KR100480829B1 - method for driving of Back light unit - Google Patents

Abstract

The present invention provides a tube voltage waveform for applying to a backlight unit applied to a large liquid crystal display device. A method of driving a backlight unit for achieving the above object is to divide the length of the entire light emitting surface of the backlight into n equal parts A backlight comprising a plurality of light emitting lamps arranged in an area and n + 1 common electrodes arranged in one direction to commonly connect end ends of the light emitting lamps arranged in the same direction, wherein the common light is arranged adjacent to each other. It is characterized in that the tube voltages of different phases are applied to the electrodes.

In addition, a method of driving a backlight unit according to another embodiment includes dividing the length of the entire light emitting surface of the backlight into two equal parts and a plurality of light emitting lamps arranged in each equal region, and each end of the light emitting lamps arranged in the same direction. In a backlight including first, second and third common electrodes arranged in one direction so as to connect the common electrodes, a tube voltage having a phase difference of 180 ° is applied to the first and third common electrodes, and the second common A ground voltage is applied to the electrode.

Description

Method for driving backlight unit {method for driving of Back light unit}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly, to a method of driving a backlight unit that presents a tube voltage waveform suitable for application to a large-screen liquid crystal display.

CRT (Cathode Ray Tube), one of the commonly used display devices, is mainly used for monitors such as TVs, measuring devices, and information terminal devices.However, due to the weight and size of the CRT itself, Could not respond actively to demands.

Therefore, in the trend of miniaturization and light weight of various electronic products, CRT has a certain limit in weight and size, and is expected to replace the liquid crystal display (LCD) and gas discharge using electro-optic effects. Plasma Display Panels (PDPs) and Electro Luminescence Displays (ELDs) using electroluminescent effects are used. Among them, research on liquid crystal displays is being actively conducted.

In order to replace the CRT, liquid crystal display devices having advantages such as small size, light weight, and low power consumption have been actively developed. Recently, the liquid crystal display device has been developed enough to perform a role as a flat panel display device. As it is used for a monitor of a desktop computer and a large information display device, the demand for a liquid crystal display device is continuously increasing.

Since most of the liquid crystal display devices are light-receiving devices that display images by controlling the amount of light coming from the outside, a separate light source, that is, a back light, for irradiating light to the LCD panel is necessary.

In general, a backlight used as a light source of a liquid crystal display device is a method of disposing a cylindrical light emitting lamp, and is divided into an edge method and a direct method.

In the double-edge method, the lamp unit is installed on the side of the light guide plate for guiding the light, and the lamp unit covers a lamp emitting light, a lamp holder inserted at both ends of the lamp to protect the lamp, and an outer circumferential surface of the lamp, and one side It is provided with a lamp reflector plate fitted to the side of the light guide plate to reflect the light emitted from the lamp toward the light guide plate.

The edge method in which the lamp unit is installed on the side of the light guide plate is applied to a relatively small liquid crystal display device such as a monitor of a laptop computer and a desktop computer, and has good uniformity of light and a long service life. It is advantageous to thin the liquid crystal display device.

On the other hand, the direct type method has been developed mainly as the size of the liquid crystal display device has increased to 20 inches or more, and a plurality of lamps are arranged in a row on the lower surface of the diffuser plate to direct light directly to the front of the LCD panel. will be.

The direct method is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

Hereinafter, a driving method of a conventional backlight unit will be described with reference to the accompanying drawings.

1 is a perspective view of a direct type backlight unit according to the prior art, and FIG. 2 is a view showing a connector connected to the light emitting lamp of FIG. 1.

As shown in FIG. 1, the backlight unit according to the related art includes a plurality of light emitting lamps 1, an outer case 3 for fixing and supporting the light emitting lamps 1, and the light emitting lamps 1. Light scattering means 5a, 5b, 5c disposed between the liquid crystal panels (not shown).

The light scattering means (5a, 5b, 5c) is to prevent the shape of the light emitting lamp from appearing on the display surface of the liquid crystal panel and to provide a light source having an overall uniform brightness distribution, in order to enhance the light scattering effect A plurality of diffusion sheets, diffusion plates, and the like are disposed between the cells.

The inner surface of the outer case 3 is disposed with a reflector 7 so that the light emitted from the light emitting lamp 1 can be concentrated to the display of the liquid crystal panel, in order to maximize the utilization efficiency of the light.

The light emitting lamp 1 is a Cold Cathode Fluorescent Lamp (CCFL) as shown in FIG. 2, and electrodes 2 and 2a are disposed at both ends of a tube to emit light when power is applied to the electrode. Both ends of the light emitting lamp 1 are fitted in grooves formed on both sides of the outer case 3 as shown in FIG. 1.

Power lead wires 9 and 9a for transmitting power for driving the lamp are connected to both electrodes of the light emitting lamp, and the power lead wires 9 and 9a are connected to a separate connector 11 and connected to the driving circuit. Therefore, a separate connector 11 is required for each light emitting lamp 1.

That is, a power lead wire 9 connected to one electrode 2 of the light emitting lamp and a power lead wire 9a connected to the other electrode 2a are connected to one connector 11, and among the power lead wires 9 and 9a. One is bent to the bottom of the outer case (3) is connected to the connector (11).

However, in the conventional backlight unit for a liquid crystal display device, since a connector is connected to a driving circuit of a light emitting lamp and connected to a driving circuit, a connector is required for each light emitting lamp, so that wiring is complicated and the thickness of the backlight is reduced. In order to be connected to the connector by bending the power lead wire for the purpose of not only to reduce the work efficiency, but also requires a separate work for this process increases the process time and productivity is reduced.

In addition, in order to connect the electrode and the connector, a hole penetrating the outer case must be drilled and both electrodes of the light emitting lamp must be inserted into the hole so that both electrodes of the light emitting lamp are exposed to the outside of the outer case. Falling and maintenance of the luminous lamp is difficult.

Next, a backlight unit according to another conventional technology will be described.

3 is a view illustrating an external electrode light emitting lamp, and FIGS. 4A and 4B are perspective views of a direct type backlight unit and a plan view of a light emitting lamp according to another conventional technology.

3 illustrates an external electrode light emitting lamp 31 having electrodes 33 and 33a formed at both ends outside the tube 31.

The backlight unit illustrated in FIG. 4 is a direct type backlight, and is disposed at predetermined intervals according to the length of the light emitting lamp 31 and includes a plurality of grooves that may accommodate both ends of the plurality of light emitting lamps 31 on one surface thereof. First and second lower mechanisms 41a and 41b (not shown) formed; The first and the second lower mechanisms 41a and 41b together with the first and the second lower mechanisms 41a and 41b to be fixed and supported at the same interval as the first and second lower mechanisms 41a and 41b and formed with the same grooves; Second upper appliance (not shown); And conductive layers 47a and 47b formed on the surfaces of the first and second upper mechanisms and the grooves of the first and second lower mechanisms 41a and 41b, respectively, to apply power to the light emitting lamp 31. do.

The groove is formed such that the end of the light emitting lamp is not visible when viewed from the outside of the device when the first and second lower mechanisms 41a and 41b and the first and second upper mechanisms are coupled to each other. And the same in form, the first and second lower mechanisms 41a and 41b receive half of the diameter of the light emitting lamp, and the first and second upper instruments receive the other half.

The conductive layers 47a and 47b are formed on a surface on which grooves of the apparatus are formed, and grooves are formed in the longitudinal direction of the apparatus, and the grooves are formed without embedding a conductive material in the grooves. It may be formed by coating a conductive material on the surface.

The light emitting lamps 31 have electrodes formed at both ends of the outside of the tube, and one electrode 33 is commonly connected to the first lower mechanism 41a and the conductive layer 47a formed on the opposite surface of the first upper mechanism. The other electrodes 33a are commonly connected to the conductive layer 47b formed on the opposing surface of the second lower mechanism 41b and the second upper mechanism.

On the other hand, although not shown in the drawings, the diffusion sheet for scattering the light emitted from the light emitting lamp 31 so that the uniform light distribution on the display surface of the liquid crystal panel on the upper side of the first, second upper mechanism light scattering means such as a sheet and a diffusion plate are further arranged.

FIG. 4B is a layout plan view of the backlight unit including the light emitting lamp 31, the first and second lower mechanisms 41a and 41b supporting the light emitting lamp 31, and the conductive layers 47a and 47b serving as common electrodes. will be.

Hereinafter, application of a tube voltage according to a conventional time for driving a light emitting lamp will be described.

5A and 5B are tube voltage waveform diagrams applied to a conventional backlight unit.

For convenience of description, the conductive layer 47a formed on the first lower mechanism 41a is called a first common electrode 'A', and the conductive layer 47b formed on the second lower mechanism 41b is called a second common electrode ( 'B').

First, the method for applying a tube voltage according to the first technique according to the first technique has a 180 ° angle to the first common electrode 'A' and the second common electrode 'B' based on the ground voltage GND as shown in FIG. 5A. It is to make the phase difference.

That is, the tube voltage is applied such that the first common electrode 'A' and the second common electrode 'B' are symmetrical with respect to the time axis.

More specifically, for example, when a tube voltage of a sine wave is applied to the first common electrode 'A' based on one cycle 1T, a maximum tube voltage of 1000 V and a minimum tube voltage of -1000 V are applied. Looking at the tube voltage applied by time as follows.

First, when 1000 V is applied to one common electrode 'A' at T / 4, -1000 V is applied to the second common electrode 'B'.

When a tube voltage of 0V is applied to the first common electrode 'A' at T / 2, 0V is also applied to the second common electrode 'B'.

And In FIG. 5, when a tube voltage of -1000 V is applied to the first common electrode 'A', 1000 V is applied to the second common electrode 'B'.

When a tube voltage of 0V is applied to the first common electrode 'A' at 1T, 0V is also applied to the second common electrode 'B'.

Next, in the conventional method of applying a tube voltage according to the second technique, as shown in FIG. 5B, a GND is connected to the second common electrode 'B', and a sine wave having a maximum tube voltage of 2000 V is connected to the first common electrode 'A'. Apply a tube voltage of.

The conventional direct type backlight unit having the above arrangement arranges the light emitting lamp 31 so as to correspond to the length of the entire light emitting surface of the backlight.

Therefore, as the size of the backlight emitting surface increases, the length of the light emitting lamp 31 also increases. For example, in the case of a liquid crystal display device of more than 30 ~ 40 "class recently, the length of the light emitting lamp needs to be 700 mm or more.

As described above, when the length of the light emitting lamp 31 is longer, not only the manufacturing of the light emitting lamp itself becomes difficult, but also when the light emitting lamp 31 is disposed on the backlight unit, it is not easy to assemble and weakens to external impact.

In addition, the brightness becomes uneven during driving for lighting of the light emitting lamp 31, and a high quality of tube voltage is required for driving, resulting in a problem of deterioration in image quality due to stability and electrical influence of the liquid crystal panel driving circuit (EMI: Electro Magnetic Interference). do.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a tube voltage waveform for applying to a backlight unit applied to a large liquid crystal display device.

Method of driving the backlight unit of the present invention for achieving the above object A plurality of light emitting lamps arranged in each equal area by dividing the length of the entire light emitting surface of the backlight by n equal parts, and the light emitting lamps arranged in the same direction In a backlight including n + 1 common electrodes arranged in one direction to commonly connect each end of the field, the tube voltages having different phases may be applied to the neighboring common electrodes.

In addition, the driving method of the backlight unit according to another embodiment of the present invention is a plurality of light emitting lamps arranged in each equal area by dividing the length of the entire light emitting surface of the backlight by two, and the light emitting lamps arranged in the same direction In a backlight including first, second, and third common electrodes arranged in one direction so as to connect common ends of the electrodes, a tube voltage having a phase difference of 180 ° may be applied to the first and third common electrodes. GND is connected to the second common electrode.

A tube voltage of 500 to 2500 Vrms (sine wave) is applied to the third common electrode.

A tube voltage of a sine wave having a maximum tube voltage of 2000 V and a minimum tube voltage of 0 V is applied to the third common electrode.

The ground voltage GND is applied to the second common electrode.

In addition, the driving method of the backlight unit according to another embodiment of the present invention is a plurality of light emitting lamps arranged in each equal region by dividing the length of the entire light emitting surface of the backlight into two equal parts, and the light emission arranged in the same direction A backlight including first, second, and third common electrodes arranged in one direction to commonly connect end portions of lamps, wherein a tube voltage of a sine wave is applied to the second common electrode. The same common voltage having a 180 ° phase difference with the second common electrode is applied to the third common electrode.

At this time, the tube voltage is 500 ~ 2500 Vrms.

In addition, the driving method of the backlight unit according to another embodiment of the present invention is a plurality of light emitting lamps arranged in each equal area by dividing the length of the entire light emitting surface of the backlight into three equal parts, and the light emission arranged in the same direction In a backlight including first, second, third and fourth common electrodes arranged in one direction to commonly connect the ends of lamps, a sine wave tube voltage is applied to the second and fourth common electrodes. In addition, a tube voltage having a 180 ° phase difference with the second and fourth common electrodes may be applied to the first and third common electrodes.

Hereinafter, a driving method of a backlight unit according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

First, a configuration of a backlight unit for applying to an embodiment of the present invention will be described.

6 is a layout plan view of a light emitting lamp of a direct type backlight unit for application to the first and second embodiments of the present invention, and FIG. 8 is a plan view of a direct type backlight unit for application to a third embodiment of the present invention. A top plan view of the light emitting lamp.

First, the direct type backlight unit for applying to the first and second embodiments of the present invention is alternately arranged on the left side and the right side by dividing the length of the entire light emitting surface as shown in FIG. First, second and third lower mechanisms 62a and 62b having a plurality of light emitting lamps 61 and a plurality of grooves (not shown) for accommodating both ends of the plurality of light emitting lamps 61. 62c and the first, second and third lower mechanisms 62a, 62b, for fixing and supporting the light emitting lamp together with the first, second, third lower mechanisms 62a, 62b, 62c. The first, second and third upper mechanisms (not shown), the first, second and third upper instruments and the first, second and third lower instruments disposed at the same interval as 62c and having the same grooves. First and second grooves 62a, 62b, and 62c formed on grooves of the grooves 62a, 62b, and 62c to apply power to external electrodes of the light emitting lamp 61 2, the common electrode comprises a third (63a, 63b, 63c).

If the length of the display screen of the liquid crystal panel is longer, the length of the light emitting surface of the backlight unit should be longer as described above, so the length of the light emitting lamp 61 should be longer.

In addition, when the light emitting lamp 61 is lengthened, the tube voltage applied to the light emitting lamp 61 is also increased.

In order to improve this, the light emitting lamp 61 is shortened (about 1/2) shorter than the length of the light emitting surface as described above, and is alternately arranged on the left and right sides based on an equal line (virtual line) of the light emitting surface. It is.

In this case, the same voltage is applied to the light emitting lamps 61 in which the external electrodes are disposed in the second lower mechanism 62b through the second common electrode 63a.

Next, the backlight unit for applying to the third embodiment of the present invention will be described.

As shown in FIG. 8, the light emitting lamps 81 are arranged on the left / center / right side by dividing the entire light emitting surface into three parts, and the top of the light emitting lamp 81 is fixed to support both ends of each light emitting lamp 81. As shown in FIG. And fourth to seventh lower mechanisms 82a, 82b, 82c, and 82d and fourth to seventh upper instruments (not shown), and fourth to seventh common electrodes 83a, 83b, 83c, 83d).

The backlight unit configured as described above can lower the tube voltage of the light emitting lamp as a whole and can also improve the occurrence of luminance unevenness in the entire screen.

Next, the tube voltage waveform diagram according to the present invention applied to the backlight unit having the above configuration will be described.

 7A and 7B are tube voltage waveform diagrams according to the first and second embodiments of the present invention applied to the backlight unit, and FIG. 9 is a tube voltage waveform diagram according to the third embodiment of the present invention applied to the backlight unit. to be.

Prior to the description, the first to third common electrodes 63a, 63b, and 63c are represented by 'C', 'D', and 'E', and the fourth to seventh common electrodes 83a, 83b, 83c, and 83d. Is expressed as 'F', 'G', 'H' or 'I'.

First, in the method of applying a tube voltage according to the first embodiment of the present invention applied to a backlight unit, a phase difference of 180 ° is applied to the first and third common electrodes 'C' and 'E' as shown in FIG. 7A. The tube voltage is applied, and GND is connected to the second common electrode 'D'.

For example, a tube voltage of a sine wave having a tube voltage of 2000 [Vrms] is applied to the third common electrode 'E', and the third common electrode 'E' is applied to the first common electrode 'C'. ') And a tube voltage of a waveform having a phase difference of 0 ° or 180 ° is applied.

In this case, tube voltages may be applied to the first and third common electrodes 'C' and 'E' in opposite directions.

A tube voltage of a sine wave in the range of 500 to 2500 [Vrms] may be applied to the third common electrode.

Next, the tube voltage waveform diagram according to the second embodiment of the present invention applied to the backlight unit is the same as the tube voltage of the first and third common electrodes 'C' and 'E' as shown in FIG. 7B. And a tube voltage having a phase difference of 180 ° with the first and third common electrodes 'C' and 'E' is applied to the second common electrode 'D'.

For example, when a tube voltage of a sine wave having a tube voltage of 1000 [Vrms] is applied to the second common electrode 'D', the first and third common electrodes 'C' and 'E' are grounded. A tube voltage (tube voltage having a phase difference of 180 °) symmetrical with the second common electrode 'D' is applied based on the voltage.

A tube voltage of a sine wave in the range of 500 to 2500 [Vrms] may be applied to the second common electrode 'D'.

Next, in the tube voltage application method according to the third embodiment of the present invention applied to the backlight unit, as shown in FIG. 9, odd-numbered common electrodes and even-numbered common electrodes have a phase difference of 180 ° based on ground voltage. The tube voltage is applied, the same tube voltage is applied to the odd common electrodes, and the same tube voltage is applied to the even common electrodes.

For example, a sinusoidal tube voltage of 1000 [Vrms] is applied to the second and fourth common electrodes 'G' and 'I'.

A tube voltage having a 180 ° phase difference from the second and fourth common electrodes 'G' and 'I' is applied to the first and third common electrodes 'F' and 'H'.

A tube voltage of a sine wave symmetrical with the first and third common electrodes 'F' and 'H' is applied.

A tube voltage of a sine wave in the range of 500 to 2500 [Vrms] may be applied to the second and fourth common electrodes.

In addition to dividing the entire light emitting surface of the backlight into two or three equal parts, the light emitting lamps may be arranged in equal parts by dividing n equal parts. In this case, each common electrode connected to each end of the light emitting lamps arranged in the same direction The tube voltage is applied to have a phase difference between neighboring common electrodes.

And the tube voltage waveform is expressed only as a sinusoidal waveform. In practice, various waveforms are available, such as a modified sinusoidal waveform, a pulse waveform, and a modified pulse waveform.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be defined by the claims.

The driving method of the backlight unit of the present invention as described above has the following effects.

First, since a light emitting lamp having a relatively short length can be used when manufacturing a backlight of a large area display device, the use of the light emitting lamp can be widened without limiting the size of the display device.

Second, as shown in the above embodiment, when the tube voltages having the phase difference are applied to three or more common electrodes, the tube voltages can be distributed and applied, and thus the large area display device can be efficiently driven.

1 is a perspective view of a direct type backlight unit according to the prior art;

2 is a view showing a connector connected to the light emitting lamp of FIG.

3 is a view showing an external electrode light emitting lamp

4A and 4B are a perspective view of a direct type backlight unit and a plan view of a light emitting lamp according to another conventional technology;

5A and 5B are tube voltage waveform diagrams applied to a conventional backlight unit.

6 is a plan view of a light emitting lamp of a direct type backlight unit for application to the first and second embodiments of the present invention;

7A and 7B are tube voltage waveform diagrams according to the first and second embodiments of the present invention applied to a backlight unit.

8 is a layout plan view of a light emitting lamp of a direct type backlight unit for application to a third embodiment of the present invention;

9 is a tube voltage waveform diagram according to a third embodiment of the present invention applied to a backlight unit.

Explanation of symbols for the main parts of the drawings

61, 81: light emitting lamp

62a, 62b, 62c: 1st, 2nd, 3rd lower mechanism

63a, 63b, 63c: first, second and third common voltages

82a, 82b, 82c, 82d: 4th, 5th, 6th, 7th lower mechanism

83a, 83b, 83c, 83d: fourth, fifth, sixth, and seventh common voltages

Claims (8)

N + 1 common electrodes arranged in one direction so as to connect the plurality of light emitting lamps arranged in each equal region by n equal lengths of the entire light emitting surface of the backlight and each end of the light emitting lamps arranged in the same direction In the backlight including the And a tube voltage having different phases is applied to the common electrodes arranged adjacent to each other. The first, second, and second arrays are arranged in one direction to mutually connect the plurality of light emitting lamps arranged in each equal area by dividing the length of the entire light emitting surface of the backlight into two equal parts and the respective ends of the light emitting lamps arranged in the same direction. In the backlight including the third common electrodes, Tube voltages having a phase difference of 180 ° are applied to the first and third common electrodes. And driving GND to the second common electrode. The method of claim 2, And said third common electrode applies a tube voltage of a sine wave of 500 to 2500 [Vrms]. The method of claim 2, And a ground voltage (0 [Vrms]) is applied to the second common electrode. The first, second, and second arrays are arranged in one direction to mutually connect the plurality of light emitting lamps arranged in each equal area by dividing the length of the entire light emitting surface of the backlight into two equal parts and the respective ends of the light emitting lamps arranged in the same direction. In the backlight including the third common electrodes, A tube voltage of a sine wave is applied to the second common electrode, And a same tube voltage having a 180 ° phase difference from the second common electrode is applied to the first and third common electrodes. The method of claim 5, wherein And a tube voltage of the second common electrode is in a range of 500 to 2500 [Vrms]. The first, second, and first arranged in one direction so as to connect the plurality of light emitting lamps arranged in each equal region by dividing the length of the entire light emitting surface of the backlight into three equal parts and each end of the light emitting lamps arranged in the same direction in common; In the backlight including the third and fourth common electrodes, A tube voltage of a sine wave is applied to the second and fourth common electrodes, And a tube voltage having a 180 ° phase difference from the second and fourth common electrodes is applied to the first and third common electrodes. The method of claim 7, wherein And a tube voltage of the second and fourth common electrodes is 500 to 2500 [Vrms].