KR101186647B1

KR101186647B1 - Light emitting diode module

Info

Publication number: KR101186647B1
Application number: KR1020060061030A
Authority: KR
Inventors: 류승렬
Original assignee: 서울반도체 주식회사
Priority date: 2006-06-30
Filing date: 2006-06-30
Publication date: 2013-01-18
Also published as: KR20080002295A

Abstract

The present invention relates to a light emitting diode module, and more particularly, to a light emitting diode module having a plurality of light emitting diode packages have a uniform brightness. According to the present invention, at least one light emitting diode package which is not driven by a light emitting diode module may be used as a light receiving element to detect a decrease in light intensity of a partial light emitting diode package. In addition, since the present invention does not require a brightness sensor, a cost thereof may be reduced, and a compact backlight unit and an electronic board, in which the brightness sensor is not mounted, may maintain uniform brightness.

Light emitting diode module, backlight unit, brightness, pulse width modulation, light receiving element

Description

Light Emitting Diode Modules {LIGHT EMITTING DIODE MODULE}

1 is a conceptual diagram of a light emitting diode module according to the present invention.

2 is a waveform diagram illustrating a pulse width modulation method.

3 is a waveform diagram of a pulse signal applied to the light emitting diode module according to the present invention;

100: drive unit 120: current measuring unit

140: control unit 160: memory unit

180: signal generator 220: first light emitting diode package

240: second LED package

The present invention relates to a light emitting diode module, and more particularly, to a light emitting diode module having a plurality of light emitting diode packages have a uniform brightness.

Recently, flat panel display devices such as liquid crystal displays (LCDs) and plasma display panels (PDPs) are rapidly developing in place of cathode ray tubes (CRTs).

Among such flat panel display devices, unlike a plasma display device or the like, a liquid crystal display device has a structure which does not have self-luminescence and requires a light source. Accordingly, the liquid crystal display device may include various light sources according to the screen display method. For example, the backlight unit including the light source may be disposed on the rear surface of the liquid crystal display panel.

Light sources of such backlight units include light sources such as electroluminescent lamps (ELs), light emitting diode (LED) modules, and cold cathode fluorescent lamps (CCFLs).

The backlight unit using the light emitting diode module of the backlight unit according to the prior art is equipped with a brightness sensor to implement a uniform white light. At this time, in the backlight using the red (R), green (G), and blue (B) light emitting diode modules, a feedback circuit and a brightness sensor are added to receive the luminance of each light source and maintain the uniformity of the luminance and color, thereby providing uniform white light. Implement

However, the light emitting diode module according to the related art increases in cost as the brightness sensor is added, and the brightness sensor cannot detect a failure of the individual light emitting diode package. In addition, in a small backlight unit, it is difficult to secure a space required for mounting a luminance sensor, and thus a color feedback circuit cannot be implemented.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a light emitting diode module having a constant luminance.

Another object of the present invention is to provide a light emitting diode module capable of luminance feedback in a small backlight unit.

In order to achieve the above object, the present invention includes a plurality of light emitting diode packages and a driver for sequentially driving the plurality of light emitting diode packages, wherein at least one light emitting diode package of the plurality of light emitting diode packages operates as a light receiving element. The driving unit provides a light emitting diode module, characterized in that for controlling the current or voltage applied to the light emitting diode package by the current or voltage measured in the light emitting diode package operating as a light receiving element.

The driving unit includes a current measuring unit for measuring current or voltage of the LED package operating as the light receiving element, a memory unit storing luminance data according to the current or voltage measured by the current measuring unit, and the current measuring unit It may include a signal generator for generating a signal for driving the light emitting diode module by the luminance data according to the measured current or voltage.

In this case, the signal generator may generate a pulse width modulated signal, and the plurality of light emitting diode packages may operate as light emitting devices when a current is applied, and as a light receiving device when no current is applied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

However, the present invention is not limited to the embodiments described below, but may be implemented in various other forms, and these embodiments are not intended to be exhaustive or to limit the scope of the invention to those skilled in the art. It is provided to let you know completely. Like reference numerals refer to like elements throughout. In addition, although the present invention may use a plurality of LED packages, in the present embodiment, for convenience of description, two LED packages will be described as embodiments.

1 is a conceptual diagram of a light emitting diode module according to a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining a pulse width modulation method, and FIG. 3 is a diagram of a pulse signal applied to a light emitting diode module according to the present invention. It is a waveform diagram.

As shown in FIG. 1, the LED module according to the first embodiment of the present invention includes a first LED package 220 and a second LED package 240 provided at a periphery of the first LED package 220. ) And a driver 100 for driving the first and second LED packages 220 and 240.

The first light emitting diode package 220 may be a light source of a light emitting diode module, and may include a light emitting chip for emitting light and a fluorescent material for exciting the light and converting the light into light having a different wavelength. The light emitting chip is a semiconductor device that generates a small number of carriers (electrons or holes) injected using a p-n junction structure of a semiconductor and emits light by recombination thereof, and may be manufactured using a compound such as gallium arsenide. The light emitting diode package emits white light using a predetermined light emitting chip and a fluorescent material, for example, a blue light emitting chip and a yellow fluorescent material, or emits red (R), green (G), and blue (B) light, respectively. The chips can be combined to emit white light. However, the present invention is not limited thereto, and the first LED package 220 may emit light other than white. That is, the first light emitting diode package 220 may emit light other than white by selecting a light emitting chip and a fluorescent material to emit light other than white.

Further, in the present embodiment, the light emitting diode module is composed of a plurality of light emitting diode packages, but is not limited thereto. The light emitting diode module may be composed of a plurality of light emitting chips.

The second light emitting diode package 240 is the same light emitting diode package as the first light emitting diode package 220, and operates as a light receiving element when not in operation. That is, the first and second light emitting diode packages 220 and 240 both serve as light emitting devices when not operating. This principle is the principle of a general photodiode or a general light emitting chip used in the present invention is also configured in the form of p-n junction, so that the photovoltaic effect of emitting electrons when irradiated with light without applying a bias.

The photovoltaic effect refers to a phenomenon in which electromotive force is generated by irradiation of light as one of the photoelectric effects, and is mainly seen at the interface of a semiconductor. That is, since there is a contact potential difference in the interface between a pn junction or a metal having a rectifying action and a semiconductor in general, when a strong light is incident on this part, electrons and holes made in the semiconductor are separated due to the contact potential difference, and thus different kinds of electricity are applied to both materials. Appears.

The driving unit 100 is a light receiving element, in the present embodiment, the current measuring unit 120 for measuring the current of the second LED package 240 and the second light emitting diode package 240 is measured Comparing the memory unit 160 in which the luminance data of the first LED package 220 according to the current value and the value measured by the current measuring unit 120 with the data stored in the memory unit 160 The controller 140 and a signal generator 180 for applying a current to the first LED package 220 by the controller 140.

The current measuring unit 120 measures the current or voltage of the second LED package 240 generated by the light emitted from the first LED package 220.

The controller 140 drives the signal generator 180 by comparing the current value of the first LED package 220 measured by the current measurer 120 with data stored in the memory unit 160. do.

The memory unit 160 stores data necessary for the controller 140, and the current value of the second LED package 240 measured according to the luminance value of the first LED package 220 is increased. It is stored in advance.

The signal generator 180 is for applying a current to the first LED package 220, and converts the DC power applied from a power supply (not shown) into a pulse shape to form the first LED package 220. To feed. In the present invention, the signal generator 180 converts the DC power applied from the power supply source into a pulse form using a pulse-width modulation (PWM) method and changes the width of the pulse according to the size of the modulation signal.

Such a pulse width modulation method has a pulse shape that turns the power supply on and off at regular intervals, and changes the duty ratio (ratio of on time and off time) of the pulse. For example, when the signal having the same pulse width as Part A is applied to the light emitting diode package as shown in FIG. It will be lower than when the same signal is applied.

The signal generator 180 according to the present invention basically supplies a pulse signal as shown in FIG. 3 to the first and second LED packages 220 and 240. That is, for example, a signal such as Part C is applied to the first LED package 220, and a signal such as Part D which shifts the signal of Part C for a predetermined time is applied to the second LED package 240. It is driven sequentially.

In the light emitting diode module according to the present invention having the structure as described above, a signal generated by the signal generator 180 is applied as shown in FIG. 3, and the signal is turned on by the first LED package 220. ① the area, the area where the first and second light emitting diode packages 220 and 240 are turned on at the same time, ② the area where the second light emitting diode package 240 is turned on, and the first and the second light emitting diode package. (220, 240) can be divided into the area ④ all off.

In the light emitting diode module, when Part C, that is, the first LED package 220 is turned on and Part D, that is, the second LED package 240 is turned off (1 region), the second LED package ( A current should not be applied to the 240, but a constant current flows in the second LED package 240 according to the intensity of light emitted from the first LED package 220. The current measuring unit 120 measures the current generated by the second LED package 240, and the measured current value is transmitted to the controller 140. In this case, the controller 140 compares the current value of the first light emitting diode package 220 measured by the current measuring unit 120 with data stored in the memory unit 160 to determine the first light emitting diode package 220. ) Luminance is checked. In this case, when the current detected by the second LED package 240 is lower than the reference current during the operation of the first LED package 220, since the luminance of the first LED package 220 is low, the duty of the Part C signal is low. By increasing the ratio to increase the current applied to the first LED package 220, a uniform white light can be obtained by matching the same with the reference voltage. On the contrary, when the current detected by the second LED package 240 is higher than the reference current, since the luminance of the first LED package 220 is high, the duty ratio of the Part C signal is reduced to reduce the duty ratio of the first LED package 220. By reducing the current to be applied, it can be made equal to the reference current.

In addition, when the second LED package is turned on and the first LED package 220 is turned off (3 region), the second LED package 220 may be set to the current or voltage value measured by the first LED package 220 in the same manner as described above. 2, the brightness of the LED package 240 may be adjusted.

However, the present invention is not limited thereto, and the luminance of the first and second light emitting diode packages 220 and 240, that is, the light receiving element and the light emitting element is equally adjusted by the current or voltage value measured by the first light emitting diode package 220. It may be.

Meanwhile, in the above-described embodiment, a light emitting diode module having only one of the plurality of light emitting diode packages as a light receiving element has been described. However, the present invention is not limited thereto, and all of the plurality of light emitting diode packages may be used as the light receiving device. Of course, the LED package to operate as the light receiving element may operate as the light receiving element only when it is in an off state. In addition, a multi-chip light emitting diode package in which a plurality of light emitting diodes are built into one light emitting diode package, for example, light emitting white light by combining light emitting diodes emitting red (R), green (G), and blue (B) light In the case of using a diode package, a uniform luminance may be maintained by checking the voltage of any one of a plurality of light emitting diodes embedded in the multi-chip LED package. At this time, if all of the light emitting diodes emitting red (R), green (G), and blue (B) light are turned on, the luminance of the other light emitting diode may be checked.

In addition, in the above-described embodiment, the plurality of light emitting diode packages are individually connected to the signal generator 180, but the present invention is not limited thereto. The plurality of light emitting diode packages may be formed in a plurality of groups connected in series or in parallel. In addition, the luminance of the other group may be adjusted by checking the current or voltage of any one of the plurality of groups.

As described above, the light emitting diode module according to the present invention does not detect when the brightness of the partial light emitting diode package is reduced in the backlight unit using the conventional brightness sensor using at least one light emitting diode package which is not driven among the plurality of light emitting diode packages. You can minimize problems that you can't. In addition, since a luminance sensor is not required, a cost can be reduced, and uniform luminance can be maintained even in a small backlight unit in which a luminance sensor cannot be mounted.

Although described above with reference to the drawings and embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit of the invention described in the claims below. I can understand.

For example, in the illustrated embodiment, the backlight unit of the liquid crystal display has been described as an embodiment. However, the present invention may be applied to an electronic board using a light emitting diode. That is, in the case of a light emitting panel in which a plurality of light emitting diodes are modularized, luminance of another light emitting diode or a group of light emitting diodes is measured by checking a current or voltage of a light emitting diode or a group of light emitting diodes that are not turned on in a light emitting diode that forms one pixel. can do.

As described above, according to the present invention, the light intensity of the partial light emitting diode package can be detected using at least one light emitting diode package not driven by the light emitting diode module as a light receiving element.

In addition, since the present invention does not require a brightness sensor, a cost thereof may be reduced, and a compact backlight unit and an electronic board, in which the brightness sensor is not mounted, may maintain uniform brightness.

Claims

A plurality of light emitting diode packages,

It includes a driver for sequentially driving the plurality of light emitting diode packages,

At least one light emitting diode package of the plurality of light emitting diode packages operates as a light receiving element,

The driving unit is a light emitting diode module, characterized in that for controlling the current or voltage applied to the light emitting diode package by the current or voltage measured in the light emitting diode package operating as a light receiving element.

The method according to claim 1,

The driving unit and the current measuring unit for measuring the current or voltage of the LED package operating as the light receiving element;

A memory unit in which luminance data generated by the light receiving element is stored in advance according to the brightness of light received by the light receiving element;

A control unit for outputting a signal by comparing the current or voltage value measured by the current measuring unit with the luminance data stored in the memory unit;

And a signal generator for generating a signal for driving the LED module by the signal output from the controller.

The method according to claim 2,

The signal generator is a light emitting diode module, characterized in that for generating a pulse width modulation signal.

The method according to claim 1,

The plurality of light emitting diode packages may operate as a light emitting device when a current is applied, and as a light receiving device when no current is applied.