JP2010019908A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device in which an image signal is surely written. <P>SOLUTION: The any potential for precharge accumulated in a first power supply 10a for precharge to a third power supply 10c for precharge is selected by a first selector switch 30a and a second selector switch 30b based on gradation of an image to be displayed and is precharged to a signal line S1 and a signal line S2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technology of a display device including a precharge power source.

In general, as shown in FIG. 17, a display device that displays a video or an image has a first display before sequentially applying image signals from the signal supply circuits to the signal lines S1 to S3 forming the pixel unit 50. The precharge voltage application switch PRSW1 to the third precharge voltage application switch PRSW3 are turned on to connect the precharge power supply to all signal lines, and the precharge potential held by the precharge power supply is applied to all signal lines. To precharge all signal lines to the same potential.
JP 2003-323160 A

  However, since the precharge is performed using one precharge power source, it is difficult to sufficiently write the image signal when the potential difference between the image signal applied later and the precharge potential is large. was there.

  The present invention has been made in view of the above, and an object thereof is to provide a display device capable of reliably writing an image signal.

  The present invention according to claim 1 is a selection switch for selectively connecting a plurality of precharge power supplies, a signal line to which an image signal is applied from a signal supply circuit, and the precharge power supplies to the signal lines. And a precharge power source selection circuit that controls the selection switch so as to select any one of the precharge power sources.

  According to a second aspect of the present invention, the plurality of precharge power supplies can supply n types (n ≧ 3) of precharge potentials, and each of the precharge power supplies and the signal line are electrically connected. The switch to be controlled is composed of two series switches, and the precharge power source selection circuit includes n or less NAND circuits, n or less NOR circuits, or a combination of n or less NAND circuits and NOR circuits, The gist of the invention is that it is composed of an inverter circuit of

  According to a third aspect of the present invention, the plurality of precharge power supplies can supply n types (n ≧ 3) of precharge potentials, and each of the precharge power supplies and the signal line are electrically connected. The switch to be controlled is composed of one switch, and the precharge power source selection circuit includes 2n or less NAND circuits, 2n or less NOR circuits, or a combination of n or less NAND circuits and NOR circuits, The gist is that it is composed of an inverter circuit.

  The gist of the present invention described in claim 4 is that there are a plurality of the signal lines, and the selection switch connects each of the precharge power supplies to any one of the plurality of signal lines. To do.

  The gist of the present invention described in claim 5 is that the signal supply circuit applies the image signal to the plurality of signal lines.

The present invention according to claim 6, wherein the plurality of precharge power supplies are capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials, The gist of the selection switch is that n switches are connected in series between each precharge power source and the signal line.

The present invention according to claim 7, wherein the plurality of precharge power supplies are capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials, The gist of the selection switch is that Σ2 ^m (m = n → 1) switches are connected between the 2 ⁿ precharge power sources and the signal lines.

  The gist of the present invention described in claim 8 is that the precharge power source selection circuit controls the selection switch based on a gradation of an image displayed in accordance with the image signal.

  The present invention according to claim 9 is characterized in that the precharge power supply selection circuit controls the selection switch based on the potential of the image signal.

  According to a tenth aspect of the present invention, the precharge power supply selection circuit is based on a gradation of an image displayed in accordance with the image signal and a polarity control signal for controlling a voltage polarity of the image signal. The gist is to control the selection switch.

  The gist of the present invention described in claim 11 is that the precharge power source is formed of a thin film transistor.

  The gist of the present invention described in claim 12 is that the selection switch and the precharge power source selection circuit are formed of thin film transistors.

  ADVANTAGE OF THE INVENTION According to this invention, the display apparatus which can write in an image signal reliably can be provided.

  Hereinafter, the present embodiment will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a functional block diagram showing functional blocks of the display device according to the first embodiment. This display device is an active matrix display device, and includes a first precharge power source 10a to a third precharge power source 10c, a signal line S1 to which an image signal is applied from the first signal supply circuit 20a, A signal line S2 to which an image signal is applied from the second signal supply circuit 20b, a first selection switch 30a for selectively connecting the first precharge power supply 10a to the third precharge power supply 10c to the signal line S1, Any of the second selection switch 30b for selectively connecting the first precharge power source 10a to the third precharge power source 10c to the signal line S2 and the first precharge power source 10a to the third precharge power source 10c A first precharge power source selection circuit 40a for controlling the first selection switch 30a to select the first precharge power source 10a to the third precharger. A configuration in which a second pre-charge power supply selection circuit 40b for controlling the second selection switch 30b to select one of the over-di power 10c. The signal line S1 and the signal line S2 form a pixel portion 50 that displays an image.

  Different precharge potentials are stored in the first precharge power supply 10a to the third precharge power supply 10c, and the first precharge power supply selection circuit 40a is connected to the signal line S1 from the first signal supply circuit 20a. Before the image signal is applied to the first selection switch 30a, a selection signal for selecting one of the precharging power supplies is transmitted to the first selection switch 30a. Based on this selection signal, the internal connection of the first selection switch 30a is controlled to be turned on (for example, when a selection signal for selecting the first precharge power supply 10a is transmitted, the A of the first selection switch 30a is When the terminal and the S terminal are connected), the precharge potential stored in the selected precharge power supply is applied to the signal line S1, and an image having a gradation corresponding to the precharge potential is applied. Is displayed on the pixel unit 50.

  On the other hand, the same applies to the signal line S2, and the second precharge power supply selection circuit 40b supplies any precharge power supply before the image signal is applied from the second signal supply circuit 20b to the signal line S2. A selection signal to be selected is transmitted to the second selection switch 30b. When the internal connection of the second selection switch 30b is controlled to be turned on based on this selection signal, the precharge potential stored in the selected precharge power supply is applied to the signal line S2, and this precharge An image having a gradation corresponding to the potential is displayed on the pixel unit 50.

  According to the present embodiment, any one of the precharge potentials stored in the first precharge power source 10a to the third precharge power source 10c is precharged to the signal line S1 and the signal line S2. Thus, it is possible to precharge more flexibly than a conventional display device that performs precharge using only a uniform precharge power source, and thereby the potential difference between the image signal potential applied later and the precharge potential is reduced. It is also possible to do. Accordingly, it is possible to provide a display device capable of reliably writing an image signal. Furthermore, since the time for writing image signals can be shortened, the number of signal selections in the signal supply circuit can be increased. In addition, since the number of DAC circuits and signal supply circuits that supply image signals to the signal supply circuit can be reduced, power consumption can be reduced and the area required for the DAC circuit and signal supply circuit can also be reduced. .

Example 1
An example of the display device according to the first embodiment will be described. FIG. 2 is a circuit diagram showing a circuit configuration of the display device of Example 1 according to the first embodiment. In this display device, the first selection switch 30a described with reference to FIG. 1 includes a first a precharge power supply connection switch PRSW1a for turning on / off the connection between the first precharge power supply 10a and the signal line S1, and the first selection switch 30a. A first b precharge power supply connection switch PRSW1b for turning on / off the connection between the second precharge power supply 10b and the signal line S1, and a first c for turning on / off the connection between the third precharge power supply 10c and the signal line S1. Precharge power supply connection switch PRSW1c and 1a precharge power supply connection switch PRSW1a to 1c precharge power supply connection switch PRSW1c are connected between signal line S1 and each precharge power supply is applied to signal line S1. And a first precharge voltage application switch PRSW1 for controlling the operation.

  Further, in this display device, the second selection switch 30b described with reference to FIG. 1 includes a second a precharge power supply connection switch PRSW2a for turning on / off the connection between the first precharge power supply 10a and the signal line S2. The second precharge power supply connection switch PRSW2b for turning on and off the connection between the second precharge power supply 10b and the signal line S2 and the connection between the third precharge power supply 10c and the signal line S2 are turned on and off. The second c precharge power connection switch PRSW2c, the second a precharge power connection switch PRSW2a to the second c precharge power connection switch PRSW2c, and the signal line S2 are connected to the signal lines S2. And a second precharge voltage application switch PRSW2 that controls application to the .

  Further, this display device outputs the first image signal application switch OSW1 for controlling the image signal output from the first signal supply circuit 20a to be applied to the signal line S1, and the second signal supply circuit 20b. A second image signal application switch OSW2 that controls application of an image signal to the signal line S2.

  FIG. 3 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the first embodiment. The first precharge power supply selection circuit 40a includes two first input terminals INa and second input terminals INb, two first inverter circuits IVa and second inverter circuits IVb, and three first NOR circuits NORa to NORa. The configuration includes a 3NOR circuit NORc and three first output terminals OUTa to third output terminals OUTc. The first output terminal OUTa to the third output terminal OUTc are connected to control the 1a precharge power connection switch PRSW1a to the first c precharge power connection switch PRSW1c shown in FIG.

  Subsequently, the operation of the display device according to the first embodiment will be described with reference to FIGS. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the first NOR circuit NORa, and after being inverted through the first inverter circuit IVa, is input to the second NOR circuit NORb. The value input to the second input terminal INb is input to the first NOR circuit NORa, and after being inverted through the second inverter circuit IVb, is input to the second NOR circuit NORb.

  Then, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the first output terminal OUTa and the third NOR circuit NORc. The second NOR circuit NORb performs a NOR operation process based on each input value, and outputs the process result to the third output terminal OUTc and the third NOR circuit NORc. Then, the third NOR circuit NORc performs a NOR calculation process based on each input value, and outputs the processing result to the second output terminal OUTb.

  With the above operation, the first precharge power supply selection circuit 40a is operated by the first precharge power connection switch PRSW1a to the first c precharge power connection switch PRSW1c based on the digital image signal applied to the signal line S1. An operation of selecting one can be performed. Specifically, when “0” is input to the first input terminal INa and the second input terminal INb (when the image signal has a low gradation), only the first-a precharging power supply connection switch PRSW1a is turned on. When “0” (or “1”) is input to one of the first input terminal INa and the second input terminal INb (when the image signal is a medium gradation), When only the charging power connection switch PRSW1b is controlled to be ON and “1” is input to the first input terminal INa and the second input terminal INb (when the image signal has a high gradation), the first c precharging Only the power connection switch PRSW1c is controlled to be turned on.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1. Specifically, when the image signal has a low gradation, a precharge potential lower than the reference potential is applied to the signal line S1, and when the image signal has a middle gradation, the reference potential precharge potential is applied to the signal line. When the image signal has a high gradation, the precharge potential higher than the reference potential is applied to the signal line S1. Thereafter, the first image signal application switch OSW1 is controlled to be turned on by the control signal OSW, whereby the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first-a precharge power connection switch PRSW1a to the first-c precharge are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of the power supply connection switches PRSW1c is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that precharges using only a uniform precharge power supply. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

(Example 2)
An example of the display device according to the first embodiment will be described. FIG. 4 is a circuit diagram showing a circuit configuration of the display device of Example 2 according to the first embodiment. The display device further includes a fourth precharge power supply 10d. The first selection switch 30a described with reference to FIG. 1 includes a first a precharge power connection switch PRSW1a and a first b precharge power connection switch PRSW1b. A first c precharging power connection switch PRSW1c, a fourth d precharging power connection switch PRSW1d for turning on / off the connection between the fourth precharging power supply 10d and the signal line S1, and a first a precharging power connection A first precharge voltage application switch PRSW1 connected between the switch PRSW1a to the first d precharge power supply connection switch PRSW1d and the signal line S1 to control application of each precharge power supply to the signal line S1. It is configured.

  Further, in this display device, the second selection switch 30b described with reference to FIG. 1 includes a 2a precharge power connection switch PRSW2a, a 2b precharge power connection switch PRSW2b, and a second c precharge power connection. Switch PRSW2c, second d precharge power supply connection switch PRSW2d for turning on and off the connection between the fourth precharge power supply 10d and the signal line S2, and second a precharge power supply connection switches PRSW2a to second d precharge power supply The second precharge voltage application switch PRSW2 is connected between the connection switch PRSW2d and the signal line S2 and controls application of each precharge power source to the signal line S2.

  FIG. 5 is a circuit diagram illustrating a circuit configuration (first example) of the first precharge power supply selection circuit in the display device according to the second embodiment. The first precharge power source selection circuit 40a includes two first input terminals INa and second input terminals INb, two first inverter circuits IVa and second inverter circuits IVb, and four first NOR circuits NORa to NORa. The configuration includes a 4NOR circuit NORd and four first output terminals OUTa to fourth output terminals OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the second embodiment will be described with reference to FIGS. 4 and 5. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the first NOR circuit NORa and the third NOR circuit NORc, and after being inverted through the first inverter circuit IVa, input to the second NOR circuit NORb and the fourth NOR circuit NORd. Is done. The value input to the second input terminal INb is input to the first NOR circuit NORa and the second NOR circuit NORb, and after being inverted through the second inverter circuit IVb, the third NOR circuit NORc and the fourth NOR circuit NORd. Is input.

  Then, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the first output terminal OUTa. The second NOR circuit NORb performs a NOR calculation process based on each input value, and outputs the processing result to the second output terminal OUTb. Further, the third NOR circuit NORc performs a NOR calculation process based on each input value, and outputs the processing result to the third output terminal OUTc. Furthermore, the fourth NOR circuit NORd performs a NOR operation process based on each input value, and outputs the process result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is connected to the first precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d based on the digital image signal applied to the signal line S1. An operation of selecting one can be performed.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1, and the control signal OSW Thus, the first image signal application switch OSW1 is controlled to be turned on, so that the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first-a precharge power connection switch PRSW1a to the first-d precharge are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of the power supply connection switches PRSW1d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that precharges using only a uniform precharge power supply. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

  FIG. 6 is a circuit diagram illustrating a circuit configuration (second example) of the first precharge power supply selection circuit in the display device according to the second embodiment. The first precharge power supply selection circuit 40a includes two first input terminals INa and second input terminals INb, six first inverter circuits IVa to IVf, and four first NAND circuits NANDa to NANDa. The configuration includes a 4 NAND circuit NANDd and four first output terminals OUTa to fourth output terminals OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the second embodiment will be described with reference to FIGS. 4 and 6. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the second NAND circuit NANDb and the fourth NAND circuit NANDd, and after being inverted through the first inverter circuit IVa, input to the first NAND circuit NANDa and the third NAND circuit NANDc. Is done. The value input to the second input terminal INb is input to the third NAND circuit NANDc and the fourth NAND circuit NANDd, and after being inverted through the second inverter circuit IVb, the first NAND circuit NANDa and the second NAND circuit NANDb. Is input.

  Then, the first NAND circuit NANDa performs NAND operation processing based on each input value, inverts the processing result by the third inverter circuit IVc, and outputs the result to the first output terminal OUTa. The second NAND circuit NANDb performs NAND operation processing based on each input value, and inverts the processing result by the fourth inverter circuit IVd, and then outputs the result to the second output terminal OUTb. Further, the third NAND circuit NANDc performs NAND operation processing based on each input value, and after inverting the processing result by the fifth inverter circuit IVe, outputs the result to the third output terminal OUTc. Still further, the fourth NAND circuit NANDd performs NAND operation processing based on each input value, and after inverting the processing result by the sixth inverter circuit IVf, outputs the result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is connected to the first precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d based on the digital image signal applied to the signal line S1. An operation of selecting one can be performed.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1, and the control signal OSW Thus, the first image signal application switch OSW1 is controlled to be turned on, so that the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first-a precharge power connection switch PRSW1a to the first-d precharge are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of the power supply connection switches PRSW1d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that precharges using only a uniform precharge power supply. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

  FIG. 7 is a circuit diagram illustrating a circuit configuration (third example) of the first precharge power supply selection circuit in the display device according to the second embodiment. The first precharge power supply selection circuit 40a includes two first input terminals INa and second input terminals INb, two first inverter circuits IVa and second inverter circuits IVb, two first NAND circuits NANDa, and first input circuits. The configuration includes two NAND circuits NANDb, two first NOR circuits NORa and second NOR circuits NORb, and four first output terminals OUTa to fourth output terminals OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the second embodiment will be described with reference to FIGS. 4 and 7. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the second NAND circuit NANDb and the first NOR circuit NORa, and after being inverted through the first inverter circuit IVa, input to the first NAND circuit NANDa and the second NOR circuit NORb. Is done. The value input to the second input terminal INb is inverted via the second inverter circuit IVb and then input to the first NAND circuit NANDa, the second NAND circuit NANDb, the first NOR circuit NORa, and the second NOR circuit NORb. .

  Then, the first NAND circuit NANDa performs NAND operation processing based on each input value and outputs the processing result to the first output terminal OUTa. The second NAND circuit NANDb performs NAND operation processing based on each input value, and outputs the processing result to the second output terminal OUTb. Further, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the third output terminal OUTc. Furthermore, the second NOR circuit NORb performs a NOR operation process based on each input value, and outputs the process result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is connected to the first precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d based on the digital image signal applied to the signal line S1. An operation of selecting one can be performed.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1, and the control signal OSW Thus, the first image signal application switch OSW1 is controlled to be turned on, so that the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first-a precharge power connection switch PRSW1a to the first-d precharge are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of the power supply connection switches PRSW1d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that precharges using only a uniform precharge power supply. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

  FIG. 8 is a circuit diagram illustrating a circuit configuration (fourth example) of the first precharge power supply selection circuit in the display device according to the second embodiment. The first precharging power supply selection circuit 40a includes three first input terminals INa to INc, five first inverter circuits IVa to fifth inverter circuits IVe, two first NAND circuits NANDa and The configuration includes two NAND circuits NANDb, four first NOR circuits NORa to fourth NOR circuit NORd, and four first output terminals OUTa to fourth output terminal OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the first d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the second embodiment will be described with reference to FIGS. 4 and 8. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. Further, a polarity control signal POL for controlling the polarity of the liquid crystal application voltage when the digital image signal is applied to the signal line S1 is input to the third input terminal INc. The value input to the third input terminal INc is input to the switch SWb and the switch SWd, and after being inverted through the fifth inverter circuit IVe, is input to the switch SWa and the switch SWc. That is, either the switch SWa or the switch SWb is controlled to be turned on by the polarity control signal POL, and either the switch SWc or the switch SWd is controlled to be turned on.

  When the switch SWa and the switch SWc are controlled to be on (the switch SWb and the switch SWd are controlled to be off), the value input to the first input terminal INa is inverted through the first inverter circuit IVa. After being input to the first NOR circuit NORa and the third NOR circuit NORc later, after being inverted through the first inverter circuit IVa and further inverted through the third inverter circuit IVc, the second NOR circuit NORb and the fourth NOR circuit NORd Is input. The value input to the second input terminal INb is inverted via the second inverter circuit IVb and then input to the first NOR circuit NORa and the second NOR circuit NORb and inverted via the second inverter circuit IVb. Then, the signal is further inverted through the fourth inverter circuit IVd and then input to the third NOR circuit NORc and the fourth NOR circuit NORd.

  On the other hand, when the switch SWb and the switch SWd are controlled to be on (the switch SWa and the switch SWc are controlled to be off), the value input to the first input terminal INa is input to the first NOR circuit NORa and the third NOR circuit NORc. In addition, after being inverted through the third inverter circuit IVc, it is input to the second NOR circuit NORb and the fourth NOR circuit NORd. The value input to the second input terminal INb is input to the first NOR circuit NORa and the second NOR circuit NORb, and after being inverted through the fourth inverter circuit IVd, the third NOR circuit NORc and the fourth NOR circuit NORd. Is input.

  Then, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the first output terminal OUTa. The second NOR circuit NORb performs a NOR calculation process based on each input value, and outputs the processing result to the second output terminal OUTb. Further, the third NOR circuit NORc performs a NOR calculation process based on each input value, and outputs the processing result to the third output terminal OUTc. Furthermore, the fourth NOR circuit NORd performs a NOR operation process based on each input value, and outputs the process result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is operated based on the digital image signal and the polarity control signal POL applied to the signal line S1, and the first precharge power connection switch PRSW1a to the first d precharge power supply. An operation of selecting one of the power supply connection switches PRSW1d can be performed.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1, and the control signal OSW Thus, the first image signal application switch OSW1 is controlled to be turned on, so that the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1, the potential of the image signal, and the polarity control signal, the first-a precharge power connection switch Since any one of the PRSW1a to the first d precharge power supply connection switch PRSW1d is selected and precharged, it can be precharged more flexibly than a conventional display device that performs precharge using only a uniform precharge power supply. It becomes possible. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

  In the first and second embodiments, the plurality of precharge power supplies have three or four types of precharge potentials, and the precharge power source selection circuit includes these three or four types of precharge potentials. Although the case where any one is selected has been described, it is not limited to these types. That is, when a plurality of precharge power supplies can supply n types (n ≧ 3) of precharge potentials, there are two or more series switches for controlling conduction between each precharge power supply and the signal line. The first precharge power supply selection circuit 40a is composed of n or fewer NAND circuits, n or fewer NOR circuits, or a combination of n or fewer NAND circuits and NOR circuits, and a plurality of inverter circuits. Any one of n types of precharge potentials may be selected.

  Further, the method of selecting the precharge power source using the polarity control signal POL shown in FIG. 8 is applicable to all examples and embodiments described later.

(Example 3)
An example of the display device according to the first embodiment will be described. FIG. 9 is a circuit diagram showing a circuit configuration of the display device of Example 3 according to the first embodiment. The display device further includes a fourth precharge power supply 10d. The first selection switch 30a described with reference to FIG. 1 includes a first a precharge power connection switch PRSW1a and a first b precharge power connection switch PRSW1b. And a first c precharge power connection switch PRSW1c and a fourth d precharge power connection switch PRSW1d for turning on and off the connection between the fourth precharge power supply 10d and the signal line S1.

  Further, in this display device, the second selection switch 30b described with reference to FIG. 1 includes a 2a precharge power connection switch PRSW2a, a 2b precharge power connection switch PRSW2b, and a second c precharge power connection. The switch PRSW2c and a second d precharge power supply connection switch PRSW2d for turning on / off the connection between the fourth precharge power supply 10d and the signal line S2.

  FIG. 10 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the third embodiment. The first precharge power supply selection circuit 40a includes three first input terminals INa to INc, six first inverter circuits IVa to IVf, and four first NOR circuits NORa to NORth. The configuration includes a 4 NOR circuit NORd, four first NAND circuits NANDa to NAND NAND circuit NANDd, and four first output terminals OUTa to fourth output terminal OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected so as to control the 1a precharge power connection switch PRSW1a to the 1d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the third embodiment will be described with reference to FIGS. 9 and 10. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The precharge signal PRC is input to the third input terminal INc. The value input to the first input terminal INa is input to the first NOR circuit NORa and the third NOR circuit NORc, and after being inverted through the first inverter circuit IVa, input to the second NOR circuit NORb and the fourth NOR circuit NORd. Is done. The value input to the second input terminal INb is input to the first NOR circuit NORa and the second NOR circuit NORb, and after being inverted through the second inverter circuit IVb, the third NOR circuit NORc and the fourth NOR circuit NORd. Is input.

  Then, the first NOR circuit NORa performs a NOR operation process based on each input value, and outputs the processing result to the first NAND circuit NANDa. The second NOR circuit NORb performs a NOR operation process based on each input value, and outputs the process result to the second NAND circuit NANDb. Further, the third NOR circuit NORc performs a NOR operation process based on each input value, and outputs the process result to the third NAND circuit NANDc. Furthermore, the fourth NOR circuit NORd performs a NOR operation process based on each input value, and outputs the process result to the fourth NAND circuit NANDd.

  Thereafter, the first NAND circuit NANDa receives the operation result of the first NOR circuit NORa and the precharge signal PRC, performs NAND operation processing based on each input value, and inverts the processing result by the third inverter circuit IVc. After that, the signal is output to the first output terminal OUTa. The second NAND circuit NANDb receives the operation result of the second NOR circuit NORb and the precharge signal PRC, performs NAND operation processing based on each input value, and inverts the processing result by the fourth inverter circuit IVd. After that, the signal is output to the second output terminal OUTb. Further, the third NAND circuit NANDc receives the operation result of the third NOR circuit NORc and the precharge signal PRC, performs NAND operation processing based on the input values, and inverts the processing result by the fifth inverter circuit IVe. After that, the signal is output to the third output terminal OUTc. Further, the fourth NAND circuit NANDd receives the calculation result of the fourth NOR circuit NORd and the precharge signal PRC, performs NAND calculation processing based on the input values, and the processing result is output by the sixth inverter circuit IVf. After inversion, the signal is output to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is operated based on the digital image signal and the precharge signal PRC applied to the signal line S1, and the first precharge power connection switch PRSW1a to the first d precharge power supply. An operation of selecting one of the power supply connection switches PRSW1d can be performed.

  Finally, the first image signal application switch OSW1 is turned on by the control signal OSW, whereby the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first-a precharge power connection switch PRSW1a to the first-d precharge are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of the power supply connection switches PRSW1d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that precharges using only a uniform precharge power supply. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

  In the third embodiment, a case where a plurality of precharge power supplies have four types of precharge potentials and the precharge power source selection circuit selects one of these four types of precharge potentials will be described. However, it is not limited to only those types. That is, as in the first and second embodiments, when a plurality of precharge power supplies can supply n types (n ≧ 3) of precharge potentials, the continuity between each precharge power supply and the signal line is established. The first precharge power source selection circuit 40a includes 2n or less NAND circuits, 2n or less NOR circuits, or a combination of n or less NAND circuits and NOR circuits. As long as it is composed of a plurality of inverter circuits, any one of n types of precharge potentials can be selected.

Example 4
An example of the display device according to the first embodiment will be described. FIG. 11 is a circuit diagram showing a circuit configuration of the display device of Example 4 according to the first embodiment. The display device further includes a fourth precharge power supply 10d. The first selection switch 30a described with reference to FIG. 1 includes a first a precharge power connection switch PRSW1a and a first b precharge power connection switch PRSW1b. A first c precharging power connection switch PRSW1c, a fourth d precharging power connection switch PRSW1d for turning on / off the connection between the fourth precharging power supply 10d and the signal line S1, and a first a precharging power connection A first precharge voltage application switch PRSW1 connected between the switch PRSW1a to the first d precharge power supply connection switch PRSW1d and the signal line S1 to control the application of each precharge power supply to the signal line S1; 1a precharge power connection switch PRSW1a to 1d Is connected is composed of a second precharge voltage application switch PRSW2 for controlling the power for each of the pre-charge is applied to the signal line S2 between the charging power supply connection switch PRSW1d a signal line S2. The first precharge voltage application switch PRSW1 and the second precharge voltage application switch PRSW2 are controlled to be turned on / off by the precharge signal PRCa or the precharge signal PRCb output from the application switch control circuit 60, respectively. A DAC (Digital Analog Converter) circuit 70 that converts an image signal from a digital signal to an analog signal supplies the image signal to a plurality of signal lines (signal line S1 and signal line S2).

  FIG. 12 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the fourth embodiment. The first precharge power source selection circuit 40a includes two first input terminals INa and second input terminals INb, two first inverter circuits IVa and second inverter circuits IVb, and four first NOR circuits NORa to NORa. The configuration includes a 4NOR circuit NORd and four first output terminals OUTa to fourth output terminals OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the 1d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the fourth embodiment will be described with reference to FIGS. 11 and 12. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 or the signal line S2 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the first NOR circuit NORa and the third NOR circuit NORc, and after being inverted through the first inverter circuit IVa, input to the second NOR circuit NORb and the fourth NOR circuit NORd. Is done. The value input to the second input terminal INb is input to the first NOR circuit NORa and the second NOR circuit NORb, and after being inverted through the second inverter circuit IVb, the third NOR circuit NORc and the fourth NOR circuit NORd. Is input.

  Then, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the first output terminal OUTa. The second NOR circuit NORb performs a NOR calculation process based on each input value, and outputs the processing result to the second output terminal OUTb. Further, the third NOR circuit NORc performs a NOR calculation process based on each input value, and outputs the processing result to the third output terminal OUTc. Furthermore, the fourth NOR circuit NORd performs a NOR operation process based on each input value, and outputs the process result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is operated based on the digital image signal applied to the signal line S1 or the signal line S2, and the first a precharge power connection switch PRSW1a to the first d precharge power supply. An operation of selecting one of the connection switches PRSW1d can be performed.

  Finally, either the first precharge voltage application switch PRSW1 or the second precharge voltage application switch PRSW2 is turned on by the precharge signal PRCa or the precharge signal PRCb output from the application switch control circuit 60. The precharge potential stored in the selected precharge power source is applied to the signal line S1 or the signal line S2, and the first image signal application switch OSW1 and the second image signal application switch OSW2 are controlled to be turned on by the control signal OSW. Thus, the image signals output from the first signal supply circuit 20a and the second signal supply circuit 20b are applied to the signal line S1 and the signal line S2.

  That is, based on the gradation of the image displayed on the pixel unit 50 in accordance with the digital image signal applied to the signal line S1 or the signal line S2 and the potential of the image signal, the first-a precharging power connection switch PRSW1a˜ Since one of the first d precharge power supply connection switches PRSW1d is selected and precharged, it is possible to precharge more flexibly than a conventional display device that performs precharge using only a uniform precharge power supply. Become. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

(Example 5)
An example of the display device according to the first embodiment will be described. FIG. 13 is a circuit diagram showing a circuit configuration of the display device of Example 5 according to the first embodiment. The display device further includes a fourth precharge power supply 10d. The first selection switch 30a described with reference to FIG. 1 includes a first a precharge power connection switch PRSW1a and a first b precharge power connection switch PRSW1b. A first c precharging power connection switch PRSW1c, a fourth d precharging power connection switch PRSW1d for turning on / off the connection between the fourth precharging power supply 10d and the signal line S1, and a first a precharging power connection A first precharge voltage application switch PRSW1 connected between the switch PRSW1a to the first d precharge power supply connection switch PRSW1d and the signal line S1 to control the application of each precharge power supply to the signal line S1; 1a precharge power connection switch PRSW1a to 1d Is connected is composed of a second precharge voltage application switch PRSW2 for controlling the power for each of the pre-charge is applied to the signal line S2 between the charging power supply connection switch PRSW1d a signal line S2. The first precharge voltage application switch PRSW1 and the second precharge voltage application switch PRSW2 are controlled to be turned on / off by the precharge signal PRCa or the precharge signal PRCb output from the first application switch control circuit 60a. The first image signal application switch OSW1 and the second image signal application switch OSW2 are controlled to be turned on / off by the control signal OSWa or the control signal OSWb output from the second application switch control circuit 60b. Further, the first signal supply circuit 20a supplies an image signal to a plurality of signal lines (signal line S1 and signal line S2).

  FIG. 14 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the fifth embodiment. The first precharge power source selection circuit 40a includes two first input terminals INa and second input terminals INb, two first inverter circuits IVa and second inverter circuits IVb, and four first NOR circuits NORa to NORa. The configuration includes a 4NOR circuit NORd and four first output terminals OUTa to fourth output terminals OUTd. The first output terminal OUTa to the fourth output terminal OUTd are connected to control the 1a precharge power connection switch PRSW1a to the 1d precharge power connection switch PRSW1d shown in FIG.

  Subsequently, the operation of the display device according to the fourth embodiment will be described with reference to FIGS. 13 and 14. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 or the signal line S2 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa is input to the first NOR circuit NORa and the third NOR circuit NORc, and after being inverted through the first inverter circuit IVa, input to the second NOR circuit NORb and the fourth NOR circuit NORd. Is done. The value input to the second input terminal INb is input to the first NOR circuit NORa and the second NOR circuit NORb, and after being inverted through the second inverter circuit IVb, the third NOR circuit NORc and the fourth NOR circuit NORd. Is input.

  Then, the first NOR circuit NORa performs a NOR calculation process based on each input value, and outputs the processing result to the first output terminal OUTa. The second NOR circuit NORb performs a NOR calculation process based on each input value, and outputs the processing result to the second output terminal OUTb. Further, the third NOR circuit NORc performs a NOR calculation process based on each input value, and outputs the processing result to the third output terminal OUTc. Furthermore, the fourth NOR circuit NORd performs a NOR operation process based on each input value, and outputs the process result to the fourth output terminal OUTd.

  With the above operation, the first precharge power supply selection circuit 40a is operated based on the digital image signal applied to the signal line S1 or the signal line S2, and the first a precharge power connection switch PRSW1a to the first d precharge power supply. An operation of selecting one of the connection switches PRSW1d can be performed.

  Finally, either the first precharge voltage application switch PRSW1 or the second precharge voltage application switch PRSW2 is controlled to be turned on by the precharge signal PRCa or the precharge signal PRCb output from the first application switch control circuit 60a. As a result, the precharge potential stored in the selected precharge power source is applied to the signal line S1 or the signal line S2. Further, the first image signal application switch OSW1 or the second image signal application switch OSW2 is turned on by the control signal OSWa and the control signal OSWb output from the second application switch control circuit 60b, so that the first signal supply circuit The image signal output from 20a is applied to the signal line S1 or the signal line S2.

  That is, based on the gradation of the image displayed on the pixel unit 50 in accordance with the digital image signal applied to the signal line S1 and the signal line S2 and the potential of the image signal, the first-a precharging power supply connection switch PRSW1a˜ Since one of the first d precharge power supply connection switches PRSW1d is selected and precharged, it is possible to precharge more flexibly than a conventional display device that performs precharge using only a uniform precharge power supply. Become. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided.

[Second Embodiment]
FIG. 15 is a functional block diagram illustrating functional blocks of the display device according to the second embodiment. This display device is an active matrix display device, and includes a first precharge power supply 10a to a fourth precharge power supply 10d, a signal line S1 to which an image signal is applied from the first signal supply circuit 20a, A signal line S2 to which an image signal is applied from the second signal supply circuit 20b and a first precharge power source selection for selectively connecting the first precharge power source 10a to the fourth precharge power source 10d to the signal line S1. And a circuit 40a. The signal line S1 and the signal line S2 form a pixel portion 50 that displays an image.

  The display device includes a first precharge voltage application switch PRSW1 that controls application of the precharge power source selected by the first precharge power source selection circuit 40a to the signal line S1, and the first precharge voltage application switch PRSW1. The first image signal application switch OSW1 for controlling the image signal output from the signal supply circuit 20a to be applied to the signal line S1, and the image signal output from the second signal supply circuit 20b are applied to the signal line S2. And a second image signal application switch OSW2 for controlling this.

  The first precharge power supply selection circuit 40a includes two first input terminals INa and second input terminals INb, four first switches SW11 to SW14, and four first inversion switches SW21 to fourth inversion. A switch SW24, a first inversion switch SW21 and a second inversion switch SW22 are connected in series between the first precharge power source 10a and the signal line S1, and the second precharge power source 10b and the signal line S1 The third inverting switch SW23 and the first switch SW11 are connected in series between the third precharging power supply 10c and the signal line S1, and the second switch SW12 and the fourth inverting switch SW24 are connected in series between the third precharging power supply 10c and the signal line S1. A third switch SW13 and a fourth switch SW14 are connected in series between the fourth precharge power supply 10d and the signal line S1. The first input terminal INa is connected to control the second inverting switch SW22, the first switch SW11, the fourth inverting switch SW24, and the fourth switch SW14, and the second input terminal INb is connected to the first inverting switch SW22. The inverting switch SW21, the third inverting switch SW23, the second switch SW12, and the third switch SW13 are connected to be controlled.

  Next, the operation of the display device in this embodiment will be described. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa controls the second inverting switch SW22, the first switch SW11, the fourth inverting switch SW24, and the fourth switch SW14, and the value input to the second input terminal INb is The first inverting switch SW21, the third inverting switch SW23, the second switch SW12, and the third switch SW13 are controlled.

  That is, the first precharge power supply selection circuit 40a selects one of the first precharge power supply 10a to the fourth precharge power supply 10d based on the digital image signal applied to the signal line S1. Do. Specifically, when “0” is input to the first input terminal INa and the second input terminal INb (when the image signal has a low gradation), only the first precharge power supply 10a is selected, When “1” is input to the first input terminal INa and “0” is input to the second input terminal INb (when the image signal is a medium gradation), only the second precharge power supply 10b is used. When “0” is input to the first input terminal INa and “1” is input to the second input terminal INb (when the image signal has a high gradation), the third precharge power supply 10c is selected. When “1” is input to the first input terminal INa and the second input terminal INb (when the image signal has a higher gradation), only the fourth precharge power supply 10d is selected. It will be.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1. Specifically, when the image signal has a low gradation, a precharge potential lower than the reference potential is applied to the signal line S1, and when the image signal has a middle gradation, the reference potential precharge potential is applied to the signal line. When the image signal has a high gradation, a precharge potential higher than the reference potential is applied to the signal line S1. When the image signal has a higher gradation, a precharge potential higher than the reference potential is applied. It is applied to the signal line S1. Thereafter, the first image signal application switch OSW1 is controlled to be turned on by the control signal OSW, whereby the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first precharge power supply 10a to the fourth precharge power supply are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of 10d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that performs precharge using only a uniform precharge power source. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided. Furthermore, since the time for writing image signals can be shortened, the number of signal selections in the signal supply circuit can be increased. In addition, since the number of DAC circuits and signal supply circuits that supply image signals to the signal supply circuit can be reduced, power consumption can be reduced and the area required for the DAC circuit and signal supply circuit can also be reduced. .

In the present embodiment, a case where a plurality of precharge power supplies have four types of precharge potentials and two switches are connected in series between each precharge power supply and the signal line S1. Although described, it is not limited to four types of precharge power supplies and two switches. That is, when the plurality of precharge power sources are power sources capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials, the first precharge power source selection circuit 40a. However, what is necessary is just to have a configuration in which n switches are connected in series between each of these precharge power supplies and the signal line S1.

[Third Embodiment]
FIG. 16 is a functional block diagram showing functional blocks of a display device according to the third embodiment. This display device is an active matrix display device, and includes a first precharge power supply 10a to a fourth precharge power supply 10d, a signal line S1 to which an image signal is applied from the first signal supply circuit 20a, A signal line S2 to which an image signal is applied from the second signal supply circuit 20b and a first precharge power source selection for selectively connecting the first precharge power source 10a to the fourth precharge power source 10d to the signal line S1. And a circuit 40a. The signal line S1 and the signal line S2 form a pixel portion 50 that displays an image.

  The display device includes a first precharge voltage application switch PRSW1 that controls application of the precharge power source selected by the first precharge power source selection circuit 40a to the signal line S1, and the first precharge voltage application switch PRSW1. The first image signal application switch OSW1 for controlling the image signal output from the signal supply circuit 20a to be applied to the signal line S1, and the image signal output from the second signal supply circuit 20b are applied to the signal line S2. And a second image signal application switch OSW2 for controlling this.

  The first precharge power source selection circuit 40a includes two first input terminals INa and second input terminals INb, three first switches SW11 to SW13, and three first inversion switches SW21 to third inversion. A switch SW23, a first inversion switch SW21 and a second inversion switch SW22 are connected in series between the first precharge power source 10a and the signal line S1, and the second precharge power source 10b and the signal line S1 The first switch SW11 and the second inversion switch SW22 are connected in series between the third precharge power source 10c and the signal line S1, and the third inversion switch SW23 and the third switch SW13 are connected in series between the first switch SW11 and the second inversion switch SW22. A second switch SW12 and a third switch SW13 are connected in series between the fourth precharge power supply 10d and the signal line S1. The first input terminal INa is connected to control the first inverting switch SW21, the first switch SW11, the third inverting switch SW23, and the second switch SW12, and the second input terminal INb is connected to the second input terminal INb. The reversing switch SW22 and the third switch SW13 are connected to be controlled.

  Next, the operation of the display device in this embodiment will be described. When the precharge potential stored in the second precharge power supply 10b is used as a reference potential, a potential lower than the reference potential is stored in the first precharge power supply 10a, and the third precharge power supply 10c. It is assumed that a potential higher than the reference potential is accumulated in the fourth precharge power source 10d and a potential higher than the potential accumulated in the third precharge power source 10c is accumulated.

  First, the most significant bit of the digital image signal applied to the signal line S1 is input to the second input terminal INb, and the next bit is input to the first input terminal INa. The value input to the first input terminal INa controls the first inverting switch SW21, the first switch SW11, the second inverting switch SW22, and the second switch SW12, and the value input to the second input terminal INb is The second inversion switch SW22 and the third switch SW13 are respectively controlled.

  That is, the first precharge power supply selection circuit 40a selects one of the first precharge power supply 10a to the fourth precharge power supply 10d based on the digital image signal applied to the signal line S1. Do. Specifically, when “0” is input to the first input terminal INa and the second input terminal INb (when the image signal has a low gradation), only the first precharge power supply 10a is selected, When “1” is input to the first input terminal INa and “0” is input to the second input terminal INb (when the image signal is a medium gradation), only the second precharge power supply 10b is used. When “0” is input to the first input terminal INa and “1” is input to the second input terminal INb (when the image signal has a high gradation), the third precharge power supply 10c is selected. When “1” is input to the first input terminal INa and the second input terminal INb (when the image signal has a higher gradation), only the fourth precharge power supply 10d is selected. It will be.

  Finally, the first precharge voltage application switch PRSW1 is turned on by the precharge signal PRC, so that the precharge potential accumulated in the selected precharge power supply is applied to the signal line S1. Specifically, when the image signal has a low gradation, a precharge potential lower than the reference potential is applied to the signal line S1, and when the image signal has a middle gradation, the reference potential precharge potential is applied to the signal line. When the image signal has a high gradation, a precharge potential higher than the reference potential is applied to the signal line S1. When the image signal has a higher gradation, a precharge potential higher than the reference potential is applied. It is applied to the signal line S1. Thereafter, the first image signal application switch OSW1 is controlled to be turned on by the control signal OSW, whereby the image signal output from the first signal supply circuit 20a is applied to the signal line S1.

  That is, the first precharge power supply 10a to the fourth precharge power supply are based on the gradation of the image displayed on the pixel unit 50 according to the digital image signal applied to the signal line S1 and the potential of the image signal. Since any one of 10d is selected and precharged, it becomes possible to precharge more flexibly than a conventional display device that performs precharge using only a uniform precharge power source. In addition, since the precharge is performed using a potential closer to the gradation of the image signal, the potential difference between the applied image signal potential and the precharge potential can be reduced, and a display device capable of writing the image signal reliably is provided. Can be provided. Furthermore, since the time for writing image signals can be shortened, the number of signal selections in the signal supply circuit can be increased. In addition, since the number of DAC circuits and signal supply circuits that supply image signals to the signal supply circuit can be reduced, power consumption can be reduced and the area required for the DAC circuit and signal supply circuit can also be reduced. .

In the present embodiment, a case where a plurality of precharge power supplies have four types of precharge potentials and two switches are connected in series between each precharge power supply and the signal line S1. Although described, it is not limited to four types of precharge power supplies and two switches. That is, when the plurality of precharge power sources are power sources capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials, the first precharge power source selection circuit 40a. However, what is necessary is just to have a configuration in which Σ2 ^m (m = n → 1) switches are connected between 2 ⁿ precharge power supplies and the signal line S1.

  Finally, it is assumed that the precharge power supply, the selection switch, and the precharge power supply selection circuit described in all of the above embodiments are formed of thin film transistors (TFTs).

It is a functional block diagram which shows the functional block of the display apparatus which concerns on 1st Embodiment. It is a circuit diagram which shows the circuit structure of the display apparatus of Example 1 which concerns on 1st Embodiment. FIG. 3 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the first embodiment. It is a circuit diagram which shows the circuit structure of the display apparatus of Example 2 which concerns on 1st Embodiment. FIG. 10 is a circuit diagram illustrating a circuit configuration (first example) of a first precharge power supply selection circuit in the display device according to the second embodiment. FIG. 10 is a circuit diagram illustrating a circuit configuration (second example) of a first precharge power supply selection circuit in the display device according to the second embodiment. FIG. 11 is a circuit diagram illustrating a circuit configuration (third example) of a first precharge power supply selection circuit in the display device according to the second embodiment. FIG. 11 is a circuit diagram illustrating a circuit configuration (fourth example) of a first precharge power supply selection circuit in the display device according to the second embodiment. It is a circuit diagram which shows the circuit structure of the display apparatus of Example 3 which concerns on 1st Embodiment. FIG. 10 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the third embodiment. It is a circuit diagram which shows the circuit structure of the display apparatus of Example 4 which concerns on 1st Embodiment. FIG. 10 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the fourth embodiment. It is a circuit diagram which shows the circuit structure of the display apparatus of Example 5 which concerns on 1st Embodiment. FIG. 10 is a circuit diagram illustrating a circuit configuration of a first precharge power supply selection circuit in the display device according to the fifth embodiment. It is a functional block diagram which shows the functional block of the display apparatus which concerns on 2nd Embodiment. It is a functional block diagram which shows the functional block of the display apparatus which concerns on 3rd Embodiment. It is a block diagram which shows the structure of the signal line vicinity in the conventional display apparatus.

Explanation of symbols

INa to INc: First to third input terminals IVa to IVf: First to sixth inverter circuits NANDa to NANDd: First to fourth NAND circuits NORa to NORd: First to fourth NOR circuits OUTa to OUTd: First to fourth 4 output terminals S1 to S3 ... signal lines SWa to SWd, SW11 to 14 ... switch SW21 to 24 ... inversion switch OSW1 to OSW2 ... first to second image signal application switches PRSW1 to PRSW3 ... first to third precharge voltage application Switches PRSW1a to PRSW1d ... 1a to 1d precharge power connection switches PRSW2a to PRSW2d ... 2a to 2d precharge power connection switches 10a to 10d ... 1st to 4th precharge power supplies 20a to 20b ... 1st ~ Second signal supply circuit 30a ~ 30b ... first to second selection switches 0A～40b ... the first and second pre-charge power supply selection circuit 50 ... pixel portion 60 ... application switch control circuit 60A～60b ... first to the second application switch control circuit 70 ... DAC circuit

Claims (12)

A plurality of precharge power supplies;
A signal line to which an image signal is applied from a signal supply circuit;
A selection switch for selectively connecting each precharge power source to the signal line;
A precharge power supply selection circuit for controlling the selection switch to select one of the precharge power supplies;
A display device comprising: The plurality of precharge power sources can supply n types (n ≧ 3) of precharge potentials, and two series switches are used to control conduction between the precharge power sources and the signal lines. Configured,
The precharge power supply selection circuit includes:
The display device according to claim 1, comprising: n or less NAND circuits, n or less NOR circuits, or a combination of n or less NAND circuits and NOR circuits, and a plurality of inverter circuits. . The plurality of precharge power sources can supply n types (n ≧ 3) of precharge potentials, and a switch for controlling conduction between each of the precharge power sources and the signal line is constituted by one switch. And
The precharge power supply selection circuit includes:
2. The display device according to claim 1, comprising: 2n or less NAND circuits, 2n or less NOR circuits, or a combination of n or less NAND circuits and NOR circuits, and a plurality of inverter circuits. . The signal lines are plural,
4. The display device according to claim 1, wherein the selection switch connects each of the precharge power supplies to any one of the plurality of signal lines. 5. The signal supply circuit includes:
The display device according to claim 4, wherein the image signal is applied to the plurality of signal lines. The plurality of precharge power sources are power sources capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials,
The selection switch is
2. The display device according to claim 1, wherein n switches are connected in series between each precharge power source and the signal line. The plurality of precharge power sources are power sources capable of supplying (2 ⁽ⁿ⁻¹⁾ +1) to 2 ⁿ types (n ≧ 2) of precharge potentials,
The selection switch is
2. The display device according to claim 1, wherein Σ2 ^m (m = n → 1) switches are connected between the 2 ⁿ precharge power supplies and the signal lines. The precharge power supply selection circuit includes:
The display device according to claim 1, wherein the selection switch is controlled based on a gradation of an image displayed in accordance with the image signal. The precharge power supply selection circuit includes:
The display device according to claim 1, wherein the selection switch is controlled based on a potential of the image signal. The precharge power supply selection circuit includes:
6. The selection switch according to claim 1, wherein the selection switch is controlled based on a gradation of an image displayed in accordance with the image signal and a polarity control signal for controlling a voltage polarity of the image signal. Item 1. A display device according to item 1. The power supply for precharging is
The display device according to claim 1, wherein the display device is formed of a thin film transistor. The selection switch and the precharge power supply selection circuit are:
The display device according to claim 1, wherein the display device is formed of a thin film transistor.

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