] The comparison unit 35 compares a triangle wave signal (T) output from a triangular wave generator 31 and the offset signal (DL) output from the offset generator 33, and outputs a switching control signal (SC) whose duty is different according to the offset signal (DL).
[34] In the LED lighting device, the constant voltage generator 30 further includes a
Shottkey diode (SD) whose one end is connected to the first node (Nl), and whose other end is connected the ground voltage (Vss) and which makes surge voltage or surge current generated from the first node (Nl), to the ground voltage when the switching unit (SW) is turned on or off.
[35] The LED lighting device further includes a first limit resistor (RTl) which is installed between the DC voltage (Vdc) output from the rectifier unit 20 and the constant voltage generator 30, and limits the maximum value of the current flowing through the constant voltage generator 30.
[36] The LED lighting device further includes a second limit resistor (RT2) which is installed between the output of the constant current generator 40 and the light emitting unit 50, and limits the maximum value of the current flowing through the light emitting unit 50. Mode for the Invention
[37] The operation of the LED lighting device having the above-described configuration according to the present invention will follow.
[38] As shown in FIG. 2, DC or AC voltage of 8V through 40V is applied to the power supply unit 10, in order to supply the power to the LEDs (LED1-LED4). The rectifier 20 uses a bridge diode circuit, to thereby convert the DC or AC voltage (Vin) supplied from the power supply unit 10 into DC voltage (Vdc) to then output the DC voltage (Vdc). That is, although the supply voltage (Vin) is the DC or AC voltage, the voltage output from the bridge diode circuit is the DC voltage (Vdc). Accordingly, although a user wrongly connects the polarities of the DC supply voltage by mistake or carelessly, the voltage output from the bridge diode circuit is always the DC voltage (Vdc).
[39] The LED lighting device further includes a smoothing capacitor (CS) between the DC voltage (Vdc) and the ground voltage (Vss). The smoothing capacitor (CS) can prevent overvoltage or excess current generated in the DC voltage (Vdc) which is the voltage output from the rectifier unit 20, and remove a ripple component formed in the DC voltage (Vdc).
[40] The distribution voltage (Va) of the distribution unit 39 including the first resistor
(Ra) and the second resistor (Rb) increases if the constant voltage (Vcc) at the output node (NO) of the constant voltage generator 30 becomes large. The offset signal (DL) of the offset generator 33 increases by an increment of the distribution voltage (Va). Accordingly, a region having a high logic value becomes smaller in the switching control signal (SC) which is the signal output from the comparison unit 35 and thus the time when the switching unit (SW) is turned on is reduced. As a result, reduced DC voltage is output as the constant voltage (Vcc).
[41] In the meantime, the distribution voltage (Va) of the distribution unit 39 including the first resistor (Ra) and the second resistor (Rb) decreases if the constant voltage (Vcc) at the output node (NO) of the constant voltage generator 30 becomes small. The offset signal (DL) of the offset generator 33 decreases by a decrement of the distribution voltage (Va). Accordingly, a region having a high logic value becomes larger in the switching control signal (SC) which is the signal output from the comparison unit 35 and thus the time when the switching unit (SW) is turned on increased. As a result, increased DC voltage is output as the constant voltage (Vcc).
[42] That is, as shown in FlG. 5 showing the operational waveform of the constant voltage generator 30, the distribution voltage (Va) decreases if the voltage at the end of the constant voltage (Vcc) decreases, and the offset signal (DL) also decreases. A region having the high logic value becomes large in the switching control signal (SC) and thus an on-time of the switching unit (SW) becomes long. As a result, the DC voltage at the end of the constant voltage (Vcc) has an increased value. Therefore, the constant voltage generator 30 applied in the present invention varies the duty ratio of the switching control signal (SC), according to the voltage at the end of the constant voltage (Vcc), and thus controls an on-time of the switching unit (SW). As a result, the constant voltage (Vcc) at the output node which is the voltage output from the constant voltage generator 30 always has a certain constant voltage. The switching unit (SW) can be implemented by a MOS (Metal-Oxide Semiconductor) transistor or bi-polar transistor.
[43] The constant voltage (Vcc) from which the ripple component has been removed is output at the output node (NO) by the filter unit 37 including the coil (L) and the capacitor (C). The Shottkey diode (SD) in the constant voltage generator 30 enables the surge voltage or surge current which is generated at the first node (Nl) according to the on- or off-operation of the switching unit (SW) to flow to the end of the ground voltage (Vss) to thereby make the constant voltage (Vcc) which is the voltage output from the constant voltage generator 30 have stabilized certain constant voltage.
[44] The first limit resistor (RTl) is connected between the end of the DC voltage (Vdc) and the constant voltage generator 30 to thus limit the maximum value of the current flowing in the constant voltage generator 30. The LED lighting device according to the present invention includes the constant voltage generator 30 to thereby make the voltage supplied to the light emitting unit 50 always have certain constant voltage.
[45] FIG. 3 is a configurational circuit diagram showing a constant current generator 40 of FIG. 2, and FIG. 4 is a configurational diagram showing another preferred embodiment of the constant current generator of FIG. 2.
[46] As shown in FIGS. 3 and 4, the constant current generators 40 according to the embodiments of the present invention receive the constant voltage (Vcc) which is the voltage output from the constant voltage generator 30 and supply the constant current (lout) having a certain current value to a plurality of LEDs (LED1-LED4) in the light emitting unit 50.
[47] As shown in FIG. 3, the constant current generator 40 includes a constant current unit 41 and an output unit 43 using a current mirror circuit. The constant current unit 41 includes first and second MOS transistors (Ml, M2) which are two N-channel MOS transistors, and third and fourth MOS transistors (M3, M4) which are two P-channel MOS transistors both of which include a generally used current mirror circuit, respectively. Here, the constant voltage (Vcc) is input to the constant current generator 40 as the supply voltage. Accordingly, the current flowing in the second MOS transistor M2 and the fourth MOS transistor M4 is determined by the current flowing in the first MOS transistor Ml and the third MOS transistor M3. The current (lout) flowing in the fifth MOS transistor M5 of the output unit 43 is output as certain constant current according to the current flowing in the fourth MOS transistor M4.
[48] As shown in FIG. 4, the constant current generator 40 according to another preferred embodiment of the present invention includes a differential amplifier (OP) and a plurality of resistors (R1-R5) in order to output the constant current (lout). The constant current (lout) outputs a certain constant current value which is determined by Vcc*R2/Rl*R3, in which Rl, R2, and R3 are resistance values of the respective resistors (Rl, R2, R3).
[49] The constant current generator 40 applied in the present invention can be implemented by the circuits shown in FIGS. 3 or 4, but can be implemented a general con stant current circuit which can output constant current.
[50] Therefore, the LED lighting device according to the present invention includes the constant voltage generator 30 and the constant current generator 40, and thus supplies the constant voltage (Vcc) having the certain constant voltage (Vcc) and the constant current (lout) having the certain constant current to the light emitting unit 50 including a plurality of LEDs (LED1-LED4) and a plurality of resistors (RE1-RE4) connected in series with the plurality of LEDs (LED1-LED4), respectively. Accordingly, although the resistance values of the plurality of resistors (RE1-RE4) are reduced by the heat generated in the plurality of resistors (RE1-RE4), the current value and the voltage value flowing in the plurality of LEDs (LED1-LED4) can be consistently maintained constant, to thereby prevent the LEDs from being damaged and to thus enable a user to use the LEDs semi-permanently.
[51] Further, the maximum value of the current flowing in the light emitting unit 50 can be limited by the second limit resistance (RT2) which is installed between the output of the constant current generator 40 and the light emitting unit 50.
[52] As described above, the present invention has been described with respect to particularly preferred embodiments. However, the present invention is not limited to the above embodiments, and it is possible for one who has an ordinary skill in the art to make various modifications and variations, without departing off the spirit of the present invention. Thus, the protective scope of the present invention is not defined within the detailed description thereof but is defined by the claims to be described later and the technical spirit of the present invention. Industrial Applicability
[53] As described above, the present invention relates to a light emitting diode (LED) lighting device which can use alternating-current (AC) or direct-current (DC) voltage as an input power source, and can apply constant voltage and current to LEDs to thereby prevent damage of the LEDs and minimizes an amount of electric power supplied to the LEDs.
[54] The light emitting diode (LED) lighting device can be applied as lighting sources using LEDs in which the current value and the voltage value flowing in the plurality of LEDs can be consistently maintained constant, to thereby prevent the LEDs from being damaged and to thus enable a user to use the LEDs semi-permanently.

Claims

Claims
[1] A lighting device using light emitting diodes (LEDs) which are turned on and emit the light, the LED lighting device comprising: a power supply unit to which direct-current (DC) or alternating-current (AC) voltage is applied in order to supply the electric power to the LEDs; a rectifier unit receiving the supply voltage supplied from the power supply unit and converting the received supply voltage into DC voltage, to then output the converted result; a constant voltage generator receiving the DC voltage which is output from the rectifier unit and generating constant voltage having a certain voltage value; and a constant current generator receiving the constant voltage which is output from the constant voltage generator and supplying constant current having a certain current value for the plurality of LEDs in the light emitting unit, wherein the constant voltage generator comprises: a switching unit which is turned on or off according to a switching control signal and outputs the DC voltage of the rectifier unit to a first node when the switching unit is turned on; a filter unit including a coil whose one end is connected to the first node and whose other end is connected to an output node and a capacitor whose one end is connected to the output node and whose other end is connected to the ground voltage, to thereby output constant voltage from which a ripple component has been removed for the output node; a distribution unit including first and second resistors, in which one end of the first resistor is connected to the output node and whose other end is connected to one end of the second resistor, to thereby output a distribution voltage, and the other end of the second resistor is connected to the ground voltage; an offset generator receiving reference voltage and the distribution voltage and outputting an offset signal according to an amount of variation of the distribution voltage when the distribution voltage has been varied; and a comparison unit comparing a triangle wave signal output from a triangular wave generator and the offset signal output from the offset generator, and outputting a switching control signal whose duty is different according to the offset signal.
[2] The LED lighting device according to claim 1, wherein the constant voltage generator further comprises: a Shottkey diode whose one end is connected to the first node, and whose other end is connected the ground voltage and which makes surge voltage or surge current generated from the first node, to the ground voltage when the switching unit is turned on or off. [3] The LED lighting device according to claim 1 or 2, further comprising a first limit resistor which is installed between the rectifier unit and the constant voltage generator, and limits the maximum value of the current flowing through the constant voltage generator. [4] The LED lighting device as to the claim 1 or 2, further comprising a second limit resistor which is installed between the constant current generator and the light emitting unit, and limits the maximum value of the current flowing through the light emitting unit.
PCT/KR2006/004363 2005-10-28 2006-10-25 Light device using lighting emitting diodes WO2007049911A1 (en)

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