TW526461B - Automatic adjusting device for common voltage of liquid crystal display - Google Patents

Abstract

There is provided an automatic adjusting device for common voltage of liquid crystal display, which is used to adjust the common voltage of the pixel unit in the pixel array of the liquid crystal display. The automatic adjusting device for common voltage includes: a transistor; a scanning line electrically connected to the gate of the transistor for turning the transistor on or off; a data line electrically connected to the drain of the transistor and having a voltage maintained at an average of a data maximum voltage and a data minimum voltage, wherein the data maximum voltage and the data minimum voltage are the maximum and minimum voltage values provided to the data signal of the pixel array, respectively; a capacitor set formed by a liquid crystal capacitor and a hold capacitor connected in parallel, and having a terminal connected to the common voltage of the pixel unit circuit of the pixel array and the other terminal connected to the source of the transistor; and a buffer having an input terminal electrically connected to the source of the transistor and an output terminal providing a voltage for use as the common voltage of the pixel unit circuit of the pixel array, wherein the circuit formed by the transistor, the data line, the capacitor set and the scanning lines is formed by the same manufacturing steps as the pixel unit circuit of the pixel array, and the corresponding components are the same.

Description

526461 V. Description of the invention (1)-[Background of the invention] [Field of the invention] The present invention relates to a common voltage automatic adjustment device for liquid crystals _ + 口 %% 日 日 4 族, especially about an adjustable liquid crystal _ + Crying man said ... Beibu | §The common voltage automatic adjustment device for the common voltage of the pixel array. [Explanation of related technology] In the active matrix of a liquid crystal display, generally speaking, a thin film transistor (TFT) transistor is used as an active element of a pixel cell. 111; a data line 13 FIG. 1 is an equivalent circuit diagram of a general daylight unit, which includes: a TFT transistor 11; a scanning line 12, connected to the gate electrode 112 of the TFT transistor;-a capacitor I 4 (let it The electric valley value is q), which is the equivalent capacitance of the liquid crystal capacitor q and the holding capacitor q in parallel. One end of the capacitor 14 is connected to the source II 3 of the TFT transistor, and the other end is connected to a common voltage. Suppose its voltage is VH. When the voltage on the scanning line 12 is low, that is, from T2 to T3, the TFT transistor 11 is cut off, and the data will be cut off.

Next, the operation of the circuit shown in FIG. 1 will be described. As shown in the timing diagram of FIG. 2, line A represents the voltage on scanning line 12, line β represents the voltage on data line 3, and line C represents the voltage on capacitor 14. When the voltage on scan line I is 咼 (assuming its voltage is VG), that is, from τι to T2, transistor 11 will be turned on, so that the data on data line 13 is written into capacitor 14, Will be stored in capacitor 1 4. However, during the turn-off process of the transistor, the electricity

Page 5 526461 V. The data value of the description of the invention (2)) will drop by a small part Vj, caused by the stray between the gate 11 1 and the source 11 3 ′ and the partial voltage of the capacitor 14. The potential at the valley 14 (that is, the storage is mainly due to the capacitance of the TFT transistor 11 (let its capacitance value be cesi)). The value 71 is as follows:

C

GSI + c

GSI • (i) In the same way, although the voltage on the shell line 13 is vL, and the scanning line 12 is a high value day ^, that is, the time from T3 to T4, the transistor " will pass = the data voltage of line 13 \ Write in capacitor 14. When the scan line 12 has a low value, that is, in the time after T4, there is a capacitor in the transistor. "Similarly, the potential on the capacitor" (beam: storage material value) will be affected by the transistor 11 The stray capacitance between the gate 111 and the source 113 decreases the voltage value of the same magnitude ^. Therefore, we can use the average value of ν 电压 and vL as the data electrical value, let it be Vcet, be U :

V cet

Vh + Vl 2 •. (2) The voltage is low, that is, common power. Next, set the common voltage to ⑽ as the average value of the data voltage stored in capacitor 14 when the value of scan line 12 is,

526461 V. Description of the invention (3) The magnitude of the voltage Vcom is the value obtained by subtracting Vi from vce. However, in the actual manufacturing process, the gate and source of the transistor Η in the circuit unit in each day element array Miscellaneous between poles 113 = CGS1, inevitably there will be some capacitors i with different daylight arrays. In other words, there will be some changes in the V1 value. But—in general, the voltages Vh and VIII on Guang 13 are fixed, so Vcet is also a fixed value. Therefore, due to the different Vl values in the different day element arrays, the four wires will have different common voltages Vcom ,. In order to make the circuit operating condition of each pixel array solid, it is necessary to adjust the common voltage Vc⑽ for each pixel array. In general, in the conventional method, the common voltage Vc⑽ is adjusted by using the resistance voltage, as shown in FIG. 3. However, this conventional method requires a labor-intensive adjustment of the variable resistor to change X, and the reliability is relatively low. [Summary of the Invention] In view of this, the object of the present invention is to provide a common voltage automatic adjustment device for liquid crystals, which can automatically adjust the common voltage of an array in a liquid crystal display :. Therefore, the common voltage automatic device for the liquid crystal display of the present invention is used to adjust the common voltage of the book element two and the circuit in the pixel array of the liquid crystal display. The common voltage automatic adjustment device includes: two two = body; A scan line is electrically connected to the transistor gate for activating the transistor = the transistor; a data line is electrically connected to the drain of the transistor, and ^ is maintained at a data highest voltage and a data lowest voltage Average value, which = the highest voltage of the data and the lowest voltage of the data are provided to the book ^

Page 7 526461 V. Description of the invention (4) The maximum and minimum voltages of the data signals in the column; a capacitor group consisting of a liquid crystal capacitor and a holding capacitor connected in parallel, one end of which is connected to the picture of the day element array The other end of the common voltage of the element unit circuit is connected to the source of the transistor, and a buffer 'input terminal is electrically connected to the source of the transistor, and the output terminal voltage is used as the day element unit circuit of the day element array. The common voltage; the circuit composed of the transistor, the data line, the capacitor group, and the scanning line is formed in the same process step as the day element unit circuit of the day element array, and the corresponding components are all The same or enlarged in relative proportions, the effect obtained is the same, and the device is located in the non-display area of the source of the daylight array. [Explanation of symbols] 11 transistor 111 transistor 11 gate 112 transistor 11 drain 113 transistor 11 source 12 scan line 13 data line 14 capacitor 41 transistor 411 transistor 41 gate 412 transistor Source of 41 413 Source of transistor 42 Scan line

526461 V. Description of the invention (5) 43 Data line 44 Capacitor A1 buffer [Detailed description of the preferred embodiment] The structure of the common voltage automatic adjustment device for liquid crystal display of the present invention and its structure are described in detail below with reference to the accompanying drawings. working principle. FIG. 4 is a circuit diagram of a common voltage automatic adjustment device for a liquid crystal display of the present invention, which is used to adjust a common voltage in a pixel array of a liquid crystal display, including a TFT transistor 41; a scanning line 4 2 connected to τ FT transistor gate 411; a data line 43, connected to the drain 412 of the transistor, and the voltage of this data line is maintained at Vcet; a capacitor 44 (to make its capacitance value) is a liquid crystal capacitor Clc and a holding capacitor Q The equivalent electricity of the two in parallel: One capacitor is connected to a common voltage at one end, and the other end is connected to the TFT transistor: the cathodic pole is 'buffered by 5', and the input terminal is electrically connected to the ^ pole of the TFT transistor and output The terminals are electrically connected to a common voltage. Among them, the circuit composed of the crystal line 42, the data line 43, and the capacitor 44 is a pixel unit circuit on the periphery, and the buffer A1 is formed by-also = on the external driving circuit or driving IC. 41, scanning Line 42, data line 43, and H: the day-to-day unit circuit point in the volume pixel array: a lulu 'and its purpose is not bad. In addition, because it lies in the non-display area of both, that is not: the content of the display area on the periphery of the array.

526461 V. Description of the invention (6) FIG. 5 is a timing diagram of the electric dust on the capacitor 44 on the scanning line 42 when the circuit shown in FIG. 4 is operating. When the voltage on the scanning line 42 is 5 (and its voltage is set to VG), that is, in the period of τ 1 to τ 2, the electricity is turned on in two directions, and the voltage Vcet of the data line 43 is written into the capacitor 44.难 41 = When the voltage on the trace 42 is low, that is, within the time period j, the sweep 41 is cut-off. Therefore, the gate 411 of the transistor 41 The stray capacitance between them (let's call it Cgs2), the stored "electricity of the capacitor": a small drop, and the input of the buffer M, Vcom 'can be obtained according to formula i and formula 2, as shown in the following formula: change

Vcom ’= Vcet

C GS2 C 2 + C GS 2 Because the transistor 41 and the scanning circuit are enlarged in the same or equal proportion in the day element array 匸 2 and CGS2 and the pixel array, the difference between the obtained V c 〇m 'same < Adjusting the common electrical component to make adjustments can be used to adjust Vcom for liquid crystal display invented under ideal conditions. However, the combination is that it is designed as the above-mentioned feedback circuit, or a circuit can be placed in a single pixel unit circuit with a larger line 42, a data line 43, and a capacitor 44 on the periphery of the column. Therefore, the capacitance value in the daytime unit circuit can be calculated to obtain Vc⑽ and > In other words, the purpose of the circuit voltage of FIG. 4 can be saved without extra labor and cost, and reliability can be improved. . ’The same pixel array only needs a common voltage automatic adjustment device in the peripheral device, but it is not true in practical applications. First, 526461 V. Description of the invention (7) = In the pixel array, the pixel unit circuit (as shown in Fig. 1) t scan line 12 is different with different pixel units. As shown in FIG. 6, the voltage on the eight-wire drawing line is the waveform of FIG. 7A, but after transmission, the voltage waveform on the scanning line will be caused by the Rc time that occurs when the transmission passes— (C time delay), but will be distorted, as shown in the waveform of Figure 7C. Therefore, the voltage values V1 dropped at points A and B are different (as shown in Figs. 7B and 7d), and an error will also occur at the same voltage Vcom. /. In order to solve the above-mentioned problems in practical applications, we can arrange multiple above-mentioned "from: adjustment devices (as shown in Figure 8, set at four corners) at different positions on the periphery of the column to compensate for electricity: At the same angle, the location of the daytime unit circuit 'VI error caused by process unevenness or scanning distortion due to transmission, and then adjust the common voltage Vcom ° Those familiar with this technology will know that there will be an input capacitor in practice, The capacitance is different from the celestial element in the celestial array. Therefore, the voltage caused by several kinds of circuits can be set to Vcet plus a compensation 411 and the source 41 3 in parallel with a load caused by the input capacitor. Therefore, the above is only the preferred embodiment of the invention, "the scope of the present invention is not limited to any changes made" are in the hairline application, the buffer A 丨 unavoidably obtained in parallel with Cs The capacitance value of the equivalent electric circuit 1 will be compensated in a slightly different way, for example: the compensation voltage 'or the transistor gate capacitor' can be used to compensate the buffer A. Compared to Preferred embodiment, where the scope of the application under this patent inventions.

526461 Brief description of the diagram-Figure 1 is an equivalent circuit diagram of a general daylight unit; Figure 2 is the scanning line voltage (line a), data line voltage (line B), and capacitor voltage when the circuit shown in FIG. 1 operates (Line c) timing diagram; FIG. 3 is a common voltage adjustment device used in FIG. 4; FIG. 4 is a circuit diagram of a common voltage automatic adjustment device for a liquid crystal display of the present invention; and FIG. 5 is when the circuit shown in FIG. 4 operates The timing diagram of the scanning line voltage (line A), data line voltage (line B), and capacitor voltage (line c). ,

Page 12

Claims (1)

526461 6. Scope of patent application 1. A common voltage automatic adjustment device for a liquid crystal display is used to adjust a common voltage of a daylight unit circuit in a daylight array of the liquid crystal display. The common voltage automatic adjustment device includes: The transistor has a gate, a drain, and a source; a scan line electrically connected to the gate of the transistor to enable or disable the transistor; a data line electrically connected to the transistor The drain, and the voltage is maintained at an average value of a data maximum voltage and a data minimum voltage, wherein the data maximum voltage and the data minimum voltage are the maximum and minimum values of the voltage of the data signal provided to the pixel array, respectively A capacitor group consisting of a liquid crystal capacitor and a holding capacitor connected in parallel, one end of which is connected to the common voltage of the pixel unit circuit of the day element array, and the other end of which is connected to the source of the transistor; and A buffer, the input terminal of which is electrically connected to the source of the transistor, and the output terminal voltage is used as the common voltage of the day element unit circuit of the day element array Circuit consisting of wherein the transistor, the depleted feed line, the capacitor bank and the scan line, based on the same process step of forming the day pixel unit circuit of the day pixel arrays, and the corresponding member are the same. 2. The common voltage automatic adjustment device as described in item 1 of the patent application scope, wherein the transistor system is a TFT transistor. 3. If the common voltage automatic adjustment device of item 1 of the patent application scope, wherein the common voltage automatic adjustment device is provided on the liquid crystal display Page 13 526461 VI. The periphery of the pixel array for which the patent is applied 4. If the common voltage automatic adjustment device of item 3 of the patent scope is declared, the transistor, the data line, the capacitor button, and the scan line are combined The circuit is a celestial unit circuit on the periphery of the celestial array. 5. If the common voltage automatic adjustment device of item 4 of the declared patent scope further includes: a compensation capacitor is connected between the gate and the source of the transistor to compensate for the load effect caused by the buffer . 6 · A common voltage automatic adjustment device for a liquid crystal display, which is used to adjust the common voltage of the pixel unit circuit in the diurnal array of the liquid crystal display. The common voltage automatic adjustment device includes: ^ a transistor with a gate , A drain and a source; a scan line electrically connected to the gate of the transistor to turn the transistor on and off; a capacitor group, which is a liquid crystal capacitor and a holding capacitor in parallel, 1 end Connected to the common voltage of the celestial array, the other end is connected to the source of the & and a buffer of the solar body for output buffering, the source is connected to the source of the input terminal, and the output terminal is powered The voltage connected to the dipole array of the day element array; and the μ /, b-electrical-data line 'connected to the transistor's' immortal' voltage is maintained at 526461 6. The average voltage of the highest voltage and the lowest voltage of the data in the scope of the patent application plus a compensation voltage, where the highest voltage of the data and the lowest voltage of the data are the maximum and minimum voltages of the data signals provided to the daylight array. Value, and the compensation voltage is used to compensate the load effect generated by the buffer; the transistor, the data line, the capacitor group, and the circuit composed of the scanning line are connected to the day element array. The pixel unit circuit is formed in the same manufacturing process, and the corresponding components are the same. 7. The common voltage automatic adjustment dream device according to item 6 of the scope of patent application, wherein the transistor system is a TFT transistor. The common voltage self-adjusting device for common voltage from item 6 of the patent scope is set on the periphery of the day element array where the liquid is crying. ^ Wenri Daily Display Device 9 · For example, Qiu Huixue, Bai Zhizhi, No. 8 in the scope of patent application, where the transistor R automatically adjusts and combines the circuit, which is performed by Yinyin Chajiluozhi. Dioxin