The present application claims priority from Japanese application JP 2011-256016 filed on Nov. 24, 2011, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to a display device and a video display method.
2. Description of the Related Art
As a display device of an information communication terminal such as a computer or of as a television receiver, liquid crystal display devices have been extensively used. Also, an organic EL display device (OLED) and a field emission display device (FED) have been known as thin display devices. The display devices of this type is incorporated into a mobile terminal such as a cellular phone, and used as an output device to a user. The mobile terminal frequently has a wireless communication function, and there has been known that electromagnetic waves emitted from the display device are affected on the wireless communication.
JP 06-037478 A discloses that a metal foil is attached to an input interface signal wiring or a power supply wiring to reduce an EMI (electromagnetic interface).
Also, JP 11-133921 A discloses a binary display and a gradation display in an SIN reflection liquid crystal display device in which any one of a clock transmitted by a clock transmitter and a clock divided by a frequency divider is selected to be used as a frame frequency, and switched, for the purpose of reducing a power consumption.
Also, JP 05-289769 A discloses that, for the purpose of reducing a power consumption of a personal digital assistant, a clock frequency is switched according to a clock frequency switching command, and the clock frequency is also switched according to a length of a processing waiting time.
Particularly, in recent tablet mobile terminals of the above-mentioned mobile terminals, a control IC (integrated circuit) is frequently separated from a driver IC. In this configuration, when an image signal is transmitted from the control IC to the driver IC, the electromagnetic waves generated from a flexible printed board have a tendency to increase, and it is conceivable that the electromagnetic waves have no small effect on the wireless communication. As a countermeasure against such electromagnetic waves, a shield member as disclosed in JP 06-037478 A can be added. However, the addition of the member and the addition of man-hour lead to an increase in the manufacturing costs of the terminal.
The present invention has been made in view of the above circumstances, and aims at reducing a wireless communication failure caused by the electromagnetic waves generated from the display device.
According to the present invention, there is provided a display device, including: a driver circuit that is arranged on a display panel, and applies a voltage corresponding to a gradation value to each pixel; a video signal line for transmitting a video signal to the driver circuit; a control signal line for transmitting a signal for controlling a timing at which the video signal is transmitted to the driver circuit; and a video signal control unit that transmits the video signal to the driver circuit through the video signal line and the control signal line, in which a transmission clock frequency at which the video signal control unit transmits the video signal to the driver circuit is different from an external clock frequency at which the video signal control unit receives the video signal from an external.
Also, in the display device according to the present invention, the video signal is transmitted at the transmission clock frequency higher than the external clock frequency.
Also, in the display device according to the present invention, the video signal control unit can transmit a plurality of the video signals corresponding to different display positions to functional portions of the driver circuit corresponding to the plurality of video signals at the same time, respectively.
Also, in the display device according to the present invention, the video signal control unit transmits the respective video signals by using a plurality of the transmission clock frequencies in a plurality of time zones, and the plurality of transmission clock frequencies includes a first transmission clock frequency and a second transmission clock frequency which is an integral multiple of the first transmission clock frequency.
Also, in the display device according to the present invention, the transmission clock frequency is set to a clock frequency that does not interfere with a wireless frequency used for the wireless communication, with respect to the wireless communication unit that conducts an external wireless communication. In this case, the clock frequency that does not interfere with the wireless frequency can be set to a frequency different from an integer multiple and an integral fraction of the wireless frequency.
According to the present invention, there is provided a video display method, including: inputting and storing a video signal at a timing of an external clock signal; transmitting the stored video signal to a driver circuit at a timing of a transmission clock signal; and outputting the transmitted video signal by the driver circuit for display, in which the transmission clock frequency is different from the external clock frequency.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or equivalent elements are denoted by identical reference numerals or symbols, and a repetitive description will be omitted.
The display panel 200 includes gate drivers 220 and source drivers 210. The gate drivers 220 each output a scanning signal which is a timing signal for writing a voltage corresponding to a gradation value to scanning signal lines of pixel transistors within a display region not shown. The source drivers 210 each output a voltage corresponding to the gradation value to each of the pixel transistors at a timing of the scanning signal. Also, the input video signal line 312 can double as the frequency setting signal line 322 in a disable period of the video signal.
The video signal line 510, the source control signal line 520, and the gate control signal line 530 for transmitting the signals to the display panel 200 from the video signal control unit 300 are provided on the flexible printed circuit 500.
As illustrated in
Therefore, according to this embodiment, a clock cycle (or frequency) used for transmission of the video signal to be transmitted by the flexible printed circuit 500 can be selected. Therefore, when the clock cycle is set to a cycle in which no wireless communication fails, the wireless communication failure caused by the electromagnetic wave generated from the display device can be reduced without any addition of components, such as a shield member, associated with changing a structure.
In this embodiment, the video signal is transmitted from the video signal control unit 300 to the display panel 200 with the use of the transmission clock signal of the shorter cycle. Alternatively, the transmission clock signal of the longer cycle can be used. Similarly, in this case, a cycle that allows data for one line in the screen to be transmitted in a period longer than the horizontal synchronizing period cannot be selected.
A second embodiment of the present invention will be described. A configuration of a display device and a system configuration according to the second embodiment are identical with those in the first embodiment except for the configurations of the source drivers 210 and the flexible printed circuit 500, and a repetitive description will be omitted.
The second embodiment will be described with reference to
As illustrated in
As described above, the first video signal to the fourth video signal are the respective parallel signals of 6 bits, and two of the first video signal to the fourth video signal are transmitted at the same time. Therefore, 12 bits in total are transmitted at the same time. Because the input video signal is 24 bits, if the first to fourth video signals are transmitted in the same period as that of the input data signal, a period T21 of the transmission clock signal is set to ½ of a period T20 of the external clock signal, thereby enabling transfer of the same amount of data in the same period.
In this embodiment, two of the four enable data signals are arranged to overlap with each other. However, the distribution of a period during which each enable data signal is high can be appropriately changed so that three or more enable data signals overlap with each other, or none of those enable data signals overlaps with each other.
Therefore, according to this embodiment, a clock cycle (or frequency) used for transmission of the video signal to be transmitted by the flexible printed circuit 500 can be selected. Therefore, when the clock cycle is set to a cycle in which no wireless communication fails, the wireless communication failure caused by the electromagnetic wave generated from the display device can be reduced without any addition of a specific component.
Also, according to this embodiment, because the transfer period is divided, a current consumption can be dispersed, and the deterioration of a power supply voltage caused by a temporal excessive current can be suppressed.
A third embodiment of the present invention will be described. A display device according to the third embodiment is identical with that in the second embodiment except that the first video signal line 512, the second video signal line 514, the third video signal line 516, and the fourth video signal line 518 each of which is the parallel signal line of 6 bits in the second embodiment are each changed to a parallel signal line of 24 bits, and a repetitive description will be omitted.
As illustrated in
A difference from the second embodiment resides in that the first video signal to the fourth video signals are the respective parallel signals of 24 bits, and two enable data signals are transmitted at the same time, and therefore 48 bits in total are transmitted at the same time. Because the input video signal is 24 bits, if the first to fourth video signals are transmitted in the same period as that of the input data signal, a period T31 of the transmission clock signal is set to twice as long as a period T30 of the external clock signal, to thereby enable the same amount of data to be transferred in the same period.
In this embodiment, two of the four enable data signals are arranged to overlap with each other. However, the distribution of a period during which each enable data signal is high can be appropriately changed so that three or more enable data signals overlap with each other, or none of those enable data signals overlaps with each other.
Therefore, according to this embodiment, a clock cycle (or frequency) used for transmission of the video signal to be transmitted by the flexible printed circuit 500 can be selected. Therefore, when the clock cycle is set to a cycle in which no wireless communication fails, the wireless communication failure caused by the electromagnetic wave generated from the display device can be reduced without any addition of a specific component.
Also, because the transfer period is divided, a current consumption can be dispersed, and the deterioration of a power supply voltage caused by a temporal excessive current can be suppressed.
A fourth embodiment of the present invention will be described. A configuration of a display device and a system configuration according to the fourth embodiment are identical with those in the first embodiment, and a repetitive description will be omitted.
In this example, in order to avoid an interference with the wireless communication, a frequency different from an integer multiple or an integral fraction of the wireless frequency used in the wireless communication can be used as the frequency of the transmission clock signal. Also, any one period of the transmission clock, of the periods T41 and T42, is set to an integral multiple of the other period of the transmission clock, to thereby enable noises of the radiated electromagnetic wave to match each other. As a result, the frequency causing the deterioration of the communication sensitivity can be avoided.
In
Therefore, according to this embodiment, a clock cycle (or frequency) used for transmission of the video signal to be transmitted by the flexible printed circuit 500 can be selected. Therefore, when the clock cycle is set to a cycle in which no wireless communication fails, the wireless communication failure caused by the electromagnetic wave generated from the display device can be reduced without any addition of a specific component.
While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims coverall such modifications as fall within the true spirit and scope of the invention.
Number | Date | Country | Kind |
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2011-256016 | Nov 2011 | JP | national |