JP2006243223A - Driving circuit, electrooptical apparatus using the same, electronic equipment and driving method for the driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving circuit and a driving method for an electrooptical apparatus, capable of displaying a video image of low grayscale in high luminance. <P>SOLUTION: The driving circuit comprises; a grayscale generating means; a scanning line changing means; and a data line changing means for supplying a current to each data line based on the grayscale signal. The grayscale signal generating means comprises; a scanning line specifying means in which a current value supplied to each data line based on an image signal is calculated and the scanning line in which the current flowing during one frame period becomes maximum is specified; a scanning line peak luminance calculating means for calculating peak luminance of the specified scanning line; a window size calculating means; a window size peak luminance calculating means for calculating the peak luminance in a window size according to a peak luminance curve; and a grayscale signal correction means in which all image signals are corrected so that the peak luminance of the specific scanning line may become the peak luminance in the window size and the grayscale signal is generated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive circuit, and more particularly to a drive circuit and a drive method for driving an electro-optical device including a display unit including an organic EL element.

  In recent years, an electro-optical device such as a flat panel display (FPD) using an organic EL (Electronic Luminescence) element has attracted attention. The organic EL element is an element that emits light by current flowing through itself, and an electro-optical device using the organic EL element displays an image by light emission of a plurality of organic EL elements arranged in a matrix. Electro-optical devices include a simple matrix type and an active matrix type using TFTs.

FIG. 14 is a block diagram showing a configuration of a conventional simple matrix type electro-optical device 500. The electro-optical device 500 includes a display unit 520, a scanning line driving circuit 530 and a data line driving circuit 540 as driving circuits, and a control circuit 550.
In the electro-optical device 500, a plurality of scanning lines 511 and a plurality of data lines 512 are arranged to intersect with each other, and a plurality of organic EL elements 521 are provided in the display unit 520 corresponding to the intersections. The anode of each organic EL element is connected to the data line 512, and the cathode is connected to the scanning line 511.
The scanning line driving circuit 530 drives the scanning line 511, and the data line driving circuit 540 drives the data line 512. Specifically, the scanning signal of the scanning line 511 corresponding to the row of the selected matrix among the plurality of scanning lines 511 is grounded for one horizontal scanning period and becomes L level, and the operation signals of other rows become H level. . On the other hand, an image signal representing gradation display of each pixel is input to the data line driving circuit 540, and the data line driving circuit 540 receives gradation data as data line driving signals Data1, Data2,. An H level pulse signal having a pulse width according to the above is output. During the pulse width period in which the data line drive signal is at the H level, the organic EL element 521 of the scanning line driven to the L level emits light.

In such a simple matrix electro-optical device, an increase in the number of scanning lines and data lines increases the current flowing in the scanning lines due to an increase in the size of the display unit. Along with this, the voltage drop caused by the wiring resistance of the scanning line also increases, and the scanning line potential rises, whereby a current flows through a non-selected organic EL element and crosstalk light emission is likely to occur. Further, there is a possibility that the current of the scanning line exceeds the allowable current (see, for example, Patent Document 1). For this reason, it is not easy to increase the light emission luminance in a large electro-optical device.
Here, Patent Document 2 discloses a technique in which an active matrix organic EL display device includes a pixel current detection circuit and controls the amount of current flowing through the pixel based on the detection result of the current flowing through the pixel. Yes. According to this configuration, when the screen is dark and the detection current is small, it is possible to increase the luminance by extending the light emission time.
Japanese Patent Laid-Open No. 2003-15604 JP 2003-195816 A

  However, in this configuration, since the brightness of the screen is detected by the current that actually flows through the pixels, when displaying an image with a fast change in brightness, if the brightness suddenly increases, the current is not controlled by current detection. In addition, the current of the scanning line may exceed the allowable current.

  The present invention relates to a drive circuit for an electro-optical device capable of displaying a low gradation image with high luminance without causing the current of the scanning line to exceed an allowable current even when displaying an image with a rapid change in luminance. It is another object of the present invention to provide a driving method and an electro-optical device and an electronic apparatus using the driving circuit.

  The drive circuit according to the present invention includes an electro-optical device including a plurality of scanning lines, a plurality of data lines, and a display unit including an organic EL element provided corresponding to the intersection of the scanning lines and the data lines. And a gradation signal generating means for generating a gradation signal for controlling the gradation of the display unit based on an input image signal, and a specific scanning line among the scanning lines is selected. Scanning line switching means for grounding the selected scanning line; and data line switching means for supplying a current to the organic EL element via the data lines based on the gradation signal. The signal generating means calculates a current value supplied to each data line based on the input image signal, and specifies a scanning line that maximizes a current flowing in one frame period based on the current value. Identifying means and this identified scan line The scanning line peak luminance calculating means for calculating the peak luminance, the window size calculating means for calculating the window size, the peak luminance at the window size is calculated according to the peak luminance curve, and the current flowing through the specific scanning line is an allowable current. Window size peak luminance calculating means for calculating a correction coefficient so that the peak luminance of the specific scanning line becomes the peak luminance in the window size within a range not exceeding the value, and the image signal based on the correction coefficient And a gradation signal correction means for generating a gradation signal by correcting all of the above.

  According to the present invention, the window size peak luminance calculating means calculates the current value supplied to each data line based on the image signal, and calculates the peak luminance of the scanning line that maximizes the current based on the calculated current value. calculate. Then, the gradation signal generating means generates the gradation signal by correcting the image signal so that the peak luminance of the scanning line becomes the peak luminance in the calculated window size. Thereby, the correction when generating the gradation signal is performed based on the calculation result based on the input image signal, not the current actually flowing in the organic EL element. Therefore, even when displaying a video with a fast change in luminance, it is possible to generate a gradation signal by correcting the image signal in advance based on the calculation result based on the image signal, and display a low gradation image with higher luminance. However, it is possible to prevent a situation in which the current of the scanning line exceeds the allowable current.

  In another aspect of the present invention, a plurality of scanning lines arranged in a matrix, a plurality of data lines, and an organic EL element provided corresponding to the intersection of the scanning lines and the data lines are provided. A driving circuit of an electro-optical device that drives the organic EL element by a simple matrix driving method, and generates a gradation signal for generating a gradation signal for controlling the gradation of the display unit based on an input image signal Means, a scanning line switching means for selecting a specific scanning line among the scanning lines, and grounding the selected scanning line, and a current to the EL element via each data line based on the gradation signal. Data line switching means for supplying the data, and the gradation signal generating means calculates a current value supplied to each data line based on the input image signal, and 1 frame based on these current values. Electricity that flows during the period According to the peak luminance curve, the scanning line specifying means for specifying the scanning line that maximizes the scanning line, the scanning line peak luminance calculating means for calculating the peak luminance of the specified scanning line, the window size calculating means for calculating the window size, and the peak luminance curve The peak luminance at the window size is calculated and corrected so that the peak luminance of the specific scanning line becomes the peak luminance at the window size within a range where the current flowing through the specific scanning line does not exceed the allowable current value. Window size peak luminance calculating means for calculating a coefficient; and gradation signal correcting means for correcting a whole of the image signal to generate a gradation signal based on the correction coefficient.

  According to the present invention, similar to the drive circuit described above, even when an image with a fast change in luminance is displayed, the gradation signal can be generated by correcting the image signal in advance based on the calculation result based on the image signal.

  Here, in the driving circuit, the gradation signal correcting means includes a current value supplied to the data line, a period during which a current is supplied to the data line, and a period during which the specific scanning line is selected. It is preferable to correct at least one.

  According to this, the correction based on the calculation result of the input image signal is any one of the current value supplied to the data line, the period during which the current is supplied, and the period during which the specific scanning line is selected. Therefore, even when an image with a fast change in luminance is displayed, a good correction with a quick response can be performed.

  Further, in the drive circuit, the window size calculation means divides the total current supplied to the data line by the total current supplied to the data line when the screen is displayed in white. It is preferable to calculate the window size.

  According to this, since the calculation of the window size is a divisor of the sum of the currents supplied to the data lines and the sum of the currents supplied to the data lines when the screen is displayed in all white, the window required for correction The size is obtained as a numerical value corresponding to the ratio of the luminance of the entire screen based on the image signal to the luminance of the entire screen when all white is displayed. Therefore, natural correction can be performed in consideration of the luminance of the entire screen.

  In addition, by providing the driving circuit in an electro-optical device such as an organic EL display device, an electric device that displays a low gradation image with higher luminance while suppressing the occurrence of a situation where the current of the scanning line exceeds the allowable current. An optical device can be provided.

  In addition, by providing the electro-optical device in an electronic apparatus, an electronic apparatus that displays a low gradation image with higher luminance while suppressing the occurrence of a situation in which the current of the scanning line exceeds the allowable current is provided. Can do.

  The present invention can also be specified as a method for driving an electro-optical device. This driving method drives an electro-optical device including a plurality of scanning lines, a plurality of data lines, and a display unit including an organic EL element provided corresponding to the intersection of the scanning lines and the data lines. A method of generating a gradation signal for controlling gradation of the pixel circuit based on an input image signal; and a specific scanning line among the scanning lines is sequentially selected. A scanning line switching procedure for grounding the selected scanning line; and a data line switching procedure for supplying a current to the data line in a state where the selected scanning line is grounded. A scanning line specifying procedure for calculating a current value supplied to each data line based on an input image signal and specifying a scanning line having a maximum current flowing in one frame period based on the current value; The peak of this identified scan line In accordance with the scanning line peak luminance calculation procedure for calculating the degree, the window size calculation procedure for calculating the window size, and the peak luminance curve, the peak luminance at the window size is calculated, and the current flowing through the specific scanning line is an allowable current value. The window size peak luminance calculation procedure for calculating the correction coefficient so that the peak luminance of the specific scanning line becomes the peak luminance in the window size within a range not exceeding, and the image signal based on the correction coefficient A gradation signal correction procedure for correcting all of them and generating a gradation signal.

  In another aspect of the present invention, a plurality of scanning lines arranged in a matrix, a plurality of data lines, and an organic EL element provided corresponding to the intersection of the scanning lines and the data lines are provided. A method of driving an electro-optical device for driving the organic EL element by a simple matrix driving method, and generating a gradation signal for generating a gradation signal for controlling the gradation of the pixel circuit based on an input image signal A procedure, a scanning line switching procedure for sequentially selecting a specific scanning line among the scanning lines, and grounding the selected scanning line; and a current to the data line in a state where the selected scanning line is grounded. A grayscale signal generation procedure that calculates a current value supplied to each data line based on an input image signal, and one frame period based on these current values. Electricity flowing through A scanning line specifying procedure for specifying the scanning line that maximizes the scanning line, a scanning line peak luminance calculating procedure for calculating the peak luminance of the specified scanning line, a window size calculating procedure for calculating the window size, and a peak luminance curve The peak luminance at the window size is calculated and corrected so that the peak luminance of the specific scanning line becomes the peak luminance at the window size within a range where the current flowing through the specific scanning line does not exceed the allowable current value. And a window size peak luminance calculation procedure for calculating a coefficient, and a gradation signal correction procedure for generating a gradation signal by correcting all of the image signals based on the correction coefficient.

  According to these inventions, for the same reason as the drive circuit described above, even when displaying a video with a fast change in luminance, the gradation signal is generated by correcting the image signal in advance based on the calculation result based on the image signal. Therefore, it is possible to prevent a situation in which the current of the scanning line exceeds the allowable current while displaying a low gradation image with higher luminance.

  In the driving method, in the gradation signal correction procedure, a current value supplied to the data line, a period during which a current is supplied to the data line, and a period during which the specific scanning line is selected. It is preferable to correct at least one.

  According to the present invention, it is possible to perform a good correction with a quick response even when displaying an image whose luminance changes quickly.

<1. First Embodiment>
First, the configuration of the electro-optical device 100 according to the first embodiment of the invention will be described with reference to the drawings.
<1-1: Configuration>

  FIG. 1 is a block diagram illustrating a configuration of the electro-optical device 100.

The electro-optical device 100 includes a plurality of scanning lines 111 arranged in a matrix, a plurality of data lines 112, and an organic EL element 121 provided corresponding to the intersection of the scanning lines and the data lines. 120, and further includes a data line driving circuit 140 and a scanning line driving circuit 130 as a driving circuit for driving the electro-optical device 100 by a simple matrix driving method, and a control circuit 150. The anode of each organic EL element 121 is connected to the data line 112, and the cathode is connected to the scanning line 111.
The control circuit 150 outputs an image signal, a timing signal, and a clock signal to the scanning line driving circuit 130 and the data line driving circuit 140.
The scanning line driving circuit 130 serving as scanning line switching means sequentially selects specific scanning lines corresponding to the matrix rows from the scanning lines 111 one by one from CH1 to CHn, and scans the selected scanning lines one horizontal scan. Ground for a period. The other scanning lines are driven to a predetermined potential.

FIG. 2 is a block diagram showing a configuration of the data line driving circuit 140. The data line driver circuit 140 includes a gradation signal generation circuit 142 and a data line driver 141.
The data line driver 141 as data line switching means supplies a current to each data line 112 based on the gradation signal generated by the gradation signal generation circuit 142. When a current is supplied to the data line 112 and turned on, a current flows through the organic EL element 121 that connects the data line and the grounded scanning line 111, and the organic EL element 121 emits light. When the current supply to the data line 112 is stopped and turned off, the organic EL element 121 stops emitting light.

A gradation signal generation circuit 142 as a gradation signal generation unit generates a gradation signal for controlling the gradation of the display unit. Here, gradation control in the electro-optical device 100 is performed by time gradation control. That is, by controlling the length of time for supplying a constant current to the organic EL element 121 through the data line 112, the total amount of current flowing through the organic EL element 121 in one horizontal scanning period is controlled, and the emission luminance is changed. Displays the key.
The gradation signal generation circuit 142 includes a scanning line specifying circuit 144a, a scanning line peak luminance calculation circuit 144b, a window size calculation circuit 144c, a window size peak luminance calculation circuit 147, a gradation signal correction circuit 149, and a frame memory. 146 and a peak luminance curve storage unit 148. The scanning line specifying circuit 144a, the scanning line peak luminance calculation circuit 144b, and the window size calculation circuit 144c constitute an image signal processing circuit 143.

The scanning line specifying circuit 144a as the scanning line specifying means calculates the current value supplied to each data line 112 based on the image signal input from the control circuit 150, and flows in one frame period based on this current value. The scanning line that maximizes the amount of current is specified.
Here, the image signal indicates the light emission luminance gradation for each organic EL element 121. In the electro-optical device 100, the scanning lines 111 are sequentially selected once during one frame period and grounded for one horizontal scanning period. The light emission luminance of the organic EL element is determined by a current value which is a value of the amount of current flowing from the corresponding data line 112 through the organic EL element to the scanning line during this period. In the electro-optical device 100, the current value is adjusted by changing the time during which current flows from the data line 112 to the organic EL element in one horizontal scanning period based on the image signal, thereby controlling the light emission luminance. Here, all of the current flowing from the data line 112 to the organic EL element in one horizontal scanning period flows to the selected scanning line. Therefore, the current flowing through the scanning line is calculated by accumulating the total amount of current supplied from the data line 112 to each organic EL element in the corresponding one horizontal scanning period, that is, the amount of current based on the gradation of the image signal. Can do. The scanning line specifying circuit 144a specifies the scanning line that maximizes the flowing current by performing the calculation of the current on the image signal corresponding to each of the scanning lines 111.

The scanning line peak luminance calculation circuit 144b as the scanning line peak luminance calculation means calculates the peak luminance of the scanning line specified by the scanning line specification circuit 144a.
A window size calculation circuit 144c as a window size calculation means calculates a window size. Here, the window size means the ratio of the luminance of display based on the image signal to the luminance when the entire screen emits light at the maximum luminance (all white screen), and specifically, the organic light emitting at the maximum luminance. It is obtained as a value corresponding to the ratio of the area (window) of the organic EL element that emits light to the entire screen of the display unit composed of the EL element and the organic EL element that does not emit light. For example, if the ratio of the number of organic EL elements that emit light at the maximum gradation is 50% with respect to the number of all organic EL elements constituting the display unit, the window size is 50%. Since the actual display is performed including the intermediate gradation, the window size is specifically a cumulative value of the amount of current supplied to the data line for displaying the input image signal for one frame period. Is divided by the sum of the amounts of current supplied to the data lines when the entire screen is displayed in full white, which is displayed at the maximum gradation, and is calculated as a ratio.

  The window size peak luminance calculation circuit 147 as the window size peak luminance calculation means calculates the peak luminance at the window size calculated by the window size calculation circuit 144c according to the peak luminance curve. The peak luminance curve is a characteristic curve representing the relationship between the window size and the luminance that can be emitted as the peak luminance of the organic EL element belonging to the window.

FIG. 3 is a graph showing a peak luminance curve.
The peak luminance curve A indicates the light emission of the organic EL element 121 with respect to the window size when the total current flowing through all the organic EL elements 121 that emit light in the display unit, that is, the total screen current value is constant. The characteristic of possible brightness is shown. Here, the light emission luminance of the organic EL element 121 is proportional to the amount of current flowing through the organic EL element 121, and therefore can be expressed as a current. Since the total screen current is the sum of the amount of current flowing in the organic EL element 121 in the window during one frame period, the window size, the light emission possible luminance of the organic EL element 121, and the current are inversely related in the peak luminance curve A. It is shown that. For example, with respect to the light emission possible luminance Lb when the window size is 100%, the luminance is doubled when the window size is 50%, and the luminance is 10 times when the window size is 10%. .
In the actual electro-optical device 100, a smaller light emission possible luminance characteristic is used from the allowable limit of the current of other wirings. A characteristic actually used in the electro-optical device 100 is shown as a peak luminance curve B. In the peak luminance curve B, when all the organic EL elements 121 of the display unit emit light at the maximum gradation, that is, when the window size is 100%, with respect to the allowable current Ib that can be passed through one scanning line, Luminous brightness Lb is required. When the number of scanning lines in the display unit is m, the total screen current at this time is Ib × m.
The peak luminance curve B is obtained in advance by actual measurement or simulation, and is stored in the peak luminance curve storage unit 148 as characteristic data.
Returning to FIG. 2, the window size peak luminance calculation circuit 147 has a peak luminance of the specific scanning line within a range in which the amount of current flowing through the scanning line specified by the scanning line specifying circuit 144a does not exceed the allowable current Ib. A luminance correction coefficient k is calculated so as to obtain a peak luminance in the window size of the input screen signal.

  A gradation signal correction circuit 149 serving as a gradation signal correction unit generates a gradation signal by correcting all the image signals based on the luminance correction coefficient k. The gradation signal is a signal that controls the timing at which a current is supplied to the data line.

  The frame memory 146 is a first-in first-out memory configured by, for example, a RAM, and temporarily stores the input image signal for one frame until the correction coefficient is calculated after the input of the image signal. That is, the data stored in the frame memory 146 can be read out with a delay of about one frame from the input. The scanning line specifying circuit 144 a calculates a current value based on the image signal input from the control circuit 150 and stores the input image signal in the frame memory 146. On the other hand, the gradation signal correction circuit 149 reads from the frame memory 146 the image signal input one frame before, which is the basis of the calculation, and corrects the read image signal by the calculated luminance correction coefficient k. To generate a gradation signal and output it to the data line driver 141.

<1-2: Action>
FIG. 4 is a flowchart showing a procedure by which the gradation signal generation circuit 142 calculates the luminance correction coefficient k.

  First, the scanning line specifying circuit 144a receives an image signal from the control circuit 150 and calculates a current value supplied to each data line 112 based on the input image signal. The image signal indicates the light emission luminance gradation of each organic EL element 121, and the light emission luminance gradation corresponds to the amount of current as a current value supplied to the corresponding data line 112. The scanning line specifying circuit 144a obtains the amount of current from the gradation by calculating a data table stored in advance or a conversion formula (S11). The scanning line specifying circuit 144 a calculates the total amount of current flowing in one horizontal period, that is, the amount of current flowing in each scanning line for each scanning line, and stores the input image data in the frame memory 146. The calculation is performed on an image signal for one frame.

  Subsequently, the scanning line peak luminance calculation circuit 144b specifies the scanning line CHs having the maximum amount of current based on the result calculated by the scanning line specification circuit 144a (S12). Further, the current Ichs of the scanning line CHs and the amount of current Ich corresponding to the highest peak luminance Lch among the scanning lines CHs are specified. These are specified by selecting the calculation result of the scanning line specifying circuit 144a.

  Subsequently, the window size calculation circuit 144c calculates the total screen current It flowing through the entire screen based on the result calculated by the scanning line specifying circuit 144a (S13). The total screen current It is a total amount of current of each scanning line.

  Subsequently, the window size calculation circuit 144c calculates the window size Ws based on the calculated total screen current It (S14). The window size is calculated as the ratio of the total screen current It to the amount of current (m × Ib) when the entire screen of the display unit displays at the maximum gradation.

  Subsequently, the window size peak luminance calculation circuit 147 calculates the light emission possible luminance Ls as the peak luminance in the window size Ws as the calculation result of the window size calculation circuit 144c according to the peak luminance curve (S15). Specifically, the window size peak luminance calculation circuit 147, based on the data of the peak luminance curve B (FIG. 3) stored in the peak luminance curve storage unit 148, can emit light corresponding to the value of the window size Ws. The current amount Is of Ls is read out.

Subsequently, the window size peak luminance calculation circuit 147 calculates a luminance correction coefficient k that makes the peak luminance of the specific scanning line the light emission possible luminance Ls in the window size Ws of the input screen signal (S16).
Specifically, the luminance correction coefficient k is calculated from the calculated current amount Is of the light emission possible luminance Ls and the current Ich flowing through the data line of the highest luminance Lch among the scanning lines CHs by the following formula.

  k = Ls / Lch (= Is / Ich)

  Subsequently, when the window size peak luminance calculation circuit 147 generates a gradation signal by correcting the image signal based on the luminance correction coefficient k, the current Ichs flowing through the data line of the peak luminance Lch calculated from the image signal. It is determined whether or not the correction value exceeds the allowable current value of the scanning line (S17). Specifically, it is determined whether or not Ichs × k is lower than the value of the allowable current Ib. In this step, if it is determined that Ichs × k is lower than Ib (Yes in S17), the value of the luminance correction coefficient k is not changed, and this value is output to the gradation signal correction circuit 149. As a result, the gradation signal correction circuit 149 generates a gradation signal by correcting all of the image signals. On the other hand, if it is determined that the value of Ichs × k is equal to or greater than the value of Ib (No in S17), the luminance correction coefficient k is set to 1 and output to the gradation signal correction circuit 149. As a result, the gradation signal correction circuit 149 generates a gradation signal without correcting the image signal (S18). In this way, the gradation signal correction circuit 149 has a window size in which the peak luminance of the specific scanning line CHs corresponds to the image signal in a range where the current Ichs × k flowing through the specific scanning line CHs does not exceed the allowable current Ib. The luminance correction coefficient k is calculated so that the peak luminance Ls at Ws is obtained.

  The gradation signal generation circuit 142 calculates the luminance correction coefficient k according to the above-described procedure. However, since the image signals are input one after another, after the image signal of one frame is input, the calculated luminance correction coefficient k is used. Based on this, a gradation signal is output, and at the same time, an image signal of the next frame is input. That is, the input of the image signal and the output of the corrected gradation signal based on the image signal of the previous frame are performed in parallel.

FIG. 5 is a timing chart showing operations of the scanning line driving circuit 130 and the data line driving circuit 140. The scanning line driving circuit 130 sequentially selects scanning lines for each horizontal scanning period (1H), and grounds the selected scanning lines to a ground (GND) level. The scanning signal that becomes the ground (GND) level sequentially moves from CH1 to CHn. The reason why the level is at the GND level at the end of all the horizontal scanning periods is to discharge the charges accumulated in the organic EL elements in the previous period and initialize the state of all the organic EL elements. .
When the signal of a certain scanning line becomes the ground (GND) level, the data line driving circuit 140 causes the gradation signal generating circuit 142 to generate light based on the gradation signal generated by the data line driving circuit 142 in order to cause the organic EL element corresponding to the scanning line to emit light. Thus, a current is supplied to the data line 112 corresponding to light emission. Note that the gradation signal has the same waveform as the drive signal for driving the data line. As a result, the data line signal is turned on only during a period corresponding to the corrected image signal, and current flows through the organic EL element during this period. Specifically, when there is no correction, the data signal is turned on for a time obtained by multiplying the time corresponding to the image signal by the luminance correction coefficient k. Since the correction using the luminance correction coefficient k is performed on the entire screen, the time of the on state is corrected over the entire screen.
Here, the peak luminance Lch of the scanning line CHs having the maximum amount of current by the luminance correction coefficient k becomes the light emission possible luminance Ls in the window size Ws corresponding to the image signal by the luminance correction coefficient k.

<1-3: Effect>
According to the data line driving circuit 140 and the scanning line driving circuit 130 that drive the electro-optical device 100, the gradation signal generation circuit 142 determines the current value supplied to each data line 112 based on the input image signal. Based on the calculated current value, the peak luminance Lch of the scanning line CHs that maximizes the current is calculated. Then, the gradation signal Data1 to Data is generated by correcting the image signal so that the peak luminance Lch of the scanning line becomes the light emission possible luminance Ls as the peak luminance in the window size Ws calculated from the image signal. Thus, when displaying an image that emits light in a limited area on the screen, the brightness of the light emitting area is corrected to the light-emitting brightness obtained based on the peak brightness curve from the window size corresponding to the display image. be able to. At this time, the correction when generating the gradation signal is performed based on the calculation result based on the input image signal, not the current actually flowing in the organic EL element 121. Therefore, even when displaying a video with a fast change in luminance, it is possible to generate the gradation signals Data1 to Data by correcting the image signal in advance based on the calculation result based on the image signal. While displaying with brightness, it is possible to prevent a situation in which the current of the scanning line exceeds the allowable current.

  Further, since the correction based on the calculation result of the image signal is performed for a period in which the current is supplied to the data line, it is possible to perform a good correction with a quick response even when displaying a video with a fast change in luminance.

  Further, since the window size Ws is calculated as a divisor of the total current It supplied to the data lines and the total current (m × Ib) supplied to the data lines when the screen is displayed in all white, The window size Ws necessary for the image is obtained as a numerical value corresponding to the ratio of the luminance of the entire screen based on the image signal to the luminance of the entire screen when all white is displayed. Therefore, natural correction can be performed in consideration of the luminance of the entire screen.

By the way, in the scanning line driving circuit 130 according to the first embodiment, when the gradation signal is generated by correcting the image signal based on the luminance correction coefficient k, the current after flowing through the data line of the peak luminance Lch is corrected. It is determined whether or not the value exceeds the allowable current Ib of the scanning line. Specifically, when it is determined that the value of Ichs × k is equal to or greater than the value of the allowable current Ib (No in S17 of FIG. 4), the luminance correction coefficient k is set to 1, that is, the image signal is not corrected. A gradation signal is generated.
For example, in the display example of the screen shown in FIG. 6, when the portion to emit light is a thick line extending in the vertical direction on the screen as shown in (a), the luminance correction coefficient obtained based on the window size Ws for the entire screen. By multiplying k, the luminance to be emitted can be displayed with high luminance as the peak luminance Ls corresponding to the window size Ws.
However, as shown in FIG. 6B, when the portion to emit light is a thick line extending in the horizontal direction on the screen, when the luminance correction coefficient k based on the window size Ws is applied, the maximum current of the thick line portion is In the scanning line, the value of Ichs × k becomes equal to or greater than the value of Ib, and correction is not performed.
Here, a second embodiment of the present invention will be described in which a gradation signal is generated by correcting an image signal even when a portion to emit light is a thick line extending in the horizontal direction on the screen.

<2. Second Embodiment>
<2-1: Configuration>
FIG. 7 is a block diagram illustrating a configuration of the electro-optical device 200 according to the second embodiment. In the electro-optical device 200 according to the present embodiment, a horizontal synchronization signal Hsync indicating one horizontal scanning period is supplied from the data line driving circuit 240 to the scanning line driving circuit 230 with respect to the configuration of the electro-optical device 100 of the first embodiment. Is different.
FIG. 8 is a block diagram showing a configuration of the data line driving circuit 240 according to the second embodiment of the present invention. The data line driving circuit 240 is different from the configuration of the data line driving circuit 140 of the first embodiment in that the gradation signal correction circuit 249 outputs a horizontal synchronization signal Hsync.
Here, in the data line driving circuit 240, in the procedure shown in FIG. 4, when it is determined that the value of Ichs × k is equal to or greater than the value of Ib (No in S16), the luminance correction coefficient k is set to 1. do not do. Instead, the gradation signal correction circuit 249 lengthens the period of the horizontal synchronization signal Hsync when this scanning line is selected in accordance with the value of the luminance correction coefficient k (section A in FIG. 9). In addition, the data signal is turned on for the time when the correction is performed by the luminance correction coefficient k. Since the correction using the luminance correction coefficient k is performed on the entire screen, the time of the on state is corrected over the entire screen. Here, the peak luminance Lch of the scanning line CHs having the maximum amount of current by the luminance correction coefficient k becomes the light emission possible luminance Ls in the window size Ws corresponding to the image signal by the luminance correction coefficient k.
The scanning line driving circuit 230 selects the scanning line and grounds the selected scanning line in synchronization with the horizontal synchronization signal Hsync output from the data line driving circuit 240. Note that the period of the horizontal synchronization signal Hsync for a specific scanning line becomes longer, so that the period of one frame in the data line driving circuit 240 and the scanning line driving circuit 230 does not deviate from the one frame period of the input image signal. For the scanning lines of the screen with low brightness, the cycle of the horizontal synchronization signal Hsync is shortened (section B in FIG. 9).
In addition, the other structure of the above-mentioned in 2nd Embodiment is the same as that of 1st Embodiment.

<2-2: Action and effect>
As shown in FIG. 9, the correction based on the calculation result of the input image signal is performed for a period during which a specific scanning line is selected. Correction can be performed. In addition, for example, even when the light emitting portion is a thick line extending in the horizontal direction on the screen, the image signal is corrected to generate a gradation signal, so that more types of pixel signals can be corrected well. Can do.

<3. Third Embodiment>
<3-1: Configuration>
FIG. 10 is a block diagram showing a configuration of a data line driving circuit 340 according to the third embodiment of the present invention. In the data line driving circuit 340 according to the present embodiment, the gradation signal correction circuit 349 outputs a gradation correction signal Vctrl to the data line driver 341 in contrast to the configuration of the data line driving circuit 140 of the first embodiment. Is different.
Here, the data line driver 341 does not fix the current for driving the data line, but changes it based on the voltage value of the gradation correction signal Vctrl. Specifically, by providing a voltage controllable current source circuit, a current proportional to the voltage value of the gradation correction signal Vctrl is output to the data line 312.
The gradation signal correction circuit 349 according to the third embodiment changes the voltage value of the gradation correction signal Vctrl based on the luminance correction coefficient k obtained by the procedure shown in FIG. Specifically, a gradation correction signal Vctrl having a voltage proportional to the luminance correction coefficient k is output.
In addition, the other structure of the above-mentioned in 2nd Embodiment is the same as that of 1st Embodiment.
<3-2: Action and effect>
As described above, since the correction based on the calculation result of the input image signal is performed on the current value supplied to the data line, even when displaying an image with a fast change in luminance, a good correction with a quick response is possible. It can be performed. Further, in the gradation signal correction circuit 349, the output of the image signal read from the frame memory 146 and the output of the correction coefficient can be separated, so that the configuration can be simplified.

<4. Modifications and improvements>
It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

  For example, in the above embodiment, the electro-optical device has been described as including a drive circuit, but the present invention is not limited to this. For example, instead of forming part or all of a drive circuit on an element substrate as an electro-optical device, for example, a drive circuit mounted on a film using a TAB (Tape Automated Bonding) technique is placed at a predetermined position on the element substrate. The electro-optical device may be configured to be electrically and mechanically connected through an anisotropic conductive film provided, or an IC chip on which a drive circuit is formed is formed using COG (Chip On Glass) technology. It is good also as a structure connected to the predetermined position of the made element board | substrate.

<5. Electronic equipment>
Next, an electronic apparatus to which the electro-optical device 100 according to the above-described embodiments and application examples is applied will be described. FIG. 11 shows a configuration of a mobile personal computer to which the electro-optical device 100 is applied. The personal computer 2000 includes an electro-optical device 100 as a display unit and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002. Since the electro-optical device 100 includes a level shift circuit whose input sensitivity is not affected by variations in the manufacturing process, it can display a homogeneous image.

  FIG. 12 shows a configuration of a mobile phone to which the electro-optical device 100 is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and the electro-optical device 100 as a display unit. By operating the scroll button 3002, the screen displayed on the electro-optical device 100 is scrolled. FIG. 13 shows a configuration of a portable information terminal (PDA: Personal Digital Assistants) to which the electro-optical device 100 is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the electro-optical device 100 as a display unit. When the power switch 4002 is operated, various types of information such as an address book and a schedule book are displayed on the electro-optical device 100.

  Electronic devices to which the electro-optical device 100 is applied include those shown in FIGS. 11 to 13, a digital still camera, a liquid crystal television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, Examples include electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, and devices equipped with touch panels. The electro-optical device 100 described above can be applied as a display unit of these various electronic devices.

1 is a block diagram showing a configuration of an electro-optical device 100 according to a first embodiment of the present invention. 3 is a block diagram illustrating a configuration of a data line driving circuit of the electro-optical device 100. FIG. It is a graph which shows a peak brightness | luminance curve. It is a flowchart which shows the procedure which calculates the brightness | luminance correction coefficient k. 3 is a timing chart illustrating operations of a scanning line driving circuit and a data line driving circuit. It is a figure which shows the example of a display of a screen. FIG. 6 is a block diagram illustrating a configuration of an electro-optical device 200 according to a second embodiment of the present invention. It is a block diagram which shows the structure of the data line drive circuit which concerns on 2nd Embodiment of this invention. 3 is a timing chart illustrating operations of a scanning line driving circuit and a data line driving circuit. It is a block diagram which shows the structure of the data line drive circuit which concerns on 3rd Embodiment of this invention. It is a perspective view showing the configuration of a mobile personal computer to which the above electro-optical device is applied. It is a perspective view which shows the structure of the mobile telephone to which the above-mentioned electro-optical apparatus is applied. It is a perspective view which shows the structure of the portable information terminal to which the above-described electro-optical device is applied. FIG. 11 is a block diagram illustrating a configuration of a conventional simple matrix type electro-optical device 500.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,200 ... Electro-optical apparatus, 111, 211 ... Scan line, 112, 212, 312 ... Data line, 121, 221, 321 ... Organic EL element, 120, 220 ... Display part, 130, 230, 340 ... Scan line drive Circuit (scanning line switching means, driving circuit), 140, 240, 340... Data line driving circuit (driving circuit), 141, 241, 341... Data line driver (data line switching means), 142, 242, 342. Signal generation circuit (gradation signal generation means), 144a, 244a, 344a... Scanning line identification circuit (scanning line identification means), 144b, 244b, 344bb... Scanning line peak luminance calculation circuit (scanning line peak luminance calculation means), 144c , 244c, 344c... Window size calculation circuit (window size calculation means), 146, 246, 346. Memory, 147, 247, 347 ... window size peak luminance calculation circuit (window size peak luminance calculation means), 148, 248, 348 ... peak luminance curve storage unit, 149, 249, 349 ... gradation signal correction circuit (gradation signal) Correction means), 150, 250 ... control circuit, 2000 ... personal computer, 3000 ... mobile phone, 4000 ... information portable terminal

Claims (10)

A drive circuit for an electro-optical device comprising a plurality of scanning lines, a plurality of data lines, and a display unit including an organic EL element provided corresponding to the intersection of the scanning lines and the data lines,
A gradation signal generating means for generating a gradation signal for controlling gradation of the display unit based on an input image signal;
Scanning line switching means for selecting a specific scanning line from among the scanning lines and grounding the selected scanning line;
Data line switching means for supplying a current to the organic EL element via the data lines based on the gradation signal,
The gradation signal generation means calculates a current value supplied to each data line based on an input image signal, and specifies a scanning line having a maximum current flowing in one frame period based on the current value. Scanning line specifying means to perform,
Scanning line peak luminance calculating means for calculating the peak luminance of the identified scanning line;
Window size calculating means for calculating the window size;
According to the peak luminance curve, the peak luminance at the window size is calculated, and the peak luminance of the specific scanning line becomes the peak luminance at the window size in a range where the current flowing through the specific scanning line does not exceed the allowable current value. Window size peak luminance calculating means for calculating a correction coefficient,
A drive circuit comprising: a gradation signal correcting unit that generates a gradation signal by correcting all of the image signals based on the correction coefficient. A plurality of scanning lines arranged in a matrix, a plurality of data lines, and an organic EL element provided corresponding to the intersection of the scanning line and the data line, the organic EL element being a simple matrix drive system A drive circuit for an electro-optical device driven by
A gradation signal generating means for generating a gradation signal for controlling gradation of the display unit based on an input image signal;
Scanning line switching means for selecting a specific scanning line from among the scanning lines and grounding the selected scanning line;
Data line switching means for supplying a current to the EL element via the data lines based on the gradation signal,
The gradation signal generation means calculates a current value supplied to each data line based on an input image signal, and specifies a scanning line having a maximum current flowing in one frame period based on the current value. Scanning line specifying means to perform,
Scanning line peak luminance calculating means for calculating the peak luminance of the identified scanning line;
Window size calculating means for calculating the window size;
According to the peak luminance curve, the peak luminance at the window size is calculated, and the peak luminance of the specific scanning line becomes the peak luminance at the window size in a range where the current flowing through the specific scanning line does not exceed the allowable current value. Window size peak luminance calculating means for calculating a correction coefficient,
A drive circuit comprising: a gradation signal correcting unit that generates a gradation signal by correcting all of the image signals based on the correction coefficient. The drive circuit according to claim 1 or 2,
The gradation signal correction unit corrects at least one of a current value supplied to the data line, a period during which a current is supplied to the data line, and a period during which the specific scanning line is selected. A drive circuit characterized by the above. The drive circuit according to any one of claims 1 to 3,
The window size calculating means calculates the window size by dividing the sum of the currents supplied to the data lines by the sum of the currents supplied to the data lines when the screen is displayed in all white. A drive circuit characterized.   An electro-optical device comprising the drive circuit according to claim 1.   An electronic apparatus comprising the electro-optical device according to claim 5. An electro-optical device driving method comprising a plurality of scanning lines, a plurality of data lines, and a display unit including an organic EL element provided corresponding to the intersection of the scanning lines and the data lines,
A gradation signal generation procedure for generating a gradation signal for controlling gradation of the pixel circuit based on an input image signal;
A scanning line switching procedure for sequentially selecting specific scanning lines among the scanning lines and grounding the selected scanning lines;
A data line switching procedure for supplying a current to the data line in a state where the selected scanning line is grounded,
In the gradation signal generation procedure, a current value supplied to each data line is calculated based on an input image signal, and a scanning line having a maximum current flowing in one frame period is specified based on the current value. Scanning line identification procedure to
A scanning line peak luminance calculation procedure for calculating the peak luminance of the identified scanning line;
A window size calculation procedure for calculating the window size;
According to the peak luminance curve, the peak luminance at the window size is calculated, and the peak luminance of the specific scanning line becomes the peak luminance at the window size in a range where the current flowing through the specific scanning line does not exceed the allowable current value. As described above, the window size peak luminance calculation procedure for calculating the correction coefficient,
And a gradation signal correction procedure for generating a gradation signal by correcting all of the image signals based on the correction coefficient. A plurality of scanning lines arranged in a matrix, a plurality of data lines, and an organic EL element provided corresponding to the intersection of the scanning line and the data line, the organic EL element being a simple matrix drive system A driving method of an electro-optical device driven by
A gradation signal generation procedure for generating a gradation signal for controlling gradation of the pixel circuit based on an input image signal;
A scanning line switching procedure for sequentially selecting specific scanning lines among the scanning lines and grounding the selected scanning lines;
A data line switching procedure for supplying a current to the data line in a state where the selected scanning line is grounded,
In the gradation signal generation procedure, a current value supplied to each data line is calculated based on an input image signal, and a scanning line having a maximum current flowing in one frame period is specified based on the current value. Scanning line identification procedure to
A scanning line peak luminance calculation procedure for calculating the peak luminance of the identified scanning line;
A window size calculation procedure for calculating the window size;
According to the peak luminance curve, the peak luminance at the window size is calculated, and the peak luminance of the specific scanning line becomes the peak luminance at the window size in a range where the current flowing through the specific scanning line does not exceed the allowable current value. As described above, the window size peak luminance calculation procedure for calculating the correction coefficient,
And a gradation signal correction procedure for generating a gradation signal by correcting all of the image signals based on the correction coefficient. The method of driving an electro-optical device according to claim 7 or 8,
In the gradation signal correction procedure, at least one of a current value supplied to the data line, a period during which a current is supplied to the data line, and a period during which the specific scanning line is selected is corrected. A method for driving an electro-optical device. The method for driving an electro-optical device according to claim 7,
In the window size calculation procedure, the window size is calculated by dividing the sum of the currents supplied to the data lines by the sum of the currents supplied to the data lines when displaying a full white screen. A driving method of an electro-optical device.

Images