KR20080020723A - Driving circuit of display apparatus - Google Patents

Abstract

A driving circuit of a display device is provided to divide an output voltage supplied to a light source of an LCD(Liquid Crystal Display) by a plurality of resistors having difference resistance values, select a divided output voltage according to surrounding brightness so as to vary the luminance of the LCD in response to the surrounding brightness. A driving circuit of a display device includes an LED(Light Emitting Diode) back light(30), a microcomputer(10), a first driving switch(21) outputting a driving signal under the control of the microcomputer, a luminance setting unit(40) for controlling an output voltage supplied to the LED back light to set the luminance of the LED back light, a second driving switch(22) providing the output voltage of the luminance setting unit to the LED back light according to the driving signal of the first driving switch, a dimming controller(50), and a ripple removal unit(60). The luminance setting unit includes a plurality of resistors(R4,R5,R6,R7) connected in parallel, a plurality of selecting switches(Q3,Q4,Q5,Q6) for selecting the plural resistors, a third resistor(R3) connected between the selecting switches and a driving voltage. The output voltage is divided by the plurality of resistors and the third resistor. A light sensor(70) senses the brightness around the display device.

Description

Driving circuit of display device {DRIVING CIRCUIT OF DISPLAY APPARATUS}

1 is a circuit diagram illustrating a driving circuit of a display device according to the prior art.

2 is a circuit diagram illustrating a driving circuit of a display device according to an exemplary embodiment of the present invention.

   -Explanation of symbols for the main parts of the drawings-

10: microcomputer 20: drive switch

21: first drive switch 22: second drive switch

30: LED backlight 40: luminance setting unit

50: dimming control unit 60: ripple removing unit

70: light sensing unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a display device. More particularly, an output voltage supplied to an LED backlight, which is a light source of an LCD panel, is divided by a plurality of resistors having different resistance values, and according to ambient brightness. The present invention relates to a driving circuit of a display device that selects and outputs an output voltage so that the brightness of the display device can be varied according to ambient brightness.

In general, kimchi storage is a household appliance equipped with a refrigeration system and heating means to ripen kimchi according to the change of seasons and the user's preference, and then maintain the proper temperature for a long time to preserve the taste of ripe kimchi.

The kimchi storage is provided with a cooling device and a heating device for adjusting the inside temperature of the storage compartment and storage compartment for storing and storing the kimchi in a container, etc. in the main body.

Therefore, when the user wants to ripen kimchi dipped in a short time to eat quickly, by raising the temperature in the storage room to the temperature required for the kimchi ripening through a preset mode of kimchi using a heating device, within a short time Kimchi can be eaten after ripening according to the taste of users.

In addition, if the user wants to take out fresh kimchi little by little while keeping it for a long time, it is possible to preserve the taste and freshness of the kimchi for a long time by maintaining the temperature of the storage room at an appropriate level through a preset storage mode of the kimchi using a cooling device. It is supposed to be.

The display unit of the kimchi storage serves to inform the consumer of the operation state or selection state by turning on the corresponding icon of the display panel provided in the kimchi storage by a method using an LED (Light Emitting Diode) or a VFD (Vacuum Fluorescent Display).

Recently, the display part of Kimchi storage is composed of LCD panel, and when selecting food or function, the LCD panel can set specific operation information precisely through animation or text information to prevent user from malfunctioning and want food. After the set operation is performed after storing and storing in a manner, the LCD panel is dimmed off gradually.

In general, LCD panels use a cold cathode fluorescent lamp (CCFL) as a backlight source, but since CCFL uses mercury gas, it can cause environmental pollution, slow response, and low color reproducibility. The LCD panel has a disadvantage that is inadequate for light and short, and has been recently progressed by using a light emitting diode (LED) device for better color reproduction.

LED device is eco-friendly, response speed of several nanoseconds, high speed response, effective for video signal stream, impulsive driving, color reproducibility of more than 100% and the amount of red, green, blue LED light Not only can it arbitrarily change brightness, color temperature, etc. by adjustment, but also has the advantage suitable for light and small size reduction of an LCD panel, and it is actively adopted as a light source for backlights, such as an LCD panel.

1 is a circuit diagram illustrating a driving circuit of a general display device.

As shown here, the LED backlight 30 composed of a plurality of LEDs, the microcomputer 10 for outputting the on-off control signal of the LED backlight 30, and driven on and off in accordance with the control signal of the microcomputer 10 are driven. A luminance setting unit 40 for setting the luminance of the LED backlight 30 by adjusting the first driving switch 21 for outputting a signal and the output voltage supplied to the LED backlight 30 by dividing the driving voltage VDD. And the second driving switch 22 for supplying the output voltage of the luminance setting unit 40 to the LED backlight 30 in accordance with the driving signal of the first driving switch 21 and the output of the luminance setting unit 40. The dimming control unit 50 and the LED backlight 30 which gradually turn off the second drive switch 22 while supplying charge to the LED backlight 30 while discharging when the first drive switch 21 is turned off by charging a voltage. Consists of a ripple removal unit 60 for removing the ripple.

In the display device configured as described above, when the microcomputer 10 outputs a control signal for turning on the LED backlight 30, the first drive switch 21 is turned on and the second drive switch 22 is turned on, thereby driving the LED. When the LED backlight 30 is turned off in the microcomputer 10 after the capacitor of the dimming control unit 50 is charged, the light is supplied to the backlight 30 and the driving voltage is applied while the first driving switch 21 is turned off. As the capacitor of the dimming controller 50 is discharged to the LED backlight 30, the second drive switch 22 is gradually turned off while the brightness is gradually decreased.

However, the maximum brightness of the LED backlight to be turned on is set according to the driving voltage output by dividing the voltage from the brightness setting part. Since the resistance values of the third and fourth resistors are fixed, the maximum brightness is always the same regardless of the surrounding brightness. There is a problem that the brightness is not adjusted.

The present invention has been made to solve the above problems, and an object of the present invention is to divide the output voltage supplied to the LED backlight which is the light source of the LCD panel by dividing the driving voltage by a plurality of resistors having different resistance values. The present invention provides a driving circuit of a display device that selects and outputs an output voltage according to brightness to change the brightness of the display device according to ambient brightness.

The present invention for achieving the above object is a LED backlight consisting of a plurality of LEDs, a microcomputer for outputting the on-off control signal of the LED backlight, and the first drive switch to output the drive signal while the on-off in accordance with the control signal of the microcomputer And a luminance setting unit for setting the luminance of the LED backlight by adjusting the output voltage supplied to the LED backlight by dividing the driving voltage, and supplying the output voltage of the luminance setting unit to the LED backlight according to the driving signal of the first driving switch. The dimming control unit charges the output voltage of the second driving switch, the brightness setting unit, and discharges when the first driving switch is turned off, while gradually discharging the second driving switch while supplying electric charge to the LED backlight. In the driving circuit of the display device including a ripple cancellation unit for, the brightness setting unit is connected in parallel with each other One side is configured to output a plurality of resistors connected to the ground, a plurality of select switches for selecting the plurality of resistors, and divided by the driving voltage by the resistor and the third resistor selected by the plurality of select switches, the display peripheral And a light sensing unit for sensing the brightness of the microcomputer, and configured to output a selection signal for selecting any one of a plurality of selection switches of the brightness setting unit based on the detection value of the light sensing unit in the microcomputer.

In the present invention, the light sensing unit is configured to divide and output the power voltage by the photodiode and the eighth resistor whose resistance value changes according to the brightness of the surroundings.

In one embodiment, the luminance setting unit includes a third to sixth transistor connected at one side thereof to ground and connected to the other side of the fourth to seventh resistors in parallel, and turned on according to a selection signal of the microcomputer; And a third resistor interposed between the third to sixth transistors and the driving voltage to output an output voltage divided by the fourth to seventh resistors.

In the present invention, the fourth to seventh resistors have different resistance values.

According to the present invention, the brightness of the LED backlight is determined according to the detected value by sensing the brightness of the surroundings of the display device through the light sensing unit, and selecting one of a plurality of selection switches of the luminance setting unit for the luminance according to the determined value. Accordingly, since the voltage applied to the LED backlight is changed, the brightness is variable, thereby actively adjusting the brightness of the display device according to the ambient brightness.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings, and the same parts as in the prior art use the same reference numerals and names. In addition, the present embodiment is not intended to limit the scope of the present invention, but is presented by way of example only and those skilled in the art will be capable of many modifications within the technical spirit of the present invention.

2 is a circuit configuration diagram showing a driving circuit of the display device according to the present invention.

As shown here, the LED backlight 30 composed of a plurality of LEDs, the microcomputer 10 for outputting the on-off control signal of the LED backlight 30, and driven on and off in accordance with the control signal of the microcomputer 10 are driven. A luminance setting unit 40 for setting the luminance of the LED backlight 30 by adjusting the first driving switch 21 for outputting a signal and the output voltage supplied to the LED backlight 30 by dividing the driving voltage VDD. And the second driving switch 22 for supplying the output voltage of the luminance setting unit 40 to the LED backlight 30 in accordance with the driving signal of the first driving switch 21 and the output of the luminance setting unit 40. The dimming control unit 50 and the LED backlight 30 which gradually turn off the second drive switch 22 while supplying charge to the LED backlight 30 while discharging when the first drive switch 21 is turned off by charging a voltage. Consists of a ripple removal unit 60 for removing the ripple.

At this time, in order to be able to set different luminance according to the ambient brightness, the fourth to seventh resistors R4 to R7 and the fourth to seventh resistors R4 connected in parallel with one side of the luminance setting unit 40 are connected to ground. Between the third to sixth transistors Q3 to Q6, the third to sixth transistors Q3 to Q6, and the driving voltage VDD, which are connected to the other side of ˜R7 and turned on according to the selection signal of the microcomputer 10; And outputs an output voltage constituted by the third resistor R3 and divided by the fourth to seventh resistors R4 to R7.

The fourth to seventh resistors R4 to R7 have different resistance values.

In addition, the optical sensing unit 70 for sensing the brightness around the display device is provided, so that the third to sixth transistors of the luminance setting unit 40 are based on the detection value of the optical sensing unit 70 in the microcomputer 10. The drive voltage VDD is divided by the resistor of any one of the selected fourth to seventh resistors R4 to R7 and the third resistor R3 by outputting a selection signal for selecting any one of Q3 to Q6. And output the different output voltages to the LED backlight 30.

In this case, the light sensing unit 70 is configured to divide and output the power supply voltage by the photodiode PD and the eighth resistor R8 whose resistance values change according to the brightness of the surroundings.

The operation of the driving circuit of the display device according to the exemplary embodiment of the present invention as described above is as follows.

First, when the LED backlight 30 is turned on, when the microcomputer 10 outputs a high potential signal as a control signal, the high potential signal is input to the base of the transistor Q1 of the first drive switch 21, thereby providing a transistor Q1. ) Is turned on to output a low potential signal as a drive signal.

Then, as the low potential signal is input to the gate G of the PMOSFET Q2 of the second driving switch 22, the PMOSFET Q2 is also turned on and the third transistor Q3 is turned on in the luminance setting unit 40. In this case, the output voltage divided by the driving voltage VDD by the third resistor R3 and the fourth resistor R4 is supplied to the LED backlight 30 to be turned on.

On the contrary, when the LED backlight 30 is turned off, when the microcomputer 10 outputs a low potential signal as a control signal, the low potential signal is input to the base of the transistor Q1 of the first drive switch 21, thereby providing a transistor Q1. Is turned off and outputs a high potential signal as a driving signal.

Then, as the high potential signal is inputted to the gate G of the PMOSFET Q2 of the second driving switch 22, the PMOSFET Q2 is also turned off and charged to the second capacitor C2 of the dimming controller 50. The discharged electric charge is discharged in a time constant with the fourth resistor R4 and is supplied to the LED backlight 30, and the luminance is gradually decreased.

As the resistance value of the photodiode PD is changed according to the ambient brightness, the ambient brightness is determined by the change of the partial pressure value output to the microcomputer 10, and the third to sixth transistors Q3 of the luminance setting unit 40 are determined. A select signal for operating any one of? Q6) is output.

For example, when the selection signal for selecting the fourth transistor Q4 is output, as the fourth transistor Q4 is turned on, a current path is formed through the fifth resistor R5 to form the third resistor R3 and the third resistor. The driving voltage VDD is divided and output by the fifth term R5.

If the fifth transistor Q5 is selected, since the divided voltages of the sixth resistor R6 and the third resistor R3 are output, the difference between the fifth resistor R5 and the sixth resistor R6 having different resistance values is different. As a result, the voltage supplied to the LED backlight 30 is changed so that the brightness of the display device is changed according to the ambient brightness.

As described above, according to the present invention, the output voltage supplied to the LED backlight, which is the light source of the LCD panel, is divided by a plurality of resistors having different resistance values, and then the output voltage is selected and supplied according to the ambient brightness. Accordingly, the brightness of the display device may be varied.

Claims (4)

A LED backlight comprising a plurality of LEDs, a microcomputer for outputting an on-off control signal of the LED backlight, a first driving switch for outputting a driving signal while being turned on and off according to the control signal of the microcomputer, and dividing a driving voltage to divide the driving voltage; A brightness setting unit for setting the brightness of the LED backlight by adjusting the output voltage supplied to the LED backlight, and a second drive for supplying the output voltage of the brightness setting unit to the LED backlight according to the drive signal of the first drive switch. A dimming control unit which charges an output voltage of the brightness setting unit and discharges when the first driving switch is turned off, and gradually turns off the second driving switch while supplying charge to the LED backlight while discharging the ripple of the LED backlight. In the driving circuit of the display device including a ripple removing unit for removing, A plurality of resistors connected in parallel with each other, and the brightness setting unit is connected to ground, a plurality of select switches for selecting the plurality of resistors, a resistor selected by the plurality of select switches, and a driving voltage by a third resistor; Is configured to output by dividing An optical sensing unit for sensing a brightness around the display device, the microcomputer configured to output a selection signal for selecting any one of the plurality of selection switches of the luminance setting unit based on the sensing value of the optical sensing unit; A drive circuit for a display device, characterized in that. The driving circuit of claim 1, wherein the photosensitive unit is configured to divide the power supply voltage by a photodiode and an eighth resistor, the resistance of which varies in accordance with ambient brightness, and to output the divided voltage. The method of claim 1, wherein the brightness setting unit One side is connected to ground and the fourth to seventh resistors connected in parallel, A third to sixth transistor connected to the other side of the fourth to seventh resistors and turned on according to the selection signal of the microcomputer; The third resistor is interposed between the third to sixth transistors and a driving voltage. And outputting an output voltage divided by the fourth to seventh resistors. 4. The driving circuit of claim 3, wherein the fourth to seventh resistors have different resistance values.

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