TW565824B - Circuit and method of driving data line by low power in a LCD - Google Patents

Abstract

The present invention relates to the source driving circuit of thin film transistor liquid crystal device (TFT-LCD). The circuit of the present invention, the low power source driving circuit for driving data line of TFT-LCD according to video data, comprises: a digital-analog converter for converting the image data into analog signals; a polarity modulator for providing multi-step charging and discharging voltages for the polarity modulation; an output buffer for receiving image signals inputted from the digital-analog converter and conducting the polarity modulation through charging and discharging at the polarity modulation period in which the output buffers are connected to the polarity modulator, wherein at the time of charging, if the charging voltage of the polarity modulator is higher than the image signals, the level of image signals becomes the saturation level and at the time of discharging, if the discharging voltage of the polarity modulator is lower than the image signals, the level of image signals becomes the saturation level, and at the gray-scale display period, the polarity modulated outputs are supplied to the relevant data lines; and switching means for connecting the polarity modulator to the output buffers at the polarity modulation period and connecting the output buffers to the power supplier at the gray-scale display period. According to the present invention, as preventing overcharging or over-discharging as charging and discharging until not fixed voltage level but level controlled by video signal in polarity modulation, it is possible to prevent unnecessary power consumption.

Description

565824 V. Description of the invention (1) [Technical category to which the invention belongs and conventional technologies in this category] The present invention relates to a thin film transistor (Th i n F i 1 m

Transistor (TFT) source driving circuit of Liquid Crystal Device (LCD), especially relates to a low power source driving circuit and method which can drive data line by low power. Generally, a liquid crystal display (Liquid Crystal Device; LCD) used to display characters, symbols, or graphics is a display device that combines the liquid crystal technology and semiconductor technology with the optical properties of liquid crystals arranged in an electric field to change molecules. As a thin film TFT, an LCD is used as a switching element for turning ON / OFF of a pixel ON / OFF. A TFT is used, and the ON / OFF of the TFT can be used to make the pixel ON / OFF. That is, a general TFT liquid crystal display device is such that the elements (130) constituting pixels are arranged in an array shape as shown in the first figure, and each element is a TFT (132) and a liquid crystal element (132) that switch functions. 134) and a storage capacitor (cs).

In addition, the source of each TFT is connected together in the row direction to form a data line (D1-DN), and then connected to the source driver (120), and the gates of each TFT are connected in common in the column direction. After forming the scanning line (gi — other), the display device is connected to the gate driver (110) and has a resolution of NX M (for example, s VGA is 800x600, XGA is 1024x768, and UXGA is 1600x1200). Here, the 'source driver (120) is also called a data line driver or a row driver, and the gate driver is also called a column driver. As shown in the first figure, the 'liquid crystal element (1 3 4) is connected to the drain of the TFT (1 3 2) via a day electrode and the other is connected to a common electrode. Pixel electrodes are made of transparent and electrically conductive indium tin oxide (I T 〇),

Page 5 565824 V. Description of the invention (2) When assigning ΛσΓΗι to the TFT gate # 咕 晚 ymm ^ Recognize N bluff, the voltage is applied to the liquid crystal element (13, knife by adding 乜 through the source driver (12)). It is made of heart oxide, and can be applied to the liquid electrolyte element strain vinegar ^ #, and the common electrode is also indium tin ν μ ′ ”to the common voltage (Vcom) to 70 pieces of liquid day. Ιτο) # 费 ', = = ( Cs) is based on the change in the state of the pixel (Pixel), which can be used to adjust the light transmission of the day: two u; (cs) one side can be connected to an independent electrode or a closed electrode ⑽meU type The structure of the pole connection is called the gate storage (in the direction of StOrage Γΐϊ the aforementioned celestial array, if you add only one pixel to the liquid crystal of the pixel: tone two i: ΐ promote the degradation of the liquid crystal, so the use of Adding to the liquid crystal = the reverse phase method in which the voltage of the prime material is periodically reversed. Zone: the cycle added in the positive direction and the opposite direction-generally changes all of them, even if the reversed area is reversed =: = = Distinguish the pixel lines of the drawing line and make the lines inversely inverse to each other. The inverse f method is the opposite of the inversion of each day element. Inverting method, etc. No matter which method is used, when it is inverted, the daylight voltage (the voltage applied to the daylight electrode from the TFT drain) shows a positive (+) direction with respect to the common voltage (Vcom). Or show negative (-) direction and change alternately. * The first picture is a schematic diagram of a part of the conventional source drive circuit, revealing the digital-to-analog converter (21), the output buffer (22) and the odd polarity Modulation section (23), even-polarity modulation section (24), and multiplexer Μυχ (25). As shown in the second figure, when a latch is generated by a shift register not shown in the figure 565824 5. Description of the invention (3 ) Clock signal, digital image data from the video card turn. Flash lock clock signal flash lock and turn number ;; analog conversion (partial picture is not IZ 1 y ° from digital-analog conversion unit (2 丨) The voltage converted to the analog & signal is divided into the odd-numbered shirt data line through the output buffer section (22), and the odd-numbered data line is modulated by the odd-numbered ^ even-numbered ^ 2 and passed through the multiplexer belly. (25) Added to == 2 rounds of production = 枓 The line number is multiplexed by the even-numbered polar modulation section (24) MUX (25) is added to the data line. However, the multiplexer [ΜΙί Y, P bow M m] is installed through the conventional source driving circuit as described above; D and water must be set to (MUX), Therefore, the additional power consumption of the circuit will become a problem.… The switch signal used on the switch will use this source drive circuit to add the image signal to the data line. The output waveform diagram of the source drive circuit in the evening stage is as follows As shown in Figure 3 and Figure 3a, the vss voltage is 0V, and the VDD voltage is ι0ν, which is used: the common voltage (vc0M) on the common electrode is 5V, . In addition, the positive intermediate voltage (VH) of the reverse polarity T applied to the day electrode is 7.75V, and the positive and negative voltage (VL) is 2.25V, and the positive image signal exists in, and the negative = middle The voltage (VH) is the center and the area with a slash is drawn, and the f Luo shirt image signal exists in the field with the negative intermediate voltage (VL) as the center and the field with a slash. The electric jack is as described above. After the polarizer modifies each data line with a fixed polarity of VH and VL (B in the third a picture), it implements color gradation display (the third a

565824 V. Description of the invention (4) Figures C and D). In addition, as shown in the third figure b, the voltage from 72 to Vi is quintile (generally N quintile). When driving the load capacitor (Clgad), the power consumption is driven as a single color as in Equation 2. The proud formula 1 is reduced to 1/5 (1 / N for N stage). [Mathematical formula 1] P (: ONV = cvjvvjf [Mathematical formula 2] PStEP = CV2 ((V2-V!) / 5) F = (l / 5) Pc_

In figure 3b, the load capacitance (cload) is the sum of the capacitance values of the rows of the N data lines. Here, N is the number of outputs of a source driver. However, the conventional source driving method of the liquid crystal display device as described above shows very high efficiency in the full black mode and the full gray mode as shown in FIG. 4a, but in the full white mode as shown in FIG. 4b It shows that it is charged / discharged to an intermediate voltage (^: 7.75 ^ ¥ 1 ^ 2.25 ¥) due to the polarity reversal, which will cause overcharging and cause unnecessary power consumption. That is, in the full black mode, 'in the positive direction, the black level is higher than the intermediate voltage 0, and in the negative direction, it is lower than the intermediate voltage VL, so even if modulated to the intermediate voltage (VH, VL), high efficiency can be obtained. , But in positive direction in all white mode

^ The color level is lower than the intermediate voltage VH and in the negative direction is lower than the intermediate voltage vl. It requires a low amplitude and is also overcharged (that is, charged to the voltage level, the voltage level is 咼). Will generate additional power consumption. Therefore, no matter what the mode is, in order to improve the efficiency of power consumption reduction, overcharge must be eliminated.

Page 8 565824 V. Description of the invention (5) [Technical problem to be solved by the invention] The present invention is to create a solution to the problem as mentioned above, it is not charged to a fixed intermediate voltage and is based on the image signal The voltage is charged / discharged to a constant voltage to prevent overcharging and improve the power efficiency. The purpose is to provide a source driving circuit and driving method that can achieve other effects. Pulling the hair: The other purpose is to provide a source drive circuit, which consists of controlling the output buffer by a number of switches: =, and removing the existing drive circuit with a conventional drive circuit: The multiple MUX switches on each line simplify the circuit configuration. [Invention of the drive circuit material line, the image data modulation using the aforementioned digital period and pole if the aforementioned saturation to the previous electric voltage is displayed on the higher order display; everything is connected to the front structure] to achieve the above purpose 'the present invention The q pull you Gan A-1 is a multi-stage source, which is driven by the image data to drive the TFT liquid crystal display. It is characterized by the following: digital-to-analog conversion a material is directly converted to an analog signal; a polarity modulation部 ° ， ## Multi-stage charge and discharge electricity provided by the supply rule; an output buffer receives the video signal input by the analog conversion unit and adjusts the polarity from the original modulation unit to perform charge and discharge to modulate the polarity The charging voltage at the power source is higher than the image signal level, and if the polarity two image signal is low during discharge, it saturates to the image signal. From the beginning of the period, the output of the aforementioned modulation polarity is added to the '$' self-color changing equipment, which means that the front shell material is rotated out of the buffer from the polarity modulation period and the color scale display period is: == Ministry, slow down output 565824

The punch is connected to the power supply. It is also characterized by "discharging at a certain voltage level for charging and discharging for inverting the data line of the aforementioned crystal display device". The following is a detailed description of the fifth figure with reference to the drawings for the purpose of the present invention. The method of the present invention is based on a low power source driving circuit for driving a TFT liquid. Controlled levels to prevent overcharge and over-fine description of the preferred embodiment of the present invention. Shape chart. The output voltage wave of the low-power source driving method is shown in the fifth figure. The electric voltage is VDD, which is 1 ον, and the common voltage added to the common electrode is Ho, v (that is, v: Representing line time 'Each line time is divided into polarity reversal time (that is, charge / discharge time (A, C)) and color gradation display time (BD). 2H for the second turn is = turn, 1H is for The positive electrode is given a period of positive charge and a positive period. In particular, VCH is the maximum charge level 'VCL controlled by the image signal 2:'! Is the maximum discharge level by the image reliability (―) side. J ^ In the present invention, the middle gate 2 does not charge to a fixed electric i (VCH, VCL) level during polar modulation in the present invention, thereby preventing overcharging. The loop is / invented, the low power source driver of the liquid crystal display device. Success !, Figure 6b shows the output slowdown shown in Figure h. 'Detailed circuit diagram of the negative amplifier (〇P_Amp). &Quot; " As shown in Figure 6a, the source drive circuit is composed of Output odd data line 565824 V. Description of the invention (7) The following & abbreviated odd line) and even data line (hereinafter The digital-to-analog conversion unit (6 丨 〇) and the polar modulation unit (Polar Uy modulat〇r; 62〇), the output buffer (63〇), and the control of charging / discharging The switch (composed of 5 and 13, 5 and 1 | 3, ^ 23, and 3 ~ 213) is used to apply a driving voltage to the I ^ D panel (640). In addition, the output buffer (63) is formed by the number of lines / shower amplifier (6 3 2), and the calculation amplifier (6 3 2) is shown by the input amplifier (634) as shown in Figure 6b. , PM0s transistor (NM0S transistor (Mn) is formed. "When the first switch (swl a) is ON, the output of the charging female (VD) of the polar modulation section (62) is connected to an even number The VH of the line, and the polarity modulation unit (6 2 0) = the discharge terminal (VS) is connected to the odd-numbered line to charge the even-numbered line and discharge the: -numbered line. When the first switch (sw 1 b) is 0N When the VDD voltage is supplied to the VH of the odd line, and the ground (GND) is connected to the even line, when the second switch (sw2a) is on, the charging terminal (VD) of the polarity modulation section (62) The output is connected to% of the odd line, and the discharge terminal (vs) output of the polar modulation section (620) is connected to the even line & to charge the odd line and discharge the even line. When the fourth switch (sw2b) For the time, connect DD and C to $ of the even line, and connect the ground (gnd) to VL of the odd line. As shown in Figure 6b, calculate the The input amplifier (634) uses the inverting (-) terminal to input the received digital-analog conversion unit (61) and the non-inverting (+) terminal to input the feedback conversion signal, and amplifies the gain (A0). The output ^, the output of the input amplifier (634) is transmitted to the P-milk semiconductor transistor (Mp ^ N gold-oxide semiconductor transistor (⑷) in series).

P.11 565824 V. Description of Invention (8) And the output. The action is shown in Figure 6 and Figure 6b. The charging / discharging in the full white mode is explained. 1. The charging operation is in the case of charging to the VG load of the data line. It is connected to the calculation amplifier (6 2 0) material I. It is known that a voltage of 6. 5 V is applied, and a voltage lower than that of the polar modulation section (M) is applied to the VH due to the lightning of the P-metal oxide semiconductor transistor. Compared with V !, a high-semiconductor amplifier (634) generates a high signal, so p metal oxide is reduced, and the body source voltage (Mp) of the gate source voltage is reduced and becomes an open circuit. Overcharge can be eliminated because it prevents charging to a voltage higher than V! 2 Discharge operation ▲ The V 1 port of the calculation amplifier (632) is lower than the I1 by the self-polarity modulation unit (62 < 〇) during discharge. At the time of voltage, the low ([抑] \) ^ generated by the input amplifier (634) reduces the gate-source voltage of the metal-oxide semiconductor transistor (MN) and is cut off. Therefore, the phenomenon of discharging at a lower voltage than Vi can be eliminated. The seventh diagram is a waveform diagram of the control signal of the ON / OFF control of the switch shown in the sixth a by using the present invention. In the seventh figure, under the initial conditions, it is assumed that the even line is a negative image, (negative image) is the discharging state, and the odd line is a positive image (^ positive image), which is the charging state. The conditions for the waveform are based on the assumption that 22 / zs is the line time (1 60 0 and 1 20 01 ^ 0 when the square wave frequency is 75 Hz) and the line time is " (75 and 12〇〇) and 11

565824

(Twice as in split drive). Time between two lines: time B is the time display time of the first line, time interval [, the time of the odd line charging and the even line discharge (polar modulation) time:, area, time D is the second time The gradation display time. ° σDay ”丨 and the seventh figure, if all swla in the interval A are thin, even-numbered lines pass through the polarity modulation section (62) for periodic charging, and odd-numbered lines pass through the polarity modulation section (620) For periodic discharge. In the interval ^ " after the pole f ± is reversed, sw, a, sw 1 a, sw 2 a is 0ρ ρ, and sw 1 &, sw 2 b is 0n, then V ^) D, the VSS voltage source is connected to all the operational amplifiers (63 2) of the output buffer (63), and the output of the output buffer (63) is added to each data line 0,. When the interval C fsw2a is ⑽, even lines are used for periodic discharge and odd lines are used for periodic charging. In section D, as in section β, the switch ON / OFF operation is the same (that is, swia, sw2a is 0ff). , Swib, sw2b is 0 N) and display the color gradation. A summary of the description is shown in Table 1 below.

Page 13 565824 V. Description of the Invention (ίο)

Off Interval A Interval B Interval C Interval D sw \ a s w lb s w2a sw2b

ON

OFF

OFF

OFF

OFF

ON

OFF

ON

OFF

OFF

ON

OFF

OFF

ON

OFF

Figure 8a is the driving waveform diagram of the all-black image of the low power source driving method of the present invention, and Figure 8b is the full white image driving waveform diagram of the low power source driving method of the present invention. As shown in Figures 8a and 8b, unlike the conventional multi-stage charging method, it can be charged / discharged to the required voltage at any time without overcharging. For example, it is a five-stage charging method. In the case of phased driving, θ has no effect on the image signal and can save 80% of the left and right driving power consumption. '' On the one hand, when comparing the low-power source drive circuit (Figure 6a) of the present invention with the conventional multi-stage source drive circuit (Figure 2), it can be seen from the comparison that the driver circuit of Mingming has its entire drive circuit during polarity modulation The open relationship of (j3〇) is divided into even and odd lines, and the unified control is performed by using the buffer as the unified control ... The special mode is that Φ A rules the multi-stage source drive: icot: i :: ---- Additional power consumption required by the switch. The ninth picture is the source driver 1 of the present invention to make the gates early. 565824

Department of the circuit diagram. As shown in the ninth figure, the polarity modulation section (62) of the present invention is composed of seven capacitors (Ci ~ C?) For step charging and switches (SW1 ~ SW7) for the electric terminals (VS) respectively connecting the capacitors. ) And a switch (SW8-SW14) and a diode (Di, D2) that respectively connect the capacitors (Ci to C7) to the charging terminal (VD). w ~ In full white mode (VH; 6 · 5V), in order to prevent the current from flowing from the capacitor (c?) to the discharge terminal (vs) during phase discharge, a diode (Di) is added. In the full white mode ( VL; 3.5V) To prevent current from flowing from the charging terminal (VD) to the capacitor (C!) During charging, a diode (%) is added. Therefore, the polar modulation section (620) of the present invention can be composed of seven external capacitors, fourteen switches, and two diodes. [Effects of the Invention] As mentioned above, the source driving circuit of the present invention controls the buffer amplifier's operational amplifier (0p — A mp) with a small number of switches, so it can remove the existing driving circuit existing on each line. The switch simplifies the circuit configuration and saves power consumption for driving the switch. In addition, during polarity modulation, the level system is controlled by the image signal from the charge / discharge to a non-fixed voltage level, which can prevent overcharge and overdischarge and prevent unnecessary power friction.

Page 15 565824 Brief description of the diagram The first diagram is a schematic diagram of an equivalent circuit of a general TFT liquid crystal display device. The first diagram is a schematic diagram of a multi-stage source driving circuit known in §. The third a is the output voltage waveform of the conventional multi-stage source driving method. Figure 3b is a circuit diagram of the polarity modulation section of the conventional multi-stage source driving method. Figure 4a is the driving waveform diagram of the all-black image signal of the conventional multi-stage source driving method.

Figure 4b is the driving waveform diagram of the all-white image signal of the conventional multi-stage source driving method. The fifth figure is an output voltage waveform diagram of the low power source driving method of the present invention. Fig. 6a is a configuration diagram of a source driving circuit of the liquid crystal display device of the present invention. Figure 6b is a detailed circuit diagram of the output operational amplifier (0p-Amp) of the present invention. The seventh diagram is a waveform diagram of the switch control signal shown in the sixth a diagram.

FIG. 8a is a driving waveform diagram of the full black image signal in the low power source driving method of the present invention. FIG. 8b is a driving waveform diagram of the all-white image signal of the low power source driving method of the present invention. The ninth figure is a circuit of the polarity modulation section of the source driving circuit of the present invention

Page 16 565824 Simple explanation of the drawings [Description of the drawing symbols] 21 ------ Digital-to-analog converter 22 ------ Output buffer section 2 3 --------- Odd number polar modulation section 24- ----- Even Polarity Modulation Unit 25 ------ Multiplexer (MUX) 120 ------ Source Driver 132 ------ Thin Film Transistor (TFT) 134 ---- --Liquid crystal element 610 ------ Digital-analog conversion section 620 ------ Polarity modulation section 630 Output buffer 632 ------ Calculation amplifier 634 ------ Input amplifier 6 4 0 ------ LCD panel

Page 17

Claims (1)

565824 6. Scope of patent application 1 · A low-power source driving method for a liquid crystal display device, which is a low-power source driving method for driving the data line of the liquid crystal display device. Its special explanation lies in its use for polarity inversion. During charging and discharging, the intermediate electrical charger is only charged and discharged to a level controlled by an image signal of a non-fixed voltage level to prevent overcharge and overdischarge. The display device I is low, and the green electrode driving circuit is driven. The 2 source driving circuit is driven by the image data to set the LCD display: =; after = is included: a digital _ analog conversion 1, the multi-stage charge / discharge voltage is set;-Self-polarity is adjusted by inputting the video signal input by the analog conversion unit: Electricity is connected by the system to perform charge-discharge and is adjusted = ^ the right-side polar modulation unit The charging voltage is lower than the previous voltage. When the electric voltage is lower than the image signal, it saturates to the front modulation section, and the aforementioned modulation will be performed from the step display period; like; D, since; connected; Department of self-polarity modulation cycle ;; ::; :; Punch ... gradation display period ^ front pole drive back :: ί: J] item J2, the low-power source calculation amplifier of the liquid crystal display device is provided by: the aforementioned round-out buffer is composed of data line number 565824 4. The driver circuit of a liquid crystal display device, such as the patent application No. 3, is characterized in that the aforementioned operational amplifier includes a μ source input amplification state, and the input receives the aforementioned image signal (V). Crystal (MP), when charging from the aforementioned polarity modulation, the oxygen signal is given to the oxygen signal (V. is 0N when the voltage is low, and becomes'; # σ is higher than before, and when high voltage is applied Then it is cut off; _Νmetal oxide semiconductor c: charge (MN) 'is added to the above-mentioned shadow from the polarity modulation part at the time of discharge; (Vl) when the voltage is high, it is ON, and becomes a staged discharge When the voltage is low, it will be cut off. In the case of a low power source circuit, such as the liquid crystal display set in item 3 of the patent application scope, it is characterized in that the aforementioned switching equipment includes a distinction; When the line is inverting, charge the control even-numbered line: / discharge, electricity " Use: 二 21 switch (swia) and control the odd-numbered line charge / even-numbered vtn * Off iSW2a) and the calculation amplifier for the odd-numbered line ^ • Ma i: The third switch of the line's calculation amplifier for grounding power supply ; Female :: ίThe amplifier for the even line is connected to VDD, and the amplifier for the odd line is connected to the fourth switch (sw2b) for ground power. "" If the low power source of the liquid crystal display device in the scope of patent application No. 5 drives the circuit urgently, its characteristics are as follows: The aforementioned first opening is related to the first line time. Even the line charging (odd line discharge) time is ⑽ and OFF in the first line time when the gradation is not %%, and the even line discharge in the second line time (odd line charge 565824 VI. Application for patent scope Electricity) Time ^ & The second line time gradation display time is OFF for UN; Month 1J describes the first P discharge) Japan Shi Kai is related to the first line time even line charging (odd number) The line time is OFF and the display time at the first line time level is 0N, -Green # @ t Even line discharge (odd line charge) time is OFF and the first line f time level display time is 0FF; brother discharge) The protection is related to the charging of the even line of the first line time (the odd line is 0FF in the second line and the color scale display time is 0FF in the first line time, and the even line in the second line 0+ 2 & is discharged (Odd line charge) time is 0N and the first line = inter-gradation display time 01 ^; the discharge of the younger brother is related to the charge of the even line of the first line time (the second line of the odd line is f and the first line is The time gradation display time is 而, and the discharge time (odd line charge) on the second line m ′ is 0 ff, and the display time on the first and the second days is 0 N. The palladium 7 moves: Please ί The low power source of the liquid crystal display device according to the second item of the profit range = loop is characterized by the aforementioned polarity modulation Department includes two phases to prevent self-charge during staged discharge = 1 full _ current reverse K pole body (D2) = 2 subs: ¥ can prevent self-charging terminal (VD) from generating current reverse current to capacitor ⑹ Charge