DRIVE CIRCUIT AND DISPLAY DEVICE

Abstract

[Object] To realize a drive circuit where settling time (stabilization time) is shortened, without incurring marked increase in electric current consumed and marked increase in manufacturing costs.

[Solution] A source drive circuit (1) has a digital gradient input converter (2) that converts gradient values of multiple image data (D1 through Dn) that are gradient 1 into multiple gradient values, where the number of the multiple source amps (AM1 through AMn) to which a gradient reference voltage (V1) corresponding to gradient 1 is supplied, is reduced, and supplied to a DAC circuit (23).

Claims

1. A drive circuit comprising: a plurality of source amps; a gradient reference voltage generating circuit that generates M (where M is a natural number of 2 or greater) different gradient reference voltages; and a digital/analog conversion circuit that selects one of the M gradient reference voltages supplied from the gradient reference voltage generating circuit via each of M bus lines, based on each of input gradient values, and supplies to each of the plurality of source amps, wherein a gradient input converter is provided that converts the plurality of gradient values of a plurality of image data that are the same value into a plurality of gradient values, where the number of the plurality of source amps to which a gradient reference voltage corresponding to the plurality of gradient values that are the same value is supplied, is reduced, and supplies to the digital/analog conversion circuit.

2. The drive circuit according to claim 1, wherein the gradient input converter converts at least part of the plurality of gradient values of a plurality of image data that are the same value to a gradient value that is one higher or a gradient value that is one lower.

3. The drive circuit according to claim 1, wherein the gradient input converter performs the conversion only in a first case where the plurality of gradient values of a plurality of image data that are the same value are a gradient value that is N (where N is a natural number of 1 or greater and 3 and smaller) below a greatest gradient value or greater, or the greatest gradient value or smaller, and in a second case where the plurality of gradient values of a plurality of image data that are the same value are a gradient value that is the smallest gradient value or greater, or N above a smallest gradient value or smaller.

4. The drive circuit according to claim 1, wherein the gradient input converter only performs the conversion in a case where a difference between the plurality of gradient values of a plurality of image data that are the same value and a plurality of gradient values of a plurality of image data supplied immediately prior is a predetermined value or greater.

5. The drive circuit according to claim 1, wherein an adjustment value for deciding a magnitude of conversion of the plurality of gradient values of a plurality of image data that are the same value is set in each of the plurality of source amps at the gradient input converter, and wherein, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is the smallest gradient value or greater and the greatest gradient value or smaller, each of the plurality of gradient values of a plurality of image data that are the same value is converted by an amount corresponding to the adjustment value.

6. The drive circuit according to claim 1, wherein the gradient input converter has a plurality of registers, wherein an adjustment value for deciding the magnitude of conversion of the plurality of gradient values of a plurality of image data that are the same value is set by each of the setting values of the plurality of registers, and wherein, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is the smallest gradient value or greater and the greatest gradient value or smaller, each of the plurality of gradient values of a plurality of image data that are the same value is converted by an amount corresponding to the adjustment value.

7. The drive circuit according to claim 1, wherein the gradient input converter has a random number generator, wherein an adjustment value for deciding the magnitude of conversion of the plurality of gradient values of a plurality of image data that are the same value is set by a random number generated by the random number generator, and wherein, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is the smallest gradient value or greater and the greatest gradient value or smaller, each of the plurality of gradient values of a plurality of image data that are the same value is converted by an amount corresponding to the adjustment value.

8. The drive circuit according to claim 1, wherein an adjustment value for deciding the magnitude of conversion of the plurality of gradient values of a plurality of image data that are the same value is set by the gradient input converter performing dithering processing on each pixel region of a predetermined size configured of part of the plurality of pixels that display the plurality of image data, and wherein, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is the smallest gradient value or greater and the greatest gradient value or smaller, each of the plurality of gradient values of a plurality of image data that are the same value is converted by an amount corresponding to the adjustment value.

9. The drive circuit according to claim 8, wherein the dithering processing includes first dithering processing that is dithering processing performed on image data of odd frames in the plurality of image data, and second dithering processing that is dithering processing performed on image data of even frames in the plurality of image data, wherein the first dithering processing and the second dithering processing are different.

10. The drive circuit according to claim 5, wherein, at the gradient input converter, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is smaller than the smallest gradient value or greater than the greatest gradient value, each of the plurality of gradient values of a plurality of image data that are the same value is output without change, without being converted by an amount corresponding to the adjustment value.

11. The drive circuit according to claim 5, wherein, at the gradient input converter, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is smaller than the smallest gradient value, the smallest gradient value is output, and wherein, in a case where a value obtained by adding the adjustment value and the plurality of gradient values of a plurality of image data that are the same value is greater than the greatest gradient value, the greatest gradient value is output.

12. A display device comprising: the drive circuit according to claim 1; and a display panel.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a diagram illustrating the overall configuration of a source drive circuit according to a first embodiment of the present invention.

[0035] FIG. 2 is a diagram illustrating the overall configuration of a display device having the source drive circuit illustrated in FIG. 1.

[0036] FIG. 3 is a diagram illustrating a digital gradient input converter provided to a source drive circuit according to a second embodiment of the present invention.

[0037] FIGS. 4(a) is a diagram illustrating a digital gradient input converter provided to a source drive circuit according to a third embodiment of the present invention, and (b) is a diagram illustrating a random number generator provided to the digital gradient input converter.

[0038] FIG. 5 is a diagram illustrating a digital gradient input converter provided to another source drive circuit according to the third embodiment of the present invention.

[0039] FIG. 6(a) is a diagram illustrating a digital gradient input converter and DAC circuit provided to a source drive circuit according to a fourth embodiment of the present invention, (b) is a diagram illustrating an example of dithering processing performed at the digital gradient input converter, and (c) is a diagram illustrating another example of dithering processing performed at the digital gradient input converter.

[0040] FIG. 7 is a diagram illustrating a conventional source drive circuit that performs multiplexed driving where multiple source lines are driven by time division.

[0041] FIG. 8 is a diagram for describing problems of the conventional source drive circuit illustrated in FIG. 7.

[0042] FIG. 9 is a diagram for describing a case where the problem becomes markedly pronounced in the conventional source drive circuit.

[0043] FIG. 10 is a diagram illustrating a schematic configuration of a conventional source drive circuit disclosed in PTL 1.

DESCRIPTION OF EMBODIMENTS

[0044] Embodiments of the present invention will be described below with reference to FIG. 1 through FIG. 6. Hereinafter, configuration that have the same functions as a configuration described in a particular embodiment may be denoted by the same symbols, and description thereof omitted, for the sake of convenience in description.

First Embodiment

[0045] A first embodiment of the present invention will be described below with reference to FIG. 1 and FIG. 2.

(Source Drive Circuit 1)

[0046] FIG. 1 is a diagram illustrating the overall configuration of a source drive circuit 1 according to the first embodiment of the present invention.

[0047] It can be seen from FIG. 1 that the source drive circuit 1 (drive circuit) includes a digital gradient input converter 2 (gradient input converter), multiple source amps AM1 through AMn, a gamma circuit 24 that outputs gradient reference voltages V0 through V255, a DAC circuit 23 that selects one of a 256 count of gradient reference voltages V0 through V255 supplied via a 256 count of reference power source bus lines BL1 through BL256 from the gamma circuit 24 based on each of gradient values from input image data D1 through Dn, and supplies to each of the multiple source amps AM1 through AMn, and a demultiplexer 25 that distributes voltage output from each of output nodes Q1 through Qn of the multiple source amps AM1 through AMn to source lines S1 through Sr, in time division based on select signals SEL1 through SEL18. The i, j, k, l, n, and r in the drawing are natural numbers, satisfying the relation of i<j<k<l<n<r.

[0048] Note that the multiple source amps AM1 through AMn, the DAC circuit 23, the gamma circuit 24, and the demultiplexer 25 are of the same configuration as the configuration provided to the conventional source drive circuit illustrated in FIG. 7, and the configurations thereof have already been described above, so description here will be omitted, and the digital gradient input converter 2 along will be described.

[0049] Although the source drive circuit 1 including the demultiplexer 25 is described as one example in the present embodiment, but it is needless to say that the present invention is applicable to a source drive circuit that does not have the demultiplexer 25.

(About Configuration of Digital Gradient Input Converter 2)

[0050] In a case of the conventional source drive circuit that does not have the digital gradient input converter 2, and in a case where all of each of the gradient values of image data D1 through Dn are gradient 1 (equivalent to gradient reference voltage VI) for example, all of the input nodes U1 through Un of the n count of source amps AM1 through AMn are electrically connected to reference power source bus line BL2 where the gradient reference voltage V1 is output, so the load on the reference power source bus line BL2 is great. Accordingly, a source drive circuit where the settling time (stabilization time) is short cannot be realized.

[0051] On the other hand, the source drive circuit 1 according to the present embodiment has the digital gradient input converter 2 that converts the multiple gradient values ox the multiple image data D1 through Dn that are of the same value (in the case in FIG. 1, gradient 1 (equivalent to gradient reference voltage V1)) into multiple gradient values, where the number of the multiple source amps AM1 through AMn to which the gradient reference value (in the case in FIG. 1, gradient reference voltage V1) corresponding to the multiple gradient values that are the same value is supplied, is reduced, and supplied to the DAC circuit 23.

[0052] Although an example will be described in the present embodiment of a case where, at the digital gradient input converter 2, adjustment values that decide the magnitude of conversion of the multiple gradient values of the multiple image data D1 through Dn are set as 0, 1, +1, . . . in order from the left edge in the drawing, and the adjustment values for each of the multiple source amps AM1 through AMn corresponding to each of the multiple image data D1 through Dn are fixed, but this is not restrictive. Note however, that in a case where the gradient value of the image data D1 through Dn is gradient 0 that is the smallest gradient value, there is need for settings where 0 or +1, that is other than 1, is set so as to be applied as an adjustment value, and in a case where gradient value of the image data D1 through Dn is gradient 255 that is the largest gradient value, there is need for settings where 0 or 1, that is other than +1, is set so as to be applied as an adjustment value. Accordingly, in the digital gradient input converter 2, the adjustment values for each of the multiple source amps AMI through AMn corresponding to the multiple image data D1 through Dn are fixed in a case where the gradient values of the image data D1 through Dn input to the digital gradient input converter 2 are other than the smallest gradient value (gradient 0) and the greatest gradient value (gradient 255), i.e., gradient 1 through gradient 254. Note that the above adjustment values are an example and are not restrictive, and the order, magnitude, and so forth of adjustment value can be set as appropriate. Although an example is described in the present embodiment as a case where 0, 1, and +1 are applied to gradient values of the image data D1 through Dn input to the digital gradient input converter 2 as adjustment values and converted to a gradient value that is one hither or a gradient value that is one lower, this is not restrictive, and the magnitude of adjustment values can be set as appropriate, so as to convert to a gradient value one higher or a gradient value one lower.

[0053] Specifically, the output E1 through En of the digital gradient input converter 2 is output E1=gradient 1 (equivalent to gradient reference voltage V1), output E2=gradient 0 (equivalent to gradient reference voltage V0), output E3=gradient 2 (equivalent to gradient reference voltage V2) . . . output En-2=gradient 1 (equivalent to gradient reference voltage V1), output En-1=gradient 0 (equivalent to gradient reference voltage V0), and output En=gradient 2 (equivalent to gradient reference voltage V2).

[0054] Thus, the digital gradient input converter 2 can reduce the number of source amps AM1 through AMn electrically connected to the reference power source bus line BL2 where the gradient reference voltage V1 is output, by performing fixed computation (+1 or 1) on image data D2, D3, . . . Dn-1, Dn decided beforehand out of the input multiple image data D1 through Dn. Accordingly, the load on reference power source bus line BL2 can be suppressed from becoming great, and a source drive circuit 1 with short settling time (stabilization time) can be realized.

[0055] In the case of the digital gradient input converter 2, the range of adjustment values is 1 to +1 which is relatively small, and is a level of converting the gradient values of the image data D1 through Dn to one gradient value higher or one gradient value lower, so deterioration in image quality is not great. Accordingly, an example has been described in the present embodiment regarding a case where a decided adjustment value is always applied to each of all image data D1 through Dn regardless of the type of image data D1 through Dn, but this is not restrictive.

[0056] Note that an arrangement may be made in order to suppress deterioration of image quality due to conversion of gradient values at the digital gradient input converter 2, where decided adjustment values are applied only in a case where the gradient values of the image data D1 through Dn input to the digital gradient input converter 2 are in a particular range. For example, an arrangement may be made where adjustment values are applied only in a case where the gradient values of the image data D1 through Dn input to the digital gradient input converter 2 are in a particular range where difference in gradient change over time might be great. For example, adjustment values may be applied only in a case where the gradient values are in a particular range such as, if expressed in eight bits, several gradients from gradient 0 (e.g., gradient 0, gradient 1, and gradient 2, if three gradients from the bottom), and several gradients from gradient 255 (e.g., gradient 255, gradient 254, and gradient 253, if three gradients from the top).

[0057] Thus, in a case of having a configuration where adjustment values are applied only in a case where the gradient values of the image data D1 through Dn input to the digital gradient input converter 2 are in a particular range, a separate determining circuit that is omitted from illustration needs to be provided.

[0058] For example, a determining circuit for gradient 0, gradient 1, gradient 2, gradient 253, gradient 254, and gradient 255 (top/bottom three gradients) can be made having a configuration of comparing the higher order six bits of the input image data D1 through Dn with 000000 and 111111, whereby the input image data D1 through Dn having gradient values that are the top/bottom three gradients can be easily determined.

[0059] Note that in the present embodiment, application of adjustment values decided for each of the image data D1 through Dn is performed using a lookup table that is omitted from illustration. When setting the aforementioned lookup table, consideration needs to be given so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 0 which is near the smallest gradient value, since this would result in underflow of gradient values, and so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 255 which is near the greatest gradient value, since this would result in overflow of gradient values.

[0060] Although an example has been described in the present embodiment regarding a case where the gradients of the image data D1 through Dn are 256 gradients, this is not restrictive, and the gradients of the image data D1 through Dn may be 512 gradients, 1024 gradients, or the like, for example.

(Display Device 10)

[0061] FIG. 2 is a diagram illustrating the overall configuration of a display device 10 including the source drive circuit 1 illustrated in FIG. 1.

[0062] The display device 10 includes the source drive circuit 1, a gate drive circuit 3, and a display panel 4. Output signals from the source drive circuit 1 are supplied to the display panel 4 via source lines S1 through Sr, output signals from the gate drive circuit 3 are supplied to the display panel 4 via gate lines G1 through Gm, and display is performed at the display panel 4.

[0063] The display panel 4 may be, for example, a liquid crystal display panel, an organic EL (Electro Luminescence: electroluminescence) panel having OLED (Organic Light Emitting Diode: organic light-emitting diodes), or the like.

[0064] The display device 10 has the source drive circuit 1 where the settling time (stabilization time) has been shortened as described above, so insufficient gradients in display, display noise, uneven display, and so forth, can be suppressed.

Second Embodiment

[0065] A second embodiment of the present invention will be described with reference to FIG. 3. For the sake of convenience, members having the same functions as the members described in the first embodiment above are denoted with the same symbols, and description thereof will not be repeated.

[0066] FIG. 3 is a diagram illustrating a digital gradient input converter 2a provided to a source drive circuit according to the second embodiment.

[0067] As illustrated in FIG. 3, the digital gradient input converter 2a (gradient input converter) has multiple registers R0, R1 . . . Rn.

[0068] Appropriately setting the multiple registers R0, R1 . . . Rn to the respective setting values, and providing adders AD1 through ADn, enables the adjustment values that decide the magnitude of conversion of the multiple gradient values of the multiple image data D1 through Dn to be, for example, 0, 1. +1 . . . . in order from the left edge in the drawing, at the digital gradient input converter 2a, in the same way as in the first embodiment described above.

[0069] That is to say, the setting value of a register that needs an adjustment value of 0, the setting value of a register that needs an adjustment value of +1, and the setting value of a register that needs an adjustment value of 1, are each different. Note that the setting value of a register that needs an adjustment value of 1 can be applied with a two's complement of the setting value of a register that needs an adjustment value of +1.

[0070] Outputs E1 through En of the digital gradient input converter 2a are gradient values obtained by the gradient values of each of the image data D1 through Dn being added with the adjustment values defined by the setting values of each of the registers R0, R1 . . . Rn by each of the adders AD1 through ADn.

[0071] Note that in this embodiment as well, consideration needs to be given so that adjustment values are not applied In a case where the gradient values of the image data D1 through Dn are near gradient 0 which is near the smallest gradient value, since this would result in underflow of gradient values, and so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 255 which is near the greatest gradient value, since this would result in overflow of gradient values, in the same way as in the first embodiment.

[0072] Accordingly, in the present embodiment, an arrangement may be made where, in a case where the gradient values obtained by the gradient values of each of the image data D1 through Dn being added with adjustment values defined by the setting values of each of the registers R0, R1 . . . Rn, fall below gradient 0 or exceed gradient 255, the gradient values of the input image data D1 through Dn are output without change, or an arrangement may be made of fixing to gradient 0 in a case of falling below gradient 0 and fixing to gradient 255 in a case of exceeding gradient 255, as measures to deal with underflow of gradient values and overflow of gradient values.

[0073] The load on a particular reference power source bus line can be suppressed from being great in the source drive circuit having the digital gradient input converter 2a, so settling time (stabilization time) can be shortened.

[0074] Note that in the present embodiment, an example has been described regarding where one adder AD1 through ADn and one register R0, R1 . . . Rn is provided for one image data D1 through Dn in the digital gradient input converter 2a, as illustrated in FIG. 3, but this is not restrictive, and a configuration may be made where the number of adders and registers is only one to a few, that is smaller than the number of input image data D1 through Dn, with the input image data D1 through Dn being each sequentially processed, for example.

Third Embodiment

[0075] A third embodiment of the present invention will be described with reference to FIG. 4 and FIG. 5. For the sake of convenience, members having the same functions as the members described in the first embodiment above are denoted with the same symbols, and description thereof will not be repeated.

[0076] (a) in FIG. 4 is a diagram illustrating a digital gradient input converter 2b provided to a source drive circuit according to the third embodiment, and FIG. 4(b) is a diagram illustrating a random number generator 5 provided to the digital gradient input converter 2b.

[0077] 1s and 0s, that are 1-bit random numbers generated at the random number generator 5, are output from outputs H1 through Hn of the random number generator 5 as illustrated in (b) in FIG. 4. Although an example will be described in the present embodiment regarding a case where 1-bit random numbers are used, this is not restrictive.

[0078] The digital gradient input converter 2b has the random number generator 5 and adders AD1 through ADn as illustrated in (a) in FIG. 4, with the i-bit random numbers output from the respective outputs H1 through Hn of the random number generator 5 being supplied to each of the adders AD1 through ADn.

[0079] Note that although an example is described in the present embodiment regarding an example where the digital gradient input converter 2b is provided with one adders AD1 through ADn and one random number generator 5 output H1 through Hn for one image data D1 through Dn, as illustrated in (a) in FIG. 4, this is not restrictive, and a configuration may be made where the number of adders and outputs of the random number generator 5 is only one to a few, that is smaller than the number of input image data D1 through Dn, with the input image data D1 through Dn being each sequentially processed.

[0080] Outputs F1 through Fn of the digital gradient input converter 2b are gradient values obtained by the gradient values of each of the image data D1 through Dn being added with the 1-bit random numbers output from the respective outputs H1 through Hn of the random number generator 5 by each of the adders AD1 through ADn.

[0081] Note that the digital gradient input converter 2b uses 1-bit random numbers, so the adjustment values that decide the magnitude of conversion of the multiple gradient values of the multiple image data D1 through Dn are 0 and +1, but this is not restrictive, and for example, the breadth of adjustment values can be widened by using 2-bit random numbers.

[0082] Also, the digital gradient input converter 2b uses random numbers and accordingly the configuration is one where the above adjustment values are not fixed for each of the multiple source amps AM1 through AMn (omitted from illustration) corresponding to each of the multiple image data D1 through Dn.

[0083] Note that in this embodiment as well, consideration needs to be given so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 0 which is near the smallest gradient value, since this would result in underflow of gradient values, and so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 255 which is near the greatest gradient value, since this would result in overflow of gradient values, in the same way as in the first embodiment.

[0084] Accordingly, in the present embodiment, an arrangement may be made where, in a case where the gradient values obtained by the gradient values of each of the image data D1 through Dn being added with the outputs H1 through Hn of the random number generator 5, fall below gradient 0 or exceed gradient 255, the gradient values of the input image data D1 through Dn are output without change, or an arrangement may be made of fixing to gradient 0 in a case of falling below gradient 0 and fixing to gradient 255 in a case of exceeding gradient 255, as measures to deal with underflow of gradient values and overflow of gradient values.

[0085] The load on a particular reference power source bus line can be suppressed from being great in the source drive circuit having the digital gradient input converter 2b, so settling time (stabilization time) can be shortened.

[0086] FIG. 5 is a diagram illustrating a digital gradient input converter 2c provided to another source drive circuit according to the third embodiment.

[0087] In the case of the above-described digital gradient input converter 2b, the configuration is such that random numbers output from the random number generator 5 are always applied as adjustment values for each of all image data D1 through Dn, regardless of the type of the image data D1 through Dn, but in the case of the digital gradient input converter 2c illustrated in FIG. 5, the configuration is such that random numbers output from the random number-generator 5 are applied as adjustment values only in a case where certain conditions are satisfied.

[0088] In the digital gradient input converter 2c, the configuration is such that the certain conditions are that the difference in display gradient is checked between the previous line and the current line, and whether or not to apply random numbers output from the random number generator 5 as adjustment values is decided based on the results thereof, as illustrated in FIG. 5.

[0089] Checking the difference in gradient ( ) gradient value between the previous line and the current line enables the magnitude in potential change among lines to be checked. For example, a certain threshold value may be decided, within random numbers output from the random number generator 5 being applied as adjustment values in a case where the difference in gradients exceeds the threshold value, and adjustment is not performed in a case of not exceeding the threshold value, which is to say that 0 is applied as an adjustment value. It is more preferable for the above threshold value to be settable to an optional value.

[0090] According to the above configuration in a case where the different in gradients is small, the input gradient can be output without change.

[0091] Note that examples of checking the difference in gradient (gradient value) between the previous line an current line include, for example, a method of obtaining the difference between the same source output for each data, a method where the difference is obtained between average values of the entire line or each predetermined region, but this is not restrictive.

[0092] The load on a particular reference power source bus line can be suppressed from being great in the source drive circuit having the digital gradient input converter 2c when particular image data, regarding which the load on a particular reference power source bus line can be predicted to be great, has been input, so settling time (stabilization time) can be shortened.

Fourth Embodiment

[0093] A fourth embodiment of the present invention will be described with reference to FIG. 6. For the sake of convenience, members having the same functions as the members described in the first embodiment above are denoted with the same symbols, and description thereof will not be repeated.

[0094] (a) in FIG. 6 is a diagram illustrating a digital gradient input converter 2d provided to a source drive circuit and DAC circuit 23 according to the fourth embodiment. FIG. 6(b) is a diagram illustrating an example of dithering processing performed at the digital gradient input converter 2d, and (c) in FIG. 6 is a diagram illustrating another example of dithering processing performed at the digital gradient input converter 2d.

[0095] Dithering processing is performed at the digital gradient input converter 2d illustrated in (a) in FIG. 6. Dithering processing means a technique where slight (artificial) noise is intentionally applied to input gradient data, thereby smoothing boundary portions and suppressing cyclicity of error or the like.

[0096] Performing such dithering processing yields effects that quasi-gradients appear to the human eye, as compared with simple image processing like rounding (rounding up, rounding down, rounding off), for example.

[0097] While there are various techniques for selecting gradients and layouts in dithering processing, these will not be described in detail here.

[0098] The load on a particular reference power source bus line can be suppressed from being great in the present embodiment by applying the digital gradient input converter 2d that performs dithering processing, and visually good image quality can be obtained as well.

[0099] An example of dithering processing that can be performed at the digital gradient input converter 2d will be described below with reference to FIGS. 6(b) and (c) in FIG. 6. One screen displaying one image on a display panel of electronic equipment 11 such as a smartphone having a display device or the like, is divided into regions that are 22 pixel regions, for example, as illustrated in FIG. 6(b). Gradient values of one image data D1 through Dn are given to each 22 pixel region.

[0100] Four types of noise corresponding to the lower order two bits of one image data D1 through Dn are set beforehand in the digital gradient input converter 2d, and noise corresponding to these settings is added to the gradient values of the image data D1 through Dn.

[0101] That is to say, the relevant position values of a 22 filter are applied in accordance with the X coordinates (even or odd) and Y coordinates (even or odd) in the 22 pixel region. At this time, the lower order two bits of the gradient values of the image data D1 through Dn are deleted, and the values +1, 1, or the like, of the relevant positions are added to the remaining higher order bits. For example, as illustrated in FIG. 6(b), in a case where the lower order two bits of one image data D1 through Dn are 00 (0/4 gradient), dithering processing of +1, 1, +1, 1 is performed in the 22 pixel region, in a case where the lower order two bits are 01 (1/4 gradient), dithering processing of +1, 0 (omitted from illustration)* +1, 1 is performed in the 22 pixel region, in a case where the lower order two bits are 10 (2/4 gradient), dithering processing of +1, 0 (omitted from illustration)* +1, 0 (omitted from illustration) is performed in the 22 pixel region, and in a case where the lower order two bits are 11 (3/4 gradient), dithering processing of +1, 0 (omitted from illustration), +2, 0 (omitted from illustration) is performed in the 22 pixel region. In this case, the adjustment values are +2, +1, 1. Thus, the digital gradient input converter 2d supplies, to the DAC circuit 23, outputs K1 through Kn after dithering processing, where adjustment values that are values of relevant positions in the 22 filter has been added to gradient values of the image data D1 through Dn. The load on a particular reference power source bus line can be suppressed from becoming great due to the dithering processing such as illustrated in FIG. 6(b), and visually good image quality can be obtained as well.

[0102] Also, dithering processing may be performed by the digital gradient input converter 2d with different noise being applied to odd-numbered frames and even-numbered frames, as illustrated in (c) in FIG. 6. This sort of dithering processing enables noise to be applied in the time direction as well, and even higher quality noise can be accurately added.

[0103] Due to the dithering processing of applying different noise between odd frames and even frames, the load on a particular reference power source bus line can be suppressed from becoming great, and also visual compensation in the time direction (display of multiple frames) 0 regarding a gradient which is desired to be expressed, so results that are even better visually than the dithering processing illustrated in FIG. 6(b) can be obtained.

[0104] Note that in this embodiment as well, consideration needs to be given so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 0 which is near the smallest gradient value, since this would result in underflow of gradient values, and so that adjustment values are not applied in a case where the gradient values of the image data D1 through Dn are near gradient 255 which is near the greatest gradient value, since this would result in overflow of gradient values, in the same way as in the first embodiment.

[0105] Accordingly, in the present embodiment, an arrangement may be made as measures against underflow of gradient values and against overflow of gradient values where, in a case where the gradient values of the outputs K1 through Kn of the digital gradient input converter 2d fall below gradient 0 or exceed gradient 255, the gradient values of the input image data D1 through Dn are output without change, or an arrangement may be made of fixing to gradient 0 in a case of falling below gradient 0 and fixing to gradient 255 in a case of exceeding gradient 255.

[0106] The present invention is not restricted to the above-described embodiments. Various modifications may be made within the scope set forth in the claims, and embodiments obtained by appropriately combining technical means disclosed in each of different embodiments are also included in the technical scope of the present invention. Further, new technical features can be formed by combining technical means disclosed in the embodiments.

REFERENCE SIGNS LIST

[0107] 1 source drive circuit (drive circuit)

[0108] 2, 2a, 2c, 2d digital gradient input converter (gradient input converter)

[0109] 3 gate drive circuit

[0110] 4 display panel

[0111] 5 random number generator

[0112] 10 display device

[0113] 11 electronic equipment

[0114] 23 DAC circuit (digital/analog conversion circuit)

[0115] 24 gamma circuit (gradient reference voltage generating circuit)

[0116] 25 demultiplexer

[0117] D1 through Dn image data

[0118] H1 through Hn output of random number generator

[0119] AM1 through AMn source amp

[0120] AD1 through ADn adder

[0121] E1 through En output of digital gradient input converter

[0122] F1 through Fn output of digital gradient input converter

[0123] Jn output of digital gradient input converter

[0124] Q1 through Qn output node of source amp

[0125] U1 through Un input node of source amp

[0126] BL1 through BL256 reference power source bus line

[0127] S1 through Sr source line

[0128] G1 through Gm gate line

[0129] V0 through V255 gradient reference voltage