KR20080069031A - Display device - Google Patents

Abstract

A display device is provided to feedback common voltage directly and immediately to compare the feedback voltage with a power level as a reference, thereby easily grasping a degree of distortion of the common voltage. A display device comprises a display panel and a power supply unit(200). The power supply unit comprises a reference power supply unit(210), a reference power output terminal(240), a feedback unit(230), and a controller(220). The reference power supply unit provides a predetermined level of reference power. The feedback unit feeds back power outputted to the reference power output terminal. The controller compares the feedback power with the reference power, and outputs the reference power of the level to the reference power output terminal. The power supply unit provides the reference power of the level to the display panel.

Description

Display device {DISPLAY DEVICE}

1 is a simplified circuit diagram of a pixel included in a display device according to an embodiment of the present invention.

2 is a schematic diagram of a power supply unit according to an embodiment of the present invention;

3 is a control flowchart illustrating a control method of a display apparatus according to an exemplary embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

100: display panel 110: gate line

120: data line 130: thin film transistor

140: pixel electrode 150: common electrode

200: power supply unit 210: reference power supply unit

220: control unit 230: feedback unit

240: reference power output stage

The present invention relates to a display apparatus, and more particularly, to a display apparatus to which a fixed power source such as a common voltage or a driving voltage is applied.

In a liquid crystal display (LCD) or an organic light emitting diode (OLED) display, a thin film transistor substrate (TFT) is used as a circuit board for driving each pixel independently. The thin film transistor substrate has a gate line transferring a scan signal and a data line transferring a data signal. The substrate includes a thin film transistor connected to a gate line and a data line, a pixel electrode connected to the thin film transistor, and the like.

In addition, a voltage of a predetermined level such as a common voltage or a driving voltage is applied to the thin film transistor substrate. For the stabilization of the signal and the normal display of the image signal, it is very important that a constant level of voltage is uniformly and stably supplied to the thin film transistor substrate. After these voltages are applied to the corresponding wiring, they are fed back at a predetermined point and the level is adjusted through the fed back voltage. In other words, the voltage is already fed through the load is fed back, the feedback voltage may cause coupling with other voltages, there is a problem that can not accurately determine the degree of distortion of the voltage due to the load.

Accordingly, it is an object of the present invention to provide a display device in which a predetermined level of power is stably supplied.

According to the present invention, there is provided a display apparatus comprising: a display panel; A reference power supply unit providing a reference power of a predetermined level, a reference power output terminal, a feedback unit for feeding back the power output to the reference power output terminal, and comparing the feedback power supply and the reference power to the reference power output terminal. It is achieved by a display device including a power supply for providing a reference power of the level to the display panel, including a control unit for outputting the reference power of the level.

The reference power supply unit may include a zener diode.

The control unit includes: a comparator for comparing a feedbacked power supply with the reference power supply and outputting a predetermined control signal; It may be connected between the comparator and the reference power output terminal, and may include a switching element for intermittently controlling the reference power output to the reference power output terminal in accordance with the control signal.

When the level of the power to be fed back is lower than the level of the reference power, the switching element is preferably turned on so that the reference power is output to the reference power output unit.

The display panel may include a common electrode to which a common voltage is applied, and the reference power source may include the common voltage.

The display panel may include a light emitting layer for emitting light and a transistor connected to the light emitting layer, and the reference power source may include a driving voltage provided to the transistor.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

1 is a simplified circuit diagram of a pixel included in a display apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a power supply unit according to the present embodiment.

The display apparatus includes a display panel 100 of FIG. 1 and a power supply unit 200 of FIG. The display panel 100 according to the present exemplary embodiment includes a liquid crystal layer having a liquid crystal injected between a first substrate on which the thin film transistor 130 is formed, a second substrate on which the common electrode 150 is formed, and both substrates. It includes a liquid crystal panel. In the display panel 100, a plurality of pixels arranged in a matrix form is formed, and the arrangement of the liquid crystals corresponds to a difference between the pixel voltage applied to each pixel and the common voltage Vcom applied to the front surface of the second substrate. Change. The transmittance of light provided from the backlight unit (not shown) is adjusted according to the arrangement of the liquid crystals, and thus an image is displayed on the display panel 100.

Specifically, the display panel 100 includes a gate line 110 extending in the long side direction of the display panel 100, a data line 120 extending in a direction substantially perpendicular to the gate line 110, and A pixel including the thin film transistor 130 formed at the intersection of the gate line 110 and the data line 120 is formed.

The gate electrode g of the thin film transistor 130 is connected to the gate line 110, and the source electrode s is connected to the data line 120. The drain electrode d of the thin film transistor 130 is connected to the pixel electrode 140 made of a transparent conductive material. The data voltage supplied through the data line 120 is transferred to the pixel electrode 140 through the thin film transistor 130 and substantially applied to the pixel voltage and the common electrode 150 applied to the pixel electrode 140. The arrangement of the liquid crystals is determined according to the voltage corresponding to the difference from the common voltage Vcom. The liquid crystal capacitor Clc corresponding to the difference between the two voltages is formed in the liquid crystal layer. In addition, the pixel further includes a storage electrode 131 formed to overlap the pixel electrode 140, and the storage electrode 131 forms a storage capacitor Cst for holding the liquid crystal capacitor Clc for one frame.

Typically, the common voltage Vcom is applied to the first substrate on which the thin film transistor 130 is formed, and is transferred to the common electrode formed on the second substrate through a means such as a contact hole. When the common voltage Vcom is unstable, the voltage applied to the liquid crystal layer becomes unstable, and the coupling of the common voltage also affects the gate-off voltage to form crosstalk in the display panel 100. Therefore, it is very important in a display apparatus that a certain level of common voltage Vcom is uniformly and stably applied to the entire common electrode. In addition, as the size of the display panel 100 increases, the stability of the common voltage Vcom becomes more important.

Currently, after the common voltage Vcom is applied to the common electrode, the feedback voltage is fed back at a predetermined point and the level of the common voltage Vcom is adjusted through the fed back voltage. That is, since the voltage through the common electrode is fed back after being already applied to the display panel 100, this feedback is referred to as a loop-feedback. The loop feedback method may generate coupling with other voltages while the feedback voltage passes through the loop, and the load cannot accurately determine the distortion of the common voltage.

Therefore, the display apparatus according to the present embodiment uses the common voltage output to the common electrode as the direct feedback voltage instead of the loop feedback method. As shown in FIG. 2, the power supply unit 200 providing a common voltage to the common electrode includes a reference power supply unit 210, a control unit 220, a feedback unit 230, and a reference power output terminal 240. .

The power supply unit 220 includes a Zener diode 211 connected between a power supply terminal to which the source power Vo is input, and a first resistor R1, a first resistor R1, and a ground terminal. The zener diode 211 maintains a constant level of power output to the controller 220, that is, a constant voltage is input to the controller 220. The constant voltage output from the power supply unit 220 to the control unit 220 is a common voltage, and the level of the common voltage may be variably set according to the characteristics and size of the display device.

The feedback unit 230 feeds back the voltage level of the power output to the reference power output terminal 240 through the controller 220 to the controller 220. The feedback unit 230 includes a second resistor R2 and a third resistor R3, and the voltage divided by the second resistor R2 and the third resistor R3 is re-input to the controller 220. . That is, unlike the related art, the feedback unit 230 may be provided adjacent to the reference power output terminal 240 to feed back the common voltage without distortion to the controller 220.

The controller 220 includes a comparator 221 for comparing the fed back power and the reference power, and a switching element 223 connected between the comparator 221 and the reference power output 240.

The comparator 221 is provided with an operational amplifier, and the reference power is input to the non-inverting terminal. The output terminal of the comparator 221 is connected to the control terminal of the switching element 223, and the comparator 221 compares the level of the input power and outputs a predetermined control signal to the switching element 223. The input terminal of the switching element 223 is connected to the inverting terminal of the comparator 221 and the output terminal is connected to the reference power output terminal 240.

The comparator 221 may output a control signal for turning on the switching element 223 when the level of the fed-back power supply is lower than that of the reference power source, and turn off the switching element 223 in the opposite case. Output a control signal. When the switching element 223 is turned on, the reference power input to the inverting terminal of the comparator 221 is directly output to the reference power output terminal 240, and in the opposite case, power is not output to the reference power output terminal 240.

3 is a control flowchart illustrating a control method of a display apparatus according to an exemplary embodiment of the present invention.

First, reference power of a predetermined level is generated (S10). The reference power source according to the present embodiment corresponds to a common voltage to be applied to the liquid crystal.

According to another embodiment, the reference power source may be a driving voltage provided to the organic light emitting diode instead of the liquid crystal panel. That is, a display panel including an organic light emitting diode generally includes a switching transistor to which a data signal is applied and a driving transistor to drive the organic light emitting diode. In this case, a predetermined level of driving voltage is applied to the input terminal of the driving transistor, and the driving voltage is transmitted by the voltage pad and the driving voltage line formed on the display panel. That is, the power supply unit according to the present invention may be applied to maintain a constant level of the driving voltage and to supply a stable driving voltage.

Next, in order to detect the power output to the reference power output terminal 240, the power output from the reference power output terminal 240 is fed back (S20). That is, in the related art, it is difficult to determine the distortion level of the common voltage by feeding back the power supply after being supplied to the display panel 100, and there is a problem in that the fed back common voltage is coupled with another voltage.

However, according to the present invention, it is possible to directly feedback the output common voltage and compare it with the level of the reference power supply, so that it is easy to understand the distortion of the common voltage, and the feedback power supply is not coupled with another power supply. .

Then, the comparator 221 compares the level of the power supply fed back with the level of the reference power supply (S30). As a result of the comparison, when the level of the feedback power source is lower than the level of the reference power source, the switching device 223 connected between the comparator 221 and the reference power output terminal 240 is turned on (S40). When the switching element 223 is turned on, the reference power is directly output to the reference power output terminal 240. As the above process is repeated, the power of the level corresponding to the reference power is immediately output to the reference power output terminal 240. That is, the common voltage can be quickly controlled through the power supply fed back.

On the other hand, as a result of the comparison, when the level of the power supply fed back is higher than the level of the reference power source, the switching element 223 is turned off so that the reference power source is not output. That is, the switching element 223 is turned off until the power source fed back reaches the level of the reference power source. When the power level fed back reaches the level of the reference power source, the switching element 223 is turned on again. The reference power supplied from the power supply unit 210 is output to the reference power output terminal 240.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a display device in which a predetermined level of power is stably supplied.

Claims (6)

In the display device, A display panel; A reference power supply for providing a reference power of a predetermined level, a reference power output stage, a feedback unit for feeding back the power output to the reference power output stage, and comparing the fed back power supply with the reference power level to the reference power output stage. And a power supply unit configured to provide the reference power of the level to the display panel, including a control unit configured to output a reference power supply. The method of claim 1, And the reference power supply unit includes a zener diode. The method of claim 1, The control unit, A comparator for comparing a feedback power supply with the reference power supply and outputting a predetermined control signal; And a switching element connected between the comparator and the reference power output terminal and intermittently controlling the reference power output to the reference power output terminal according to the control signal. The method of claim 3, And the switching element is turned on when the level of the supplied power is lower than the level of the reference power. The method of claim 1, The display panel includes a common electrode to which a common voltage is applied. And the reference power supply includes the common voltage. The method of claim 1, The display panel includes a light emitting layer for emitting light and a transistor connected to the light emitting layer. The reference power supply may include a driving voltage provided to the transistor. Display device to be gong.

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