Background technology
In general, liquid crystal indicator uses and exchanges (AC) driving method.This is that will shorten its serviceable life because if drive liquid crystal layer with direct current (DC) voltage.As the driving method that is used to reduce flicker during well-known AC drives is the horizontal line inverting method of horizontal synchronizing cycle (1H cycle) reversed polarity in each unit.
For example, as shown in Figure 1, adopt the liquid crystal indicator of existing driving method to have switched circuit 107, the synchronizing signal that it and control circuit 101 provide is synchronously switched the output that comes from first normal voltage generation circuit 106a that produces the positive polarity normal voltage and the second normal voltage generation circuit 106b that produces the negative polarity normal voltage.The output of switched circuit 107 is connected to a plurality of horizontal drivers 103 that are connected with the signal line of liquid crystal board 105 jointly.
Control circuit 101 response is presented at the input data of the image on the liquid crystal board 105, and the input gray level data corresponding to 1H cycle of a unit make horizontal driver 103 that the voltage that the first normal voltage generation circuit 106a provides is applied to liquid crystal board 105.During the next 1H cycle, it makes horizontal driver 103 that the voltage that the second normal voltage generation circuit 106b provides is applied to liquid crystal board 105.
In addition, control circuit 101 makes common electric voltage generation circuit 104 that common electric voltage is applied to liquid crystal board 105.For each pixel capacitors in the liquid crystal board 105, when vertical driver 102 had been selected the one scan circuit, horizontal driver 103 provided a signal voltage corresponding to gradation data.Simultaneously, common electric voltage generation circuit 104 provides common electric voltage for the public electrode with respect to this pixel capacitors.Then, at the gray scale image that is presented on the liquid crystal board 105 between pixel capacitors and the public electrode corresponding to voltage gap.Counter-rotating this common electric voltage and offer LCD panel 105 in the cycle of each 1H is so that amplify the effective voltage of each pixel that imposes on liquid crystal board 105.It is to reverse by going of each 1H cycle to realize that the AC of this liquid crystal board drives.
Fig. 2 A shows is that the gray scale-γ of liquid crystal indicator revises voltage relationship.Dotted line represents that the gray scale that the applies voltage-transfer characteristic-γ that does not consider liquid crystal layer revises voltage relationship, and solid line has represented to add the relation that the gray scale-γ of the correction of the voltage-transfer characteristic that is applied of considering liquid crystal layer revises voltage.Because the voltage-transfer characteristic that applies of liquid crystal layer is not that represent with straight line or nonlinear, revise the relation of voltage according to the gray scale of representing with solid line among the figure-γ, driving voltage is imposed on liquid crystal board, to realize that corresponding to the input data in actual liquid crystal indicator gray scale shows.
Impose on the liquid crystal board 105 of prior art liquid crystal indicator that the gray scale of representing based on solid line shown in Figure 1-γ revises the relation of voltage if γ is revised voltage, the voltage that gray scale X1 is applied will be VF, and will be VG in the next 1H cycle to gray scale X2.Then, the effective voltage that imposes on the liquid crystal layer of liquid crystal board 105 will be respectively | VF-VC| and | VG-VC|, notice that VC represents to impose on the common potential of the public electrode on pixel capacitors opposite.As a result, shown in Fig. 2 B, effective voltage level between the cycle of 1H cycle and next 1H (F, G) different each other.The reason of flicker that Here it is.
In addition, because switched circuit 107 selects to produce the normal voltage generation circuit 106a or the 106b of positive or negative polarity normal voltage, to provide normal voltage to horizontal driver 103, complexity so the circuit structure of the liquid crystal indicator of prior art shown in Figure 1 will become.Owing to the power source voltage Vcc that offers normal voltage generation circuit 106a, 106b is very high, switched circuit 107 must be stood high pressure again.The cost of this device will be very high like this.
Embodiment
Now, will describe embodiments of the invention with reference to the accompanying drawings in detail.Fig. 3 is the liquid crystal indicator block scheme of explanation according to the first embodiment of the present invention.Liquid crystal indicator according to the present invention has liquid crystal board 5, normal voltage generation circuit 6, vertical driver 2, a plurality of horizontal drivers 3, and control circuit 1.Liquid crystal board 5 is equipped with a plurality of trace wirings and a plurality of signal line.Normal voltage generation circuit 6 provides a plurality of normal voltages.Vertical driver 2 scans the trace wiring of liquid crystal board 5 one by one.A plurality of horizontal drivers 3 offer grayscale voltage the signal line that receives the liquid crystal board 5 of a plurality of normal voltages from normal voltage generation circuit 6.Polarity by counter-rotating input data produces gradation data to control circuit 1 in each unit level synchronizing cycle, and the controlling level driver 3 then, so that normal voltage corresponding to gradation data is provided for liquid crystal board 5.
Normal voltage generation circuit 6 has the ladder type resistance between power source voltage Vcc of being connected and the normal voltage, and the normal voltage V0-V10 of 11 grades is provided for a plurality of horizontal drivers 3.
According to above-mentioned normal voltage, during a horizontal synchronizing cycle (1H cycle), control circuit 1 receives the digital input data of n position, and controlling level driver 3 will be so that will offer liquid crystal board 5 corresponding to this voltage of importing data.In addition, the polarity of each that control circuit 1 is imported data by reversing is come the gradation data of polarization counter-rotating, and, make horizontal driver 3 that the signal line of liquid crystal board 5 will be provided corresponding to the voltage based on the gradation data of above-mentioned normal voltage that is produced in the next 1H cycle.For example, under the situation of 64 grade gray scales,, can obtain 60 and as gray scale X2 by each position at these 6 X1 (3) of next 1H periodic reversal if be 3 at 1H cycle gray scale X1.If gray scale X2 is 60 in the 1H cycle, then when the counter-rotating this 6 bit data X2 (60) each the time, X2 becomes 3 to next 1H cycle gray scale.
In addition, the signal that reversed at each 1H horizontal synchronizing cycle of control circuit 1 output signal level.The signal of common electric voltage output circuit 4 amplification levels counter-rotatings, and they are offered the relative public electrode of pixel capacitors of liquid crystal board 5 as common electric voltage.If this common electric voltage also is the voltage of level counter-rotating, the effective voltage of the liquid crystal layer that imposes on liquid crystal board 5 of then can raising.
Fig. 4 A is that the gray scale-γ that uses in the driving method of explanation according to the liquid crystal indicator of first embodiment of the invention revises voltage relationship figure; Fig. 4 B is presented at the oscillogram that imposes on the signal of liquid crystal board according to above-mentioned driving method operating period.
Solid line among Fig. 4 A shows that positive polarity gray scale-γ revises voltage relationship, and dotted line shows that negative polarity gray scale-γ revises voltage relationship.In an embodiment of the present invention, being used for this gray scale-γ that gray scale shows, to revise voltage relationship be symmetrical with respect to the central point between the highest gray shade scale and the minimum gray shade scale, and can represent with straight line.For satisfying this relation between gray scale and the voltage, in response to the gradation data of input, horizontal driver 3 applies γ correction voltage to the signal line of liquid crystal board 5.Under the situation of 64 grade gray scales, the highest ranking gray scale is 63, and the lowest class gray scale is 0.
To the gradation data of input when the 1H cycle produces the γ correction voltage that will apply, revise voltage relationship with reference to positive polarity gray scale-γ, and to the gradation data of input when the next 1H cycle produces the γ correction voltage that will apply, revise voltage relationship with reference to negative polarity gray scale-γ.For example, the voltage that applies in the 1H cycle for display gray scale X1 will be the VA that revises voltage relationship according to positive polarity gray scale-γ, and the voltage that is applied in the next 1H cycle will be the VB that revises voltage relationship according to negative polarity gray scale-γ.In this case, because VC is the center voltage of the common electric voltage of the level counter-rotating that provides from common electric voltage output circuit 4, so the effective voltage that imposes on the liquid crystal layer of liquid crystal board 5 will be | VA-VC|, | VB-VC| corresponds respectively to 1H cycle and next 1H cycle.Because it is to be symmetrical in a bit that gray scale-γ revises voltage relationship, shown in Fig. 4 B, (A, absolute value B) equate (A=B) mutually to these voltage differences.
Note, according to as described in the liquid crystal indicator of present embodiment, when the digital input signals of n position has been received, come gradation data of polarization counter-rotating by each of counter-rotating input data as top.Then according to above-mentioned normal voltage in the next 1H cycle, will be applied to the signal line of liquid crystal board 5 corresponding to the voltage of gradation data.As a result, can simplify circuit structure, no longer needing to prepare independent normal voltage generation circuit provides negative polarity gray scale-γ to revise voltage relationship.
As described in above-mentioned liquid crystal indicator of the present invention, realize that gray scale shows owing to revise voltage relationship according to gray scale-γ, and this gray scale-γ revises voltage relationship with respect to the central point between the highest gray shade scale and the minimum gray shade scale, and because the polarity of control circuit 1 by the input data of each horizontal synchronizing cycle that reverses produces gradation data, to impose on liquid crystal board 5 corresponding to the normal voltage of gradation data then, can simplify so produce the structure of the normal voltage generation circuit 6 of normal voltage.In addition, because constant between the cycle in 1H cycle and next 1H in the absolute voltage difference between the voltage that imposes on pixel capacitors and public electrode, can prolong the serviceable life of liquid crystal board 5, and its reliability also can strengthen.Then, because absolute voltage difference remains constant, can reduce flicker.
In addition, according to the driving method of the liquid crystal indicator of the embodiment of the invention, this gray scale-γ revises voltage relationship with respect to the central point between the highest gray shade scale and the minimum gray shade scale, and gray scale-γ revises voltage relationship and can represent with straight line.These horizontal driver 3 response input gray level data are revised the signal line that voltage imposes on liquid crystal board 5 with γ, revise voltage relationship so that satisfy gray scale-γ.Then, the absolute voltage difference that imposes on pixel capacitors and public electrode during 1H cycle and ensuing 1H cycle becomes equal (A=B).Therefore, can prolong the serviceable life of liquid crystal board 5 with and reliability can increase.In addition, because absolute voltage difference remains constant, can reduce flicker.
Various details second embodiment.Second embodiment has a feature, and its gray scale-γ revises institute's making alive transport property that voltage relationship has been considered liquid crystal layer.Because this circuit arrangement almost circuit with first embodiment shown in Figure 3 is identical, will not describe the configuration of this circuit in detail here.
Fig. 5 A is the curve map that gray scale-γ of using in the driving method according to liquid crystal indicator of the present invention revises voltage relationship; Fig. 5 B is presented at the oscillogram that imposes on the signal of liquid crystal board according to this driving method operating period.Shown in Fig. 5 A, in the present embodiment, this gray scale-γ revises voltage relationship with respect to the central point between the highest gray shade scale and the minimum gray shade scale, but represents (representing with the polygon line in this embodiment) without straight line.These horizontal driver 3 response input gray level data are revised voltage with γ and are imposed on liquid crystal board 5 to satisfy this relation.The resistance value of each ladder type resistance of the normal voltage generation circuit 6 by change constituting liquid crystal indicator shown in Figure 3 also can provide this relation.
With with the identical mode of first embodiment shown in Fig. 4 A, gray scale-γ that generation will apply to the input gray level data during the 1H cycle revises in the voltage, revise voltage relationship with reference to the positive polarity gray scale-γ that in Fig. 5 A, shows with solid line, revise in the voltage and produce the gray scale-γ that will apply during the next 1H cycle, the negative polarity gray scale-γ that shows with reference to dashed lines revises voltage relationship.For example, the voltage that applies for display gray scale X3 will be the VD that the positive polarity gray scale-γ according to the 1H cycle revises voltage relationship, and will be the VE that revises voltage relationship according to negative polarity gray scale-γ to the voltage in next 1H cycle.In this case, the effective voltage that imposes on the liquid crystal layer of liquid crystal board 5 will be | VD-VC|, | VE-VC| corresponds respectively to 1H cycle and next 1H cycle.Because it is the line symmetry that gray scale-γ revises voltage relationship, shown in Fig. 5 B, (D E) equates (D=E) mutually to the absolute value of these voltage differences.
Except the result that first embodiment obtains, this embodiment also has an advantage, promptly can realize considering the capable inversion driving of the voltage-transfer characteristic that applies of this liquid crystal layer, can realize the nature gray scale then on liquid crystal indicator.In addition, only indivedual resistances of the ladder type resistance by changing normal voltage generation circuit 6 just can provide above-mentioned advantage, and needn't increase independent circuit.Like this, reduced because the cost that the change on circuit design causes increases.
The present invention at length is described with different embodiment, to one skilled in the art, from the instruction of front, obviously can make some variations and modification, and can not depart from the scope of the present invention, therefore, in the claim that the present invention adds, covered all this variation and modifications, it is fallen within the true spirit of the present invention.For example, the gray scale of using in display gray scale-γ correction voltage relationship is not limited to Fig. 4 A and Fig. 5 A is described like that, but can represent those relations with other curve and polygon line rather than straight line, as long as just passable with respect to the central point between the highest gray shade scale and the minimum gray shade scale.
As mentioned above, liquid crystal indicator according to the present invention makes the circuit arrangement of simplifying and dwindling normal voltage generation circuit become possibility.Because switching is deleted from the switch of the high pressure that normal voltage generation circuit provides, therefore can simplify this circuit arrangement and reduced in size.Owing to be not operated in the switch of high pressure, can save the loss of power yet.In addition, in control circuit, revise voltage relationship, realize the row counter-rotating in each 1H cycle according to gray scale-γ with respect to the line symmetry at the center between the highest gray shade scale and minimum gray shade scale.As a result, when reversed polarity, the effective voltage that imposes on liquid crystal layer remains constant.Like this, just reduced flicker.
In addition, in driving method, revise voltage relationship, realize the row counter-rotating in each 1H cycle according to gray scale-γ with respect to the line symmetry at the center between the highest gray shade scale and minimum gray shade scale according to liquid crystal indicator of the present invention.As a result, when reversed polarity, the effective voltage that imposes on liquid crystal layer remains constant.Like this, just reduced flicker.