KR20060071657A - Backlight unit and its control method - Google Patents

Abstract

The present invention relates to a backlight unit, comprising: a lamp; An inverter for applying a lamp driving voltage to the lamp; A temperature sensing unit sensing a temperature of a lamp; And an inverter controller for controlling the inverter to maintain the temperature of the lamp in an appropriate temperature range of 60 ° C to 70 ° C based on the detection result from the temperature detection unit. As a result, the luminance stabilization time of the lamp can be shortened, and the normal luminance can be maintained continuously.

Description

BACKLIGHT UNIT AND CONTROL METHOD OF THE SAME}

1 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention;

2 is a block diagram of a backlight unit according to an embodiment of the present invention;

3 to 5 are graphs of voltage, brightness and temperature versus time of a lamp according to one embodiment of the invention.

Explanation of Signs of Major Parts of Drawings

10: top chassis 20: color filter substrate

30 thin film transistor substrate 40 driver integrated circuit

50: PCB 60: Bottom Chassis

70: diffusion sheet 80: flat lamp

100: backlight unit 110: temperature detection unit

112: temperature sensor 114: A / D converter

120: inverter control unit 130: inverter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a control method thereof, and to a liquid crystal display device and a method for controlling the same, by applying an excess voltage when a power is supplied to a lamp to shorten the luminance stabilization time and continuously maintain the normal brightness.

In general, a liquid crystal display is a device for displaying a desired image by adjusting the light transmittance of liquid crystal cells arranged in a matrix according to image signal information. The panel forms an image.

The liquid crystal display includes a liquid crystal panel in which liquid crystal cells forming a pixel unit are arranged in a matrix, a driver integrated circuit for driving the liquid crystal cells, and a backlight unit for uniformly supplying light to the liquid crystal panel.

Here, a cold cathode fluorescent lamp (CCFL) is usually used for the backlight unit, but as the display device becomes larger, a light source having high brightness, low cost, and low power consumption is required. Therefore, recently, it has been rapidly replaced by an external electrode fluorescent lamp (EEFL), a light emitting diode (LED) and a flat lamp (FFL).

However, the light sources have a problem that a long time is required to reach and stabilize at a normal luminance after power is applied. In particular, the flat lamp is a light source whose surface is uniformly shined and has no thickness, and has a high brightness and uniformity in comparison with other light sources, low power consumption, and long life, as well as light guide plate, prism sheet and Components such as a reflector can be omitted, thus greatly reducing manufacturing costs. However, there is a problem that a long time is required to reach the normal luminance.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a method of controlling the same, by applying an excess voltage when a power is supplied to a lamp to shorten the luminance stabilization time and maintain the normal luminance continuously.

The object is a lamp; An inverter for applying a lamp driving voltage to the lamp; A temperature sensing unit sensing a temperature of a lamp; And an inverter controller for controlling the inverter to maintain the temperature of the lamp in an appropriate temperature range of 60 ° C to 70 ° C based on the detection result from the temperature detection unit.

Here, it is preferable that the inverter controller controls the inverter to apply a predetermined reference voltage when the temperature is in the proper temperature range and to apply an excess voltage higher than the reference voltage when it is within the appropriate temperature range.

In addition, the inverter controller preferably controls the inverter to apply a reduction voltage lower than a predetermined reference voltage when the temperature is detected as a result of the temperature sensing.

The temperature sensing unit includes a temperature sensing means configured to be connected in series with a thermistor and a thermistor whose resistance value is determined according to temperature, and to divide a voltage with the thermistor, and output a predetermined voltage according to the sensed temperature, and a temperature sensing means. And an A / D converter for receiving the voltage output from the digital signal corresponding to the applied voltage.

In addition, an object of the present invention, the lamp; An inverter for applying a lamp driving voltage to the lamp; Temperature sensing means for sensing the temperature of the lamp and the thermistor whose resistance value is determined according to the temperature, and connected in series with the thermistor to divide the voltage with the thermistor, and outputting a predetermined voltage according to the sensed temperature; A temperature sensing unit including a comparator receiving the voltage output from the output unit and outputting two signals according to the magnitude of the case compared with the reference voltage; And an inverter controller for controlling an inverter to apply an excess voltage higher than a predetermined reference voltage when power is supplied to the lamp based on the signal output from the comparator, and to apply a decrease voltage lower than the reference voltage when the signal is changed. Is achieved by the backlight unit.

Another object of the present invention is to detect the temperature of the lamp and outputting a detection result; Determining whether the lamp driving voltage applied to the lamp is increased or decreased based on the detection result; When the temperature of the lamp is in the proper temperature range of 60 ℃ to 70 ℃, a predetermined reference voltage is applied; when it is below the suitable temperature range, an excess voltage higher than the reference voltage is applied; And stabilizing the brightness of the lamp by applying a reduced voltage.

An object of the present invention, the flat lamp; An inverter for applying a lamp driving voltage to the flat lamp; A temperature sensing unit sensing a temperature of the flat lamp; As a result of temperature sensing from the temperature sensing unit, when the temperature of the flat panel lamp is below the proper temperature range of 60 ° C to 70 ° C, an excess voltage higher than the predetermined reference voltage is applied; It is achieved by a backlight unit, characterized in that it comprises an inverter control unit for controlling the inverter to lower the voltage supplied step by step to maintain the temperature of the flat lamp in the appropriate temperature range.

In this case, the inverter controller preferably maintains an appropriate temperature range by applying a reduced voltage lower than a predetermined reference voltage when the temperature of the flat lamp is greater than or equal to the predetermined temperature range as a result of the detection from the temperature sensing unit.

In addition, the temperature sensing unit is attached to the flat lamp at a predetermined interval and outputs a detection result reflecting the temperature of the flat lamp to the inverter controller, the inverter controller determines the current temperature of the flat lamp based on the detection result Therefore, it is preferable to control the inverter to supply one of an excess voltage, a reference voltage and a reduced voltage to the lamp.

The temperature sensing unit preferably outputs a detection signal by sensing the temperature of a plurality of points of the flat lamp and using the average value as the temperature sensing result.

Here, it is preferable that the multiple points are distributed over the entire surface of the flat lamp.

Hereinafter, a liquid crystal display and a control method thereof according to the present invention will be described in detail with reference to the drawings. Prior to the description, the present invention will be described taking a liquid crystal display using a flat lamp as an example.

As shown in FIG. 1, the liquid crystal display device 1 according to an exemplary embodiment of the present invention includes a liquid crystal panel 35 for forming an image, a driver integrated circuit 40 for driving the liquid crystal panel 35, and The mold frame 55 supporting the edge of the liquid crystal panel 35, the backlight unit 100 for irradiating light to the rear surface of the liquid crystal panel 35, and the backlight unit 100 are accommodated and the mold frame 55 is accommodated. The bottom chassis 60 supports the top chassis, and the top chassis 10 coupled to the bottom chassis 60 to cover the front surface of the liquid crystal panel 35.

The liquid crystal panel 35 is injected between the thin film transistor substrate 30, the color filter substrate 20 attached to face the thin film transistor substrate 30, and the thin film transistor substrate 30 and the color filter substrate 20. It includes a liquid crystal (not shown). In addition, the liquid crystal panel 35 further includes a front polarizer (not shown) attached to the front surface of the color filter substrate 20 and a rear polarizer (not shown) attached to the rear surface of the thin film transistor substrate 30. The liquid crystal panel 35 is arranged in a matrix form of the liquid crystal cells forming a pixel unit, and forms an image by adjusting the light transmittance of the liquid crystal cells according to the image signal information transmitted from the driver integrated circuit 40.

The driver integrated circuit 40 has terminals for electrical connection, and is mounted on the thin film transistor substrate 30 to end portions of the gate wiring and the data wiring of the thin film transistor substrate 30 extending from the display area to the non-display area. Connected.

The PCB 50 is a circuit board in which circuits for mounting various chips (CHIP) are integrated, and transfers a driving signal to the driver IC 40.

The mold frame 55 is formed along the edge of the liquid crystal panel 35 and has a substantially rectangular shape and supports the liquid crystal panel 35 spaced apart from the backlight unit 100.                     

As shown in FIGS. 1 and 2, the backlight unit 100 irradiates light to the rear surface of the liquid crystal panel 35 through the diffusion sheet 70 disposed in parallel to the rear surface of the liquid crystal panel 35. Lamp 80, the temperature sensing unit 110 for sensing the temperature of the flat lamp 80 and delivers the detection results, the inverter 130 and the temperature sensing unit for applying or blocking the voltage to the flat lamp 80 The inverter controller 120 controls the inverter 130 to maintain the temperature of the flat lamp 80 in a proper temperature range based on the detection result from the 110.

The temperature sensing unit 110 includes a temperature sensing unit 112 and an analog / digital converter 114 or a comparator (not shown).

The flat lamp 80 is a flat fluorescent lamp, the surface of which is uniformly shining and generates light without thickness. Conventional long rod-shaped fluorescent lamps have a small area and can reach a normal luminance within a short time with a supplied reference voltage. However, the flat lamp 80 has a large area to supply a reference voltage to reach a normal luminance. This takes However, the flat lamp 80 which has reached the normal brightness has advantages such as high brightness and uniformity of brightness, low power consumption and long life compared with other conventional light sources, as well as configuration of a light guide plate, a prism sheet, and a reflector. Since the element can be omitted, the manufacturing cost reduction effect is great.

In order to solve the above problem, as shown in FIG. 2, a lamp driving control means including an inverter 130, an inverter controller 120, and a temperature sensing unit 110 is provided. The lamp driving control means applies an excess voltage higher than a predetermined reference voltage when the power supply is supplied to the flat lamp 80 so that the normal brightness can be reached in a short time, and after the normal brightness is reached, the voltage is gradually lowered. Maintain normal brightness by applying reference voltage and stabilize brightness.

The inverter 130 applies a lamp driving voltage to the lamp according to the inverter control signal from the inverter controller 120, and the flat lamp 80 blinks and the brightness of the flat lamp 80 is controlled by the voltage. . The inverter 130 includes a lamp driving module and a lamp blocking module, and the lamp driving module and the lamp blocking module interact with each other based on the detection result from the inverter controller 120 to flash the flat lamp 80 or the flat plate. Adjust the brightness of the lamp 80. The inverter 130 receives the inverter control signal of the analog signal or the PWM signal from the inverter controller 120 to control the brightness of the flat lamp 80.

The inverter controller 120 maintains the temperature of the flat lamp 80 at an appropriate temperature range in a short time when power is supplied to the flat lamp 80 based on the detection result from the temperature sensor 110. ). The inverter controller 120 applies the predetermined reference voltage when the flat lamp 80 is in the proper temperature range as a result of the temperature sensing, and applies the excess voltage higher than the reference voltage when the flat lamp 80 is below the proper temperature range. To control. In addition, when the temperature detection result is the flat lamp 80 is above the appropriate temperature range, the inverter 130 is controlled to apply a reduced voltage lower than the predetermined reference voltage. Here, it is preferable to gradually lower the lamp driving voltage to apply the reduced voltage to stabilize the brightness. This is because it is possible to minimize the quality problems of the lamp and the liquid crystal display due to the rapid environmental change. When the flat lamp 80 reaches the normal brightness, the predetermined reference voltage must be continuously applied to stabilize the brightness.                     

For example, when power is supplied to the flat lamp 80, since the temperature of the flat lamp 80 is below an appropriate temperature range, an excess voltage is supplied to reach the normal luminance in a short time. When the temperature of the lamp 80 is in the proper temperature range, the supply voltage is gradually lowered to supply a predetermined reference voltage to continuously maintain the normal brightness and stabilize the brightness. Luminance refers to the brightness of light and is proportional to the current supplied to the flat lamp 80. Since the current is proportional to the voltage, the brightness may be adjusted by adjusting the voltage supplied to the flat lamp 80. The normal brightness refers to the brightness of light that is 80% or more of the maximum output brightness, and is the brightness that the display device must maintain in order to produce a clear image.

The appropriate temperature range refers to a temperature range in which the lamp can give a normal brightness, and is usually a temperature range of 60 ℃ to 70 ℃.

The temperature sensing unit 110 is composed of a resistor R1 that is connected in series with a thermistor RT1 and a thermistor RT1 whose resistance value changes with temperature, and divides a voltage with the thermistor RT1 and is determined according to the sensed temperature. And a temperature sensing means 112 for outputting a voltage, and an A / D converter 114 for receiving a voltage output from the temperature sensing means 112 and outputting a digital signal corresponding to the applied voltage. As shown in FIG. 2, the thermistor RT1 is connected to a power supply VCC, and a resistor is connected in series between the thermistor RT1 and ground. Thermistor RT1 is a temperature sensing element whose resistance value decreases according to the sensed temperature. Therefore, the voltage applied to the flat lamp 80 can be obtained. The thermistor RT1 may be mounted around the inverter PCB or the flat lamp 80, but the operation characteristics or the mounting position of the thermistor RT1 may be changed.

In the case of a CCFL or EEFL light source, a temperature sensing unit corresponding to each lamp must exist, or a few temperature sensing units must sense the temperatures of a plurality of lamps. Therefore, additional equipment and manufacturing cost is high, the internal structure of the backlight unit is complicated and the temperature of the lamp is not accurately sensed. However, when the flat lamp 80 is used, since there is no thickness in one light source and constant light is generated, the temperature of the light source can be sensed with only one temperature sensing unit 110, thereby reducing the cost of additional equipment and manufacturing costs. . The temperature detecting unit 110 may output the average value by sensing the temperature of a plurality of positions of the flat lamp 80 as a temperature detection result signal, and approximately reflects the temperature of the lamp by sensing the temperature of one place. The temperature detection result signal can also be output. The inverter controller 120 calculates the temperature of the current flat lamp 80 based on the approximate detection signal to control the inverter 130.

The A / D converter 114 converts the voltage value output from the thermistor RT1 into a corresponding digital signal and applies it to the inverter controller 120. In another embodiment, a comparator (not shown) may be used. The comparator compares a preset reference voltage with an input voltage and applies two signals, such as "0" or "1", to the inverter controller.

The operation principle of the liquid crystal display device having such a structure will be described.

First, the temperature detector 110 outputs a voltage obtained by dividing the power supply VCC by the voltage divider resistance of the thermistor RT1 and the resistor R1 whose resistance value changes depending on the temperature at which it is mounted. In the embodiment of the present invention, the thermistor RT1 of the temperature sensing unit 110 has a resistance value which is inversely proportional to the ambient temperature. Therefore, the higher the sensing temperature, the lower the internal resistance, and conversely, the lower the sensing temperature, the higher the internal resistance. As a result, since the resistance value of the thermistor RT1 is inversely proportional to the sensing temperature, the magnitude of the voltage output from the temperature sensing unit 110 is proportional to the sensing temperature. In the embodiment of the present invention, the thermistor RT1 in which the internal resistance value is inversely determined according to the sensing temperature is used. However, a temperature sensing element having the opposite operation characteristic can be used.

If the temperature of the flat lamp 80 at the time of initial lighting is below the predetermined appropriate temperature range, the resistance value of the thermistor RT1 becomes more than the initial setting value, and accordingly, the voltage output from the temperature sensing unit 110 becomes small. On the other hand, if the temperature of the flat lamp 80 is more than the appropriate temperature range, the resistance value of the thermistor (RT1) is less than the initial set value, the voltage output from the temperature sensing unit 110 is increased.

The output voltage is an analog value, and the A / D converter 114 outputs a digital signal corresponding to the output voltage and transmits the digital signal to the inverter controller 120.

The inverter controller 120 recognizes the temperature of the current flat lamp 80 based on the applied digital signal, and when the flat lamp 80 is in an appropriate temperature range, applies a predetermined reference voltage to stabilize the normal luminance. Inverter 130 is controlled to maintain. When the flat lamp 80 is below the proper temperature range, as shown in FIGS. 3 to 5, an excess voltage higher than a predetermined reference voltage is applied to the flat lamp 80 so as to be normal at a fast time T. The inverter 130 is controlled to reach the luminance.

After the time T, if the brightness is stabilized, the brightness is stabilized by controlling the voltage to be gradually lowered and applying a predetermined reference voltage. As a result, as shown in FIGS. 4 to 5, the normal brightness can be maintained continuously after the time T, and the flat plate lamp 80 maintains a temperature of 60 ° C to 70 ° C. Then, when the flat lamp 80 is above the appropriate temperature range, the voltage is gradually lowered to control the inverter 130 to apply a reduced voltage lower than a predetermined reference voltage. The luminance is stabilized by applying a voltage. In this case, the voltage may be gradually lowered to prevent quality problems of the liquid crystal display device due to the instantaneous change in luminance.

The inverter controller 120 determines whether the voltage is increased or decreased according to the condition of the current flat lamp 80 and transmits the inverter control signal of the analog signal or the PWM signal to the inverter 130.

The inverter 130 applies a predetermined excess voltage, a reference voltage, and a reduced voltage to the flat lamp 80 by the interaction of the lamp driving module and the lamp blocking module according to the control signal received from the inverter controller 120. Adjust the brightness of the lamp 80.

Here, the temperature detector 110 may be driven using a comparator (not shown) instead of the A / D converter 114. The comparator (not shown) compares the preset voltage with the voltage output from the temperature sensor 112 and applies two signals to the inverter controller 120 depending on the magnitude. For example, when the output voltage is larger than the preset voltage, a signal of "0" is output, and when it is small, a signal of "1" is output. When the signal output from the comparator (not shown) is "0", the inverter controller 120 applies an excess voltage higher than the predetermined voltage, and if "1", the inverter controller 120 applies a reduction voltage lower than the predetermined voltage. ) So that the lamp reaches the normal luminance at a fast time and stabilizes the luminance when the normal luminance is reached.

As a result, when the power is supplied to the flat lamp 80, an excessive voltage may be applied to reach a normal luminance within a short time, and when the normal luminance is reached, a predetermined reference voltage may be applied to stabilize the luminance to display the display device with high luminance. Clear images can be obtained.

Although the present invention has been described using a flat lamp as an example, it can be applied to other light sources.

As described above, according to the present invention, it is possible to shorten the luminance stabilization time of the lamp, and to provide a liquid crystal display device and a control method thereof capable of stabilizing and maintaining the normal luminance continuously.

Claims (12)

With a lamp; An inverter for applying a lamp driving voltage to the lamp; A temperature sensing unit sensing a temperature of the lamp; And an inverter controller configured to control the inverter to maintain the temperature of the lamp in an appropriate temperature range of 60 ° C to 70 ° C based on the detection result from the temperature detection unit. The method of claim 1, The inverter controller applies a predetermined reference voltage when the temperature is within the proper temperature range as a result of the temperature sensing, and controls the inverter to apply an excess voltage higher than the reference voltage when the temperature is below the proper temperature range. . The method of claim 1, And the inverter controller controls the inverter to apply a reduced voltage lower than a predetermined reference voltage when the inverter senses the temperature within the appropriate temperature range. The method of claim 1, And the temperature sensing unit is attached to the periphery of the lamp to output a detection result reflecting the temperature of the lamp to the inverter controller. The method of claim 1, The temperature sensing unit includes a thermistor having a resistance value determined according to a temperature, and a temperature sensing unit configured to be connected in series with a resistor for distributing a voltage together with the thermistor and outputting a predetermined voltage according to the sensed temperature; And an A / D converter which receives the voltage output from the temperature sensing means and outputs the digital signal corresponding to the applied voltage. With a lamp; An inverter for applying a lamp driving voltage to the lamp; Temperature sensing means for sensing the temperature of the lamp and the thermistor having a resistance value is determined in accordance with the temperature and a resistor connected in series with the thermistor to divide the voltage with the thermistor and outputs a predetermined voltage according to the sensed temperature; A temperature sensing unit including a comparator receiving the voltage output from the temperature sensing unit and outputting two signals according to the magnitude of the case compared with the reference voltage; And And an inverter controller configured to apply an excess voltage higher than a predetermined reference voltage when the power is supplied to the lamp based on the signal output from the comparator, and control the inverter to apply a decrease voltage lower than the reference voltage when the signal is changed. The backlight unit characterized by the above-mentioned. Sensing the temperature of the lamp and outputting a detection result; Determining whether the lamp driving voltage applied to the lamp is increased or decreased based on the detection result; When the temperature of the lamp is in the appropriate temperature range of 60 ℃ to 70 ℃ a predetermined reference voltage is applied, if it is below the suitable temperature range, an excess voltage higher than the reference voltage is applied, and the temperature is above the appropriate temperature range And stabilizing the brightness of the lamp by gradually applying a decreasing voltage. A flat lamp; An inverter for applying a lamp driving voltage to the flat lamp; A temperature sensing unit sensing a temperature of the flat lamp; As a result of temperature sensing from the temperature sensing unit, an excess voltage higher than a predetermined reference voltage is applied when the temperature of the flat lamp is below an appropriate temperature range of 60 ° C. to 70 ° C., and when the temperature is within the appropriate temperature range. And an inverter controller which controls the inverter to maintain the temperature of the flat lamp in the appropriate temperature range by gradually lowering the voltage supplied to the flat lamp. The method of claim 8, The inverter controller may be configured to maintain a proper temperature range by applying a reduction voltage lower than a predetermined reference voltage when the temperature of the flat lamp is greater than or equal to the predetermined temperature range as a result of the detection from the temperature sensing unit. Backlight unit. The method of claim 8, The temperature sensing unit is attached to be spaced apart from the flat lamp by a predetermined interval and outputs a detection result reflecting the temperature of the flat lamp to the inverter controller, And the inverter controller determines the current temperature of the flat lamp based on the detection result and controls the inverter to supply one of the excess voltage, the reference voltage, and the decrease voltage to the lamp. The method of claim 8, And the temperature sensing unit outputs a detection signal by sensing a temperature of a plurality of points of the flat lamp and using the average value as a temperature sensing result. The method of claim 11, And the plurality of points are distributed over the entire surface of the flat lamp.

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