KR102465558B1 - Organic Light Emitting diode Display and Driving Method thereof - Google Patents

Abstract

The organic light emitting diode display device of the present invention includes a display panel, a pixel power consumption calculation unit, a line power consumption calculation unit, an accumulated line power consumption calculation unit, and a voltage setting unit. In the display panel, pixels driven using a high potential driving voltage are respectively disposed on a plurality of pixel lines. The pixel power consumption calculator calculates pixel power consumption corresponding to each of the pixels. The line power consumption calculation unit calculates line power consumption by summing the pixel power consumption for each pixel line. The accumulated line power consumption calculation unit calculates the accumulated line power consumption by accumulating line power consumption within one frame. When the accumulated line power consumption is equal to or greater than the threshold, the voltage setting unit lowers the voltage of the high potential driving voltage supplied to the pixels so that the accumulated line power consumption becomes the threshold.

Description

Organic Light Emitting diode Display and Driving Method thereof

The present invention relates to an organic light emitting diode display and a driving method thereof.

Flat panel displays (FPDs) are widely used in portable computers such as notebook computers and PDAs, mobile phone terminals, etc., as well as monitors of desktop computers due to their advantages in miniaturization and weight reduction. Such a flat panel display device is a liquid crystal display device; LCD), Plasma Display Panel (PDP), Field Emission Display; FED) and organic light emitting diode display (OLED).

Among them, the organic light emitting diode display has advantages of fast response speed, high luminance efficiency, and a large viewing angle. In general, an organic light emitting diode display device applies a data voltage to a gate electrode of a driving transistor using a switching element transistor that is turned on by a scan signal, and the organic light emitting diode emits light using the data voltage supplied to the driving transistor. make it That is, the current supplied to the organic light emitting diode is controlled by the data voltage applied to the gate electrode of the driving transistor.

The organic light emitting diode is deteriorated due to driving, and the light emitting characteristic of the organic light emitting diode is deteriorated due to the deterioration. Accordingly, the degree of deterioration of the organic light emitting diode is proportional to the emission luminance, and the emission luminance is proportional to the grayscale value of the image data.

The organic light emitting diode display sets a limit power consumption in order to increase driving reliability without accelerating deterioration of the organic light emitting diode, and controls so that power consumed in each frame does not exceed the limit power consumption. To this end, the organic light emitting diode display sums the grayscale values of the image data in units of frames, and when the grayscale values of the summed image data are equal to or greater than a predetermined value, the overall image data of the corresponding frame is lowered.

In order to compare the power consumption in each frame with the limit power consumption, a method of analyzing image data in units of each frame is used, and for this, a frame memory is used. As a result, the organic light emitting diode display requires an additional configuration of a frame memory to limit power consumption.

An object of the present invention is to provide an organic light emitting diode display device capable of limiting power consumption of a display panel without using a frame memory, and a driving method thereof.

The organic light emitting diode display device of the present invention includes a display panel, a pixel power consumption calculation unit, a line power consumption calculation unit, an accumulated line power consumption calculation unit, and a voltage setting unit. In the display panel, pixels driven using a high potential driving voltage are respectively disposed on a plurality of pixel lines. The pixel power consumption calculator calculates pixel power consumption corresponding to each of the pixels. The line power consumption calculation unit calculates line power consumption by summing the pixel power consumption for each pixel line. The accumulated line power consumption calculation unit calculates the accumulated line power consumption by accumulating line power consumption within one frame. When the accumulated line power consumption is equal to or greater than the threshold, the voltage setting unit lowers the voltage of the high potential driving voltage supplied to the pixels so that the accumulated line power consumption becomes the threshold.

The organic light emitting diode display device according to the present invention can calculate power consumption without using a frame memory, and limit the power consumption of the display panel based on the calculation.

1 is a view showing an organic light emitting diode display device according to the present invention.
Fig. 2 is a diagram showing a pixel array of the present invention;
3 is a diagram showing the configuration of a driving voltage control unit;
4 is a diagram showing a pixel structure of the present invention;
5 is a flowchart illustrating a method of driving an organic light emitting diode according to the present invention.
6 is a diagram showing input image data in units of lines;
7 is a diagram illustrating an example of modeling the relationship between line grayscale values and line power consumption;
8 is a diagram illustrating a method of varying a high potential driving voltage according to the first embodiment;
9 is a diagram illustrating a method of varying a high potential driving voltage according to a second embodiment;

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals refer to substantially identical elements throughout. In the following description, if it is determined that a detailed description of a known function or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a diagram showing the configuration of an organic light emitting diode display according to the present invention, and FIG. 2 is a diagram showing a connection structure of a pixel structure and a data line unit according to the present invention. An organic light emitting diode display device of the present invention will be described with reference to FIGS. 1 and 2 .

The organic light emitting diode display device according to the present invention includes a display panel 10 in which pixels P are arranged in a matrix form, a timing controller 11 , a data driver 12 , a gate driver 13 , and a driving voltage controller 400 . ) and a voltage supply unit 500 .

The display panel 10 includes a plurality of pixels P, and is for displaying an image based on a gray level displayed by each pixel P. A plurality of pixels P are arranged at regular intervals on each of the first to mth pixel lines, and thus are arranged in a matrix form in the display panel 10 .

The data lines DL include n data voltage supply lines 14A_1 to 14A_n and n reference voltage lines 14B_1 to 14B_n corresponding to n (n is a positive integer) pixel columns. In addition, the gate lines GL connect m scan lines 15A_1 to 15A_m and m sense lines 15B_1 to 15B_m corresponding to m (n is a positive integer) pixel lines HL1 to HLm. include

The pixels P receive the high potential driving voltage ELVDD and the low potential driving voltage ELVSS from the voltage supply unit 500 . The pixels P arranged in the first column are connected to the first data voltage supply line 14A_1 and the first reference voltage line 14B_1 , and the pixels P arranged in the second column are connected to the second data voltage supply line 14A_2 ) and the second reference voltage line 14B_2. Similarly, the pixels P arranged in the ith column (i is a natural number less than or equal to n) are connected to the ith data voltage supply line 14A_i and the ith reference voltage line 14B_.

The pixels P disposed on the first pixel line HL1 are connected to the first scan line 15A_1 and the first sense line 15B_1 , and the pixels P disposed on the second pixel line HL2 are It is connected to the second scan line 15A_2 and the second sense line 15B_2. Similarly, the pixels P disposed on the j-th (j is a natural number less than or equal to m) pixel line HLj are connected to the j-th scan line 15A_j and the j-th sense line 15B_j.

The timing controller 11 controls driving timings of the data driver 12 and the gate driver 13 . The timing controller 11 rearranges digital video data RGB input from the host system 5 to match the resolution of the display panel 10 and supplies it to the data driver 12 . In addition, the timing controller 11 operates the data driver 12 based on timing signals such as the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the dot clock signal DCLK, and the data enable signal DE. A data control signal DDC for controlling timing and a gate control signal GDC for controlling an operation timing of the gate driver 13 are generated.

Also, the timing controller 11 modulates the digital video data DATA with reference to the digital sensing data supplied from the data driver 12 to generate the digital compensation data MDATA. The digital compensation data MDATA is for compensating for deterioration of the organic light emitting diode (OLED). The timing controller 11 supplies the generated digital compensation data MDATA to the data driver 12 . The timing controller 11 may periodically update the digital sensing data supplied from the data driver 12 to the memory 16 . In this process, the timing controller 11 controls the first and second switching elements SW1 and SW2 to obtain digital sensing data.

The data driver 12 converts the digital video data RGB input from the timing controller 11 into an analog data voltage based on the data control signal DDC and supplies it to the data lines 14 . In addition, the data driver 12 is an analog-to-digital-converter (Analog-Digital-) for converting a sensing voltage for detecting a threshold voltage Vth of an organic light emitting diode (OLED) fed back from each pixel P into sensing data. Converter; hereinafter ADC).

The data driver 12 supplies a predetermined data voltage to the pixels P during the threshold voltage compensation driving of the organic light emitting diode OLED, and receives the data from the pixel P through the reference voltage lines 14B_1 to 14B_m. The input sensing voltages may be converted into digital values and supplied to the timing controller 11 .

The data driver 12 is connected to the pixel P through the data voltage supply line 14A and the reference voltage line 14B. As shown in FIG. 3 , the data driving unit 12 converts the analog sensing voltage into a digital sensing value during sensing driving for a digital-analog converter (DAC) that converts digital compensation data into a data voltage for image display, and an external compensation method. It may include an analog-to-digital converter (ADC) operated for this purpose, a first switching device (SW2) for supplying an initialization voltage (Vref), and a second switching device (SW2) for detecting a sensing voltage.

The gate driver 13 generates a scan signal SCAN and a sense signal SENSE using the gate control signal GDC provided from the timing controller 11 . The gate control signal GDC includes a gate start pulse (GSP) indicating a start scan line from which a scan is started, and a gate shift clock (GSC) for sequentially shifting the gate start pulse (GSP). and a gate output enable (GOE) indicating an output of the gate driver.

The driving voltage control unit 400 includes a pixel power consumption calculation unit 410 , a line power consumption calculation unit 420 , an accumulated line power consumption calculation unit 430 , and a voltage setting unit 440 as shown in FIG. 3 . .

The pixel power consumption calculator 410 calculates power consumption of each pixel. The line power consumption calculation unit 420 calculates line power consumption by summing the power consumption of pixels included in one line. The accumulated line power consumption calculation unit 430 accumulates line power consumption within one frame to generate an accumulated line. Calculate the power consumption. The voltage setting unit 440 compares the accumulated line power consumption with a preset threshold, and lowers the voltage of the high potential driving voltage ELVDD supplied to the pixels P when the accumulated line power consumption is equal to or greater than the threshold.

The voltage supply unit 500 supplies the low potential driving voltage ELVSS and the high potential driving voltage ELVDD to the pixels P. The voltage supply unit 500 varies the voltage level of the high potential driving voltage ELVDD in response to the amount of power consumption of the image data calculated by the driving voltage control unit 400 .

4 is a diagram illustrating a pixel structure according to the present invention.

Referring to FIG. 4 , each of the pixels P includes an organic light emitting diode OLED, a driving transistor DT, a scan transistor ST1 , a sense transistor ST2 , and a storage capacitor Cst.

The organic light emitting diode OLED has an anode electrode connected to the second node N2 and a cathode electrode connected to the low potential power supply ELVSS.

The driving transistor DT controls the current Ioled flowing through the organic light emitting diode OLED according to the gate-source voltage Vgs. The driving transistor DT includes a gate electrode connected to the first node N1 , a drain electrode connected to the high potential power supply ELVDD, and a source electrode connected to the second node N2 .

The storage capacitor Cst is connected between the first node N1 and the second node N2 .

The scan transistor ST1 is switched according to the scan signal SCAN, and transmits the data voltage or the compensation data voltage MVdata for which a change in the threshold voltage of the organic light emitting diode (OLED) is compensated for to the data voltage supply line 14A to the first node. Apply to (N1). The scan transistor ST1 includes a gate electrode connected to the scan line 15A, a drain electrode connected to the data voltage supply line 14A, and a source electrode connected to the first node N1 .

The sense transistor ST2 is switched according to the sense signal SENSE, and applies the initialization voltage Vref provided from the reference line 14B to the second node N2. In addition, the sense transistor ST2 is switched according to the sense signal SENSE, and provides the threshold voltage sensing voltage of the organic light emitting diode (OLED) to the ADC. The gate electrode of the sense transistor ST2 is connected to the second gate line 15B, the drain electrode is connected to the second node N2, and the source electrode is connected to the reference line 14B.

5 is a flowchart illustrating the operation of the driving voltage control unit. Hereinafter, a method of controlling the high potential driving voltage by the organic light emitting diode display according to the present invention will be described as follows.

The pixel power consumption calculator 410 calculates power consumption of each of the pixels included in the pixel line.

6 is a diagram illustrating an example of image data of an i-th pixel line HLi. When the pixel line HL includes n pixel columns, the pixel power consumption calculator 410 calculates the pixel power consumption based on image data of each of the pixels. The pixel power consumption W_P may be calculated using a preset lookup table. That is, the lookup table may be set to match the grayscale value of the image data and power consumption.

7 is a diagram schematically illustrating a method by which the pixel power consumption calculation unit 410 calculates power consumption corresponding to the image data Data1 to Data3. 7 illustrates the amount of current I according to the size of each image data Data when the pixel P is driven with the high potential driving voltage ELVDD. For example, the pixel power consumption calculator W_P acquires the first current amount I[1] in response to the first grayscale value gray1. The pixel power consumption calculation unit 420 calculates the product of the amount of current and the high potential driving voltage ELVDD as the pixel power consumption W_P, as shown in Equation 2 below (S501).

[Equation 1]

The line power consumption calculation unit 420 calculates the line power consumption W_L by summing the power consumption of pixels included in one line. For example, when the pixel power consumption W_P of the i-th (i is a natural number less than or equal to n) pixel Pi is W_P[i], the line power consumption calculation unit 420 generates a line as shown in Equation 2 below. Calculate the power consumption (W_L). (S503)

[Equation 2]

The accumulated line power consumption calculator 430 accumulates the line power consumption W_L calculated for each pixel line HL, and calculates the accumulated power consumption Wsum. [Equation 3] below is an expression indicating that the cumulative power consumption calculation unit 430 calculates the cumulative power consumption Wsum from the first pixel line HL1 to the i-th pixel line HLi. (S505) )

[Equation 3]

The voltage setting unit 440 compares the accumulated line power consumption Wsum[i] with a threshold value Wlim, and sets the voltage of the high potential driving voltage ELVDD when the accumulated power consumption Wsum[i] is equal to or greater than the threshold value. lower it

The threshold Wlim is set below the instantaneous maximum power consumption Wmax. The instantaneous maximum power consumption Wmax refers to a limit value of power consumption consumed by the display panel 10 within one frame, and is preset.

Since the cumulative power consumption calculation unit 430 calculates the cumulative power consumption for each pixel line, the cumulative consumption exceeding the threshold Wlim even when the threshold Wlim is set to a value close to the instantaneous maximum power consumption Wmax. The power does not exceed the instantaneous maximum power consumption (Wmax). Accordingly, the threshold Wlim may be set to a very close approximation to the instantaneous maximum power consumption Wmax, for example, 99.5% or more of the instantaneous maximum power consumption Wmax and smaller than the instantaneous maximum power consumption Wmax.

8 is a diagram illustrating a relationship between the accumulated power consumption Wsum and the high potential driving voltage ELVDD. Since the power consumption is proportional to the voltage, the relationship between the accumulated power consumption Wsum and the high potential driving voltage ELVDD can be modeled as shown in FIG. 7 .

Accordingly, in FIG. 8 , when the cumulative power consumption Wsum[i] of the i-th pixel line HLi exceeds the threshold Wlim, the cumulative power consumption Wsum[i] is proportional to the amount of power consumption exceeding the threshold Wlim. to lower the high potential driving voltage ELVDD. For example, as shown in FIG. 7 , when the accumulated power consumption Wsum exceeds 'ΔW', the high potential driving voltage ELVDD decreases by 'ΔV'. Since the power consumption (W) is calculated as the product of the high potential voltage and the current as in [Equation 4], it can be expressed as ΔW = ΔV × I. Accordingly, the voltage setting unit 440 may calculate the variable amount ΔV of the high potential driving voltage ELVDD using the equation 'ΔV = ΔW / I ' ( S507 , S509 ).

Although FIG. 8 shows that the high potential driving voltage ELVDD and the accumulated power consumption Wsum[i] are linearly proportional, the accumulated power consumption is actually the high potential driving voltage depending on the characteristics and driving conditions of the display panel. may not be linearly proportional to (ELVDD). Accordingly, the modeling of the accumulated power consumption Wsum[i] and the high potential driving voltage ELVDD may use another preset relational expression.

The voltage setting unit 440 repeats the above driving for all the pixel lines HL. Then, after the high potential driving voltage ELVDD for all the pixel lines HL in one frame is changed, the same operation is repeated from the first pixel line HL1 of the next frame (S511).

According to the size of the threshold value Wlim, the voltage setting unit 440 may determine the tendency of the accumulated power consumption Wsum[i] to change the high potential driving voltage ELVDD in advance. That is, in the above-described embodiment, the threshold value Wlim is set to a very close approximation to the instantaneous maximum power consumption Wmax, and the high potential driving voltage ELVDD is set so that the accumulated power consumption Wsum converges to the power consumption threshold Wlim. How to change is explained.

The voltage setting unit 440 according to another exemplary embodiment may set the threshold Wlim to a lower value, and may vary the high potential driving voltage ELVDD based on the change amount of the accumulated power consumption Wsum.

9 is a view for explaining an embodiment in which the threshold value Wlim is set to a size of a%, for example, 80%, of the instantaneous maximum power consumption Wmax.

The voltage setting unit 440 calculates the accumulated power consumption (Wsum[k]) up to the k-th pixel line HL[k] corresponding to a%, for example, 80% of the total pixel line, and sets it to a threshold value ( Wlim). That is, since the ratio of the k-th pixel line HL[k] to the entire pixel line HL[m] becomes a(%), the relationship becomes (k/m)*100=a, and eventually k can be calculated as (ma)/100.

If the cumulative power consumption (Wsum[k]) up to the k-th pixel line (HL[k]) is greater than or equal to the threshold (Wlim), the cumulative power consumption up to the m-th pixel line (HL[m]) is the instantaneous maximum power consumption ( Wmax) is likely to be exceeded. Accordingly, when the accumulated power consumption Wsum[k] up to the k-th pixel line HL[k] is equal to or greater than the threshold value Wlim, the voltage setting unit 440 lowers the high potential driving voltage ELVDD.

The method of lowering the instantaneous maximum power consumption (Wmax) is similar to the above-described embodiment, in which the cumulative power consumption (Wsum[k]) up to the k-th pixel line (HL[k]) is proportional to the amount exceeding the threshold value (Wlim). It is possible to vary the high potential driving voltage ELVDD by the magnitude.

As described above, in the method of driving an organic light emitting diode display according to the present invention, power consumption is calculated using image data transmitted in real time, and the high potential driving voltage (ELVDD) is varied based on the calculation of the power consumption of the display panel. It can be controlled so that the power does not exceed the instantaneous maximum power consumption. In particular, since the present invention varies the high potential driving voltage, it is possible to reflect power consumption even for pixels in which data is already written. Therefore, it is possible to control the instantaneous power consumption of the display panel not to exceed the maximum limit value in real time without using the frame memory.

Those skilled in the art from the above description will be able to see that various changes and modifications can be made without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: display panel 11: timing controller
12: data driver 13: gate driver
14: data line unit 15: gate line unit

Claims (8)

a display panel in which pixels driven using a high potential driving voltage are respectively disposed on a plurality of pixel lines;
a pixel power consumption calculator configured to calculate pixel power consumption corresponding to each of the pixels;
a line power consumption calculation unit calculating line power consumption by summing the pixel power consumption for each pixel line;
an accumulated line power consumption calculator configured to calculate an accumulated line power consumption by accumulating the line power consumption within one frame; and
a voltage setting unit for lowering the voltage of the high potential driving voltage supplied to the pixels so that the accumulated line power consumption becomes the threshold when the accumulated line power consumption is equal to or greater than a threshold value;
The threshold is set to a size of a% (a is a natural number less than 100) of the instantaneous maximum power consumption,
The voltage setting unit compares the accumulated power consumption up to the k (k is a natural number that satisfies the condition k=(m×a)/100, where m is the total number of pixel lines) with the threshold value with the threshold value. display device. delete The method of claim 1,
The voltage setting unit reduces the high potential driving voltage in proportion to the excess of the accumulated line power consumption when the accumulated line power consumption exceeds the threshold. delete In the driving method of an organic light emitting diode display including a display panel in which pixels driven using a high potential driving voltage are arranged in a plurality of pixel lines,
calculating pixel power consumption corresponding to each of the pixels;
calculating line power consumption by summing pixel power consumption for each pixel line;
calculating the accumulated line power consumption by accumulating the line power consumption within one frame; and
lowering the voltage of the high potential driving voltage supplied to the pixels so that the accumulated line power consumption becomes the threshold when the accumulated line power consumption is equal to or greater than a threshold value;
The threshold is set to a size of a% (a is a natural number less than 100) of the instantaneous maximum power consumption,
In the step of lowering the high potential driving voltage, the cumulative power consumption up to the k (k is a natural number satisfying the condition k = (m × a) / 100, where m is the total number of pixel lines) up to the pixel line is equal to the threshold value. A method of driving an organic light emitting diode display comprising the step of comparing. delete 6. The method of claim 5,
The lowering of the high potential driving voltage may include reducing the high potential driving voltage in proportion to the excess amount of the accumulated line power consumption when the accumulated line power consumption exceeds the threshold. delete

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