KR100810595B1 - Power Supplying Circuit and Liguid Crystal Display using the same - Google Patents

Abstract

A scan signal power supply circuit for supplying a power supply voltage to a common drive circuit provided to supply a scan signal to a liquid crystal panel, and a liquid crystal display device using the same. The power supply voltage of any one of the power supply voltages supplied is a boosted voltage, and the other power supply voltage is applied a voltage that is not boosted. In addition, when the voltage boosted in the positive direction is applied in one frame, the voltage boosted in the negative direction is applied alternately in the next frame. The common drive circuit, which receives the supply voltages, forms a scan signal with a positive level on the basis of the positive boost voltage in one frame for inversion driving, and a scan with a negative level on the negative boost voltage in the subsequent frame. Form a signal. Therefore, it is possible to reduce power consumption by simultaneously forming a positive power supply voltage and a negative power supply voltage.

Description

Scanning signal power supply circuit and liquid crystal display device using the same {Power Supplying Circuit and Liguid Crystal Display using the same}

1 is a block diagram illustrating a passive matrix liquid crystal display device according to the prior art.

FIG. 2 is a timing diagram showing an output waveform of the scan signal power circuit shown in FIG. 1 according to the prior art.

3 is a timing diagram illustrating an output signal of the common drive circuit 120 shown in FIG. 1 according to the related art.

4 is a block diagram illustrating a scan signal power supply circuit according to a preferred embodiment of the present invention.

FIG. 5 is a timing diagram for describing an operation of the scan signal power supply circuit shown in FIG. 4 according to a preferred embodiment of the present invention.

6 is a block diagram illustrating a liquid crystal display according to a preferred embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100, 300: liquid crystal panel 120, 320: common drive circuit

140, 340: scan signal power supply circuit 160, 360: segment drive circuit

200: first voltage generator circuit 220: second voltage generator circuit

240: bidirectional boost circuit 260: switching unit

The present invention relates to a passive matrix liquid crystal display device, and more particularly, to a liquid crystal driving circuit for controlling an image of a passive matrix liquid crystal display device.

The liquid crystal display used to display an image is divided into an active matrix type and a passive matrix type according to its driving method.

The active matrix type uses a switching transistor which is a thin film transistor for each pixel, and applies an operation of applying a turn-on voltage to a gate terminal of the switching transistor and applying a data voltage necessary for alignment of liquid crystal to the turned-on switching transistor. In the active matrix type, an on / off operation of a switching transistor is applied to apply a data voltage to a pixel, and a predetermined image is realized through a backlight.

In the case of the passive matrix type, the common electrode wirings and the segment electrode wirings are vertically intersected above and below the substrate filled with the liquid crystal. When an activated scan signal is applied through the common electrode wiring, each pixel connected to the common electrode wiring is activated. The gray level signal is applied to the activated pixel through the segment electrode wiring.

In particular, in a liquid crystal display device that implements full color, pixels are divided by a color matrix for implementing color and a black matrix disposed between the color filters. In particular, in the case of the passive matrix type, an area where the common electrode wiring and the segment electrode wiring intersect is formed of a pixel.

1 is a block diagram illustrating a passive matrix liquid crystal display device according to the prior art.

Referring to FIG. 1, a passive matrix type liquid crystal display device includes a liquid crystal panel 100, a common drive circuit 120, a scan signal power supply circuit 140, and a segment drive circuit 160.

The liquid crystal panel 100 includes a liquid crystal filled between the upper and lower substrates, and a common electrode wiring and a segment electrode wiring for applying an electric field between the liquid crystal and the substrate. In addition, a pixel defined by a black matrix is provided in an area where the common electrode wiring and the segment electrode wiring intersect. When the pixel implements full color, the pixel may further include a color filter.

The common drive circuit 120 supplies a scan signal through the common electrode wiring of the liquid crystal panel 100. In addition, whenever the image of one frame is displayed, the common drive circuit 120 may supply a scanning signal having a different polarity to perform inversion driving. By the activation of the scan signal, the pixels provided in the corresponding common electrode wirings are selected.

The scan signal power supply circuit 140 applies at least two kinds of power supply voltages to the common drive circuit 120. That is, the positive power supply voltage and the negative power supply voltage are supplied to the common drive circuit 120. The positive power supply voltage and the negative power supply voltage are applied to the common drive circuit 120 at a predetermined level without a change in the level.

The segment drive circuit 160 applies the gray voltage to the liquid crystal through the segment electrode line. The liquid crystal is aligned in accordance with the applied gradation voltage and the voltage difference of the scan signal, and the light transmittance of the liquid crystal is determined according to the alignment of the liquid crystal.

FIG. 2 is a timing diagram showing an output waveform of the scan signal power circuit shown in FIG. 1 according to the prior art.

Referring to FIG. 2, the scan signal power supply circuit 140 continuously supplies a positive power supply voltage and a negative power supply voltage to the common drive circuit 120 through a predetermined boosting process. That is, the scan signal power supply circuit 140 must simultaneously boost two kinds of voltages to simultaneously form a positive power supply voltage and a negative power supply voltage.

3 is a timing diagram illustrating an output signal of the common drive circuit 120 shown in FIG. 1 according to the related art.

First, while an image of one frame is displayed, a signal having a first level, which is a positive voltage level, is applied. While the signal having the first level is applied, the pixels of the common electrode wiring to which the signal is applied are selected, and a gray voltage is applied to the selected pixels. The liquid crystal is aligned by the gray level voltage and the voltage difference of the first level signal, and a predetermined gray level is expressed.

Subsequently, in the following frame, inversion driving with respect to the liquid crystal is performed. The inversion driving is used to maintain or improve the reaction rate of the liquid crystal layer by changing the electrode applied to the liquid crystal. That is, when the electric field in the same direction is always applied to the liquid crystal layer, the arrangement of the affection layer is rigid, and the liquid crystal does not move smoothly according to the electric field. Therefore, the electric field applied to the liquid crystal layer is inverted and applied every frame.

In a subsequent frame to perform inversion driving for the liquid crystal, the scan signal is applied at a second level, which is a negative level. According to the difference between the second level and the applied gradation voltage, the liquid crystal is aligned, and a predetermined gradation is expressed.

The first level and the second level of the scan signal are formed based on the positive power supply voltage and the negative power supply voltage supplied to the power supply terminals. Thus, the first level does not exceed the positive power supply voltage, and the absolute value of the second level does not exceed the absolute value of the negative power supply voltage.

As described above, the scan signal power supply circuit supplies the positive power supply voltage and the negative power supply voltage to the common drive circuit. In principle, the scan signal power supply circuit has a boosting circuit therein, and simultaneously boosts and outputs a positive power supply voltage and a negative power supply voltage. In order to perform the above operation, the scan signal power supply circuit must include a circuit capable of withstanding the difference between the positive power supply voltage and the negative power supply voltage. For example, when driving at 16V, the positive power supply voltage should be at least 16V and the negative power supply voltage should be -16V. Therefore, the scan signal power supply circuit must be provided with a circuit capable of forming a voltage difference of 32V. That is, regardless of the progress of the frame, the scan signal power supply circuit must continuously output a positive power supply voltage and a negative power supply voltage having a constant magnitude. The common drive circuit may continuously receive a negative power supply voltage that is not used for the formation of the scan signal during the first frame, or the common drive circuit may receive a positive power supply voltage that is not used for the formation of the scan signal during the second frame. It must be received continuously.

Accordingly, it is a first object of the present invention to provide a scan signal power supply circuit capable of selectively supplying a positive power supply voltage and a negative power supply voltage according to the state of a frame.

A second object of the present invention is to provide a liquid crystal display device using a scan signal power supply circuit provided according to the first object.

The present invention for achieving the above-described first object, the first voltage generating circuit for generating a first voltage; A second voltage generation circuit for generating a second voltage having a level lower than the first voltage; A bidirectional boost circuit for selectively boosting a first voltage and a second voltage to output a first boosted voltage boosted by the first voltage or a second boosted voltage boosted by the second voltage; And a switching unit for selectively selecting the first voltage and the second voltage, and alternatively selecting the first boosted voltage and the second boosted voltage, wherein the switching unit selects and outputs the first voltage. In this case, when the second boosted voltage is selected and output, and when the second voltage is selected and output, the scan signal power supply circuit of the liquid crystal display device is provided. .

In addition, the present invention for achieving the second object, the liquid crystal panel for displaying an image; A common drive circuit for supplying a scan signal to the liquid crystal panel; A segment drive circuit for applying a gray voltage to the liquid crystal panel; And a scan signal power supply circuit for supplying a positive power supply voltage and a negative power supply voltage to the common drive circuit, the scan signal power supply circuit comprising: a first voltage generating circuit for generating a first voltage; A second voltage generation circuit for generating a second voltage having a level lower than the first voltage; A bidirectional boost circuit for selectively boosting a first voltage and a second voltage to output a first boosted voltage boosted by the first voltage or a second boosted voltage boosted by the second voltage; And a switching unit for selectively selecting the first voltage and the second voltage, and alternatively selecting the first boosted voltage and the second boosted voltage, wherein the switching unit selects the first voltage to select the first voltage. When outputting with a positive power supply voltage, the second boosted voltage is selected and output as the negative power supply voltage, and when the second voltage is selected and output as the negative power supply voltage, the first boosted voltage is selected. A liquid crystal display device is characterized by outputting the positive power supply voltage.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and duplicate descriptions of the same components are omitted.

Example

4 is a block diagram illustrating a scan signal power supply circuit according to a preferred embodiment of the present invention.

Referring to FIG. 4, the scan signal power supply circuit according to the present embodiment includes a first voltage generator circuit 200, a second voltage generator circuit 220, a bidirectional boost circuit 240, and a switching unit 260.

The first voltage generation circuit 200 forms a first voltage having a positive level, and outputs the formed first voltage to the bidirectional boost circuit 240 and the switching unit 260.

The second voltage generator circuit 220 forms a second voltage having a polarity opposite to that of the first voltage generator circuit 200. The formed second voltage is input to the bidirectional boost circuit 240 and the switching unit 260. Therefore, it is preferable that the second voltage has a negative level.

The bidirectional boost circuit 240 receives the first voltage from the first voltage generator circuit 200 and the second voltage from the second voltage generator circuit 220. In addition, the first boosted voltage is selectively output through the first output line 241, and the second boosted voltage is selectively output through the second output line 243. Accordingly, the bidirectional boost circuit 240 boosts the first voltage to form a first boosted voltage, and boosts the second voltage to form a second boosted voltage. However, in the case of the second boosted voltage, the voltage is boosted in the negative direction.

In addition, the boosting operation of the bidirectional boosting circuit 240 is time-divisionally performed. That is, when the first boosted voltage is formed and output to the first output line 241, the second voltage may be output or floated on the second output line 243. In other words, the boosting operation with respect to the second voltage does not occur while boosting the first voltage in the positive direction. In addition, when the second boosted voltage is formed and output to the second output line 243, the first voltage may be output or floated on the first output line 241. Therefore, the boosting operation with respect to the first voltage does not occur while boosting the second voltage in the negative direction.

The switching unit 260 includes a first switch 261 and a second switch 263.

The first switch 261 is connected to the output terminal of the first voltage generating circuit 200 and the first output line 241 of the bidirectional boost circuit 240, and the second switch 243 is connected to the second voltage generating circuit ( It is connected to the output terminal of 220 and the second output line 243 of the bidirectional boost circuit 240. Accordingly, the first switch 261 selectively outputs the first voltage or the first boosted voltage to the first output terminal 265, and the second switch 263 outputs the second voltage or the second boosted voltage to the second output. Output to terminal 267 selectively.

Therefore, when the first switch 261 selects the first boosted voltage, the second switch 263 selects the second voltage. In addition, when the first switch 261 selects the first voltage, the second switch 263 selects the second boosted voltage.

In addition, the switching unit 260 may further include a capacitor C between the first output terminal 265 and the second output terminal 267. The capacitor C maintains a voltage difference between the first output terminal 265 and the second output terminal 267 and removes noise that may be included in voltages applied to the output terminals 265 and 267.

FIG. 5 is a timing diagram for describing an operation of the scan signal power circuit shown in FIG. 4 according to a preferred embodiment of the present invention.

Referring to FIG. 5, a first boosted voltage is output to the first output terminal 265 through the first switch 261 of FIG. 4 during the first frame. In addition, a second voltage is output to the second output terminal 267 through the second switch 263 during the first frame.

The first output terminal 265 and the second output terminal 267 are electrically connected to the power terminals of the common drive circuit shown in FIG. 1. That is, voltages of the first output terminal 265 are input to the power supply terminals of the common drive circuit as positive power supply voltages, and voltages of the second output terminal 267 are input as negative power supply voltages, respectively.

First, the first boosted voltage is output through the first output terminal 265 in the first frame. In addition, a second voltage is output through the second output terminal 267. The common drive circuit receiving these power supply voltages forms a scan signal based on the two power supply voltages. Thus, the voltage difference between the high level and the low level in the scan signal is substantially equal to the voltage difference between the first boosted voltage and the second voltage. In addition, the voltage difference between the high level and the low level of the scan signal may have a different value depending on the configuration of the common drive circuit, but the scan signal is formed based on two power supply voltages received in the first frame.

Further, in the second frame subsequent to the first frame, complementary power supply voltages are output from the scan signal power supply circuit to realize inversion driving. That is, the first voltage is output through the first output terminal 265 and the second boosted voltage is output through the second output terminal 267 by the operation of the switches provided in the scan signal power supply circuit. However, the second boosted voltage means that the second voltage is boosted in the negative direction. Therefore, the first voltage is applied to the positive power supply terminal of the common drive circuit, and the second boosted voltage is applied to the negative power supply terminal. The common drive circuit having received these power supply voltages forms a scan signal based on the first voltage and the second boosted voltage. Thus, the voltage difference between the high level and the low level in the scan signal is substantially equal to the voltage difference between the first voltage and the second boosted voltage. In addition, the voltage difference between the high level and the low level of the scan signal may have a different value depending on the configuration of the common drive circuit, but the scan signal is formed based on two power supply voltages received in the second frame. In addition, the voltage difference between the first boosted voltage and the second voltage is preferably equal to the voltage difference between the first voltage and the second boosted voltage.

Therefore, the scan signal power supply circuit according to the present embodiment outputs the first boosted voltage and the second voltage during the first frame. That is, the bidirectional boosting circuit provided in the scan signal power supply circuit boosts the voltage in the positive direction and supplies the boosted voltage. Also, during the second frame subsequent to the first frame, the scan signal power supply circuit outputs a first voltage and a second boosted voltage. That is, the bidirectional boost circuit boosts the voltage in the negative direction and supplies the boosted voltage to the power supply of the common drive circuit.

Therefore, the scan signal power supply circuit boosts the voltage only in one direction for each frame. That is, the voltage is boosted in the positive direction in the first frame, and the voltage is boosted in the negative direction in the subsequent second frame.

6 is a block diagram illustrating a liquid crystal display according to a preferred embodiment of the present invention.

Referring to FIG. 6, the liquid crystal display according to the present exemplary embodiment includes a liquid crystal panel 300, a common drive circuit 320, a scan signal power supply circuit 340, and a segment drive circuit 360.

The liquid crystal panel 300 includes a liquid crystal filled between the upper and lower substrates, and common electrode wiring and segment electrode wiring for applying an electric field between the liquid crystal and the substrate. In addition, a pixel defined by a black matrix is provided in an area where the common electrode wiring and the segment electrode wiring intersect. When the pixel implements full color, the pixel may further include a color filter.

The common drive circuit 320 supplies a scan signal through the common electrode wire of the liquid crystal panel 300. In addition, whenever the image of one frame is displayed, the common drive circuit 320 may supply a scanning signal having a different polarity to perform inversion driving. By the activation of the scan signal, the pixels provided in the corresponding common electrode wirings are selected.

The scan signal power supply circuit 340 supplies a positive power supply voltage and a negative power supply voltage to the common drive circuit 320. When the positive power supply voltage is a boosted voltage, the negative power supply voltage becomes a voltage that is not boosted. In addition, when the positive power supply voltage is not boosted, only the negative power supply voltage becomes the boosted voltage. That is, in the first frame, the first boosted voltage is supplied at the positive power supply voltage, and the second voltage is supplied at the negative power supply voltage. In addition, in the second frame subsequent to the first frame, the first voltage is supplied at the positive power supply voltage, and the second boosted voltage is supplied at the negative power supply voltage.

Thus, the scan signal power supply circuit 340 alternately supplies one boosted voltage to the common drive circuit 320 alternately with a positive power supply voltage or a negative power supply voltage for each successive frame. That is, a boosted voltage is applied to one of the power supply voltages every frame, and a voltage that is not boosted is applied to the remaining power supply voltages.

The common drive circuit 320 receiving the power supply voltages from the scan signal power supply circuit 340 forms a scan signal based on the power supply voltages, and supplies the formed scan signal to the liquid crystal panel 300. The formation of the scan signal in the common drive circuit 320 may be implemented in various ways. However, in order to form the scan signal as shown in FIG. 3, the common drive circuit 320 should refer to the applied power voltages.

The segment drive circuit 360 applies the gray voltage to the liquid crystal through the segment electrode line. The liquid crystal is aligned in accordance with the applied gradation voltage and the voltage difference of the scan signal, and the light transmittance of the liquid crystal is determined according to the alignment of the liquid crystal.

Therefore, according to the present invention, the power supply voltage boosted in one direction is applied to the common drive circuit 320 generating the scan signal, and the boosted power supply voltage is applied with different polarities for each frame. The scan signal power supply circuit 340 generating the power supply voltages supplies a power supply voltage boosted by the switching operation and a power supply voltage not boosted. Therefore, the burden of enduring a high voltage difference due to the simultaneous boosting in both directions for generation of the power supply voltage is eliminated. In addition, since only 50% of the voltage difference is supplied as the power supply voltage, power consumption of the liquid crystal display may be reduced.

According to the present invention as described above, the power supply voltage boosted in only one direction is applied as the power supply voltage of the common drive circuit which supplies the scan signal to the liquid crystal panel, and the other power supply voltage is applied with the voltage not boosted. Accordingly, the power supply voltage boosted in both directions may not be generated and applied simultaneously in each frame, but may be alternately applied to each frame, and the power supply voltage boosted in the positive direction and the power supply voltage boosted in the negative direction may be supplied. According to the supply of the power supply voltage boosted in only one direction, the scan signal power supply circuit can simultaneously reduce the power loss due to the bidirectional boost and the burden on the high voltage difference of the circuit. In addition, the liquid crystal display using the same may reduce power consumption as the difference between the power supply voltages is reduced.

Although described with reference to the embodiments above, those skilled in the art will understand that the present invention can be variously modified and changed without departing from the spirit and scope of the invention as set forth in the claims below. Could be.

Claims (8)

A first voltage generator circuit for generating a first voltage; A second voltage generation circuit for generating a second voltage having a level lower than the first voltage; A bidirectional boost circuit for selectively boosting a first voltage and a second voltage to output a first boosted voltage boosted by the first voltage or a second boosted voltage boosted by the second voltage; And And a switching unit for selectively selecting the first voltage and the first boosted voltage, and alternatively selecting the second voltage and the second boosted voltage. The switching unit, In the case of selecting and outputting the first voltage, selecting and outputting the second boosted voltage, And selecting and outputting the first boosted voltage when selecting and outputting the second voltage. The method of claim 1, wherein the switching unit, A first switch for selectively selecting the first voltage and the first boosted voltage and outputting the first voltage to the first output terminal; And And a second switch for selectively selecting the second voltage and the second boosted voltage and outputting the second voltage to the second output terminal. The scan signal power supply circuit of claim 2, wherein the voltage difference between the first boosted voltage and the second voltage is substantially the same as the voltage difference between the first voltage and the second boosted voltage. The method of claim 1, wherein the switching unit, And the first boosted voltage and the second boosted voltage are alternately selected for each successive frame. The scan signal power supply circuit of claim 4, wherein the first boosted voltage is a voltage boosted in a positive direction, and the second boosted voltage is a voltage boosted in a negative direction. A liquid crystal panel for displaying an image; A common drive circuit for supplying a scan signal to the liquid crystal panel; A segment drive circuit for applying a gray voltage to the liquid crystal panel; And A scan signal power supply circuit for supplying a positive power supply voltage and a negative power supply voltage to the common drive circuit; The scan signal power supply circuit, A first voltage generator circuit for generating a first voltage; A second voltage generation circuit for generating a second voltage having a level lower than the first voltage; A bidirectional boost circuit for selectively boosting a first voltage and a second voltage to output a first boosted voltage boosted by the first voltage or a second boosted voltage boosted by the second voltage; And And a switching unit for selectively selecting the first voltage and the first boosted voltage, and alternatively selecting the second voltage and the second boosted voltage. The switching unit, When the first voltage is selected and output as the positive power supply voltage, the second boosted voltage is selected and output as the negative power supply voltage, And when the second voltage is selected and output as the negative power supply voltage, the first boosted voltage is selected and output as the positive power supply voltage. The method of claim 6, wherein the switching unit, A first switch for selectively selecting the first voltage and the first boosted voltage and outputting the first voltage to the first output terminal; And And a second switch for selectively selecting the second voltage and the second boosted voltage and outputting the second voltage to the second output terminal. The method of claim 7, wherein the switching unit, And the first boosted voltage and the second boosted voltage are alternately selected for each successive frame.

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