KR100585205B1 - Organic electroluminescent display device capable of partial scanning of display panel, and method of driving the same - Google Patents

Abstract

Disclosed is a passive matrix organic electroluminescent display device capable of increasing light emission luminance and reducing driving voltage by selectively driving only some scan lines among all scan lines of a display panel. The organic electroluminescent display includes a display panel, a scan driver, a data driver, and a light emission controller, wherein the scan driver receives a clock pulse and a scan start signal and sequentially increases n-bit signals during one display frame period. N-bit counter for outputting; A scan controller configured to receive the n-bit signal, change a bit value of at least one of the n-bit signals, and output a changed n-bit signal in a predetermined range in response to a scan control signal; And a plurality of selectors configured to receive the changed n-bit signal and to output a scan driving signal to a scan line corresponding to the input n-bit signal when a preset n-bit signal is input.

Organic electroluminescent display, scan line, frame, partial drive, n-bit counter

Description

Organic electroluminescent display device capable of partial scanning of display panel, and method of driving the same}             

1 is a view for explaining the configuration of a conventional passive matrix organic electroluminescent display.

2 is a block diagram illustrating a passive matrix organic electroluminescent display device according to the present invention.

3 is a view showing a screen display according to time when a partial scanning method of a display panel according to the present invention is applied to a text / graphic mixing mode.

4 is a view for explaining a screen display state when a scanning method of a display panel according to the present invention and the prior art is applied to a text / graphic mixing mode.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent display, and more particularly, to a passive matrix organic light emitting diode which can increase light emission luminance and reduce driving voltage by selectively driving only some scan lines among all scan lines of a display panel. The present invention relates to an electroluminescent display and a driving method thereof.

An organic electroluminescent device inserts a low molecular or polymer light emitting organic material between a transparent electrode (cathode) and a metal electrode (anode), and generates light by applying power to an opposite electrode. As a display element, there is no need for a backlight as in a liquid crystal display (LCD), a fast response speed, and a spontaneous light emitting element, so that the display device has excellent brightness and viewing angle characteristics. The organic electroluminescent display is classified into a passive matrix type and an active matrix organic electroluminescent display according to a driving method.

1 is a view for explaining the configuration of a conventional passive matrix organic electroluminescent display. As illustrated in FIG. 1, the passive matrix organic electroluminescent display 100 includes a display panel 110 in which a plurality of organic electroluminescent elements 150 (here, referred to as diodes as circuit elements) are arranged in a matrix. ), A scan driver 120 supplying a scan driving signal to the scan line 220 connected to the cathode of the organic electroluminescent device 150, and a data line 210 connected to the anode of the organic electroluminescent device 150. A data driver 130 for supplying an image data signal, and a control unit 140 for receiving an image signal from the outside and controlling the operations of the scan driver 120 and the data driver 130. In a typical organic electroluminescent display device 100, the scan driver 120 is composed of a plurality of shift registers, and has a cascade structure in which the output of the front shift register is input to the rear shift register. . Therefore, when the clock signal and the scan start signal are input to the scan driver 120 from the control unit 140, the scan driver 120 receives the last column from the scan line 220 in the first row of the display panel 110. The scan driving signal is sequentially supplied to the scan line 220. In this case, the data driver 130 supplies an image data signal to be displayed on the selected scan line 220 through a plurality of data lines 210 crossing the scan line 220, thereby supplying a predetermined image to the display panel 110. Display.

In the passive matrix organic electroluminescent display 100 as described above, all the scan lines of the display panel 110 are sequentially selected as long as the clock signal and the scan start signal are input to the shift register of the scan driver 120. Accordingly, in the passive matrix organic electroluminescent display device 100 of FIG. 1, even when only a part of the display panel 110 is used for image display, as in the “screen saving mode”, all the scan lines 220 are all sequentially. Since this is selected, there is a problem that power is consumed unnecessarily. In addition, as shown in FIG. 4I, when a graphic image is displayed on the upper portion of the display panel 110 and a text image is displayed on the lower portion, within one display frame period a + b, When the graphic image portion is scanned once ("a" section), the text image portion is also scanned once ("b" section). In such a graphic / text mixed mode, the display of the graphic image generally uses about 30% of the total usable luminance, and the display of the text image uses all 100% of the total available luminance. Therefore, when the graphic image and the text image are displayed together on the screen of the passive matrix organic electroluminescent display 100, the brightness of the text portion is made brighter than the brightness of the graphic portion.

In order to solve this problem and reduce power consumption, in a display device such as an LCD, as shown in (ii) of FIG. 4, the scanning of the graphic portion is performed in the "a" section of the first display frame period (a + b). Only the line is selected, and the driving voltage is not supplied to the LCD itself in the " b " section. Repeat the process of selecting all the scan lines. By reducing the number of display of the text portion ("b" section) in this way, the difference in brightness and power consumption of the graphic image and the text image can be reduced. However, the power consumption is reduced, but the brightness of the text portion (“b” section) is reduced.

Accordingly, an object of the present invention is to passively drive only a necessary portion of the display panel, thereby passively emitting only the selected portion during the light emission time of the non-selected portion, and a passive matrix organic electroluminescent display device capable of increasing the brightness and It is to provide a driving method.

Another object of the present invention is to provide a passive matrix organic electroluminescent display device and a method of driving the same, which can reduce the luminance difference between the graphic image and the text image by making the number of times of scanning the graphic image portion more than the number of scanning of the text image portion. It is.

In order to achieve the above object, the present invention provides a display panel comprising a plurality of data lines and a plurality of scan lines are crossed in a matrix shape, the organic electroluminescent element is formed at the intersection of the data line and the scan line; Scan driver; Data driver; And a light emission controller,

The scan driver may include a n-bit counter that receives a clock pulse and a scan start signal and outputs n-bit signals sequentially increased during one display frame period; A scan controller configured to receive the n-bit signal, change a bit value of at least one of the n-bit signals, and output a changed n-bit signal in a predetermined range in response to a scan control signal; And a plurality of selectors configured to receive the changed n-bit signal and to output a scan driving signal to a scan line corresponding to the input n-bit signal when a preset n-bit signal is input, wherein the data driver includes the scan driver. Outputs the image data signals corresponding to the scan lines selected by the plurality of data lines, and the light emission controller supplies the clock pulse and the scan start signal to the n-bit counter and, according to the input image data signals, A passive matrix organic electroluminescent display device adapted to control a data driver is provided.

The present invention also includes receiving a clock pulse and a scan start signal to generate an n-bit signal that is sequentially increased during one display frame period; Generating at least one modified n-bit signal in a range by controlling at least one bit value of the n-bit signal; Selecting a scan line according to the changed n-bit signal; And outputting an image data signal corresponding to the selected scan line to a plurality of data lines crossing the scan line.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a block diagram illustrating a passive matrix organic electroluminescent display device according to the present invention. As shown in FIG. 2, the passive matrix organic electroluminescent display 10 according to the present invention includes a display panel 2, a scan driver 8, a data driver 9, and a light emission controller 1. In the display panel 2, a plurality of data lines 3 and a plurality of scan lines 4 intersect in a matrix shape, and an organic electroluminescent device is formed at an intersection point of the data line 3 and the scan line 4. (Not shown) is formed.

In addition, as shown in FIG. 2, the scan driver 8 includes an n-bit counter 5, a scan controller 6, and a plurality of selectors ST0, ST1, ST2, ST3,..., STq-1. ) The n-bit counter 5 constituting the scan driver 8 receives the clock pulse CLK and the scan start signal SP from the light emission controller 1, and sequentially n-bits increased during one display frame period. Outputs a signal, and the scan controller 6 receives an n-bit signal sequentially increasing from the n-bit counter 5 and controls at least one bit value of the n-bit signal in response to a scan control signal. Outputs a modified n-bit signal in a certain range. Here, the predetermined range corresponds to a range to be partially driven among the entire display panels 2. In addition, the plurality of selectors ST0, ST1, ST2, ST3,..., And STq-1 receive the changed n-bit signal from the scan controller 6, and a preset n-bit signal is selected by each selector ( When input to ST0, ST1, ST2, ST3, ..., STq-1, each of the plurality of selectors ST0, ST1, ST2, ST3, ..., STq-1 is connected 1: 1 to it. The scan drive signal is output to the scan lines 4: X1, X2, X3, ..., Xq.

The scan control unit 6 changes the output value of the n-bit counter 5 to a value within a predetermined range, and thus describes, for example, a process of selectively driving only a necessary portion of the display panel. The n-bit counter 5 outputs an n-bit signal incremented by one each time the clock pulse CLK is input. If the n-bit counter 5 is a 6-bit counter, (000000) to (111111) Outputs 6 bit signals up to. Of the plurality of selection units ST0, ST1, ST2, ST3, ..., STq-1, the selection unit ST0 outputs a scan driving signal to the scan line X1 when the input signal is (000000), and selector ST1 When the input signal is (000001), the scan driving signal is output to the scan line X2, and the remaining selection units ST1, ..., STq-1 also sequentially perform the same function. Therefore, when there is no scan control section 6, every time the clock pulse CLK enters, the n-bit signals sequentially increasing from the n-bit counter 5 are selected by the selection sections ST0, ST1, ST2, ST3, ... , STq-1), and the selection units ST0, ST1, ST2, ST3, ..., STq-1 are sequentially turned on in accordance with the sequentially increasing n-bit signals, thereby scanning line 4 : X1, X2, X3, ..., Xq) drives the whole sequentially.

In response to the scan control signal, the scan control unit 6 changes the n-bit signal that is sequentially increased to a value in a predetermined range, so that the scan lines 4: X1, X2, X3,..., Xq are To be partially selected. For example, in the case where the 6-bit counter is used as the n-bit counter 5 and all the scan lines 4 of the display panel 2 are 64, the 32 scan lines 4 above the display panel 2 are used. When a scan control signal for selecting) is input, the scan control unit 6 fixes and outputs the data of the maximum bit position among the 6-bit signals output from the n-bit counter 5 at " 0 " Outputs 32 6-bit signals indicated by **** ". Here, "*" is a value that is sequentially incremented and output from the n-bit counter 5, so that the selection units ST0, ST1, ..., ST31 are sequentially turned on, and from the first scan line X1 The 32nd scan line X32 is sequentially selected. On the contrary, when a scan control signal for selecting the 32 scan lines 4 under the display panel 2 is input, the scan control unit 6 selects the maximum bit position among the 6-bit signals output from the n-bit counter 5. By fixing the data to "1" and outputting the data, the thirty-third scan line X33 to the sixty-fourth scan line X64 are sequentially selected. In addition, when the display panel 2 is to be divided into four parts and partially driven, the scan control unit 6 selects up to two digits of the maximum six bits of the six-bit signal output from the n-bit counter 5. By controlling by "," 01 **** "," 10 **** "or" 11 **** ", the display panel 2 can be divided into four parts to drive a desired portion. As described above, when the display panel 2 is divided into four and only the upper quarter portion is driven, the output of the n-bit counter 5, the output of the scan control unit 6, and the driving scan lines 4 (X1, X2, The relationship between X3, ..., Xq) is shown in Table 1 below.

Output of n-bit counter 5 → output of scan control unit 6 (below, **** sequentially increases from 0000 to 1111) Driven scan line "00 ****" → "00 ****" (ST0, ST1, ..., ST15) "01 ****" → "00 ****" (ST0, ST1, ..., ST15) "10 ****" → "00 ****" (ST0, ST1, ..., ST15) "11 ****" → "00 ****" (ST0, ST1, ..., ST15)

Similarly, when the scan control unit 6 fixes the maximum bit two digits of the 6-bit signal output from the n-bit counter 5 as "01 ****", the seventeenth scan line X17 to the thirty-third scan When only the line X32 is selected and the scan control unit 6 fixes the maximum bit two digits of the 6-bit signal to "10 ****", the 33rd scan line X33 to the 48th scan line X48 ) Is selected and only the 49th scan line X49 to the 64th scan line X64 are selected when the scan control unit 6 fixes the maximum bit 2 digits of the 6-bit signal to "11 ****". do. In the same way, the scan control section 6 is set to "000 ***", "001 ***", "010 ***", "011 ***", "100 ***", in accordance with the scan control signal. When outputting a 6-bit signal of " 101 *** ", " 110 *** " or " 111 *** ", only a predetermined eight scan lines are selected from the 64 scan lines. Therefore, by limiting the output signal of the scan controller 6 to a predetermined range, it is possible to select only the scan line of the desired portion to be driven. In this way, the scan control section 6 controls at least one or more of the output bits of the n-bit counter 5, for example, to the output terminal of the n-bit counter 5, as is commonly known in the art. The AND gate, OR gate, NOT gate, NAND gate, or NOR gate can be configured in combination.

In this manner, when the output of the n-bit counter 5 is changed to select only some scan lines by the scan control unit 6 so that 1 / m of the entire display panel 2 is partially driven, the clock pulse without loss of luminance and power is lost. The period of (CLK) can be increased by m times. For example, when only one quarter of the display frame 2 is scanned, one scan line 4 is selected four times during one display frame period. Accordingly, while keeping the period of the display frame 2 constant, the light emission controller 1 has a clock pulse having a period four times compared to the clock pulse CLK applied when all 64 scan lines are selected. CLK) can be generated and provided to the n-bit counter 5. In this case, since the time for which each scan line 4 is selected is increased four times, the luminance is also increased four times, thus reducing the power consumption by reducing the luminance of each scan line 4, even though 64 scan lines are used. The same luminance as in the case where all of (4) is selected can be obtained from each scan line 4. In addition, even when the scan line 4 is partially selected, the clock pulse CLK is always applied to the passive matrix organic electroluminescent display 10, so that the entire screen does not turn off.

Meanwhile, the data driver 9 outputs an image data signal corresponding to the scan line 4 selected by the scan driver 8 to a plurality of data lines 3 that intersect the scan line 4. Do it. For example, when the sixteenth scan line X16 to the sixteenth scan line X16 are selected, each time the clock pulse CLK is input, the twelfth scan line X12 to the sixteenth scan line X16 are selected. The corresponding image data signal is supplied to the organic electroluminescent element positioned at the intersection of the scan line 4 and the data line 3 through the data lines 3: Y1, Y2, .... Yp. In addition, the light emission controller 1 receives an image data signal provided to the display device 10 and receives a data signal corresponding to the selected scan line 4 from the data lines 3: Y1, Y2, .... Yp) may control the operation of the data driver 9 to change the signal period of the clock pulse CLK according to the scan control mode as necessary. As shown in FIG. 2, the scan control signal may be input from the light emission controller 1 to the scan controller 6 according to a user input or a programmed scan control mode, and for generating the scan control signal. The controller may be provided separately from the light emission controller 1. As such, when a separate controller for generating a scan control signal is installed, the separate controller may control the light emission controller 1 to change the signal period of the clock pulse CLK.

The present invention also provides a method of driving an organic electroluminescent display device capable of partial scanning of a display panel, wherein the driving method receives a clock pulse CLK and a scan start signal SP and sequentially performs one display frame period. Generating an increased n-bit signal, controlling at least one bit value of the n-bit signal, generating a changed n-bit signal in a predetermined range, and selecting a scan line according to the changed n-bit signal And outputting an image data signal corresponding to the selected scan line to a plurality of data lines crossing the scan line.

The partial scanning method of the display panel according to the present invention can be usefully used when the display screen of a mobile phone or the like is operated in the "screen saving mode". In the "screen saving mode", a screen such as a clock is displayed only on a part of the display panel 2, so that only a certain range, for example, 16 scan lines 4 are selected from all the scan lines, to display a screen such as a clock. The organic light emitting display device used in a mobile phone as a whole may be reduced by increasing the duty by increasing the duty of the scan line 4 to be driven, or by reducing the driving voltage when the brightness is not increased. It can increase the service life and lower the power consumption. In addition, since the position of the selected scan line 4 can be arbitrarily adjusted by changing the range of the changed n-bit signal at a predetermined time interval, for example, at 2 second intervals, the displayed screen such as scrolling or table tennis ball is moved. You can move the. For example, in the case where the 6-bit counter 5 is used and the total scan lines are 64, the scan control unit 6 may perform the first scan line X1 to the sixteenth scan line for a predetermined time, for example, two seconds. Outputs a six-bit signal changed to select (X16), and does not overlap with the scan line selected during the display frame during the next predetermined time, for example, two seconds, from the seventeenth scan line X17 to the thirty-third scan line X32 Repeating the process of outputting the changed 6-bit signal to select), the light emitting screen is repeatedly moved up and down.

In addition, the partial scanning method of the display panel according to the present invention may be usefully applied to a text / graphic mixed mode in which a graphic image and a text image are displayed in combination. 3 is a diagram illustrating a screen display according to time when a partial scanning method of a display panel according to the present invention is applied to a text / graphic mixing mode. As shown in FIG. 3, when the partial scanning method of the display panel according to the present invention is applied to the text / graphic mixing mode, first, a scan line corresponding to the graphic scan screen is selected during the first display frame, and then During the two display frames, the process of selecting all of the scan lines corresponding to the graphic image and the text image may be repeated so that the luminance of the graphic screen portion and the luminance of the text screen portion may appear similarly. In this way, if the number of times of selecting the graphic image and the text image is different, in the usual method, as shown in (ii) of FIG. . However, when the partial scanning method of the display panel according to the present invention is applied, as shown in FIG. 4 (iii), the period of the clock pulse CLK is increased to reduce the period "a '" of the graphic screen display frame. It is possible to set larger than the period "a" of the normal graphic screen display frame, and set larger than the period "b" of the text screen display frame as well. Even in this case, the time (2a '+ b) until the second frame in which the graphic screen portion is scanned twice is the same as in the case of Figs. 4 (i) and (ii). That is, in the case of (iii) of FIG. 4, compared with (i) of FIG. 4, the scan line selection time of the graphic portion is increased (2a '> 2a), and the scan line selection time of the text portion is decreased (b' < 2b), thereby reducing the brightness of the text portion and increasing the brightness of the graphics portion. In addition, compared with FIG. 4 (ii), the scan line selection time of the graphic portion is increased (2a '> 2a), the scan line selection time (b'> b) of the text portion is increased, and the display panel 2 is increased. If all of the scan lines are not selected, they do not occur. Therefore, using the partial scan driving method according to the present invention, it is possible to efficiently increase the scan line selection time of the graphic portion with respect to the scan line selection time of the text portion. Here, the number of scan line selections of the graphic portion with respect to the number of scan line selections of the text portion is not limited to two times, and the scan ratio of text: graphic may be set to 1: 3 or more as necessary.

 As described above, the passive matrix organic electroluminescent display and the driving method thereof according to the present invention selectively drive only a part of the entire scan line of the display panel, thereby increasing the luminance of the selected portion. In addition, the method according to the present invention can increase the number of scans of the graphic image portion more than the number of scans of the text image portion, thereby improving the luminance of the graphic image by reducing the luminance difference between the graphic image and the text image, using only a portion of the screen Is used in the "screen saving mode" to reduce the supply voltage as it corresponds to the increased brightness, it is possible to extend the life of the organic material and reduce the power consumption.

Claims (8)

A display panel in which a plurality of data lines and a plurality of scan lines are intersected in a matrix shape, and an organic electroluminescent element is formed at an intersection point of the data lines and the scan lines; An n-bit counter that receives a clock pulse and a scan start signal and outputs n-bit signals sequentially increased during one display frame period; A scan controller configured to receive the n-bit signal, change a bit value of at least one of the n-bit signals, and output a changed n-bit signal in a predetermined range in response to a scan control signal; And a plurality of selectors configured to receive the changed n-bit signal and to output a scan driving signal to a scan line corresponding to the input n-bit signal when a preset n-bit signal is input. A data driver configured to output image data signals corresponding to scan lines selected by the scan driver to the plurality of data lines; And And a light emission controller for supplying the clock pulse and the scan start signal to the n-bit counter and controlling the data driver according to the input image data signal. The organic light emitting display of claim 1, wherein the light emission controller changes a signal period of a clock pulse according to the scan control mode. The organic electroluminescent display device according to claim 2, wherein when the 1 / m of the display panel is partially driven by the scan line selected by the changed n-bit signal, the light emission controller increases the signal period of the clock pulse by m times. . The organic light emitting display device of claim 1, wherein the scan control signal is output from the light emission controller. The organic light emitting display device of claim 1, wherein the scan controller is configured to partially drive only one quarter of the display panel by fixing two digits of the maximum number of n-bit signals output from the n-bit counter. Receiving a clock pulse and a scan start signal to generate an n-bit signal that is sequentially increased during one display frame period; Generating at least one modified n-bit signal in a range by controlling at least one bit value of the n-bit signal; Selecting a scan line according to the changed n-bit signal; And And outputting an image data signal corresponding to the selected scan line to a plurality of data lines crossing the scan line. The method of claim 6, further comprising changing a range of the changed n-bit signal at predetermined time intervals to move the displayed screen. 7. The method according to claim 6, wherein the range of the changed n-bit signal is adjusted to display only the graphic screen during one display frame period, and the graphic and text screens are displayed during the other display frame period. A method of driving an organic electroluminescent display device to adjust the range.

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