JP2007241225A - Driving method of display device using organic light emitting element and driving circuit of same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method of a display device using an organic light emitting element and a driving circuit of a display device using an organic luminous element that can reduce display unevenness due to characteristic fluctuation of driving transistors while keeping decline in electric power and a life at a minimum limit. <P>SOLUTION: Only in screen display with a low lighting ratio in which low gradation display, which tends to cause writing insufficiency, is often performed, a writing current is multiplied by N to increase a characteristic fluctuation compensation ability of driving and transistors and reduce display unevenness. In addition, the number of frames to which an N-fold electric current is fed is reduced. Consequently, display with influences of an increase in electric power and a decline in a life controlled to a minimum limit is achieved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a driving method of a display device using an organic light emitting element that drives a display device that performs gradation display by an amount of current, such as an organic electroluminescent element, and a drive circuit of the display device using the organic light emitting element. It is.

  Since the organic light emitting element is a self light emitting element, a backlight required for a liquid crystal display device is unnecessary, and it is expected as a next generation display device from the advantages such as a wide viewing angle.

  Since the organic light emitting element emits light by injecting electric charge into the element, even when used as a display device, driving of controlling the luminance of the organic light emitting element by the amount of current in each pixel is general. .

  There are roughly two types of driving methods in an active matrix display device, and a current output corresponding to a gradation is made from a source driver, and this is held for one frame in each pixel circuit to be an organic light emitting element. A current driving method for displaying by supplying current and a voltage output from the source driver according to the gradation are made, held for one frame in each pixel circuit, and further converted from voltage data to current data. There is a voltage driving method in which display is performed by supplying current to an organic light emitting element.

  In the voltage driving method, voltage data is converted into current data by a transistor provided in a pixel, so that luminance variation of each pixel due to transistor characteristic variation is likely to occur and is not easily affected by transistor characteristic variation. It is easier to achieve a display with less unevenness.

  As an example of a driving circuit using a current driving method, an active matrix display device having a pixel circuit having a current copier configuration shown in FIG. 1 or a current mirror configuration shown in FIG.

  FIG. 1 is a diagram showing a pixel circuit 17, a source driver 16, and a gate driver 15 having a current copier configuration. FIG. 2 is a diagram showing a pixel circuit 17, a source driver 16, and a gate driver 15 having a current mirror configuration.

  In the pixel circuit shown in FIGS. 1 and 2, a p-type TFT is used. As shown in FIGS. 1 and 2, a MOS transistor is used as the transistor.

  1 and 2 are diagrams used in the embodiment of the present invention.

  As a problem of the current driving method, when the current value becomes small, the current is not written into the pixel circuit due to the stray capacitance existing in the source signal line.

  As a technique for solving this problem, as shown in Patent Document 1, a function of “voltage precharge” and “current precharge” is added to a source driver that outputs current, and the current value of the source signal line is set to a predetermined gradation. I try to change it quickly in response.

Further, as shown in Patent Document 2, there is a method of increasing the change speed by multiplying the current value supplied to the organic light emitting element by N (N> 1) and increasing the write current value. In this case, since an increase in luminance occurs due to an increase in writing current, the organic light emitting element 13 is controlled by controlling the gate signal line 11b shown in FIG. 1 or the gate signal line 11d shown in FIG. The period in which the current flows is 1 / N times so that the luminance is not changed during one frame.
International Publication No. 2005/055183 Pamphlet JP 2004-029755 A

  In the pixel circuit arrangement as shown in FIG. 3, the drive transistor 12a of the pixel A (17a) and the drive transistor 12c of the pixel C (17c) have the characteristics 41 of FIG. 4, and the drive transistor 12b of the pixel B (17b). 4 has the characteristic of 42 in FIG. 4, when the current of I1 is supplied to all the pixels and the same gradation display is performed for each pixel, when the current value of I1 is small (10 nA or less), FIG. As shown in b), the current flowing through the organic light emitting element 13 is different for each pixel, and as a result, there is a problem that uneven display is caused.

  This is because the source signal line voltage must be V1 for the pixels A and C and V2 for the pixel B due to the characteristics of the drive transistor 12, but as shown in FIG. As a result, the pixel B cannot be changed to a predetermined value within the writing time, and as a result of applying a voltage higher than V2 to the pixel B, the current decreases, and the pixel C applies a voltage lower than V1. Occurs because the current value increased.

  In the method of improving writing by precharging, a voltage value that makes an average black display state of all pixels is applied when performing voltage precharging, and depending on the gradation by current precharging from the black display state to the vicinity of a predetermined luminance. 3 is a method of changing the potential faster than the normal writing of current by a certain amount of voltage fluctuation, and it is possible to quickly change the average voltage value of all the pixels with respect to the display gradation. Such a change in luminance due to characteristic variations of the drive transistors 12a and 12b of each pixel cannot be dealt with.

  In addition, in the method of multiplying the write current by N times, the instantaneous current flowing through the organic light emitting element is N times, and there is a problem that the luminance half-life is shortened in the organic light emitting element in which the luminance deterioration is accelerated as the amount of current increases.

  As shown in FIG. 6, when white display is performed, the voltage value required for the organic light emitting element increases as N increases, and as a result, the voltage of the EL power source 14b in FIG. 1 or FIG. It is necessary to increase the voltage of the EL power source 14a. Since the power consumption of the display device using the organic light emitting element is determined by the product of the potential difference between the EL power sources 14a and 14b and the average value of the current flowing through the organic light emitting element 13, the average current value does not change in N-fold driving. Since the potential difference increases, there is a problem that the power increases as N increases.

  In view of the above problems, the present invention provides a method for driving a display device using an organic light-emitting element capable of reducing display unevenness due to specific variations in drive transistors while keeping power and lifetime reduction at a minimum source, and organic An object of the present invention is to provide a driving circuit for a display device using a light emitting element.

In order to solve the above-described problem, the first present invention
At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A lighting rate calculator that calculates the lighting rate of the entire screen in a predetermined frame;
A current frame current magnification storage unit that stores a current magnification of the predetermined frame one frame before;
A current magnification calculator for calculating an applied current magnification corresponding to the lighting rate calculated by the lighting rate calculator;
An organic light emitting element for driving a display device using an organic light emitting element, comprising: an electronic volume control unit that increases or decreases a current value applied in accordance with a first applied current magnification determined by the current magnification calculating unit. A driving method of the display device used,
When the lighting rate per frame is lower than the predetermined value,
Determining the first current magnification by the current magnification calculator;
Applying a predetermined current by the current volume control unit,
When the lighting rate per frame is lower than a predetermined value, a current value of N times (N is a real number larger than 1) is applied as the current magnification when normal video display is performed.
This is a method for driving a display device using an organic light emitting element.

The second aspect of the present invention
The determination of the current magnification is a method of driving a display device using the organic light emitting element of the first aspect of the present invention, which is performed by multiplying a gradation value indicated by a video signal in each frame by a predetermined value.

The third aspect of the present invention
The determination of the current magnification is performed by simultaneously multiplying the current value of a reference current source for each display color prepared for applying a video signal by a predetermined number for each color. This is a driving method of the display device.

The fourth aspect of the present invention is
The predetermined lighting rate is 12.5% or less, and the display device driving method using the organic light-emitting element according to the first aspect of the present invention.

The fifth aspect of the present invention provides
In the method of driving a display device using the organic light emitting element of the first aspect of the present invention, the magnification of the predetermined current is greater than 1 and 4 or less.

The sixth aspect of the present invention provides
The application time of the current signal to the organic light emitting element when a current value of N times as the predetermined current magnification is applied to the organic light emitting element constituting each pixel of the display device using the organic light emitting element is as follows: , N = 1, where 1 (t) is 1 / N (t), which is a driving method of a display device using the organic light emitting element of the first aspect of the present invention.

The seventh aspect of the present invention
A display device using the organic light emitting element is:
At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A current magnification calculator for multiplying an applied current magnification;
An electronic volume control unit that increases or decreases a current value applied in accordance with a second applied current magnification determined by the current magnification calculation unit;
Applying a predetermined current determined by the second applied current magnification to each pixel during a predetermined period;
And a step of applying a predetermined current determined by the first applied current magnification after the elapse of a predetermined period. The display device driving method using the organic light-emitting element according to the first aspect of the present invention.

In addition, the eighth aspect of the present invention
At least one current source circuit for determining at least one current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A precharge unit for applying a predetermined electrical signal before applying the video signal;
In the precharge unit, an organic light emitting element for driving a display device using an organic light emitting element, in which a precharge signal value corresponding to each display gradation at the time of 1 × driving which is normal driving is stored, is used. A driving method of a display device,
When displaying a gradation M (M is an integer of 0 or more) as a current value applied to a display device using the organic light-emitting element as N times N (N is a real number of 1 or more) during normal driving, precharging is performed. An organic light emitting device comprising a step of using a value obtained by multiplying the stored precharge signal by 1 / N and performing a precharge period by a normal precharge period N / M. It is the drive method of the used display apparatus.

The ninth aspect of the present invention provides
In the method of driving a display device using the seventh or eighth aspect of the present invention, the electrical signal for precharging is a current.

The tenth aspect of the present invention is
A driving circuit for a display device using an organic light emitting element,
At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A lighting rate calculator that calculates the lighting rate of the entire screen in a predetermined frame;
A current magnification storage unit that stores the current magnification of one frame before the predetermined frame;
A current magnification calculator for calculating an applied current magnification corresponding to the lighting rate calculated by the lighting rate calculator;
An electronic volume control unit that increases or decreases the current value applied according to the applied current magnification determined by the current magnification calculation unit;
The current magnification calculation unit is a drive circuit for a display device using an organic light emitting element that determines a current value N times (N is a real number equal to or greater than 1) for normal video display.

  According to the driving method of the display device using the organic light emitting element and the driving circuit of the display device using the organic light emitting element according to the present invention, the display due to the characteristic variation of the driving transistor is maintained while minimizing the decrease in power and life. There is an effect of reducing unevenness.

  Embodiments of the present invention will be described below with reference to the drawings.

  In order to reduce display unevenness due to variations in characteristics of the drive transistor 12, it is preferable to use a current drive method that enables uniform display even if the characteristics of the drive transistor 12 are inherently varied.

  As described above, the cause of display unevenness in the current driving method is that it is difficult to change the source signal line potential when the write current value is small. On the other hand, when the write current value is large, display without display unevenness is possible without increasing the write current N times.

  Therefore, in principle, even when there is a variation in the characteristics of the drive transistors as shown in FIG. 4, the source signal line potential changes, and in the gradation in which the source signal line current flows so that the same current is written to all pixels, If writing is performed with a current of 1 times and the current value is increased by a factor of N, uniform display is possible, and power consumption increases only for pixels that are written with N times. Become.

  In this case, in the white display, since the same current can be written to all the pixels, it is possible to use a current that is one time. Therefore, there is no power increase in white display. On the other hand, in 1 gradation display, display unevenness is improved because writing is performed with N times the current. Since the power for one gradation display is written with N times the current, it increases by, for example, a potential difference of 30%. The current that flows in the organic light emitting element during one gradation display is 1/255 of the white display when the write current is not increased N times. When the write current is increased N times during one gradation display, even if the power is increased, it is 0.5% of the power during white display. Therefore, even if the write current is increased N times during one gradation display, there is no significant effect on the amount of increase in power, and there is no problem because it is not necessary to increase the power supply capacity.

  However, in the active matrix display device, the light emission period of each pixel is controlled by a gate driver having a shift register configuration. Therefore, it is difficult to control the light emission time by gradation, that is, to control the light emission time for each pixel. In order to realize the control of the light emission time for each pixel, a gate signal line 11b shown in FIG. 1 or a gate signal line 11d shown in FIG. 2 is prepared for the number of pixels, and a control unit for controlling each signal is provided. I need it. For this reason, wiring and a circuit scale become quite large. Therefore, it is difficult to lay out the gate signal lines 11b or 11d and the control unit for the number of pixels on the array substrate.

  Therefore, in the embodiment of the present invention, the sum of the display data of all pixels is taken and normalized by setting 100% when the maximum luminance is displayed on the entire screen and 0% when the minimum luminance is displayed on the entire screen. Based on the data (hereinafter referred to as the lighting rate), we devised a method of multiplying the write current by N times for all pixels. The calculation formula for the lighting rate can be calculated by (total of display data of one frame) / (total of display data when all pixels display the maximum gradation) × 100.

  For example, according to the embodiment of the present invention, when the lighting rate is 12.5% or less, the driving is N times (N> 1), and when the lighting rate is larger than 12.5%, the driving is 1 time (normal driving). It is. Generally, the lighting rate decreases as the number of low gradation pixels where display unevenness easily occurs, and the lighting rate increases as the number of high gradation pixels where display unevenness hardly occurs. Therefore, changing the value of N for N-fold drive according to the lighting rate is almost synonymous with driving for increasing the value of N only in low gradation pixels where display unevenness is likely to occur.

  Therefore, in the embodiment of the present invention, the value of N of the N-fold current is changed based on the lighting rate, not the display gradation (N ≧ 1 here), and the lighting period is correspondingly 1 / N times (N ≧ 1). FIG. 7 shows the relationship between the write current and light emission period and the lighting rate. In the upper diagram of FIG. 7, the horizontal axis represents the lighting rate, and the vertical axis represents the write current magnification, that is, the N value of N-fold drive. In the lower diagram of FIG. 7, the horizontal axis indicates the lighting rate, and the vertical axis indicates the ratio of the light emission period.

  Since the probability of occurrence of display unevenness varies depending on the write current value, it is preferable to increase the magnification (that is, increase the value of N of the N-fold current) as the write current decreases. For this reason, as shown in FIG. 7, the lighting rate is 12.5% or less, and the writing current magnification is gradually increased as the lighting rate decreases.

  Note that the lighting rate for increasing the magnification is not limited to 12.5% and may be set to an arbitrary value. However, if it is too large, it is driven N times in most display images, and there are few advantages in terms of power and life in comparison with the conventional N times drive. In general, data displayed as a video signal has a display data with a lighting rate of about 25 to 35%, and driving N times at 12.5% or less is almost the conventional one in terms of power and life in terms of actual use. There is an advantage that a display that is the same as that of double current writing can be obtained.

  Next, a method for increasing the write current N times will be described. In the embodiment of the present invention, two methods are devised. A description will be given in order.

(Embodiment 1)
First, the first method for increasing the write current N times will be described in the first embodiment. The same parts as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 8 shows a configuration example of the output stage of the current output type source driver.

  As shown in FIG. 8, the source driver that performs current output prepares the current source 82 (meaning 82a, 82b, etc. in FIG. 8) by the number of bits as shown in FIG. The output of each current source 82 is made different so that each current source 82 outputs a current corresponding to the weight of the bit.

  As shown in FIG. 8, the least significant bit is a current source 82a that outputs an I current, and the current source becomes twice as large as the higher order bit is reached. In the most significant bit, a current of 128I flows through the current source (where I indicates a current amount per gradation. For any I, a current output corresponding to the weight of the bit results in I˜ 128I expression).

  I indicates the current per gradation, and the reference current generator 81 determines the current value.

  There is a switching unit 88 for performing current output according to the gradation. When a high level signal is received with respect to the video data 80, the switching unit 88 becomes conductive, and current output corresponding to the gradation is performed from the output line 83. For this reason, the current output is proportional to the display gradation.

  In addition, as shown in FIG. 8, the current source of the source driver is an externally drawn current type.

  Using this, the video signal is multiplied by N, so that the write current is multiplied by N. For example, when displaying gradation 1 at the time of double driving, gradation 2 is output from the source driver. As a result, twice the current flows.

  Similar to FIG. 7, if the signal magnification is changed as shown in FIG. 9, the same effect as in FIG. 7 can be obtained. FIG. 9 is a diagram showing changes when the gradation signal magnification and the ratio of the light emission period are changed according to the lighting rate. In the upper diagram of FIG. 9, the horizontal axis represents the lighting rate and the vertical axis represents the gradation magnification. In the lower diagram of FIG. 9, the horizontal axis represents the lighting rate, and the vertical axis represents the ratio of the light emission period.

  FIG. 10A, FIG. 10B, and FIG. 10C show the relationship of the driver output gradation with respect to the input video signal when the lighting rate is less than 1%, 8%, and 12.5%, respectively. . Moreover, the relationship of the light emission period corresponding to FIG. 10 (a) to FIG. 10 (c) is shown in FIG. 11 (a) to (c).

  In Embodiment 1 of the present invention, video signal data is changed according to the lighting rate and input to the driver.

  FIG. 12 shows a circuit block for changing the driver output gradation according to the lighting rate for the input video signal data and controlling the light emission period in accordance with the change.

  The circuit block of FIG. 12 includes a gamma correction circuit 120, a lighting rate calculation unit 128, a precharge determination signal generation unit 122, a gradation level conversion unit 123, and a gate driver control unit. Reference numeral 125 denotes an output to the source driver, and 127 denotes a gate driver control line.

  As shown in FIG. 12, a gradation level conversion unit 123 is inserted after the gamma correction circuit 120. Then, the gradation level conversion unit 123 performs level conversion of the video signal 121 after gamma correction in accordance with the value of the lighting rate data 124 that is the calculation result of the lighting rate calculation unit 128. This level conversion relationship is the relationship shown in FIGS. 10 (a), 10 (b), and 10 (c).

  The command input 129 is used to change the curve of the relationship between the magnification and the lighting rate shown in FIG. 9, and the maximum magnification and the lighting rate value at which the gradation signal magnification increases from 1 can be variably set. It is what you want to do.

  The precharge determination signal generator 122 determines the precharge length and the precharge on / off based on the output of the gradation level converter 123. The reason why the precharge determination signal generation unit 122 performs the above determination based on the output of the gradation level conversion unit 123 is that it is necessary to perform the precharge length and the on / off determination based on the current actually output to the panel. Because there is. That is, the determination is performed based on the video signal output to the source driver.

  In order to implement the relationship shown in FIGS. 10 (a), 10 (b), and 10 (c), in which the current flows up to four times when the lighting rate is low, the number of input display gradations is set. On the other hand, the number of gradations of the driver is required four times, and the circuit scale of the driver output stage is increased.

  Therefore, a case where the circuit scale of the output stage of the driver does not increase will be described as a modification of the first embodiment of the present invention.

  That is, in order to obtain the same effect as the driving shown in FIG. 9 with the same number of output gradations of the driver as the input gradation data, the gradation level conversion unit 123 shown in FIG. As shown in (b) and FIG. 13 (c), there was provided a relationship between input data and driver output corresponding to the lighting rate.

  In this case, as shown in FIG. 13C, when the lighting rate is 12.5% or more, it is possible to display with a predetermined luminance for all gradations, but FIG. 13A and FIG. 13B. In the gray scale in which the data magnification does not correspond to the change in the ratio of the light emission period, the writing current does not increase sufficiently with respect to the decrease of the light emission period, and the luminance decreases. The range of input data shown in 134 and 138 corresponds to this. Note that 131 shown in FIG. 13A and 135 shown in FIG. 13B are lines indicating the case where the number of gradations of the driver is increased from the number of gradations of the input data, and are described for reference. Yes. Further, the range 133 shown in FIG. 13A and the range 137 shown in FIG. 12B indicate the range of input data whose data magnification corresponds to the change in the ratio of the light emission period.

  However, when the lighting rate is low, the number of pixels that perform high gradation display is considered to be small, and there is a high possibility that data in the range indicated by 134 or 138 does not exist in one screen. Even if it exists, the decrease in luminance is not conspicuous with respect to the screen display at about several points. Therefore, even if the relationship between the input data and the driver output gradation is as shown in FIGS. 13A, 13B, and 13C, display with reduced image quality is possible.

  However, as the magnification of the input data is increased, the number of gradations to be output at a predetermined magnification with respect to the input data is decreased, so that it is assumed that the number of pixels in which the luminance is reduced is increased. Therefore, it is desirable to keep the magnification of input data at about 4 times at the maximum.

(Embodiment 2)
Next, a second method for increasing the write current N times will be described in the second embodiment. The same parts as those described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 14 is a diagram illustrating a relationship between the reference current generation unit and the output stages of the respective colors. As shown in FIG. 14, a MOS transistor is used as the transistor.

  In the current output type driver, the current output stage is configured as shown in FIG.

  At this time, the gradation is determined by the number of transistors connected to the output, and the current per gradation depends on the value of the current flowing through the resistor 144 (meaning the resistors 144a, 144b, and 144c in FIG. 14). It is decided. This is because the current flowing through the resistor 144 is transmitted to each gradation display current source of each output by the current mirror configuration. Although the current value per gradation with respect to the current of the resistor 144 is determined by the channel size ratio of the transistors forming the current mirror, the current increases or decreases in a proportional relationship.

  That is, by multiplying the current flowing through the resistor 144 (referred to as a reference current) N times, it becomes possible to output N times the write current from the source driver. The reference current can be changed by the electronic volumes 143a to 143c. However, the electronic volume is used to adjust the luminance variation due to the efficiency variation of each color of the organic light emitting element. On the other hand, in order to increase the current N times, an operation circuit for register values for N times the register values of each color after adjustment is required, which increases the circuit scale. Since there is an arithmetic circuit for each color, it is disadvantageous to the fact that the circuit scale is increased in that three circuits are required.

  Therefore, in the second embodiment of the present invention, as shown in FIG. 15, an electronic volume for multiplying the current value by N times is provided for each color as compared with FIG. In FIG. 15, an electronic volume for multiplying the current value by N times in common for each color is shown as an electronic volume 143d. Further, as shown in FIG. 15, a MOS transistor is used as the transistor.

  If the current flowing at 1 time is assumed to be the minimum value of the electronic volume, the current increase rate by resistance division of the electronic volume 143d is designed to be 1 to 4 times as shown in FIG. The electronic volume value can be uniquely determined for the specified magnification without calculation, and a circuit that realizes N-fold driving without the need for an arithmetic circuit can be configured.

  Also, in the electronic volume circuit unit 143a to 143c, from the viewpoint of white balance adjustment, the change in the amount of current per step must be performed in increments of 1% at most and about 2%. In order to make it variable, 150 steps of adjustment are required. In order to realize this, an 8-bit electronic volume circuit is required (a total of three circuits are required since this is necessary for each color).

  On the other hand, in the configuration of FIG. 15 in which the common electronic volume 143d is provided, since there is no restriction on the step size, even if the electronic volume 143d is provided with a current variable function of four times, for example, four steps (1, 2, 3,. (4 times) 2-bit electronic volume may be used. It can be determined how many kinds of current magnifications can be taken in the line 162 shown in FIG. In the electronic volume 143d, there is no problem even if there is a current difference of 2% or more. Therefore, the electronic volume 143d only needs to be about 6 bits at most. From the viewpoint of the total area of the electronic volume unit 143, it is shown in FIG. Such a configuration using four electronic volumes 143a to 143d is preferable.

  The write current value can be increased by increasing the electronic volume circuit by one as shown in FIG. 15 and controlling the value of the electronic volume 143d so that the current increase ratio as shown in FIG. 16 is obtained. In a driver circuit having a current precharge function, there is a problem in that a decrease in luminance or an increase in luminance occurs in a current precharge pixel due to a difference in precharge amount due to a change in reference current, resulting in a decrease in display quality.

  The reason why the luminance change in the precharged pixel occurs due to the change in the reference current will be described with reference to FIG.

  FIG. 17 is a diagram illustrating the relationship of the source signal line current (vertical axis) with respect to the source signal line voltage (horizontal axis) in the circuit configuration of FIG. 1 or FIG. In FIG. 17, the voltage for each gradation at the time of 1 × driving is Va, and the current corresponding thereto is Ia. The number after a corresponds to the gradation. Similarly, Vb and Ib are used for double driving, and Vc and Ic are used for quadruple driving.

  An example in which gradation 1 display is performed in the next horizontal scanning period after gradation 0 display will be described.

  If the characteristic of the driving transistor 12 is indicated by a curve 171 in the gradation 1 at the time of 1 × driving, it is necessary to change the source signal line potential to the point Va1 if the current for the gradation 1 is Ia1. is there. The potential change amount at this time is ΔV1.

  The principle of changing the current from the gradation 0 state to the gradation 1 state by the current precharge is that the precharge current value Ip, the precharge period T1, and the source line capacitance Cs, the source signal line potential change is Ip × Ip and T1 are determined such that ΔV1 = Ip × T1 / Cs (Ip is the maximum gradation current because the output stage of the source driver is configured in FIG. 8). The current value when the maximum gradation is output at the time of 1 × driving).

  Here, when current writing is performed at twice, the potential change amount up to gradation 1 requires a potential change corresponding to two gradations of 1-time driving. In the case of FIG. 17, ΔV2. When precharge is performed in the same manner as in the 1 × drive, the precharge current is doubled, so that the potential change amount is (2 × Ip) × T1 / Cs, and ΔV2 = 2 × ΔV1. However, in practice, the characteristics of the drive transistor 12 are in a non-linear relationship, and ΔV2 <2 × ΔV1. Therefore, the potential change is larger than a predetermined value, and as a result, the current becomes large and the luminance is displayed high.

  Similarly, in gray scale 2 display, if current precharge (ΔV2 = Ip × T2 / Cs: T2 is a precharge period corresponding to 2 gray scales) that expresses gray scale 2 of 1 × drive is applied as it is, double drive is performed. In this case, the change in potential of gradation 2 becomes too large, and the luminance increases.

  As a method for solving this problem, there is a method of changing the precharge period (T1, T2, etc.) for each magnification. However, the number of precharge periods of (number of precharge stages) × (number of magnifications set) is set. Therefore, the memory for holding the precharge pulse data becomes large.

  Therefore, in the second embodiment of the present invention, the current value of the precharge current value Ip is changed according to the magnification, and the precharge period is also precharged corresponding to the gradation converted to the current value at the time of 1 × driving. By applying the period, the required amount of voltage change was always obtained.

  For example, in order to perform gradation 1 display at the time of double driving, the precharge current value is set to 1/2 and the precharge period is set to a period corresponding to gradation 2. As a result, the amount of potential change is (2 × Ip) / 2 × T2 / Cs = Ip × T2 / Cs = ΔV2. Since the gradation 2 for 1 × driving and the gradation 1 for 2 × driving have the same amount of current, it is equal to the potential change (ΔV 2) for changing to the 1 × driving gradation 2. It becomes that.

  In general, in order to perform precharge with gradation M display during N-fold driving, the precharge current value may be 1 / N times, and the precharge period may be a period corresponding to gradation (N × M).

  As for the precharge period, if the precharge period corresponding to each gradation at the time of 1 × driving is held, the selection of the held precharge period may be changed at the time of N × driving. There is no need to newly hold a precharge period.

  With regard to the precharge current value, as shown in FIG. 8, up to 255 gradations, only current corresponding to 255 gradations is allowed to flow. However, it is necessary to keep the precharge current value constant. is there. Since the current value per gradation is multiplied by N, the number of gradations to be output is set to 1 / N.

  Therefore, in the second embodiment of the present invention, as shown in FIG. 18, a precharge current value control signal 184 for controlling the current value for performing the current precharge is newly provided, and even during the current precharge period, The current output is performed only for the gradation set by the precharge current value control signal 184. During the period other than the current precharge period, gradation current output is performed by the gradation data line 80. Therefore, the switching unit 183 that controls the output of the current source 82 operates as shown in FIG.

  Next, a method of making the precharge current constant by using the output stage 185 shown in FIG. 18 is shown in FIG. Since the precharge current value is determined by the current value per gradation × the number of output gradations, the current value is kept constant by setting the number of gradations to 1 / N when the reference current is multiplied by N. Can be.

  FIG. 21 shows the configuration of the output stage 185 having a function of varying the reference current and a precharge function. Since the precharge current value control signal 184 employed in the second embodiment of the present invention is changed according to the magnification of the reference current, and further, the current magnification is variable for each color, all output stages It is configured to be input in common.

  In order to optimize the precharge amount when the reference current is increased N times, the function of making the precharge current value constant can be realized by the configuration of the driver IC of FIG. A function for determining a precharge period corresponding to N times is required. Further, a circuit for realizing FIG. 20 is necessary.

  Therefore, in the second embodiment of the present invention, the controller unit is changed to the input unit of the precharge determination unit, and a precharge current value generation unit is added.

  FIG. 22 is a diagram illustrating a configuration of a determination circuit for changing the reference current according to the lighting rate. The determination circuit shown in FIG. 22 includes a lighting rate calculation unit, a current magnification calculation unit 222, a current magnification storage unit for one frame, a precharge current calculation unit 223, a voltage control unit 228, an electronic volume control unit, a precharge determination unit 225, And a data operation unit 224.

  In FIG. 22, the magnification of the current magnification calculator 222 is calculated based on the lighting rate calculated from the video signal. This magnification is the reference current magnification in FIG. Therefore, the reference current is first multiplied by N based on this value. The magnification data 227 is input to the electronic volume control unit, and the value of the electronic volume 143d is determined. The precharge current calculation unit 223 outputs a precharge current value control signal 184 based on the magnification data 227 so that the output gradation has the relationship shown in FIG. 20 according to the magnification. By setting the values of the precharge current value control signal 184 and the electronic volume control signal 142d in accordance with the lighting rate, the precharge current value is always a constant value (in FIG. 20, reference current magnification × precharge current value control). The signal value is constant in every row).

  Next, a circuit configuration for setting the precharge period will be described. In order to perform precharge with gradation M display during N-fold driving, the precharge period is set to a period corresponding to gradation (N × M), so that a precharge flag corresponding to the gradation is generated. In the precharge determination unit 225, gradation data is preliminarily multiplied N times (where N is a magnification calculated by the current magnification calculation unit 222) in the data calculation unit 224, and (N × M) for the input gradation M Since the precharge determination is performed with gradation, the precharge period corresponds to (N × M) gradation.

  This method has an advantage that it is possible to determine whether to perform precharging and to determine the length of precharging without increasing the circuit scale of the precharge determining unit 225. The length of the precharge is as described above. If a precharge period is set for each grayscale current at a single current regardless of the magnification of the reference current, an optimum precharge for any N value is set. You can set the charge period.

  As to determination as to whether or not to perform precharge, the case where precharge is necessary is a case where the source signal line potential cannot be changed up to a predetermined gradation with a current corresponding to the display gradation. The time required for the change is expressed as Δt = Cs × ΔV / Iw. (Cs: source signal line capacitance, ΔV: amount of voltage change from source signal line state in previous row to source signal line state in the row, Iw: write current value) When writing is difficult, the write current value is small In other words, first, the current value corresponding to the current display gradation is small, or the case where a large potential change is required compared to the state of the previous row.

  Accordingly, whether or not to perform precharge is determined according to the flow shown in FIG. Since gradation 0 display can only be displayed by voltage precharge, it is first determined whether gradation 0 or not (231) (current at gradation 0 display is normally 0, and even when multiplied by N, it becomes 0 current) Therefore, there is no effect, and it is necessary to use voltage precharge in which a voltage corresponding to black display is applied to the gate electrode of the driving transistor).

  Next, in a case other than the gradation 0, the gradation is compared with the gradation of the previous line (232). When writing is performed at the same gradation as the previous row, the source line state does not change if there is no variation in transistors, and the reference current according to Embodiment 2 of the present invention is multiplied by N even if there is variation. This makes it possible to change the source signal line to a predetermined value, so that precharge is not performed (237).

  Next, when the write current is larger in the previous row, the smaller the current gradation, the smaller the write current and the larger the amount of potential to be changed. Therefore, it is determined whether the write current value is equal to or less than a certain value (for example, 200 nA) (233). Then, precharge may be performed when the write current value is equal to or less than a predetermined value (238). If the write current value is not less than a certain value, precharge may be avoided (237).

  On the other hand, when the write current is smaller in the previous row, the larger the current gradation, the larger the potential change, but the larger the write current. Considering the characteristics of the general driving transistor 12, ΔV / Iw varies depending on the current value corresponding to the gradation of the previous row and the current value in the row, and if the row is greater than a certain current value, If the current before the row is greater than or equal to a certain value, precharging may be avoided (conditional branching at 234 and 235).

  In conditional branching of 233, 234, and 235, it is difficult to make a determination based on the current value, and conditional branching based on the video signal gradation is necessary. Since the current value at the time of white display is determined by the material efficiency and the panel configuration, the write current value with respect to the video signal gradation can be known when the module is actually drawn. Therefore, when it is actually mounted on the controller, the determination is made based on whether or not it is a certain gradation or more.

  When the write current is multiplied by N, multiplying the data by N in the data calculation unit 224 before the precharge determination unit 225 as shown in FIG. 22 is the same as the operation of the precharge determination unit 225 regardless of the current magnification. Can be operated. Therefore, it is advantageous in that it is not necessary to increase the circuit scale of the precharge determination unit 225.

  For example, in the conditional branch 233, if the gradation 10 at the time of 1 × driving is a write current of 200 nA, precharge is performed at the gradation 10 or less. The 200 nA at the time of double driving is gradation 5, and it is sufficient to precharge at gradation 5 or less. In the configuration according to the second embodiment of the present invention, the conditional branch 233 is not changed, and the input gradation is doubled, so that the write current is determined as the gradation 10 and precharged. Since it is possible to support N-fold driving without changing the condition branching condition, a configuration in which a data operation unit is provided in front of the precharge determination unit 225 to multiply the data by N as in the second embodiment of the present invention. This is a preferred configuration.

  Furthermore, the second embodiment of the present invention has a function of varying the voltage value of the EL power source 14b (FIG. 1 or FIG. 2) in accordance with the write current magnification from the viewpoint of reducing power consumption. Such a function is due to the voltage controller 228 in FIG. That is, the voltage controller 228 varies the power supply voltage of the EL power supply 14b in accordance with the output data.

  In FIG. 6, the voltage required for the organic light-emitting element is 4V for 1 × driving and 8V for 4 × driving, and the voltage required for 4V is different. If an extra voltage of 4V is always supplied to the EL power supply 14b, the power of 4V × (total current flowing through the organic light emitting element) will increase.

  Therefore, in the second embodiment of the present invention, for example, as shown in FIG. 24, a voltage of −2 V, for example, is used for the purpose of supplying a necessary voltage to the EL power supply 14b in accordance with the write current magnification. For example, a voltage of −6V can be supplied during 4 × driving. In this way, at a lighting rate of around 30%, which is a high appearance rate in a general video signal, the voltage of the EL power supply 14b is supplied with the same voltage equivalent to 1 × driving as before, so there is no increase in power. Only in the low lighting rate region where writing is difficult, writing is given priority and the voltage of the EL power supply 14b is increased. In this case, although the power increases, the total current flowing through the organic light emitting element is small because the lighting rate is low, and the amount of power increase is small.

  According to the second embodiment of the present invention, the magnification of the reference current, the ratio of the light emission period, the number of output gradations for precharge current, the data magnification for precharge determination, and the cathode voltage change according to the lighting rate. It becomes a structure and changes as shown in FIG. Thereby, it is possible to realize a display device that improves display unevenness while suppressing an increase in power.

(Embodiment 3)
Next, a third embodiment of the present invention will be described.

  In the third embodiment, a case will be described in which the luminance of the display screen is changed by command control using the source driver in the second embodiment.

  If the source driver in Embodiment 2 of this invention is used, the electric current value per gradation can be changed at arbitrary timings. Until now, the light emission period has been shortened in response to the increase in the current value. However, if the light emission period is made constant, the luminance can be increased. Since the current value can be changed by the electronic volume 143d in the configuration as shown in FIG. 21, the luminance can be changed by command control.

  FIG. 26 is a diagram showing a digital camera in which the display device according to the second embodiment of the present invention is incorporated. The digital camera 261 includes a photographing unit 262, a shutter switch 263, a finder 264, and a display panel 265.

  For example, in the digital camera shown in FIG. 26, it is possible to display the imaging data with high luminance on the display panel 265 for a while after the shutter switch 263 is pressed. This can be dealt with by enlarging the data of the electronic volume 143d and multiplying the current N times when the shutter switch 263 is pressed. If the electronic volume 143d is operated so as to return to the original value after a certain period of time, the display panel 265 is displayed with a predetermined luminance.

  FIG. 27 shows changes in the electronic volume control signal 142d and the ratio of the light emission period with respect to the operation of the shutter switch 263. Only the period 271 in FIG. 27 can be displayed with high luminance (in this case, four times higher luminance). However, in order to increase the luminance only when it is desired to check the content displayed on the display panel 265 and to reduce the power during normal times, it is possible to display the image with a predetermined luminance. In particular, since it can be controlled by an electronic volume, it is possible to easily set a luminance increase rate and a time for high luminance by control of a microcomputer or the like on a command basis.

  In addition, since the current value can be changed according to the step size of the electronic volume 143d, the luminance can be changed gradually by gradually changing the electronic volume control signal 142d. For example, as shown in FIG. 28, the brightness of the display panel 265 is increased from the moment the shutter switch 263 is pressed, and after a certain period (a period 271 in FIG. 28), gradually as shown in a period 281 in FIG. It is also possible to reduce the luminance to the luminance before the shutter switch 263 is pressed.

  If the current changing function by the electronic volume 143d is used, the brightness setting of the panel can be changed. In the case of a conventional driver, if the reference current is changed, the precharge setting is shifted. Therefore, the luminance can be changed only by adjusting the light emission period. However, by using the driver IC according to the second embodiment of the present invention, the current can be changed. Since the value itself can be changed, there are various ways of changing the luminance.

  Further, it is possible to combine N-time driving at a low lighting rate and luminance adjustment in combination. When the lighting current is low, the writing current is quadrupled, and when the luminance is doubled, the writing current is four times the maximum normal luminance. The relationship is shown in FIGS. 29 (a) and 29 (b).

  29 (a) and 29 (b) are characterized by the fact that the reference current is reduced at both double luminance and single luminance, as shown by a point 293, with respect to insufficient writing at low current. The magnification is set to 4 times. The difference in luminance is adjusted by the ratio of the light emission period (297 and 298). In the region (291) where the lighting rate is 12.5% or less, the reference current is changed for the purpose of improving the writing characteristics. In the region where the lighting rate is 12.5% or more, the light emission period is 100%, and the luminance difference is realized by the ratio of the reference current. For normal brightness, the reference current was 1 ×, and for double brightness, the reference current was 2 ×.

  As shown in FIGS. 29 (a) and 29 (b), by changing the reference current with respect to the lighting rate and the ratio of the light emission period, display characteristics can be improved at a low lighting rate, and temporary brightness adjustment or brightness enhancement function can be achieved. A display panel with a combination of can be realized.

  In the case of double luminance display, there is a method of changing the reference current magnification in the area 291 with a curve 294 that changes in the same manner as in the normal display. In this case, an increase in the instantaneous current flowing through the organic light emitting element can be suppressed, and the voltage of the EL power supply 14b can be made shallower. Also in the writing characteristics, the writing current is larger than that in the normal display, and the image quality higher than the normal display can be realized with respect to the display unevenness.

  In the description of each of the first to third embodiments, the current source of the source driver is an external current source type and the pixel circuit is described as a p-type TFT. However, the source current source is a discharge type current source. (FIG. 31), even a circuit using an n-type TFT as a pixel circuit (FIG. 30) exhibits the same effect. The difference is that the current flowing through the source signal line is reversed and that the voltage is reversed in black and white, and the problem is that the potential fluctuation is less likely if the current flowing through the source signal line is small. Therefore, if the write current is multiplied by N, the same effect is exhibited.

  In the above invention, the transistor has been described as a MOS transistor, but a MIS transistor or a bipolar transistor can be similarly applied.

  The present invention can be applied to any material such as crystalline silicon, low-temperature polysilicon, high-temperature polysilicon, amorphous silicon, and gallium arsenide compound.

  According to the driving method of the display device using the organic light emitting element and the driving method of the display device using the organic light emitting element according to the present invention, even if the number of output bits of the current driver is increased, the circuit scale is further increased. A driving method of a display device using an organic light emitting element that drives a display device that performs gradation display by an amount of current, such as an organic electroluminescent element, and a driving circuit of the display device using the organic light emitting element Etc. are useful.

The figure which showed the pixel circuit by the current copier structure in Embodiment 1-3 of this invention, a source driver, and a gate driver The figure which showed the pixel circuit by the current mirror structure in Embodiment 1-3 of this invention, a source driver, and a gate driver The figure which showed the circuit structure when arrange | positioning to the pixel of the same signal line in the pixel transistor 12 which has the characteristic shown by 41 and 42 of FIG. FIG. 5 shows that the gate voltage is different even when the same drain current flows due to the characteristic variation of the driving transistor 12. (A) The display device shown in FIG. 3 is driven, and the source signal line voltage when the three pixels are written when the same current is output to the source signal line, and the current value flowing through the organic light emitting element at that time (B) Drives the display device shown in FIG. 3 and writes the three pixels when the same current is output to the source signal line. The relationship between the source signal line voltage and the current value flowing through the organic light emitting element at that time, and the relationship between time and the current value flowing through the organic light emitting element 13 Diagram showing the relationship between current magnification and voltage required for organic light-emitting elements during white gradation display The figure which showed the relationship between the write current magnification by the difference in the lighting rate in embodiment of this invention, and the ratio of the light emission period The figure which showed the example of a structure of the output stage of the current output type source driver in Embodiment 1 and 2 of this invention The figure which showed the change when changing the ratio of a gradation signal magnification and the light emission period with the lighting rate in Embodiment 1 of this invention. (A) The figure which showed the relationship of the source driver output gradation with respect to the input data in the lighting rate less than 1% in Embodiment 1 of this invention (b) With respect to the input data in the lighting rate of 8% in Embodiment 1 of this invention The figure which showed the relationship of the source driver output gradation (c) The figure which showed the relationship of the source driver output gradation with respect to the input data in the lighting rate 12.5% or more in Embodiment 1 of this invention The figure which showed the operation | movement in the case of changing the period which an EL element light-emits with the gate signal line 2 in Embodiment 1 of this invention. The figure which showed the circuit block for changing the driver output gradation with respect to the input data in Embodiment 1 of this invention with a lighting rate, and controlling the light emission period according to a change. (A) The figure which showed the relationship between the input data and driver output gradation when the lighting rate in Embodiment 1 and 2 of this invention is less than 1% (b) The lighting rate in Embodiment 1 and 2 of this invention (C) The input data and driver output gradation when the lighting rate is 12.5% or more in the first and second embodiments of the present invention Figure showing the relationship The figure which showed the relationship between the reference current production | generation part in Embodiment 2 of this invention, and the output stage of each color The figure which showed the circuit structure which can change the reference current in Embodiment 2 of this invention irrespective of a display color. (A) The figure which showed the relationship between the lighting rate and reference current in the case of implementing the drive which changes a reference current according to the lighting rate in Embodiment 2 of this invention (b) Lighting in Embodiment 2 of this invention The figure which showed the relationship between the lighting rate and light emission period in the case of implementing the drive which changes a reference current according to a rate The figure which showed the relationship between the source signal line voltage by the drive transistor 12, and an electric current value in case the electric current is written in the said pixel in Embodiment 2 of this invention. The figure which showed the circuit structure of 1 output of the source driver which has the precharge current value variable function in Embodiment 2 of this invention The figure which showed operation | movement of the switch part 183 of FIG. 18 in Embodiment 2 of this invention. The figure which showed the relationship of the precharge electric current value control signal with respect to the reference current multiplication factor in Embodiment 2 of this invention. The figure which showed the circuit structure of the source driver which has the function which can change the reference current of all the output stages which has the output stage shown in FIG. 18 in Embodiment 2 and 3 of this invention The figure which showed the structure of the determination circuit for changing a reference current according to the lighting rate in Embodiment 2 of this invention. The figure which showed the flow of determination of the precharge determination part in FIG. 22 in Embodiment 2 of this invention. (A) The state of the potential change of the EL power supply 14b with respect to the reference current magnification due to the difference in the lighting rate in Embodiment 2 of the present invention, and the diagram showing the relationship between the lighting rate and the current flowing through the resistor 144 (b) The figure which shows the mode of the electric potential change of EL power supply 14b with respect to the reference current magnification by the difference in the lighting rate in Embodiment 2, and shows the relationship between the lighting rate and the power supply voltage of EL power supply 14b. The figure which showed the change of the reference current magnification by the lighting rate in Embodiment 2 of this invention, the ratio of the light emission period, the gradation output for precharge current, the data magnification for precharge determination, and a cathode voltage. The figure which incorporated the display apparatus of embodiment of this invention in the digital camera in Embodiment 3 of this invention (A) A diagram showing how to change the reference current magnification with respect to the operation of the shutter switch 263 in Embodiment 3 of the present invention, and a diagram showing the relationship between the operation of the shutter switch 263 and the reference current magnification (b) Embodiment of the present invention 3 shows how the reference current magnification is changed with respect to the shutter switch 263 operation in FIG. 3, and shows the relationship between the shutter switch operation and the light emission period ratio (A) A diagram showing how to change the reference current magnification with respect to the operation of the shutter switch 263 in Embodiment 3 of the present invention, and a diagram showing the relationship between the operation of the shutter switch 263 and the reference current magnification (b) Embodiment of the present invention 3 shows how the reference current magnification is changed with respect to the shutter switch 263 operation in FIG. 3, and shows the relationship between the shutter switch operation and the light emission period ratio (A) The figure which showed the change of the reference current magnification by the difference in the lighting rate in the case of making it display with a brightness | luminance twice as high as normal at the time of normal display in Embodiment 3 of this invention, (b) Implementation of this invention The figure which showed the change of the light emission period ratio by the difference in the lighting rate in the case of making it display by the brightness | luminance twice as high as normal at the time of the normal display in the form 3. The figure which showed the current copier structure in case the pixel circuit in each of the 1st-3rd embodiment of this invention is comprised by n-type TFT. The figure which showed the output stage structure of the discharge type current output type source driver in each of the first to third embodiments of the present invention

Explanation of symbols

10, 10a, 10b Source signal line 11b Gate signal line 11d Gate signal line 12, 12a, 12b, 12c Drive transistor 13, 13a, 13b, 13c Organic light emitting element 14 EL power source 14a EL power source 14b EL power source 17 pixel 17a pixel A
17b Pixel B
18c Pixel C
18 Storage capacity 80a, 80b, 80c, 80d, 80e, 80f Control signal of switching unit 146 81 Reference current generating unit 82 Current source 82a, 82b, 82c, 82d, 82e, 82f, 82g, 82h
83 Output line 85a, 85b, 85c, 85e, 85f, 85f
86 Current precharge control line 87 Current output unit 120 Gamma correction circuit 121 Video signal after gamma correction 122 Precharge determination signal generation unit 123 Gradation level conversion unit 124 Lighting rate data 128 Lighting rate calculation unit 129 Command input 141a, 141b, 141c , 141d, 141e, 141f Current output 142a, 142b, 142c Electronic volume control signal 142d Electronic volume control signal 143a, 143b, 143c, 143d Electronic volume 144 Resistance 144a, 144b, 144c Resistance 181 Current output section 182 Current precharge period control line 184 Precharge current value control signal 185 Output stage 186 Current precharge pulse group 186a, 186b, 186c
187 Voltage precharge pulse group 222 Current magnification calculation unit 223 Precharge current calculation unit 224 Data operation unit 225 Precharge determination unit 227 Magnification data 228 Voltage control unit 291 Lighting rate 12.5% or less

Claims (10)

At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A lighting rate calculator that calculates the lighting rate of the entire screen in a predetermined frame;
A current frame current magnification storage unit that stores a current magnification of the predetermined frame one frame before;
A current magnification calculator for calculating an applied current magnification corresponding to the lighting rate calculated by the lighting rate calculator;
An organic light emitting element for driving a display device using an organic light emitting element, comprising: an electronic volume control unit that increases or decreases a current value applied in accordance with a first applied current magnification determined by the current magnification calculating unit. A driving method of the display device used,
When the lighting rate per frame is lower than the predetermined value,
Determining the first current magnification by the current magnification calculator;
Applying a predetermined current by the current volume control unit,
When the lighting rate per frame is lower than a predetermined value, a current value of N times (N is a real number larger than 1) is applied as the current magnification when normal video display is performed.
A display device driving method using an organic light-emitting element.   2. The method of driving a display device using an organic light emitting element according to claim 1, wherein the current magnification is determined by multiplying a gradation value indicated by a video signal in each frame by a predetermined value.   The organic light-emitting element according to claim 1, wherein the current magnification is determined by multiplying a current value of a reference current source for each display color prepared for applying a video signal by a predetermined number simultaneously for each color. A driving method of a display device.   The method for driving a display device using an organic light emitting element according to claim 1, wherein the predetermined lighting rate is 12.5% or less.   The method of driving a display device using an organic light-emitting element according to claim 1, wherein the predetermined current magnification is greater than 1 and 4 or less.   The application time of the current signal to the organic light emitting element when a current value of N times as the predetermined current magnification is applied to the organic light emitting element constituting each pixel of the display device using the organic light emitting element is as follows: The driving method of a display device using an organic light emitting element according to claim 1, wherein 1 (t) is 1 / t when N = 1. A display device using the organic light emitting element is:
At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A current magnification calculator for multiplying an applied current magnification;
An electronic volume control unit that increases or decreases a current value applied in accordance with a second applied current magnification determined by the current magnification calculation unit;
Applying a predetermined current determined by the second applied current magnification to each pixel during a predetermined period;
The method for driving a display device using an organic light-emitting element according to claim 1, further comprising: applying a predetermined current determined by the first applied current magnification after a predetermined period has elapsed. At least one current source circuit for determining at least one current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A precharge unit for applying a predetermined electrical signal before applying the video signal;
In the precharge unit, an organic light emitting element for driving a display device using an organic light emitting element, in which a precharge signal value corresponding to each display gradation at the time of 1 × driving which is normal driving is stored, is used. A driving method of a display device,
When displaying a gradation M (M is an integer of 0 or more) as a current value applied to a display device using the organic light-emitting element as N times N (N is a real number of 1 or more) during normal driving, precharging is performed. An organic light emitting device comprising a step of using a value obtained by multiplying the stored precharge signal by 1 / N and performing a precharge period by a normal precharge period N / M. A driving method of the display device used.   The method of driving a display device using an organic light-emitting element according to claim 7 or 8, wherein the electrical signal for precharging is a current. A driving circuit for a display device using an organic light emitting element,
At least one current source circuit for determining a current output per gradation;
A current control unit for controlling a current value of the current source circuit;
A lighting rate calculator that calculates the lighting rate of the entire screen in a predetermined frame;
A current magnification storage unit that stores the current magnification of one frame before the predetermined frame;
A current magnification calculator for calculating an applied current magnification corresponding to the lighting rate calculated by the lighting rate calculator;
An electronic volume control unit that increases or decreases the current value applied according to the applied current magnification determined by the current magnification calculation unit;
The current magnification calculation unit is a drive circuit for a display device using an organic light-emitting element that determines a current value N times (N is a real number equal to or greater than 1) with respect to normal video display.

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