WO2008126972A1

WO2008126972A1 - Led including driver chip

Info

Publication number: WO2008126972A1
Application number: PCT/KR2007/006137
Authority: WO
Inventors: Jung Sub Kim; Hee Wook Ahn
Original assignee: Jung Sub Kim; Hee Wook Ahn
Priority date: 2007-04-12
Filing date: 2007-11-30
Publication date: 2008-10-23
Also published as: KR100807925B1

Abstract

The present invention relates to a light-emitting diode (LED) including a driver chip that is mounted in an LED case together with a light-emitting chip, electrically connected to the light- emitting chip, and electrically connected to a lead terminal projected to the outside of the case through a wire so as to individually control the LED.

Description

Description LED INCLUDING DRIVER CHIP

Technical Field

[1] The present invention relates to a light-emitting diode (LED) including a driver chip and, more particularly, to an LED including a driver chip, that is mounted in an LED case together with a light-emitting chip to provide a driver chip integrated package to thereby individually control the LED and simplify a circuit configuration. Background Art

[2] An LED used in various lightings and display devices emits light using luminescence (also referred to as "electroluminescence") generated when a voltage is applied to a semiconductor.

[3] The LED is fabricated using materials that satisfy conditions in which an emission wavelength exists in a visible region or a near-infrared region, luminous efficiency is high and a p-n junction can be formed. These materials include compound semiconductors such as GaN, GaAs, GaP, GaAs P , Ga Al As, InP and In Ga P. The l-x x 1-x x 1-x x compound semiconductors are mounted inside LEDs in the form of a flip chip.

[4] Luminescence is largely divided into luminescence by recombination of free carriers and luminescence by recombination at the impurity luminescent center. The wavelength of light generated by recombination at the impurity luminescent center varies depending on the type of impurity doped into a light-emitting chip constituting an LED. For example, in the case of Gap, light generated according to luminescence in which zinc and oxygen atoms are involved red (having a wavelength of 700nm) and light generated according to luminescence in which nitrogen atoms are involved is green (having a wavelength of 500nm). That is, light generated from the LED has a unique color (wavelength) that depends on the type of an impurity doped into the light- emitting chip and the material of the light-emitting chip.

[5] The aforementioned conventional LED has an advantage merit in that it is a small size and a long lifespan. In addition, the conventional LED advantageously has high energy efficiency and a low operating voltage due to direct conversion of electric energy into light energy.

[6] Accordingly, the LED having the above-described advantages is used as a light source of a back- light module of a liquid crystal display (LCD) that is a light-receiving type flat panel display device using an external light source called a back- light so as to decrease the thickness and size of the LCD and improve color reproducibility.

[7] A direct light type LED back-light for an LCD is constructed in such a manner that

LEDs are arranged in series/parallel and controls an IC driver corresponding to each serial LED line to maintain the current of each serial LED line uniformly so as to control the luminance, uniformity and color difference of the LCD.

[8] However, the LCD back-light entails a problem in that it controls a plurality of conventional LEDs in series or in parallel to generate white light, and thus color reproducibility and color uniformity are decreased due to a control error of LEDs and LED drivers or the back- light. In addition, when LEDs are serially arranged, back light units (BLUs) are controlled on a line unit basis so that there is a limitation in increasing the color uniformity of the back light units. Accordingly, the conventional method of controlling LEDs in series or parallel has been recently changed to an individual LED control method. The individual LED control method controls dot lights of a back- light and provides relatively high image reproducibility as compared to an existing product.

[9] However, an LED is electrically controlled by a constant current driver, a constant voltage driver or a driving element mounted on a board separated from the LED, and thus a board having a plurality of driving elements mounted thereon is required for individual LED control. Accordingly, the LED still has a problem in that it is difficult to manufacture and a circuit configuration becomes complicated. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the conventional art, and a primary object of the present invention is to provide an LED including a driver chip, in which the driver chip and a light-emitting chip are mounted together in an LED case such that the LED can be independently controlled and a circuit configuration of the LED can be simplified. Technical Solution

[11] To accomplish the object of the present invention, there is provided a light-emitting diode (LED) including a driver chip, wherein a driver chip 60(6Oa) and at least one light-emitting chip 50(50a) are mounted together in an LED case, and the driver chip 60(6Oa) and the light-emitting chip 50(50a) are electrically connected to each other and electrically connected to lead terminals 70, 70a, 70b, 70c and 7Od projected to the outside of the case through wires 80 and 80a.

[12] The driver chip 60 and the light-emitting chip 50 are mounted on a sub-mount 40 located on a heat sink 30 in such a manner as to be spaced apart from each other and connected to each other through the wire 90.

[13] The heat sink 30 includes a plurality of parts formed through injection molding and spaced apart from each other in the case, the driver chip 50 and the at least one light- emitting chip 50 are respectively located on the plurality of parts of the heat sink 30, and a heat-radiating material 32 is filled between the parts of the heat sink 30. [14] The driver chip 60a and the light-emitting chip 50a are selectively mounted on a power supply lead terminal, a ground lead terminal and input/output lead terminals projected to the outside of the case, the driver chip 60a and the light-emitting chip 50a are connected to each other through the wire 90a, the driver chip 60a is electrically connected to the power supply lead terminal, the ground lead terminal and the input/ output lead terminal, and the light-emitting chip 50a is electrically connected to the power supply lead terminal and the ground lead terminal.

[15] The driver chip 60(6Oa) comprises a constant current driver 61 for stably driving the driver chip 50, a current controller 62 for controlling the constant current driver 61 to output uniform current, a PWM controller 63 for controlling brightness according to the constant current driver 61, an LED open detector 64 for detecting whether the light-emitting chip 50 is normally connected, a thermal error detector 65 for determining whether the circuit is overheated, an address memory 66 storing the address of the driver chip 60, a current detector 67 for detecting the output current of the constant current driver 61, and a controller 68 for controlling the operations of the current controller 62 and the PWM controller 63 according to data transmitted from an external device and the signal output from the current detector 67, outputting the signal output from the LED open detector 64 or the signal output from the thermal error detector 65 together with an address signal corresponding thereto, and stopping the operation of the driver chip 60 when a thermal error is generated.

Advantageous Effects

[16] According to the present invention, an LED includes a driver chip integrated thereinto, and thus each LED can be independently controlled when a plurality of LEDs are used. Accordingly, LEDs can be used as dot lights of a back light unit of an LCD no linear lights so that a technique of controlling an image displayed on a screen of the LCD in connection with the back light unit through individual dot control, that is, a back light image processing technique, can be used. This maximizes a contrast ratio of the LCD.

[17] Furthermore, since the driver chip is included in the LED, initial current drift of the

LED can be prevented, LCD monitor luminance uniformity calibration can be automated, LED overheating due to current sensing can be solved and LED short- circuiting can be detected.

[18] Moreover, light sources as well as LCD back lights can be individually controlled through dot light control, and thus the LED can be applied to application fields such as an electric bulletin board that uses the LED as a dot light.

[19] Furthermore, when the LED including the driver chip according to the present invention is used, the manufacturing cost of the LED can be reduced compared to a conventional LED and power consumption can be decreased so as to solve a heat- generating problem of a device employing the LED.

[20] In addition, since each LED includes an individual driver chip, individual accurate control is simplified so as to achieve excellent luminance uniformity and color reproducibility, and thus the quality of products using the LED is improved. Brief Description of the Drawings

[21] Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[22] FIG. 1 illustrates an SMD type LED including a driver chip according to an embodiment of the present invention;

[23] FIG. 2 illustrates an SMD type LED including a driver chip according to another embodiment of the present invention;

[24] FIG. 3 illustrates a LEAD type LED including a driver chip according to an embodiment of the present invention; and

[25] FIG. 4 illustrates a configuration of a driver chip according to the present invention.

[26] *Explanation on reference numerals of main elements of the drawings*

[27] 20: Case

[28] 40: Sub mount

[29] 50, 50a: Light-emitting chip

[30] 60, 60a: Driver chip

[31] 80, 90: Wire

Mode for the Invention

[32] The present invention mounts a driver chip and a light-emitting chip together in an

LED case, electrically connects the driver chip and the light-emitting chip to each other, forms a power supply lead terminal, a ground lead terminal and input/output lead terminals connected to the driver chip and the light-emitting chip such that the lead terminals are projected to the outside of the case and electrically connects the light-emitting chip, the driver chip and the lead terminals through wires to achieve individual LED control.

[33] In the case of an LED that reproduces white using red, green and blue light-emitting chips or a package in which a plurality of light-emitting chips are mounted, a plurality of light-emitting chips and a driver chip can be integrated into a single LED case.

[34] In the aforementioned configuration, the driver chip and the light-emitting chip are separated from each other and connected to each other through a wire. The driver chip communicates with an external device through the input/output lead terminals with its own address to stably drive the light-emitting chip and achieve individual LED control. [35] Embodiments of the present invention are explained with reference to the attached drawings.

[36] FIG. 1 illustrates an SMD type LED including a driver chip according to an embodiment of the present invention, FIG. 2 illustrates an SMD type LED including a driver chip according to another embodiment of the present invention, FIG. 3 illustrates a LEAD type LED including a driver chip according to an embodiment of the present invention, and FIG. 4 illustrates a configuration of a driver chip according to the present invention.

[37] Referring to FIG. 1, the SMD type LED including a driver chip according to an embodiment of the present invention includes a case 20 having a light-emitting lens 10 provided thereon, which emits light at a predetermined angle, a heat sink 30 that is located at the bottom of the case 20 and radiates heat generated inside of the case 20, a sub-mount 40 located on the heat sink 30, a light-emitting chip 50 and a driver chip 60 mounted on the sub-mount 40, a lead terminal projected to the outside of the case 20, a first wire 80 for connecting the lead terminal 70 with the driver chip 60 and the light- emitting chip 50, and a second wire 90 for connecting the driver chip 60 and the light- emitting chip 50. In this manner, the driver chip 60 and the light-emitting chip 50 are packaged in the case 20.

[38] In the aforementioned configuration, the light-emitting chip 50 and the driver chip

60 are mounted on the sub-mount 40 through soldering connection, spaced apart from each other and connected to each other through the second wire 90 in order to prevent overheating.

[39] The lead terminal 70 includes a power supply lead terminal, a ground lead terminal and input/output lead terminals. The input/output lead terminals are electrically connected to the driver chip 60 through the first wire 80.

[40] In the SMD type LED illustrated in FIG. 2, the heat sink 30 is divided into two parts during a molding process and located having a predetermined gap between the two parts. A plurality of sub-mounts 40 are respectively located on the divided sub-mounts 30, and the light-emitting chip 50 and the driver chip 60 are respectively mounted on the plurality of sub-mounts 40 and connected to each other through the second wire 90. A heat-radiating material 32 is filled in the gap between the heat sinks 30 to reduce thermal interference between the driver chip 60 and the light-emitting chip 50.

[41] Referring to FIG. 3, the LEAD type LED includes a power supply lead terminal

70a, a ground lead terminal 70b, input/output lead terminals 70c and 7Od, a light- emitting chip 50a mounted on the power supply terminal 70a, a driver chip 60a mounted on one of the input/output lead terminals 70c and 7Od, a second wire 90a for connecting the light-emitting chip 50a and the driver chip 60a, a plurality of first wires 80a for electrically connecting the driver chip 60a to the input/output lead terminals 70c and 7Od, the power supply lead terminal 70a and the ground lead terminal 70b and electrically connecting the light-emitting chip 50a to the power supply lead terminal 70a and the ground lead terminal 70b, and a light-emitting lens 10a formed by molding the tops of the lead terminals 70a, 70b, 70c and 7Od including the light-emitting chip 50a and the driver chip 60b with transparent silicon. The light-emitting lens 10a serves as a case.

[42] Referring to FIG. 4, the driver chip 60 and 60a includes a constant current driver 61 for stably driving the driver chip 50, a current controller 62 for controlling the constant current driver 61 to output uniform current, a pulse width modulation (PWM) controller 63 for controlling brightness according to the constant current driver 61, an LED open detector 64 for detecting whether the light-emitting chip 50 is normally connected, a thermal error detector 65 for determining whether the circuit is overheated, an address memory 66 storing the address of the driver chip 60 and 60a, a current detector 67 for detecting the output current of the constant current driver 61, and a controller 68 for controlling the operations of the current controller 62 and the PWM controller 63 according to data transmitted from an external device and the signal output from the current detector 67, outputting the signal output from the LED open detector 64 or the signal output from the thermal error detector 65 together with an address signal corresponding thereto, and stopping the operation of the driver chip 60 when a thermal error is generated.

[43] In FIG. 4, reference numeral 69 denotes an over- voltage detector for protecting the driver chip 60 and 60a from over- voltage.

[44] The current and voltage of the driver chip 60 having the aforementioned configuration are accurately controlled, and thus the color reproducibility and color uniformity of the LED including the driver chip 60 can be improved.

Claims

[1] A light-emitting diode (LED) including a driver chip, wherein a driver chip

60(6Oa) and at least one light-emitting chip 50(5Oa) are mounted together in an LED case, and the driver chip 60(6Oa) and the light-emitting chip 50(5Oa) are electrically connected to each other and electrically connected to lead terminals 70, 70a, 70b, 70c and 7Od projected to the outside of the case through wires 80 and 80a.

[2] The LED including a driver chip according to claim 1, wherein the driver chip 60 and the light-emitting chip 50 are mounted on a sub-mount 40 located on a heat sink 30 in such a manner as to be spaced apart from each other and connected to each other through the wire 90.

[3] The LED including a driver chip according to claim 2, wherein the heat sink 30 includes a plurality of parts formed through injection molding and spaced apart from each other in the case, the driver chip 50 and the at least one light-emitting chip 50 are respectively located on the plurality of parts of the heat sink, and a heat-radiating material 32 is filled between the parts of the heat sink 30.

[4] The LED including a driver chip according to claim 1, wherein the driver chip

60a and the light-emitting chip 50a are selectively mounted on a power supply lead terminal, a ground lead terminal and input/output lead terminals projected to the outside of the case, the driver chip 60a and the light-emitting chip 50a are connected to each other through the wire 90a, the driver chip 60a is electrically connected to the power supply lead terminal, the ground lead terminal and the input/output lead terminal, and the light-emitting chip 50a is electrically connected to the power supply lead terminal and the ground lead terminal.

[5] The LED including a driver chip according to claim 2 or 4, wherein the driver chip 60(6Oa) comprises a constant current driver 61 for stably driving the driver chip 50, a current controller 62 for controlling the constant current driver 61 to output uniform current, a PWM controller 63 for controlling brightness according to the constant current driver 61, an LED open detector 64 for detecting whether the light-emitting chip 50 is normally connected, a thermal error detector 65 for determining whether the circuit is overheated, an address memory 66 storing the address of the driver chip 60, a current detector 67 for detecting the output current of the constant current driver 61, and a controller 68 for controlling the operations of the current controller 62 and the PWM controller 63 according to data transmitted from an external device and the signal output from the current detector 67, outputting the signal output from the LED open detector 64 or the signal output from the thermal error detector 65 together with an address signal corresponding thereto, and stopping the operation of the driver chip 60 when a thermal error is generated.