JP2005338463A - Drive method and circuit of liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display drive method and circuit which can reduce the power consumption while improving the image quality. <P>SOLUTION: Continuous N frames are made a group and the liquid crystal display panel is driven by reversing the line in continuous arbitrary m frames within a group. In the remaining (N-m) frames, the liquid crystal display panel is driven by reversing the frame. The value of m is set to an even number. One sequence is completed when driving has finished for a group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a driving method and a driving circuit of a liquid crystal display device using AC driving.

  In general, AC driving is used as a driving method for driving a liquid crystal display panel because the life of the liquid crystal display panel is shortened when the liquid crystal display panel is driven with a DC voltage. When line-sequential driving is used, as AC driving, a line inversion driving method in which the voltage applied to the liquid crystal is inverted each time the scanning electrode to be scanned is switched, or a frame inversion driving in which the voltage applied to the liquid crystal is inverted every frame. There are laws. The frame means a period required for all the scanning electrodes to be scanned once.

  When a liquid crystal display panel using TFT (Thin Film Transistor) is driven using the frame inversion driving method, the polarity of the data voltage applied to the data electrode (source electrode) is inverted. In order to prevent the drive voltage from increasing, it is common to reverse the polarity of the common voltage applied to the common electrode and drive the common voltage and the data voltage to have opposite polarities. is there. When driving using the line inversion driving method, the polarity of the data voltage is inverted every time the scan electrode to be scanned is switched. Similarly to the case of driving using the frame inversion driving method, the polarity of the common voltage applied to the common electrode is inverted every time the scanning electrode to be scanned is switched.

  It is known that when the line inversion driving method is used, the image quality is improved as compared with the case where the frame inversion driving method is used. In particular, crosstalk is reduced (see, for example, Patent Document 1).

JP 2003-280601 A (paragraphs 0010-0011, FIG. 36, FIG. 38)

  However, when the line inversion driving method is used, a so-called swinging line may be observed. In the line inversion driving method, the polarity of the data voltage and the voltage applied to the common electrode is changed every time the scanning electrode to be scanned is switched, so that the signal frequency in the source driver is increased and the switching frequency of the common voltage is increased. As a result, power consumption increases. Therefore, it is not suitable for driving a liquid crystal display panel mounted on a portable device that requires low power consumption.

  Therefore, the present invention can improve the image quality as compared with the case where the frame inversion driving method is used, and can reduce the power consumption as compared with the case where the line inversion driving method is used. An object is to provide a driving circuit.

  A driving method of a liquid crystal display device according to the present invention is a driving method for driving a liquid crystal display panel in which a plurality of scanning electrodes and a plurality of data electrodes are arranged in a matrix, and is a series of N (2 ≦ N) frames. The liquid crystal display panel is driven by the line inversion driving method in the m (1 ≦ m <N) frame, and the liquid crystal display panel is driven by the frame inversion driving method in the other (N−m) frames. And

  It is preferable to drive in an even number of consecutive frames of N frames by the line inversion driving method. That is, m is preferably an even number.

  A driving circuit of a liquid crystal display device according to the present invention is a driving circuit for driving a liquid crystal display panel in which a plurality of scanning electrodes and a plurality of data electrodes are arranged in a matrix, and sequentially applies a selection voltage to each scanning electrode. A scan electrode driver, a data electrode driver that applies a data voltage to each data electrode in synchronization with the application of a selection voltage to the scan electrode by the scan electrode driver, and m (N (2 ≦ N) frames) An instruction signal instructing that the liquid crystal display panel is driven by the line inversion driving method in the frame of 1 ≦ m <N) and the liquid crystal display panel is driven by the frame inversion driving method in the other (N−m) frames, And a control circuit for outputting to the scan electrode driver and the data electrode driver.

  The control circuit preferably causes the scan electrode driver and the data electrode driver to drive the line inversion driving method in an even number of consecutive frames of N frames.

  According to the present invention, the liquid crystal display panel is driven by the line inversion driving method in a part of the continuous frames, and the liquid crystal display panel is driven by the frame inversion driving method in the other frames. The image quality can be improved as compared with the case of using, and the power consumption can be reduced as compared with the case of using the line inversion driving method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram for explaining the concept of the present invention. As shown in FIG. 1A, N consecutive frames are made into one group, and in any m consecutive frames in the group, the liquid crystal display panel is driven by the line inversion driving method, and the other (N− In the frame m), the liquid crystal display panel is driven by the frame inversion driving method. When the driving of all the frames constituting one group is completed, the same driving as the previous group is executed for the next group. That is, for the (N + 1) th to 2nd N frames, m consecutive frames in the group are driven by the line inversion driving method, and in the other (N−m) frames, the liquid crystal display panel is driven by the frame inversion driving method. Is done. In each group, the arrangement positions of m consecutive frames may be different. For example, in the example shown in FIG. 1A, the first m frame is driven by the line inversion driving method, but in other groups, m frames other than the first m frame may be driven by the line inversion driving method. Good.

  Although FIG. 1A illustrates the case of m = 2, the value of m may be 4 or more as long as the value of m is an even number. N is a value of 2 or more, and for example, the upper limit is the total number L of lines in the liquid crystal display panel. When the driving for one group is completed, one sequence of the driving method of the present invention is completed. FIG. 1B illustrates the case where N = 6 and m = 2.

  A line driven with a positive polarity in a certain frame among the m frames is driven with a negative polarity in the next frame. Conversely, a line driven with a negative polarity in one frame is driven with a positive polarity in the next frame.

  In the following description, driving with positive polarity means that the common voltage is higher than the common voltage center (a voltage intermediate between the positive polarity voltage and the negative polarity voltage). Driving means that the common voltage is lower than the common voltage center. The data voltage has a polarity opposite to that of the common voltage.

  FIG. 2 is a block diagram showing a configuration example of a drive circuit for realizing the drive method according to the present invention. In the example shown in FIG. 2, a TFT type liquid crystal display panel 10 in which TFTs are arranged in a matrix and liquid crystal is sandwiched between a pixel electrode and a common electrode is used. A driving circuit for driving the liquid crystal display panel 10 includes a source driver (data electrode driver) 12 in which each source electrode (source wiring) as a data electrode connected to the source of the TFT in the same column in the liquid crystal display panel 10 is connected, liquid crystal A gate driver (scanning electrode driver) 13 connected to each gate electrode (gate wiring) as a scanning electrode connected to the gate of the TFT in the same row in the display panel 10, and a voltage for creating a data voltage to the source driver 12 A power supply circuit 14 is provided for supplying the gate driver 13 with a voltage for generating a selection voltage and a non-selection voltage.

In this embodiment, the common voltage output unit 131 built in the gate driver 13 applies the positive or negative common voltages V _COMH and V _COML to the common electrode (common wiring) of the liquid crystal display panel 10. Accordingly, a voltage for generating a common voltage is supplied from the power supply circuit 14 to the gate driver 13.

  The controller 11 as a control circuit outputs an FLM (First Line Marker) signal, which is a signal indicating the start of a frame, to the source driver 12 and the gate driver 13, and a selection voltage is applied to each selection period (one gate line). An LP (Latch Pulse) signal is output at every applied period). In this embodiment, a data signal input from the outside of the drive circuit is output to the source driver 12 via the controller 11. Further, the controller 11 outputs an M signal, which is a signal indicating polarity, to the source driver 12 and the gate driver 13. Assume that the M signal is output for each selection period. The M signal is driven by the line inversion driving method in m (1 ≦ m <N) frames among consecutive N (2 ≦ N) frames, and frame inversion in other (N−m) frames. This corresponds to an instruction signal for instructing driving by the driving method.

  The gate driver 13 has a built-in counter, and resets the counter when the FLM signal is input, and increments the counter value by +1 when the LP signal is input. Then, a selection voltage for making the TFT gate conductive is applied to the gate line indicated by the counter value, and a non-selection voltage for making the TFT gate shut off is applied to the other gate line. The gate driver 13 applies a positive common voltage to the common line if the M signal indicates positive polarity, and applies a negative common voltage to the common line if the M signal indicates negative polarity. .

  When the LP signal is input, the source driver 12 latches the data signal and applies a data voltage corresponding to the latched data signal to the source line. Since the gate driver 13 applies the selection voltage to the gate line in synchronization with the LP signal, the source driver 12 applies the data voltage to each source line in synchronization with the application of the selection voltage to the gate line. At this time, if the M signal indicates positive polarity, a data signal having a polarity (negative data voltage) corresponding to the positive common voltage is applied, and if the M signal indicates negative polarity, the negative polarity is applied. A data signal having a polarity corresponding to the common voltage (positive data voltage) is applied.

  FIG. 3 is an explanatory diagram showing an example of the polarity of the M signal in each selection period in each frame. FIG. 3 shows an example in which the total number of lines L is eight. Therefore, one frame is composed of first to eighth selection periods. In each selection period, any one of the first to eighth lines is sequentially selected, and a selection voltage is applied to the gate line. FIG. 3 shows an example where N = 6 and m = 2. Further, M = 1 indicates driving with a positive polarity, and M = 0 indicates driving with a negative polarity.

  As shown in FIG. 3, in the first frame, in the first line, that is, in the first selection period, the liquid crystal display panel 10 is driven with a negative polarity, and the M signal is output so that the entire display area is driven by the line inversion driving method. Is set. In the second frame, the M signal is set so that the first line is driven with a positive polarity and the entire display area is driven with the line inversion driving method.

  In the third frame and the fourth frame, the M signal is set so that the entire display area is driven by the frame inversion driving method. Specifically, in the third frame, the M signal is set so that the entire display area is driven with a negative polarity, and in the fourth frame, the entire display area is driven with a positive polarity.

  In the fifth frame and the sixth frame, the M signal is set so that the entire display area is driven by the frame inversion driving method. Specifically, in the fifth frame, the M signal is set so that the entire display area is driven with a negative polarity, and in the sixth frame, the entire display area is driven with a positive polarity.

  Data indicating the polarity of the M signal in each selection period shown in FIG. 3 is set in the controller 11 as a data table, for example.

  Next, the operation of the controller 11 will be described with reference to the flowchart of FIG. In this embodiment, the controller 11 has a frame counter for counting the number of frames and a line counter for counting the number of lines in each frame.

  First, the controller 11 sets “1” as an initial value in the frame counter (step S1). When the frame start timing comes (step S2), the table indicated by the value of the frame counter is selected (step S3). If the value of the frame counter is “1”, the table for the first frame at the upper left in the data table illustrated in FIG. 3 is selected. Further, “1” is set as an initial value in the line counter (step S4). At this time, the controller 11 outputs an FLM signal.

  Next, when the output timing of the LP signal comes (step S5), data indicated by the value of the line counter is input from the table selected in step S3 (step S6). If the value of the line counter is “1”, data for the first line is input. Then, the data input from the table is output as an M signal and an LP signal is output (step S7). Note that the output timing of the LP signal has arrived when one selection period has elapsed.

  Next, the controller 11 increments the value of the line counter by 1 (step S8). When the value of the line counter exceeds L as the total number of lines (step S9), the process proceeds to step S10 in order to start control of the next frame. If the value of the line counter does not exceed L, the process returns to step S5.

  In step S10, the frame counter value is incremented by one. If the value of the frame counter exceeds N, one sequence has been completed, and the process returns to step S1 to start the next sequence. If the value of the frame counter does not exceed N, the process returns to step S2, and control of the next frame in the group is started. Note that N is 6 when the data table illustrated in FIG. In step S2, the frame start timing comes after a period (period) determined by the frame frequency has elapsed from the previous frame start timing.

  Through the processing as described above, a driving method in which line inversion driving is temporally dispersed can be realized as shown in FIG. The above-described control method and drive circuit configuration are merely examples, and some frames in a group composed of a plurality of frames are driven by the line inversion drive method, and other frames in the group are driven by frame inversion drive. If you can control to drive in the law. Other control methods and drive circuits may be used. For example, a general controller that drives the liquid crystal display panel 10 using the line inversion driving method is used, and the controller is used as the first controller, and the first controller is connected between the source driver 12 and the gate driver 13. The second controller is configured so that the second controller converts the M signal output by the first controller (the M signal inverted every selection period) into an M signal based on the above data table. Also good.

  The controller 11 is a general controller that drives the liquid crystal display panel 10 using the line inversion driving method. The source driver 12 and the gate driver 13 incorporate the above data table in the source driver 12 and the gate driver 13. However, it is also possible to convert the M signal output from the controller 11 (the M signal inverted every selection period) based on the data table. In the case of such a configuration, m (1 ≦ m <N) frames among consecutive N (2 ≦ N) frames are driven by the line inversion driving method, and other (N−m) frames. Then, a control circuit for instructing driving by the frame inversion driving method is incorporated in the source driver 12 and the gate driver 13.

  In the above embodiment, since N frames are one group, m frames of the group are driven by the line inversion driving method, and (N−m) frames are driven by the frame inversion driving method. The power consumption can be made closer to m / N than when the entire display area is driven by the line inversion driving method. That is, power consumption can be reduced. Also, if the crosstalk when driven by the line inversion driving method is extremely small compared to when driving by the frame inversion driving method, the crosstalk is higher than when all the frames in the group are driven by the frame inversion driving method. Can be reduced to (N−m) / N, and the overall display quality can be improved. In addition, the degree of occurrence of a swing line can be reduced to m / N as compared with the case where all the frames in a group are driven by the line inversion driving method, and a liquid crystal display device with reduced discomfort can be obtained. it can.

  Note that if the value of m is very small with respect to the value of N, the power consumption is greatly reduced, but the display quality is not improved so much. Therefore, m is preferably selected within a range of 50% or less, for example, 10 to 30% with respect to the value of N when importance is placed on the reduction of power consumption. Further, for example, in the QVGA suitable for mounting on a portable device as the size of the liquid crystal display panel 10, N is selected to be about 3 to 10. However, the present invention can also be applied to the case where a liquid crystal display panel having a display area having a size larger than that of QVGA is used.

  In the above-described embodiment, the active matrix liquid crystal display panel 10 is used as an example. However, the present invention can be applied even when a passive matrix liquid crystal display panel such as an STN liquid crystal display panel is used. .

  The present invention is particularly useful when applied to a liquid crystal display panel mounted on a device that requires a reduction in power consumption.

Explanatory drawing for demonstrating the concept of this invention. The block diagram which shows one structural example of the drive circuit for implement | achieving the drive method by this invention. Explanatory drawing which shows an example of the polarity of the M signal of each selection period in each frame. The flowchart which shows operation | movement of a controller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display panel 11 Controller 12 Source driver 13 Gate driver 14 Power supply circuit 131 Common voltage output part

Claims (4)

In a driving method for driving a liquid crystal display panel in which a plurality of scanning electrodes and a plurality of data electrodes are arranged in a matrix,
Of the consecutive N (2 ≦ N) frames, m (1 ≦ m <N) frames are driven by the line inversion driving method,
A driving method of a liquid crystal display device, wherein the other (Nm) frames are driven by a frame inversion driving method. The driving method of the liquid crystal display device according to claim 1, wherein driving is performed by a line inversion driving method in an even number of consecutive frames of N frames. In a drive circuit for driving a liquid crystal display panel in which a plurality of scan electrodes and a plurality of data electrodes are arranged in a matrix,
A scan electrode driver that sequentially applies a selection voltage to each scan electrode;
A data electrode driver that applies a data voltage to each data electrode in synchronization with the application of a selection voltage to the scan electrode by the scan electrode driver;
Of the consecutive N (2 ≦ N) frames, m (1 ≦ m <N) frames are driven by the line inversion driving method, and other (N−m) frames are driven by the frame inversion driving method. A drive circuit for a liquid crystal display device, comprising: a control circuit that outputs an instruction signal for instructing to the scan electrode driver and the data electrode driver. 4. The drive circuit for a liquid crystal display device according to claim 3, wherein the control circuit causes the scanning electrode driver and the data electrode driver to drive the line inversion driving method in an even number of consecutive frames of N frames.

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