KR101537794B1 - Backlight unit employing light emitting diode package for ac source operation - Google Patents

Abstract

A backlight unit for illuminating a liquid crystal display panel with light is disclosed. The backlight unit includes a light emitting diode package for driving an AC power source, the package having first and second lead terminals, a first array of light emitting cells connected in series with each other on a single substrate, A light emitting diode chip electrically connected to the two lead terminals, and a molding part covering the light emitting diode chip. Accordingly, the LED light source of the backlight unit can be driven under an AC power source without an AC-DC converter.

Liquid crystal display, backlight unit, ac power source, light emitting diode

Description

BACKLIGHT UNIT EMPLOYING LIGHT EMITTING DIODE PACKAGE FOR AC SOURCE OPERATION BACKGROUND OF THE INVENTION [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit of a liquid crystal display panel, and more particularly, to a backlight unit employing a light emitting diode package for driving an AC power source.

A passive display device, such as a liquid crystal display, can reflect or absorb ambient sunlight or room light to create an image. Therefore, in order to view an image to be displayed, surrounding sunlight or room light is required. However, there is a problem that if the intensity of ambient light or room light is not enough to illuminate a liquid crystal display (LCD) panel, the displayed image can not be seen. As an alternative to such a problem, a backlight unit (BLU) for backlighting a display panel is generally adopted.

The backlight unit includes a light source such as an incandescent lamp, a fluorescent lamp, or a light emitting diode (LED). An image is realized by the light emitted from the light source illuminating the LCD panel. On the other hand, LED has excellent color reproducibility and is often used as a backlight light source, and is expected to be used in the future because it is environmentally friendly.

1 is a schematic view showing an LCD module having a conventional backlight unit employing an LED light source.

Referring to FIG. 1, a conventional LCD module includes an LCD panel 10 and a backlight unit 20. The LCD panel 10 includes a liquid crystal layer 15 between an upper substrate 11 and a lower substrate 13 and includes an upper polarizing film 17 and a lower polarizing film 17 disposed on the upper substrate 11, And a lower polarizing film (19) positioned below the lower polarizing film (13). Generally, the upper polarizing film 17 and the lower polarizing film 19 are arranged so that their polarization directions are orthogonal to each other. The backlight unit 20 includes LEDs 23 as a light source and includes a diffusion plate 25 and a brightness enhancement film (BEF) for mixing light emitted from the light sources 23, . In addition, the backlight unit may further include a double brightness enhancement film (DBEF).

The LEDs 23 may be arranged on a substrate 21 such as a printed circuit board to form an array and may include red, green, and blue LEDs or may include white LEDs to improve color reproducibility. have. These LEDs are regularly arranged on a printed circuit board to constitute an LED module, and a plurality of LED modules can be used for backlighting the LCD panel 10. [ The LED module is disposed at a predetermined distance from the diffuser plate 25 for uniform mixing of the light emitted from the LEDs 23, or the LEDs are densely arranged to form a uniform surface light source. A reflective film is disposed below the light exit surface of the LEDs 23 to reflect the light emitted from the LEDs toward the upper side.

The light L having passed through the diffusion plate 25, the BEF 27 and the DBEF 29 after being emitted from the LEDs 23 is incident on the LCD panel 10. The lower polarizing film 19 polarizes the light L, and the polarized light is incident on the liquid crystal layer. The light incident on the liquid crystal layer keeps the polarization direction according to the arrangement of the liquid crystal layer or rotates by 90 degrees and is incident on the upper polarizing film. Thereafter, the light that maintains the polarization direction is shielded by the upper polarizing film 17, and the light rotated by 90 degrees passes through the upper polarizing film 17 to realize an image.

On the other hand, the LEDs 23 used as a light source are capable of emitting light when a forward current flows, and are extremely vulnerable to a reverse current. Therefore, when driving an LED light source under an AC power source, an AC-DC converter for converting AC to DC should be provided between the power source and the LEDs. The use of such an AC-DC converter complicates the circuitry for driving the backlight unit, especially the circuitry for driving the LEDs, and increases the manufacturing cost of the LCD module.

SUMMARY OF THE INVENTION An object of the present invention is to provide an LED backlight unit capable of irradiating an LCD panel with uniform surface light.

Another object of the present invention is to provide a backlight unit employing an LED package that can be driven without an AC-DC converter.

Another object of the present invention is to provide a backlight unit employing an LED light source which can be driven under an AC power source and has excellent color reproducibility.

In order to solve the above-described problem, the present invention provides a backlight unit for emitting light to a liquid crystal display panel, the backlight unit including a light emitting diode package for driving an AC power source. The light emitting diode package includes first and second lead terminals, a light emitting diode chip having a first array of light emitting cells connected in series to each other on a single substrate and electrically connected to the first and second lead terminals, And a molding part covering the chip.

Here, 'light emitting diode package for AC power driving' is a light emitting diode (LED) package that can be driven by being connected to an AC power source without an AC-DC converter and is an LED package capable of emitting light irrespective of polarity direction of an AC power source . In operation, a single LED package may be driven to be connected to an alternating current source, but may be electrically connected to other LED packages and driven under an alternating current source.

According to the embodiments of the present invention, since the LED package for driving the AC power source is adopted, the LED light source can be driven without using the AC-DC converter, and the circuit configuration for driving the LED light source can be simplified As a result, the manufacturing cost of the LCD module can be reduced.

Meanwhile, a light guide plate may be disposed between the liquid crystal display panel and the light emitting diode package. The light guide plate has a receiving groove for receiving the light emitting diode package. When a plurality of LED packages are used, the light emitted from the LED packages is incident on the light guide plate through the receiving grooves and mixed in the light guide plate. Accordingly, a uniform surface light can be provided while using a small number of LED packages.

In addition, the light guide plate may have a concave portion and a convex portion on the lower surface thereof, and the receiving groove is formed in the convex portion.

Meanwhile, the molding part of the LED package may be dome-shaped, and the molding part may be received in the package receiving groove. And the light emitted from the molding portion is incident on the light guide plate through the receiving groove.

In some embodiments, the light emitting diode package may further include at least one kind of fluorescent material positioned on the LED chip. The phosphor may include, for example, a yellow phosphor that converts blue light into green or yellow and / or a red phosphor that converts red light into red.

The light emitting diode chip may be a blue light emitting diode chip emitting blue light. The light emitting diode package may further include a green light emitting diode chip and / or a red light emitting diode chip connected in series to the first array of the light emitting cells in the blue light emitting diode chip. Accordingly, an LED package capable of emitting white light excellent in color reproducibility can be provided.

The blue light emitting diode chip may further include a second array of light emitting cells connected in series with the light emitting cells. The light emitting diode package may include a green light emitting diode chip and / or a red light emitting diode chip As shown in FIG.

The first array and the second array are connected in antiparallel to each other to provide an LED package capable of AC driving.

The light emitting diode package may further include a bridge rectifier for supplying a rectified current to the first array of the light emitting cells. Accordingly, an LED package capable of AC driving can be provided. The bridge portions of the bridge rectifier may include at least one of a red light emitting diode chip and a green light emitting diode chip so that white light having excellent color reproducibility can be realized.

According to the present invention, an AC-DC converter used in a conventional LED light source can be removed by adopting an LED package for driving an AC power source. Further, by adopting the light guide plate having the LED package receiving groove, it is possible to provide a backlight unit that can provide uniform surface light while using a small number of LED packages. In addition, a combination of a blue LED chip, a phosphor, and a red LED chip can provide a backlight unit employing an LED package capable of driving under an AC power source and having excellent color reproducibility.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

2 is a schematic view illustrating an LCD module having a backlight unit according to an embodiment of the present invention.

Referring to FIG. 2, the LCD module includes an LCD panel 50 and a backlight unit 60. The LCD panel 50 includes an upper substrate 51, a lower substrate 53, a liquid crystal layer 55 positioned between the upper substrate 51 and the lower substrate 53, And an upper polarizing film 57 and a lower polarizing film 59 positioned below the lower substrate 13. [

The backlight unit 60 includes LED packages 63 for driving AC power as a light source and includes a light guide plate 64 and a diffusion plate 65 for mixing light emitted from the light sources 63, And a brightness enhancement film (BEF, 67). In addition, the backlight unit 60 may further include a double brightness enhancement film (DBEF) 69.

The LED packages 63 may be mounted on a substrate 61 such as a printed circuit board. These LED packages are regularly arranged on the printed circuit board 61 to constitute an LED module, and a plurality of LED modules can be used for backlighting the LCD panel 50. [

The LED package 63 includes first and second lead terminals, a light emitting diode chip having a first array of light emitting cells connected in series to each other on a single substrate and electrically connected to the first and second lead terminals, And a molding part covering the light emitting diode chip. The molding part may have various shapes and, as shown, may be dome-shaped. The LED package 63 will be described later in detail with reference to Fig.

The light guide plate 64 may have a receiving groove 64a for receiving the LED package 63. [ For example, the dome-shaped molding part can be received in the receiving groove 64a. The light guide plate 64 mixes and uniformizes light incident from the LED packages 63 and converts the light into surface light. The light guide plate 64 may be made of a single plate according to the size of the LCD panel 50, but is not limited thereto. In order to irradiate the large area LCD panel 50, a plurality of light guide plates 64 may be used in combination. That is, it is possible to form an entire light guide plate for irradiating the large-area LCD panel 50 by combining the light guide plates 64 having a standard size (indicated by a dotted line). Various techniques may be adopted to couple the plurality of light guide plates 64. For example, the light guide plate may be provided with a recessed portion and a protruded portion on the side surface thereof, and a projection portion of the light guide plate adjacent to the recessed portion of one light guide plate may be coupled can do. Further, it is possible to adhere the light guide plates having the standard size using an adhesive member containing a reflective material. Such an adhesive member is formed on the lower surface of the light guide plates to couple the light guide plates, and in particular, prevents the formation of the dark portion at the interface between the light guide plates. The advantage of using a light guide plate having a standard size is that the same kind of light guide plate can be applied to various sizes of the LCD panel 50. [

Reflecting means for reflecting light may be provided on the lower surface of the light guide plate 64. For example, the total reflection (TIR) patterns may be provided on the lower surface of the light guide plate 64 to totally reflect light. In addition, a reflection film 62 may be attached to the lower surface of the light guide plate 64 to increase light reflectance and reduce light loss.

In addition, as shown in FIG. 3, the light guide plate 74 may have a convex portion and a concave portion, and the LED package receiving groove 74a may be formed in the convex portion. As described above, it is possible to combine the light guide plates 74 having a standard size indicated by a dotted line to form a large light guide plate. At this time, grooves may be formed in the bottom of the concave portion to which the light guide plates are coupled, and an adhesive member containing a reflective material may be filled in the grooves to join the light guide plates. Reflecting patterns such as a TIR pattern may be formed on the lower surface of the light guide plate 74, and a reflective film 72 may be attached thereto.

The light emitted from the LED packages can be mixed by separating the LED packages 63 and the diffuser plate 65 by a predetermined distance or by densely arranging the LED packages as described in the background art with reference to Fig. In this case, the light guide plate 64 may be omitted. However, according to the present invention, an array in which a plurality of light emitting cells are connected in series is used, thereby increasing the driving voltage of the LED package. Therefore, when the LED packages 63 for driving the AC power source are used, there is a limitation in using these packages 63 in series. Accordingly, when the light guide plate 64 is used, the number of the LED packages 63 can be reduced.

The light L having passed through the light guide plate 64, the diffusion plate 65, the BEF 67 and the DBEF 69 after being emitted from the LED packages 63 is incident on the LCD panel 50. The light transmitted through the lower polarizing film 59 is incident on the liquid crystal layer, and the light incident on the liquid crystal layer is incident on the upper polarizing film while keeping the polarization direction or rotating 90 degrees according to the arrangement of the liquid crystal layer, An image is realized by blocking or passing the light by the upper polarizing film 57.

4 and 5 are a schematic sectional view and a plan view for explaining an LED package 100 applicable as a light source to a backlight unit according to an embodiment of the present invention.

4 and 5, the LED package 100 includes first and second lead terminals 111 and 113, a light emitting diode chip 120, and a molding part 117. The LED package 100 includes a package body 110 for supporting the first and second lead terminals 111 and 113 and mounting the LED chip 120 and a heat sink 115 And a phosphor may be disposed on the light emitting diode chip to wavelength convert at least a part of the light emitted from the light emitting diode chip 120.

The package body 110 may be formed of, for example, a printed circuit board, plastic molded by injection molding, or ceramics. Further, the first and second lead terminals 111 and 113 may be formed from a lead frame or by plating or the like. The heat sink 115 dissipates the heat generated from the LED chip 120 and may be made of a metal or a ceramic having excellent thermal conductivity. The heat sink 115 is supported by the package body 110, and the lower surface of the heat sink 115 is exposed to the outside.

The molding part 117 covers the light emitting diode chip 120 to protect the light emitting diode chip and may have various shapes to control the light directing angle. For example, the molding part 117 may be a dome-shaped, as shown. The molding part 117 forms a light emitting surface through which light emitted from the light emitting diode chip 120 flows out of the package 100. The molding part 117 is received in the receiving groove 64a of the light guide plate 64 in Fig. 2, and the light is incident on the light guide plate 64. [

On the other hand, a phosphor may be positioned above the LED chip 120. The phosphor converts a portion of the light emitted from the light emitting diode chip 120, for example, blue light within the range of 400 to 500 nm, to light of a longer wavelength. The phosphor may include, for example, a yellow phosphor having a peak wavelength of 500 to 600 nm and / or a red phosphor having a peak wavelength of 600 to 700 nm. As the yellow phosphor, a conventional YAG-based or ososilicate phosphor may be used, and as the red phosphor, a sulfide, a thiogallate or a nitride phosphor may be used.

The phosphor may be located on the LED chip 120 or on the molding part 120 covering the chip 120 or may be distributed in the molding part 117 covering the chip 30b .

The light emitting diode chip 120 may be electrically connected to the first and second lead terminals 111 and 113 through bonding wires. The light emitting diode chip 120 includes an array of light emitting cells 121 connected in series on a single substrate. An array of light emitting cells is described below with reference to Fig. 6 or Fig. The light emitting cells 121 are formed by patterning a compound semiconductor grown on a single substrate, and the light emitting cells 121 are connected to each other through wiring to form an array. The structure of the light emitting cells 121 and the connection through the wiring are described below with reference to Fig. 8 or Fig.

6 is an equivalent circuit diagram according to an example of the LED package of FIG.

Referring to FIG. 6, the light emitting diode chip 120 includes a first array 121a and a second array 125a, in which the light emitting cells 121 formed on a single substrate are connected to each other in series. The first array 121a and the second array 125a are connected in reverse parallel to each other between the lead terminals 111 and 113. When the AC power is connected to the first and second lead terminals 111 and 113, a forward voltage is applied to the first array 121a for half a period of the AC power, and during the other half period of the AC power, 2 array 125a by applying a forward voltage thereto. Accordingly, when the AC power source is driven, the light emitting diode chip 120 can continuously emit light. The light emitting cells 121 may be connected to each other by wires, and the light emitting diode chip 120 and the lead terminals 111 and 113 may be connected to each other by a bonding wire.

7, the light emitting diode chip 120 includes a bridge rectifier including first through fourth bridge units 131, 132, 133, and 134, and an array 121a of light emitting cells 121 connected to the bridge rectifier. . Each of the first to fourth bridge units 131, 132, 133 and 134 may include the light emitting cells 121 and may include only the light emitting cells 121.

The first bridge part 131 and the second bridge part 132 are connected to the input terminal 141 and the third bridge part 133 and the fourth bridge part 134 are connected to the output terminal 143. [ . Here, the input terminal 141 and the output terminal 143 are defined for convenience of explanation, and can be reversed according to the direction of the current input to the AC power source.

The first bridge part 131 and the second bridge part 122 are connected to the input terminal 141 so as to be opposite in polarity to the voltage applied between the input terminal 141 and the output terminal 143, The third bridge portion 133 and the fourth bridge portion 134 are also connected to the output terminal 143 so as to be opposite in polarity to each other with respect to the voltage applied between the input terminal 141 and the output terminal 143.

The first bridge part 131 and the fourth bridge part 134 are connected to the first node 145 and the second bridge part 132 and the third breeb part 133 are connected to the second node 145 147). The first bridge part 131 and the fourth bridge part 134 are connected to the first node 145 so as to have opposite polarities with respect to the voltage applied between the input terminal 141 and the output terminal 143, The bridge portion 132 and the third bridge portion 133 are also connected to the second node 147 so as to be opposite in polarity to the voltage applied between the input terminal 141 and the output terminal 143.

On the other hand, the array of light emitting cells 121a is electrically connected to the first node 145 and the second node 147. The array 121a is electrically connected to the first node 45 and the second node 47 so as to be in a forward direction with respect to the current input from the first lead terminal 111 or the second lead terminal 113. [

The light emitting cells 121 in the bridge units 131 to 134 and the array 121a may be electrically connected to each other through wirings.

AC power is connected to the first lead terminal 111 and the second lead terminal 113 and a positive voltage is applied to the first lead terminal 111 and a negative voltage is applied to the second lead terminal 113, The current is inputted through the input terminal 141 of the bridge rectifier and is supplied to the output terminal of the bridge rectifier via the second bridge portion 132, the array 121a of the light emitting cells 121, and the fourth bridge portion 134. [ (143). Accordingly, the light emitting cells 121 in the second and fourth bridge portions 22 and 24 and the light emitting cells 121 in the array 121a are driven to emit light.

Now, the case where the voltage application direction of the AC power source is changed will be described.

The current flows through the output terminal 143 of the bridge rectifier and flows through the third bridge section 133 of the bridge rectifier, the array of light emitting cells 121a and the first bridge section 131, And exits through the input terminal 141. The light emitting cells 121 in the first and third bridge units 131 and 133 and the light emitting cells 121 in the array 121a are driven to emit light.

As a result, the light emitting cells 121 in the first and third bridge portions connected to the array 121a or the light emitting cells 121 in the second and fourth bridge portions, together with the array of light emitting cells 121a, Are alternately driven to emit light continuously.

Hereinafter, the structure of the light emitting cells and the connection through the wiring will be described with reference to FIGS. 8 and 9. FIG. 8 and 9 are partial cross-sectional views illustrating a light emitting diode chip including an array of light emitting cells according to an embodiment of the present invention. 8 is a partial cross-sectional view for explaining the series connection of the light emitting cells by the wirings formed by the air bridging process, and FIG. 9 is a view for explaining that the light emitting cells are connected in series by the wirings formed by the step cover process Fig.

Referring to FIG. 8, a plurality of light emitting cells 158 are disposed on a substrate 151 so as to be spaced apart from each other. Each of the light emitting cells includes a first conductive type lower semiconductor layer 155, an active layer 157, and a second conductive type upper semiconductor layer 159. The active layer 157 may be a single quantum well structure or a multiple quantum well structure, and its material and composition are selected according to the required emission wavelength. For example, the active layer may be formed of an AlInGaN-based compound semiconductor, for example, InGaN. The lower and upper semiconductor layers 155 and 159 are formed of a material having a larger bandgap than the active layer 157 and may be formed of an AlInGaN-based compound semiconductor, for example, GaN.

A buffer layer 153 may be interposed between the lower semiconductor layer 155 and the substrate 151. The buffer layer 153 is adopted to alleviate the lattice mismatch between the substrate 151 and the lower semiconductor layer 155. The buffer layer 153 may be spaced apart from each other as shown in the drawing. However, the buffer layer 153 may be continuous with the buffer layer 153 when the buffer layer 153 is formed of a material having high insulation or resistance.

The upper semiconductor layer 159 is located above a partial region of the lower semiconductor layer 155 and the active layer is interposed between the upper semiconductor layer 159 and the lower semiconductor layer 155. In addition, the transparent electrode layer 161 may be positioned on the upper semiconductor layer 159. The transparent electrode layer 161 may be formed of a material such as indium tin oxide (ITO) or Ni / Au.

On the other hand, the wires 167 electrically connect the light emitting cells 158. The wirings 167 connect the lower semiconductor layer 155 of one light emitting cell and the transparent electrode layer 161 of the adjacent light emitting cell. The wirings may connect the electrode pad 164 formed on the transparent electrode layer 161 and the electrode pad 165 formed on the exposed region of the lower semiconductor layer 155, as shown in the figure. Here, the wirings 167 are formed by an air bridge process, and a portion except for the contact portion is physically separated from the substrate 151 and the light emitting cells 158. An array 121a or 125a in which light emitting cells are connected in series on a single substrate 151 is formed by the wirings 167. [

Referring to FIG. 9, wirings connecting the light emitting cells 158 may be formed by a step cover process. That is, all the layers of the light emitting cells and the substrate 151 are covered with the insulating layer 185, except for portions for contacting the wirings 187. The wires 187 electrically connect the light emitting cells on the insulating layer 185.

For example, the insulating layer 185 has openings exposing the electrode pads 164 and 165, and the wirings 187 are electrically connected to the electrode pads 164 and 165 of neighboring light emitting cells through the openings. Thereby connecting the light emitting cells in series.

In the foregoing embodiments, the LED package 100 including the light emitting diode chip 120 has been described. The light emitting diode chip 120 may be a blue light emitting diode chip emitting blue light. On the other hand, in order to realize color using the LCD module, the light source needs to emit RGB, and also has excellent color reproducibility. To this end, the LED package 100 may implement white light including yellow and / or red phosphors. However, compared with the YAG-based or ososilicate-based yellow phosphors, the red phosphors still have unsatisfactory wavelength conversion efficiency. Accordingly, there is a limit to providing an LED light source that emits white light suitable for a backlight unit using a red phosphor. Accordingly, it is necessary to use a red LED chip together with a blue LED chip.

Hereinafter, an LED package 200 for driving an AC power source including a red LED chip will be described.

10 is a schematic plan view for explaining an LED package 200 including a red LED chip according to another embodiment of the present invention.

10, the LED package 200 includes first and second lead terminals 111 and 113, a package body 110, and an LED package 100 similar to the LED package 100 described with reference to FIGS. And a light emitting diode chip 220b having an array of light emitting cells 121. Preferably, the light emitting diode chip 220b emits blue light of 400 to 500 nm.

Meanwhile, a yellow phosphor (not shown) may be disposed on the blue light emitting diode chip 220b. The yellow phosphor may convert part of the blue light emitted from the blue LED chip into yellow light having a peak wavelength within a range of 550 to 600 nm. As the yellow fluorescent material, a conventional YAG-based or ososilicate fluorescent material may be used.

In addition, the LED package 200 includes red light emitting diode chips 220r. The red light emitting diode chips 220r may be AlInGaP series LEDs, and these red LED chips have an emission wavelength in the range of 600 to 700 nm. The red light emitting diode chips 220r are connected to the array of light emitting cells 121, as described below with reference to Fig. 11 or 12.

11 is an equivalent circuit diagram according to an example of the LED package 200 of FIG.

Referring to FIG. 11, the light emitting diode chip 220b includes a first array 221a and a second array 225a of light emitting cells 121 connected in series on a single substrate. Meanwhile, the red light emitting diode chips 220r are connected in series to the first array 221a and the second array 225a, respectively. As shown, between the first lead terminal 111 and the second lead terminal 113, the first array 221a and the red LED chips 220r connected thereto in series are connected to the second array 225a, And are connected in antiparallel with the red light emitting diode chips 220r connected in series with the red light emitting diode chips 220r. In this case, it is possible to drive the LED package 200 by directly connecting the first lead terminal 111 and the second lead terminal 113 to the AC power source, without installing a separate rectifier outside. That is, according to the polarity of the AC power source, the first array 221a and the red LED chips 220r connected thereto in series are driven during the half period, and the second array 225a and the red light emitting diode The diode chips 220r are driven to realize white light continuously.

12 is an equivalent circuit diagram according to an example of the LED package 200 of FIG.

Referring to FIG. 12, the LED package 200 according to the present example includes red light emitting diode chips 220r, a blue light emitting diode chip 220b, and a yellow phosphor (not shown). In addition, the LED package 200 includes a bridge rectifier formed by the first through fourth bridge portions 231, 232, 233, and 234. Each of the first to fourth bridge units 231 to 234 may include at least one red LED chip 220r. In addition, the first to fourth bridge units may be formed of only the red LED chips 220r.

The first bridge part 231 and the second bridge part 232 are connected to the input terminal 241 and the third bridge part 233 and the fourth bridge part 244 are connected to the output terminal 243. [ do. Here, the input terminal 241 and the output terminal 243 are defined for convenience of explanation, and can be reversed according to the direction of the current input to the AC power source.

The first bridge portion 231 and the second bridge portion 232 are connected to the input terminal 241 such that the first bridge portion 231 and the second bridge portion 232 have opposite polarities with respect to a voltage applied between the input terminal 241 and the output terminal 243, The second bridge 233 and the fourth bridge 234 are also connected to the output terminal 243 so as to have opposite polarities with respect to the voltage applied between the input terminal 241 and the output terminal 243.

The first bridge portion 231 and the fourth bridge portion 234 are connected to the first node 245 and the second bridge portion 232 and the third breeze portion 233 are connected to the second node 247, respectively. The first bridge portion 231 and the fourth bridge portion 234 are connected to the first node 245 so as to be opposite in polarity to the voltage applied between the input terminal 241 and the output terminal 243, The bridge portion 232 and the third bridge portion 233 are also connected to the second node 247 so as to be opposite in polarity to the voltage applied between the input terminal 241 and the output terminal 243.

On the other hand, a blue light emitting diode chip 220b having an array of light emitting cells 121 connected to each other on a single substrate is electrically connected to the first node 245 and the second node 247 of the bridge rectifier. The array of the light emitting cells 121 is electrically connected to the first node 245 and the second node 247 such that the first node 245 and the second node 247 are in a forward direction with respect to the current input from the first lead terminal 111 or the second lead terminal 113 Lt; / RTI >

The bridge portions 231 to 234 and the blue light emitting diode chip 220b may be electrically connected to each other through bonding wires or wires.

The bridge rectifier according to this example has the same structure and function as the bridge rectifier described with reference to Fig. 7, except that each bridge portion includes the red LED chip 220r. Accordingly, the LED package 200 can be continuously driven by being connected to the AC power source by the bridge rectifier.

In this example, the bridge portions 231 to 234 of the bridge rectifier include the red LED chip 220r. However, the bridge portions 231 to 234 may be formed of a general diode. In this case, the red light emitting diode chip 220r may be connected in series to the blue light emitting diode chip 220b between the first node 245 and the second node 247.

According to the present embodiment, the LED package 200 including the blue light emitting diode chip 220b and the red light emitting diode chip 220r together with the yellow phosphor can be used as the light source, thereby improving the color reproducibility of the backlight unit .

Although a yellow phosphor is used in the present embodiment, it is also possible to mount a nitride-based green light emitting diode chip in an LED package together with a blue light emitting diode chip 220b and a red light emitting diode chip 220r without using a phosphor, White light with excellent reproducibility can be realized. In addition, the blue light emitting diode chip 220b and the green light emitting diode chip may be mounted, and white light may be realized using a red phosphor. The green light emitting diode chip may have an array of light emitting cells like the blue light emitting diode chip 220b. In addition, each of the bridge units 231 to 234 may include a green light emitting diode chip instead of or in addition to the red light emitting diode chip.

1 is a schematic view for explaining an LCD module having a conventional backlight unit.

2 is a schematic view illustrating an LCD module having a backlight unit according to an embodiment of the present invention.

3 is a cross-sectional view for explaining another example of a light guide plate used in the backlight unit of the present invention.

4 is a schematic cross-sectional view illustrating an LED package according to an embodiment of the present invention.

Figure 5 is a schematic plan view of the LED package of Figure 4;

6 is an equivalent circuit diagram according to an example of the LED package of FIG.

7 is an equivalent circuit diagram according to another example of the LED package of Fig.

8 is a cross-sectional view illustrating a light emitting diode chip including an array of light emitting cells according to an embodiment of the present invention.

9 is a cross-sectional view illustrating a light emitting diode chip including an array of light emitting cells according to another embodiment of the present invention.

10 is a schematic plan view for explaining an LED package according to another embodiment of the present invention.

11 is an equivalent circuit diagram according to an example of the LED package of FIG.

12 is an equivalent circuit diagram according to another example of the LED package of Fig.

Claims (13)

A backlight unit for emitting light to a liquid crystal display panel, A light emitting diode package for driving an AC power source, The light emitting diode package First and second lead terminals; A light emitting diode chip having a first array of light emitting cells connected in series to each other on a single substrate and electrically connected to the first and second lead terminals; A molding part covering the light emitting diode chip; And And a light guide plate disposed between the liquid crystal display panel and the light emitting diode package, Wherein the light guide plate has a concave portion and a convex portion on a lower surface thereof, The concave portion is formed as a flat surface, Wherein the convex portion includes a receiving groove corresponding to the light emitting diode package to receive the light emitting diode package and a tilted outer surface formed between the concave portion and the convex portion so that the light emitted from the light emitting diode chip is not irradiated to another adjacent light pipe Including, (TIR) pattern or a reflecting film is attached to the inclined outer surface of the light guide plate and the lower surface of the concave portion. delete delete The backlight unit according to claim 1, wherein the molding portion is dome-shaped and accommodated in the receiving groove. The backlight unit of claim 1, wherein the light emitting diode package further comprises at least one kind of fluorescent material positioned on the light emitting diode chip. The backlight unit of claim 1, wherein the light emitting diode chip emits blue light, and the light emitting diode package further comprises a light emitting diode chip connected in series to the first array of light emitting cells in the blue light emitting diode chip. 7. The backlight unit of claim 6, wherein the light emitting diode chip connected in series to the first array comprises at least one of a green light emitting diode chip and a red light emitting diode chip. 7. The backlight unit of claim 6, wherein the blue light emitting diode chip further comprises a second array of light emitting cells connected in series with the light emitting cells, and the light emitting diode package further comprises a light emitting diode chip connected in series to the second array. The backlight unit according to claim 8, wherein the first array and the second array are connected in anti-parallel to each other. The backlight unit of claim 1, wherein the light emitting diode package further comprises a bridge rectifier for supplying a rectified current to the first array of light emitting cells. 11. The backlight unit of claim 10, wherein the bridge portions of the bridge rectifier each include at least one of a red light emitting diode chip and a green light emitting diode chip. delete The backlight unit according to claim 1, wherein the light guide plate has a coupling region formed by coupling a plurality of light guide plates, and a coupling region is located in a recess of the light guide plate.

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