WO2008038984A1

WO2008038984A1 - Light emitting diode assembly

Info

Publication number: WO2008038984A1
Application number: PCT/KR2007/004682
Authority: WO
Inventors: Sung Ho Hong; Jung Yun Kim
Original assignee: Seoul Semiconductor Co., Ltd.
Priority date: 2006-09-29
Filing date: 2007-09-21
Publication date: 2008-04-03

Abstract

The present invention relates to a light emitting diode assembly, and more particularly, to a light emitting diode assembly using a transistor. The present invention can provide a light emitting diode assembly in which when any one of a plurality of light emitting diodes serially connected does not operate, the others can operate by bypassing the non-operating light emitting diode using a transistor.

Description

Description LIGHT EMITTING DIODE ASSEMBLY

Technical Field

[1] The present invention relates to a light emitting diode assembly, and more particularly, to a light emitting diode assembly using a transistor. Background Art

[2] A light emitting diode (LED) refers to a device which generates minority carriers

(electrons or holes) using a P-N junction structure of a compound semiconductor and emits light through recombination of the minority carriers. A light emitting device using such a light emitting diode is superior in terms of power saving and durability since it has less electric power consumption and a longer life span of several to several ten times as compared an existing electric light bulb or a fluorescent lamp. In order to use the device having such a light emitting diode for illumination, a light emitting diode assembly having a plurality of light emitting diodes is used conventionally.

[3] The conventional light emitting diode assembly includes a plurality of light emitting diodes, which are serially connected to one another.

[4] At this time, since the conventional light emitting diode assembly has the plurality of light emitting diodes serially connected with one another, when any one of the plurality of light emitting diodes does not operate, the others do not also operate.

[5] Further, when the plurality of light emitting diodes are connected in parallel in order to solve such a problem, luminance of each light emitting diode is not uniform since current is not uniformly distributed. Disclosure of Invention Technical Problem

[6] The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a light emitting diode assembly where even when any one of a plurality of light emitting diodes serially connected with one another does not operate, the others can operate normally. Technical Solution

[7] The present invention for achieving the object, there is provided a light emitting diode assembly comprising a plurality of light emitting diodes serially connected to each other; a switching unit connected to a circuit including the plurality of light emitting diodes; a measuring unit for measuring whether or not each of the plurality of light emitting diodes operate; and a controller for determining whether or not each of the plurality of light emitting diodes operate from the measuring unit and for operating the switching unit. [8] At this time, the switching unit may include transistors respectively connected to the plurality of light emitting diodes, and the respective transistors are configured so as to bypass current applied to the responding light emitting diodes when the responding emitting diodes do not operate.

[9] The controller may include a microcomputer.

[10] Further, the light emitting diode assembly of the present invention may further inc lude an amplifier for amplifying a signal output from the controller.

[11] At this time, the amplifier may include an operational amplifier.

Advantageous Effects

[12] As described above, the present invention can provide a light emitting diode assembly in which when any one of a plurality of light emitting diodes serially connected does not operate, the others can operate by bypassing the non-operating light emitting diode using a transistor. Brief Description of the Drawings

[13] FIG. 1 is a plan view of a light emitting diode assembly according to the present invention.

[14] FIG. 2 is a circuit diagram of the light emitting diode assembly according to the present invention.

[15] [Explanation of Reference Numerals for Major Portions Shown in Drawings]

[16] 100: Base plate 200a: First light emitting diode

[17] 200b: Second light emitting diode 200c: Third light emitting diode

[18] 20Od: Fourth light emitting diode 300a: First transistor

[19] 300b: Second transistor 300c: Third transistor

[20] 300d: Fourth transistor 400a: First measuring unit

[21] 400b: Second measuring unit 400c: Third measuring unit

[22] 40Od: Fourth measuring unit 500: Controller

[23] 600: Amplifier

[24]

Best Mode for Carrying Out the Invention

[25] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[26] However, the present invention is not limited to the embodiment set forth herein but can be implemented in various forms. In addition, the embodiments are merely provided to allow the present invention to be completely described herein and to fully convey the scope of the present invention to those skilled in the art. Throughout the drawings, like reference numerals are used to designate like elements.

[27] FIG. 1 is a plan view of a light emitting diode assembly according to the present invention, and FIG. 2 is a circuit diagram of the light emitting diode assembly according to the present invention.

[28] As shown in FIG. 1, the light emitting diode assembly according to the present invention comprises a base plate 100, a plurality of light emitting diodes 200 mounted on the base plate 100, a switching unit 300, a measuring unit 400, and a controller 500. At this time, the base plate 100 may be formed with an electrode pattern for applying external power to the light emitting diodes.

[29] The base plate 100 is mounted with the plurality of light emitting diodes and is to apply external power to the plurality of light emitting diodes. To this end, electrodes (not shown) are formed at predetermined positions of the base plate 100. Such a base plate 100 may be a printed circuit board PCB for heat radiation of the plurality of light emitting diodes and for application of external power. That is, for example, when a metal core printed circuit board MCPCB is used as the printed circuit board, metal cores of the metal core printed circuit board are connected to the electrodes, so that the plurality of light emitting diodes 200 are electrically connected to the electrodes through the metal cores.

[30] The plurality of light emitting diodes 200, which are light sources of the light emitting diode assembly of the present invention, have light emitting chips mounted therein. That is, the light emitting diode has a structure in which a light emitting chip is mounted to emit light by external power, for example, a structure in which a light emitting chip is mounted on a board, on which an electrode pattern is formed, to be electrically connected to the electrode pattern. Such a light emitting chip generates minority carriers (electrons or holes) using a p-n junction structure of a semiconductor and emits light through recombination of the minority carriers. However, the light emitting diode according to the present invention is not limited thereto, but may be constructed with a plurality of light emitting chips. That is, the light emitting chips may be mounted directly on the base plate 100 in stead of mounting the light emitting diodes thereon. For example, the light emitting chips may be mounted on the base plate 100, and the electrode pattern of the base plate 100 and the light emitting chips may be connected with each other using predetermined wires. Further, the light emitting diode can emit various colors according to the types of the light emitting chips and phosphors. In this embodiment, such light emitting diodes will be described by way of examples of 4 light emitting diodes, i.e., first to fourth diodes 200a to 20Od. However, the present invention is not limited thereto, but the light emitting diode may be plural.

[31] The switching unit 300, which is to bypass the power applied to non-operating one of the plurality of light emitting diodes 200, includes transistors in the present invention. This embodiment includes first to fourth transistors 300a to 300d as the switching unit, and the first to fourth transistors 300a to 300d are connected to the first to fourth diodes 200a to 20Od, respectively. At this time, it is desired that the number of the transistors of the switching unit is identical to that of the light emitting diodes. Further, although FIG. 1 shows that the switching unit 300 is mounted on the base plate 100, the present invention is not limited thereto. For example, the switching unit 300 may be mounted in the light emitting diode.

[32] The measuring unit 400, which is to check current of the plurality of light emitting diodes 200 and the operational state thereof, includes a logic device. That is, the measuring unit 400 individually connected to each of the plurality of light emitting diodes 200 measures current values of each light emitting diodes to be measured, and checks the operational state of the light emitting diodes according to the measured current values. At this time, the measuring unit 400 is connected to the controller 500 to transfer information on the operational state of the light emitting diodes, i.e., an operational signal, thereto. Further, the measuring unit 400 is included in not the base plate 100 but the light emitting diodes like the switching unit 300.

[33] The controller 500, which is to control the switching unit 300, includes a microcomputer in this embodiment. Such a controller 500 controls the switching unit 300 according to the operational state of the light emitting diodes according to the operational signal applied to the measuring unit 400.

[34] Meanwhile, the light emitting diode assembly of the present invention may further include an amplifier 600 for amplifying the signal applied to the switching unit 300 from the controller 500. The amplifier 600 may include an operational amplifier (OPAMP).

[35] In the light emitting diode assembly of the present invention having such a configuration, the first to fourth light emitting diodes 200a to 20Od are respectively connected to the first to fourth transistors 300a to 300d, and the firth to fourth transistors 300a to 300d are respectively connected to the first to fourth measuring units 400a to 40Od (400). Further, the first to fourth measuring units 400a to 40Od (400) are connected to the controller 500, and the controller 500 is connected to the switching unit 300 through the amplifier 600. Accordingly, the first to fourth measuring units 400a to 40Od (400) continuously measure the operational states of the first to fourth light emitting diodes 200a to 20Od. Then, when there is a non-operating light emitting diode in the first to fourth light emitting diodes 200a to 20Od, the controller 500 determines the non-operating light emitting diode by the measuring unit 400 connected to the non-operating light emitting diode, and bypasses the non- operating light emitting diode by turning on the transistor connected thereto.

[36] For example, if the second light emitting diode among the first to fourth light emitting diode 200a to 20Od does not operate, the operational state of the second light emitting diode 200b is measured by the second measuring unit 400b connected thereto. Then, the operational signal of the second light emitting diode 200b is applied to the controller 500 connected to the second measuring unit 400b, and the controller 500 determines from the operational signal that the second light emitting diode 200b does not operate.

[37] The controller 500 applies a signal to the second transistor 300b connected to both ends of the second light emitting diode 200b. Then, the second transistor 300b is turned on by the signal, so that the current applied to the second light emitting diode 200b is bypassed to the second transistor 300b. The current to be applied to the second light emitting diode 200b which does not operate is bypassed to the second transistor 300b, so that current is normally applied to the third and fourth light emitting diodes 200c and 20Od.

[38] According to the present invention, although there is non-operating one of the plurality of light emitting diodes, the non-operating light emitting diode is bypassed by means of the switching unit 300, so that the others can operate. Further, the present invention has the same effect that the plurality of light emitting diodes 200 are connected in parallel, and at the same time, has an advantage of serial connection, i.e., uniform luminance of the plurality of light emitting diodes due to uniform current applied thereto.

[39] Although the present invention has been described in connection with the accompanying drawings and the preferred embodiment, it will be understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the invention defined by the appended claims.

[40] For example, although in the illustrated embodiments, a general light emitting diode assembly for illumination has been described as an example, the present invention is not limited thereto but can be applied to a light emitting diode assembly for an automobile head light which requires uniform luminance. That is, in a case where the present invention is applied to the light emitting diode assembly for an automobile head light which is equipped with has a plurality of light emitting diodes, the light emitting diode assembly for an automobile head light can be prevented from not operating even though any one of the plurality of light emitting diodes does not operate.

Claims

[1] A light emitting diode assembly, comprising: a plurality of light emitting diodes serially connected to each other; a switching unit connected to a circuit including the plurality of light emitting diodes; a measuring unit for measuring whether or not each of the plurality of light emitting diodes operate; and a controller for determining whether or not each of the plurality of light emitting diodes operate from the measuring unit and for operating the switching unit. [2] The light emitting diode assembly as claimed in claim 1, wherein the switching unit comprises transistors respectively connected to the plurality of light emitting diodes, the respective transistors bypassing current applied to the responding light emitting diodes when the responding light emitting diode do not operate. [3] The light emitting diode assembly as claimed in claim 1, wherein the controller comprises a microcomputer. [4] The light emitting diode assembly as claimed in claim 1, further comprising an amplifier for amplifying a signal output from the controller. [5] The light emitting diode assembly as claimed in claim 4, wherein the amplifier comprises an operational amplifier.