TWI277936B - Driving method for a liquid crystal display - Google Patents

Abstract

The present invention provides a driving method for a liquid crystal display. According to the present invention, the scan signal follows a RC curve to turn off the thin film transistor. Therefore, the real voltage difference for turning off the thin film transistor can be reduced to improve the LCD display.

Description

1277936 玖 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明 发明/, night display [prior technology] Recently, 'liquid crystal display elements because of its small size, low power consumption and low power consumption characteristics, it has been widely used in each - in the TV and image display screen two: 兀In the active array type, for example, as a switching element, thin film electro-crystals and large size advantages are used. It has a high display quality. It is used as an active 切换 & & Λ ^ ^ ^ ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( ( 。 。 。 。 。 。 。 。 。 。 。 。 。 。 The pixel electrode is formed on an active column i, the opposite phase of the substrate is oppositely disposed on the substrate=71 substrate and the array and the (10) plate field are formed with a common electrode, and the liquid crystal layer is located on the two substrates. The two polarizing plates are respectively placed on the outer sides of the two substrates. Refer to Figure 1 for an equivalent circuit diagram of a pixel area of a conventional active array type liquid crystal display. An N-type thin film transistor is formed at the intersection of the signal line 101 and the scanning line 1〇3, and the drain electrode (D) of the N-type thin film transistor 105 is connected to the image signal line (8), and the inter-electrode electrode j G) 1 09 is connected to the scan line 〇3, and the source electrode (s) Η 1 is connected to the pixel electrode 113. A liquid crystal layer 119 is placed in the pixel electrode m and the common electrode U7. The pixel electrode 11 3 and the common electrode 11 7 form a liquid crystal 1277936 electric valley (CLC)' and the common electrode 117 and a common electrode voltage are generated. Circuit 115 is connected. A storage capacitor (Cs) 123 is formed by the pixel electrode 113 and the storage capacitor electrode 121. The storage capacitor electrode 121 is connected to a common electrode voltage generating circuit 115. Traditionally, there are two modes of operation. One is to apply a common electrode voltage (vc) inverted from the image signal voltage (Vx) to the common electrode 117 to reduce the magnification required for the image signal, such as the second. Figure A shows. The other is applied to the common electrode U7 using a fixed common electrode voltage (Vc) as shown in Fig. 2B. Refer to Figure 3 for the drive wave on the traditional active array LCD. See also Figure 1. A scan signal is applied to the gate electrode (g) 109 of the thin film transistor 105 via a scan line, and the image signal voltage is applied to the image signal line 1 〇 1. When a scan signal is applied to the electrode electrode (G) 109, the image signal voltage is written to the pixel electrode 113 to form a halogen electrode voltage (Vs). During a field period, a voltage difference is generated between the common electrode voltage (Vc) and the halogen electrode voltage (Vs), assuming Vp, which is applied to the liquid crystal capacitor (cLC) to cause liquid crystals stored therein. Layer 119 rotates to reveal an image. On the other hand, this voltage difference Vp is also applied to the storage capacitor (Cs) 123. This storage capacitor is used to maintain the liquid crystal capacitance (CLC) at a fixed voltage difference to maintain the image when the signal is scanned and removed. . However, please refer to the fi diagram again. For a thin film transistor, there will be parasitic between the gate (G"09 and the source (s) lu and between the drain (9) and the source (S) (1). Capacitors Cgs and Cds. 1277936, today CGS and cDs will cause the halogen electrode when the sweep signal Vy is removed.

Under voltage (Vs) _ V

Vp value. The ΔVp value causes the liquid crystal screen to flicker. [Invention] In the above-mentioned background of the invention, the Δvp value has a great relationship with the liquid crystal display product, because if each of the liquid crystal display screens If the Vp value is different, it will cause the LCD screen to flicker. This will cause the LCD screen quality to drop. Therefore, there is an ideal solution to avoid the flickering of the LCD screen. The main purpose of the present invention is to provide a driving method for the liquid crystal display, which reduces the ΔVp value and slows down the flickering of the liquid crystal screen. Another object of the present invention is to provide a driving method for a liquid crystal display, which reduces the value of Δνρ by gently scanning the signal waveform. It is still another object of the present invention to provide a driving circuit for a liquid crystal display which can reduce the AVp value and slow the liquid crystal screen flicker. Another object of the present invention is to provide a driving circuit for a liquid crystal display which generates a waveform such as an RC discharge when the scanning signal is removed, thereby reducing the AVp value to slow down the liquid crystal screen. According to the above object, the present invention provides a liquid crystal display driving circuit and method for utilizing a portion of the time during which the thin film transistor is turned on in the active array type liquid crystal display to generate a scanning signal via an RC discharge waveform. The circuit is converted from a high level to a low level. The driving circuit structure of the present invention comprises at least a power supply circuit, a multiplex 1277936 and an RC discharge waveform generating circuit. The active array type liquid crystal display is connected to a power supply circuit or an RC discharge waveform generating circuit through a multiplexed operation. When the scanning signal is used to switch the film transistor conduction, the power supply circuit supplies the scanning signal power, and when the scanning signal is used to turn off the thin film transistor, the rc discharge waveform generating circuit supplies power. The embodiments of the present invention are described below by way of an embodiment without departing from the spirit and scope of the present invention. Those skilled in the art, after understanding the spirit of the present invention, may apply the present invention. The drive circuit and its method are used in a variety of different liquid crystal displays. Since the ΔVp value has a great relationship with the quality of the liquid crystal display, the conventional driving circuit and the driving method often cause the ΔVp value of each display element on the liquid crystal display to change drastically when the scanning signal is removed, so that The LCD screen flickers. Therefore, the present invention provides a liquid crystal display driving circuit and a driving method, and the power supply circuit is externally connected to an RC discharge waveform generating circuit, and when the scanning signal is removed, the Japanese signal will be converted from a high level via an RC discharge waveform. For a low level, the Δ 值 value is reduced by scanning the high and low levels of the signal to reduce the flicker of the LCD screen. In the following, the application of the present invention will be described by way of example only, but it should be noted that this embodiment is not intended to limit the scope of the invention. Please refer to the driving waveform diagram of the conventional active array type liquid crystal display shown in FIG. 3 again. Referring to FIG. 1 , it is assumed that when T1 is applied, a scanning signal (vy) is applied to the gate of the thin film transistor 105 via the scanning line. Electrode 1277936

At the time, the image signal voltage is written to the pixel electrode 11 3, and the shape of the A, the A U is a pixel voltage (Vs). The liquid crystal capacitor (CLC) and the storage capacitor are charged to a voltage difference Vp with respect to the pixel voltage (Vs) and the common electrode voltage (vc). When the scanning signal (vy) is removed at time T2, the germanium film 105 is turned off, and the voltage across the liquid crystal capacitor (Clc) is maintained by the storage capacitor (Cs), but in the film. The transistor 丨05 ^ The moment when the temple is closed' Vp will drop by △ Vp value, the magnitude of this ΔVp value, the parasitic capacitance Cgs of the gate source of the fish/film, and the liquid crystal capacitance (Ct φ6, Lc It is related to the voltage difference (ΔV) experienced by switching the electric storage valley (Cs) and the primary film transistor 105 from the conduction state to 0B Ub At and the full-closed noise. The size is as follows: AVp-^ xCgs/(Cgs+Clc+Cs) However, if the starting voltage of the thin film transistor 105 is assumed to be Vt, only the scanning signal (Vy) is lower than the starting voltage of %, the thin germanium transistor 1〇5 will It is completely turned off, in other words, under the traditional scanning signal waveform, when the time is T2, the scanning signal (Vy) is instantaneously changed from the high voltage u to the second voltage vGate_Qff, so the thin film transistor 1〇5 is turned on. The voltage difference Δ鸲Vcate__VQ_ff experienced when switching to the fully off state. See Figure 4 for The driving waveform diagram of the active array type liquid crystal display according to the preferred embodiment of the present invention is different from the conventional driving waveform, and the method occupies the thin film transistor from the on state to the off state. An RC discharge waveform, that is, a scan signal (Vy) 疋L over & day (between 如, as shown in Fig. 4) is converted from a high potential of 1277936 to a low potential vGate_Qff. Therefore, the thin film transistor 1〇5 is turned on. The voltage difference Δ experienced by the state switching full-off state is 70 _ n ^ electric left two (VT-VGate_off). At this time, when the thin gland transistor is turned off, the household soil, > Λ λ7 & . The relationship between the Vp value and the switching voltage is as follows: P (Vt ^Gate-off ) XC〇s /(C〇s + Cw + C^) Since the present invention switches the thin film transistor from the on state to The voltage change ΔV' of the off state is smaller than the voltage difference ΔV caused by the conventional scan signal waveform, so the scan signal driving waveform of the present invention can form a small ΔVp value. It is noted that the driving of the present invention Method can also be used to drive other types of liquid crystal display The multi-diagram 5 is a circuit structure diagram for generating the driving waveform of the present invention, and includes at least one power supply circuit 5, one multiplexer 5〇2 and one foot (: discharge waveform generating circuit 504. The circuit 500 provides various power supplies required for an active array type liquid crystal display 506. Generally, the logic circuit portion uses 3.3V, the Gamma circuit portion uses 9V, and the thin film transistor is turned on using 23V, and the turn-off is used at -6V. The high voltage portion of the supply scan line is coupled to the multiplexer 502 of the present invention, and the multiplexer 502 is coupled to an RC discharge waveform generating circuit 504. The RC discharge waveform generating circuit 504 is composed of an inverter 508, a switching transistor 510 and an Rc circuit composed of a resistor 512 and a capacitor 514. The inverter 508 is externally connected with a signal 控制 to control the switching. The transistor 5 10 is turned on. When the switching transistor 5 is in the on state, the capacitor $ 14 10 1277936 is charged to a high voltage. When the switching transistor 510 is in the off state, the capacitor 514 discharges the resistor 512. And generate an RC discharge waveform. The multiplexer 502 is also controlled by an external signal M. The power required to determine the active array type liquid crystal display 506 is provided by the power supply circuit 5 or by the rc discharge waveform generating circuit 504. It is to be noted that the circuit configuration of the Rc discharge waveform generating circuit 504 described above is only an embodiment, and other circuits capable of generating an RC discharge waveform can be applied to the present invention. Referring to Figure 6, there is shown a waveform diagram for use in a preferred embodiment of the present invention. Please also refer to Figure 5. Wherein CPV represents a clock signal, and "the signal is a control signal applied to the multiplexer 502 and the RC discharge waveform generating circuit 5〇4, respectively, and the N signal represents a scan signal applied to the Nth scan line. For example, suppose At T3, the low level of the external signal 502 of the multiplexer 502 is selected by the power supply circuit 500 to provide the high voltage required for the active array type liquid crystal display 5 to 6 scan signals to turn on the thin film transistor, and then the RC discharge waveform generating circuit 504 In part, the low level of the external signal M is converted to a high level via an inverter 5〇8, and the switching transistor 51 is turned on. At this time, a high voltage of 23V charges the capacitor 514 to 23v via the switching transistor 510. Then, if at T4, the multiplexer 5〇2 is switched to the high level, and the multiplexer 502 selects the rc discharge waveform generating circuit 5〇4 to provide the active array type liquid crystal display 5〇6 scanning signal. The power supply is required. At this time, in the RC discharge waveform generating circuit 5〇4, the high level of the external signal μ is converted to a low level via an inverter 508, and the switching transistor 51 is turned off, and the power supply 514 is turned on. 512 The RC discharge waveform is generated and applied to the active array type liquid crystal display 5〇6, and the scan signal is converted from a high level to a low level via the 11 1277936. The method of the present invention is matched with Different requirements of the user can obtain a plurality of different rc discharge waveforms by changing the resistance value and the capacitance c value in FIG. 5 to form a plurality of different scanning signals. See FIG. 7 for other different according to the present invention. For the different scan signal waveforms formed in the embodiment, please refer to FIG. 5 again, and the size of the resistor 512 and the capacitor 514 can be adjusted to change the discharge speed of the capacitor 514 to the resistor 512 to form a different Rc discharge waveform. The voltage can be converted from the surface level Vgate-C)n voltage to the low level voltage predetermined by the user by changing the discharge speed by using different RC discharge waveforms, such as VI, V2 shown in FIG. ...etc., the low level voltage in > should be between Vgat_ff. In addition, when the m Λ sign is switched to the low level, the multiplexer 5〇2 selects the power supply circuit $(10) and the active array. The liquid crystal display 506 is connected, so that the scanning signal voltage is instantaneously dropped from the low level voltages VI, V2, ... to Vgate-w. The driving method according to the present invention is to use the film in the active array type liquid crystal display. During the period when the transistor is turned on, one of the parts of the time is used to allow the known signal to be converted from a high level to a low level via an RC discharge waveform generating circuit, because the method is not as conventional as in switching thin film transistors. When the scan signal is switched from a high voltage to a low voltage for a moment, the voltage is gently lowered as a discharge, so the voltage change that can be actually required to switch the thin film transistor from the on-state to the off state does react. Point. The present invention has been disclosed in a preferred embodiment as described above, but it is not intended to limit the invention, and any person skilled in the art without departing from the spirit of the invention and 12 1277936 [simple description of the drawings] The above and other objects, features and advantages of the present invention will become more apparent. The preferred embodiments of the invention are described below, and in conjunction with the accompanying drawings, which are as follows: The first detail of the leaf is not the conventional active array type liquid crystal. The equivalent circuit diagram of one area of the display; the 2A and 2B of the constant crystal display show the driving waveform of the conventional active array type liquid; the group, rsrt · picture, Fig. 5 is not preferred according to the present invention. The embodiment produces a schematic diagram of the Rc discharge driving circuit; FIG. 6 is a waveform diagram of the control signal according to the preferred embodiment of the present invention, and is not according to other embodiments of the present invention. Shaped waveform waveform. It is not known that the driving waveform which is not caused by the voltage drop of the conventional scanning signal in FIG. 4 is not a simple description of the representative symbol of the scanning line element of the driving wave used in the preferred embodiment of the present invention] 1 〇1 Image signal line 13 1277936 105 N-type thin film transistor 107 drain electrode (D) 109 gate electrode (G) 111 source electrode (S) 113 pixel electrode · 115 common electrode voltage generating circuit ' 11 7 common electrode 119 liquid crystal Layer 121 storage capacitor electrode 123 storage capacitor (Cs) 500 power circuit 502 multiplexer 504 RC discharge waveform generation circuit 506 active array type liquid crystal display 508 inverter 510 switch transistor '512 resistor 514 capacitor ·

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Claims (1)

Ϊ 277 936 pick up, patent application scope 1. A liquid crystal display driving method, wherein the liquid crystal display comprises at least a plurality of scanning lines and image data lines arranged in a cross each other, forming a control at the intersection of any two scanning lines and data lines The image data is written into the thin film transistor, and the method comprises at least the following steps: applying a first voltage on a scan line to turn on the corresponding thin film transistor 'to write the image data contained on the corresponding image data line And converting the first voltage to a second voltage to turn off the thin film transistor, and the first voltage is higher than the second voltage. 2. The driving method according to claim 1, wherein the discharge curve is an RC discharge curve. The driving circuit of the liquid crystal display comprises at least: a pixel array, wherein the pixel array has at least a plurality of scan lines and image data lines arranged to cross each other; and a power circuit for supplying the first voltage to the pixel a plurality of scan lines; a discharge circuit providing a discharge curve waveform to the (four) scan lines to cause the scan lines to be discharged from the first voltage to the second voltage via the & electrical circuit, wherein the first voltage The voltage system is higher than the second voltage; and the circuit is used to select the pixel array and the power circuit or the discharge 15 1277936. 4. The driving circuit according to claim 3, wherein the discharge is The curve is an RC discharge curve. 5. The driving circuit of claim 3, wherein the discharge circuit further comprises a resistor and a capacitor arranged in parallel, and an inverter, wherein the parallel arrangement of the resistor and the capacitor can be via a transistor The first voltage is connected, and. The inverted inverter is connected to the gate of the transistor, and a control signal is externally connected to control the turn-on and turn-off of the transistor. 6. The driving circuit of claim 5, wherein the control signal further controls the multiplexer, and the multiplexer can provide the pixel array and the power circuit or the discharging circuit according to the control signal The connection. 7. The driving circuit of claim 6, wherein when the control signal is off, the multiplexer provides a connection between the pixel array and the power circuit and the transistor is turned on to enable The first voltage can charge the capacitor through the transistor. 8. The driving circuit according to claim 6, wherein when the control signal is turned on (ο η ), the multiplexer provides a connection between the pixel array and the discharge circuit and the transistor is turned off to The capacitor is discharged through the parallel resistor. The driving circuit of claim 3, wherein the power circuit further provides a third voltage to the scan lines to instantaneously convert the scan lines from the second voltage to the a third voltage, and the second voltage is at the third voltage. A driving method of a liquid crystal display, wherein the liquid crystal display has an array of pixels, a power supply circuit, a discharge circuit, and a multiplexer, the pixel array having a plurality of scans that are arranged in crossover each other a line and an image data line, and a thin film transistor for controlling image writing is formed at an intersection of any two scanning lines and a data line, the method comprising at least the following steps: Providing a connection between the power circuit and the pixel array. The power circuit provides a first voltage to the scan lines to turn on the corresponding thin film transistor, thereby writing the image data contained on the corresponding image data line. Corresponding to the pixel region; controlling the multiplexer to provide a connection between the discharge circuit and the pixel array; and, by the discharge circuit, converting the scan lines from the first voltage to the second voltage, wherein the first The voltage system is higher than the second voltage. 11. The driving method according to claim 10, wherein the discharge curve is an RC discharge curve. The driving method of the first aspect of the invention, wherein the discharge circuit of the 1277936 further comprises a resistor and a capacitor arranged in parallel, and an inverter, wherein the parallel arrangement of the resistor and the capacitor can be via a The transistor is coupled to the first voltage, and the inverter is coupled to the gate of the transistor and externally coupled with a control signal for controlling conduction and deactivation of the transistor. 13. The driving method of claim 12, wherein the control signal further controls the multiplexer, and the multiplexer can provide the pixel array and the power circuit or the discharge circuit according to the control signal The connection. 14. The driving method according to claim 13 , wherein when the control signal is off, the multiplexer provides a connection between the pixel array and the power circuit, and the transistor is turned on to The first voltage is passed through the transistor to charge the capacitor. 15. The driving method according to claim 13, wherein when the control k is turned on, the multiplexer provides a connection between the pixel array and the discharge circuit and the transistor is turned off to The capacitor is discharged through the parallel resistor. The driving method of claim 1, wherein the power circuit further provides a third voltage to the scan lines to instantaneously convert the scan lines from the second voltage to the first Three voltages, and the second voltage is higher than the third voltage. 18