TWI416491B - Pixel circuit and display panel - Google Patents

Abstract

A pixel circuit includes: a first display unit, a second display unit, a connecting capacitor, and a switching unit. The switching unit performs a switching operation according to whether a first scanning line or a second scanning line is enabled. When the first scanning line is enabled, a common voltage is supplied to the connecting capacitor. When the first scanning line is disabled and the second scanning line is enabled, the data voltage is supplied to the connecting capacitor, so as to push up the voltage difference of the crystals in the first display unit.

Description

Pixel circuit and display panel

The present invention relates to a pixel circuit and a display panel having the pixel circuit, and more particularly to a pixel circuit for improving liquid crystal color shift problem and a display panel having the pixel circuit.

Liquid crystal display devices have been widely used in daily life, but most of today's liquid crystal display devices generally have a problem of color shift (Washout), and the technology applied to process color shift problems according to the current stage can be roughly divided into the following two ways: One way is to use the coupling capacitor method, such as: US Patent Nos. 6078367, 5126865 and other patents, all of which use this method to improve the color shift problem, but the biggest disadvantage of this method is that the input is due to the capacitive coupling relationship. The voltage drops sharply. For example, the data voltage is 7 volts, but the voltage received by the liquid crystal in the main and secondary areas of the display will drop to 6.94 volts and 4.6 volts respectively. The voltage drop will cause the main area and the secondary area. The maximum voltage cannot be reached, and the liquid crystal brightness (Luminance) is greatly reduced. Therefore, although this method can improve the color shift problem, it limits the efficiency of the liquid crystal display.

The second way is to control the voltage of the main area and the secondary area by inputting a reference potential that continuously oscillates at a high and low level, such as: US Patent Publication No. 2008/0024689, 2006/0262237, etc. the way. However, the biggest disadvantage of this method is that, since a reference potential input from the outside is required, a considerable number of amplifiers are often required to drive the circuit design, so that the area overhead of the driving circuit is caused, and at the same time, In order not to affect the driving of the liquid crystal due to the wire delay factor of the input reference potential, it is necessary to widen the wire width of the common voltage (Vcom) to reduce the wire resistance value, which also causes an increase in the area cost of the driving circuit. The problem, therefore, how to effectively find a way to deal with the color shift problem of liquid crystal without causing additional production cost and reducing the display efficiency of liquid crystal has been an urgent problem for people in related fields.

Therefore, an object of the present invention is to provide a pixel circuit adapted to receive a data voltage outputted from a data line and a common voltage output from a common power supply and coupled to a first scan line and a second scan line. The first display unit has a first end coupled to the data line for receiving the data voltage, a second end, a third end coupled to the common power source, and a first a control line coupled to the scan line, and the control end turns on between the first end and the second end when the first scan line is enabled, and when the first scan line is disabled The first display unit is non-conductive; the second display unit has a first end coupled to the data line for receiving the data voltage, a second end, and a third coupled to the common power source And a control end coupled to the first scan line, and the control end turns on between the first end and the second end when the first scan line is enabled, and is in the first scan line When the energy is removed, the first end and the second end are not turned on; a connecting capacitor has one and the first a first end coupled to the second end of the display unit, and a second end; and a switching unit that receives the common voltage, the data voltage, and the second end of the connection capacitor, the first scan line, and the second The scan line is coupled to switch based on an enabling condition of the first scan line and the second scan line, to provide the common voltage to the second end of the connection capacitor when the first scan line is enabled, and The data voltage is supplied to the second end of the connection capacitor when the first scan line is disabled and the second scan line is enabled.

In addition, another object of the present invention is to provide a display panel suitable for receiving a common power supply, comprising: n scan lines, which are first to nth scan lines, respectively, and the scan lines are sequentially m; data lines, respectively, are 1st to mth data lines, and each data line outputs a data voltage; n×m are matrix-arranged pixel circuits, wherein the pixel circuits in the i-th column are coupled To the ith scan line, the i+1th scan line, and the jth data line, i=1~n-1, j=1~m, wherein each pixel circuit includes: a first display unit having one and the The data line is coupled to receive the first end of the data voltage, a second end, a third end coupled to the common power source, and a control end coupled to the first scan line, and the control end is When the first scan line is enabled, the first end and the second end are turned on, and when the first scan line is deactivated, the first end and the second end are not turned on; The display unit has a first end coupled to the data line to receive the data voltage, a second end, a third end coupled to the common power source, and a a control line coupled to the scan line, and the control end turns on between the first end and the second end when the first scan line is enabled, and when the first scan line is disabled The first end and the second end are non-conducting; a connecting capacitor has a first end coupled to the second end of the first display unit, and a second end; and a switching unit receiving the common voltage and The data voltage is coupled to the second end of the connection capacitor and the ith, i+1th scan line to switch based on the enabling condition of the ith and i+1th scan lines. When the i scan line is enabled, the common voltage is supplied to the second end of the connection capacitor, and when the i+1th scan line is enabled, the data voltage is instead supplied to the second end of the connection capacitor. To thereby change the potential of the first end of the first liquid crystal capacitor.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Referring to Figure 1, one preferred embodiment of the pixel circuit applicable to the present invention is coupled to a first scan line G _n, and a second scan line G _{n + 1,} and receives a common power supply output a common voltage (Common voltage embodiment , Vcom), a data voltage V _data output by a data line, and the first scan line G _n and the second scan line G _n+1 are sequentially enabled (Enable). The pixel circuit of this embodiment includes a first display unit 1, a second display unit 2, a connection capacitor 3, and a switching unit 4.

The first display unit 1 has a first end coupled to the data line to receive the data voltage V _data , a second end, a third end coupled to the common power source, and a first scan The control terminal of the line G _{n is} coupled, and the control terminal turns on between the first end and the second end when the first scan line G _n is enabled, and is disabled on the first scan line G _n (Disable), the first end and the second end are not turned on.

The second display unit 2 is similar to the first display unit 1 and has a first end coupled to the data line to receive the data voltage V _data , and a second end coupled to the common power source. And a control end coupled to the first scan line G _n , and the control end turns on between the first end and the second end when the first scan line G _n is enabled, and the first when the scanning line G _n is de-energized, so that between the first and second ends nonconductive.

The connection capacitor 3 has a first end coupled to the second end of the first display unit 1, and a second end.

The switching unit 4 receives the common voltage Vcom and the data voltage V _data , and is coupled to the second end of the connection capacitor 3, the first scan line G _n and the second scan line G _n+1 to be based on the first scan. lines and second scan lines G _n G _{n + 1} enable the switch case. I.e., to the first scanning line G _n, when enabled, provides a second terminal of the common voltage Vcom is connected to the capacitor 3, and in the first scan line G _n is de-energized and the second scanning line G _{n + When 1} is enabled, the data voltage V _{data is} supplied to the second end of the connection capacitor 3.

In detail, the switching unit 4 includes a first transistor 41 and a second transistor 42. The first transistor 41 has a first end coupled to the common power source, a second end coupled to the second end of the connection capacitor 3, and a control end coupled to the first scan line G _n , and the control end to the first scan line G _n, when enabled, such that the first and second ends Q is turned on to provide the common voltage Vcom to the second terminal of the capacitor 3 is connected. While in the first scan line G _n is de-energized, so that between the first and second ends of the non-conductive stop providing the common voltage Vcom to the second terminal of the capacitor 3 is connected.

The second transistor 42 has a first end receiving the data voltage V _data , a second end coupled to the second end of the connection capacitor 3, and a control end coupled to the second scan line, and the control end is When the second scan line Gn ₊₁ is enabled, the first end and the second end are turned on to provide the data voltage _Vdata to the second end of the connection capacitor 3. When the second scan line Gn ₊₁ is deenergized, the first end and the second end are not turned on, and the supply of the data voltage _Vdata to the second end of the connection capacitor 3 is stopped.

The operation mode of the pixel circuit of this embodiment is divided into the following two phases: a charging phase and a voltage boosting phase.

Charging stage

When the first scan line G _n is enabled and the second scanning line G _{n + 1} is de-energized, the first and second display units of the first end and the second end 2 will be respectively turned on, The potentials of the second ends of the first and second display units 1 and 2 are all the data voltage V _data , and the first transistor 41 is turned on and the second transistor 42 is not turned on. Therefore, the connection capacitor is The second terminal of the third terminal is the common voltage Vcom. Therefore, the voltage difference between the two terminals of the connection capacitor 3 and the voltage difference between the second terminal and the third terminal of the first display unit 1 are both V _data -Vcom.

Voltage boost phase

After completion of the charging phase, the first scan line G _n is de-energized and the second scanning line G _{n + 1} is enabled, at this time, the first transistor 41 will not conduct, and the second transistor 42 Is turned on, so the second end of the connection capacitor 3 receives the data voltage V _data outputted by the second end of the second display unit 2, and because the connection capacitor 3 has no discharge path for discharging, the connection capacitor 3 The voltage at the first end will be boosted to 2V _data -Vcom. Because the first end of the connection capacitor 3 is coupled to the second end of the first display unit 1, the voltage difference between the second end of the first display unit 1 and the third end is raised to 2V _data -2Vcom .

As an example, if the common voltage is 0v and the data voltage is 7v, the voltage of the second terminal of the first display unit 1 can be increased from 7v to 14v during the voltage boosting phase, and the first end of the second display unit 2 is The voltage can be 7v, so the liquid crystal molecules of the two liquid crystal capacitors are subjected to different operating voltages to produce different degrees of twisting, so that multi-domain display effects can be achieved to expand the viewing angle of the display panel. Compared with the prior art, the two operating voltages of the present invention not only increase the voltage value, but also have a large gap, so that the multi-domain display effect can be better, and the problem of color shift is effectively improved. Moreover, since it is not necessary to additionally input a reference voltage from the outside, it is more convenient and effective in use.

It should be noted that, in this embodiment, the first and second transistors 1, 2 are all a thin film transistor (TFT), but not limited thereto.

Referring to FIG. 2, a preferred embodiment of the display panel of the present invention is adapted to receive a common voltage Vcom provided by a common power source, and includes n spaced-apart scan lines G(1) G(n) and m spaced data. Lines D(1) to D(m), and n x m pixel circuits as described above. And the n×m pixel circuits are respectively located between any two scan lines and any two data lines, and the pixel circuits in the i-th column are all coupled to the ith scan line and the i+1th scan line. And the pixel circuits in the jth row are all coupled to the jth data line. m data lines respectively output m data voltages, and the scan lines are sequentially enabled, and when the scan lines coupled to each pixel circuit are enabled, the aforementioned charging phase or voltage is performed. Promotion phase.

Referring to FIG. 3, the gamma curve of the present invention and related prior art, it can be seen from FIG. 3 that the effect of the present invention on color shift processing is comparable to that of the related prior art, however, the pixel circuit according to the present invention is directed to each After the pixel processing, the voltage received by the corresponding liquid crystal of each pixel can be increased. Therefore, the known improved color shifting technique can often have a better effect in the case of a large voltage range.

In summary, the voltage difference between the second end and the third end of the first display unit 1 can effectively increase the voltage value received by the liquid crystal in the first display unit 1 compared with the prior art. Improve the display efficiency of the liquid crystal. In addition, the method provided by the present invention does not require an additional input reference potential compared to the method of the prior art, and therefore does not cause an increase in area cost, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

1. . . First display unit

2. . . Second display unit

3. . . Connection capacitor

4. . . Switching unit

41. . . First transistor

42. . . Second transistor

Figure 1 is a circuit diagram of a pixel circuit of the present invention;

2 is a schematic view of a display panel of the present invention; and

Figure 3 is a gamma plot of the prior art and the prior art.

1. . . First display unit

2. . . Second display unit

3. . . Connection capacitor

4. . . Switching unit

41. . . First transistor

42. . . Second transistor

Claims (6)

A pixel circuit is configured to receive a data voltage of a data line output and a common voltage of a common power output, and is coupled to a first scan line and a second scan line, and includes: a first display unit, a first end coupled to the data line for receiving the data voltage, a second end, a third end coupled to the common power source, and a control end coupled to the first scan line, and The control terminal turns on between the first end and the second end when the first scan line is enabled, and prevents the first end and the second end from being turned on when the first scan line is disabled a second display unit having a first end coupled to the data line for receiving the data voltage, a second end, a third end coupled to the common power source, and a first scan line a control end, wherein the control terminal turns on between the first end and the second end when the first scan line is enabled, and makes the first end when the first scan line is disabled And a non-conducting between the second end; a connecting capacitor having a first end coupled to the second end of the first display unit And a second terminal; and a switching unit that receives the common voltage and the data voltage, and is coupled to the second end of the connection capacitor, the first scan line, and the second scan line to be based on the first scan line and The enabling condition of the second scan line is switched, so that when the first scan line is enabled, the common voltage is supplied to the second end of the connection capacitor, and the first scan line is disabled and the second scan is performed. When the line is enabled, the data voltage is supplied to the second end of the connection capacitor. The pixel circuit of claim 1, wherein the switching unit comprises: a first transistor having a first end coupled to the common power source and a second end coupled to the second end of the connection capacitor a second end and a control end coupled to the first scan line, and the control end is electrically connected between the first end and the second end to enable the second end to receive the common voltage when the first scan line is enabled And a non-conducting between the first end and the second end when the first scan line is deenergized; a second transistor having a first end coupled to the second end of the second display unit a second end coupled to the second end of the connection capacitor and a control end coupled to the second scan line, and the control end enables the first end and the second when the second scan line is enabled The terminals are turned on to enable the second terminal to receive the data voltage, and when the second scan line is deenergized, the first end and the second end are not turned on. The pixel circuit of claim 2, wherein the first and second transistors are respectively a thin film transistor. A display panel is adapted to receive a common power supply, comprising: n scan lines, which are respectively 1st to nth scan lines, and the scan lines are sequentially enabled; m data lines are respectively 1~ The mth data line, and each data line outputs a data voltage; n×m pixels arranged in a matrix, wherein the pixel circuit in the i-th column is coupled to the ith scan line and the i+1th scan line And a jth data line, i=1~n-1, j=1~m, wherein each pixel circuit comprises: a first display unit having a first coupled to the data line to receive the data voltage a second end, a third end coupled to the common power source, and a control end coupled to the first scan line, and the control end enables the first scan line to be enabled The first end and the second end are electrically connected to each other, and when the first scan line is deenergized, the first end and the second end are not turned on; and a second display unit has a coupled to the data line Receiving a first end of the data voltage, a second end, a third end coupled to the common power source, and a control end coupled to the first scan line, and the control When the first scan line is enabled, the first end and the second end are turned on, and when the first scan line is deactivated, the first end and the second end are not turned on; The capacitor has a first end coupled to the second end of the first display unit, and a second end; and a switching unit that receives the common voltage and the data voltage and is coupled to the connection capacitor The two ends and the i-th and i-th scan lines are switched according to an enabling condition of the i-th and i-th scan lines, so that when the i-th scan line is enabled, the common voltage is supplied to Connecting the second end of the capacitor, and when the i+1th scan line is enabled, providing the data voltage to the second end of the connection capacitor to further change the first end of the first liquid crystal capacitor Potential. The display panel of claim 4, wherein the switching unit comprises: a first transistor having a first end coupled to the common power source and a second end coupled to the second end of the connection capacitor And a control end coupled to the first scan line, and the control end is electrically connected between the first end and the second end to enable the second end to receive the common voltage when the first scan line is enabled, And when the first scan line is deenergized, the first end and the second end are not turned on; a second transistor has a first end coupled to the second end of the second display unit, a second end coupled to the second end of the connection capacitor and a control end coupled to the second scan line, and the control end enables the first end and the second end when the second scan line is enabled The second terminal receives the data voltage, and when the second scan line is deenergized, the first end and the second end are not turned on. The display panel of claim 5, wherein the first and second transistors are respectively a thin film transistor.