ORGANIC LIGHT EMITTING DIODE DISPLAY AND DRIVING METHOD THEREOF

An organic light emitting diode (OLED) display device and a driving method thereof which compensates for hysteresis of a driving transistor is disclosed. In one aspect, an OLED display device includes a pixel unit; a scan driver that supplies a scan signal to the scan lines; a data driver that supplies a data signal to the data lines; a data compensator that extracts a hysteresis compensation value by comparing current and previous data, and outputs compensation data using the hysteresis compensation value and a luminance/color coordinate compensation value stored in a luminance correction process of a panel. Furthermore, it includes a timing controller that supplies a control signal to the scan driver, the data driver and the data compensator, and provides the data driver with the compensation data supplied from the data compensator.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE ASPECTS

FIG. 1depicts an embodiment of an OLED display device.

Referring toFIG. 1, the OLED display device according to this embodiment includes a scan driver10, a data driver20, a pixel unit30, a timing controller40and a data compensator50.

The scan driver10generates a scan signal, corresponding to a control signal such as a clock signal supplied from the timing controller40, and supplies the generated scan signal to scan lines S1to Sn. If the scan signal is supplied to the scan lines51to Sn, pixels35are selected for each horizontal line.

The data driver20generates a data signal, corresponding to the control signal and data, supplied from the timing controller40, and supplies the generated data signal to data lines D1to Dm. In some embodiments, the data driver20receives a compensation data signal, herein referred to as “compensation data DATA′,” which has been changed so that hysteresis and a process tolerance of the panel transistors can be compensated through the timing controller40. DATA′

The pixel unit30includes a plurality of pixels35positioned at the intersections the scan lines S1to Sn and the data lines D1to Dm. The pixel unit30displays an image corresponding to the data signal supplied by the data lines D1to Dm.

The timing controller40controls operations of the scan driver10, the data driver20and the data compensator50while supplying a control signal such as a clock signal to the scan driver10, the data driver20and the data compensator50. In addition, the timing controller40provides the data driver20with the compensation data DATA′ supplied from the data compensator50. Then, the data driver20generates a data signal corresponding to the compensation data DATA′.

The data compensator50extracts a hysteresis compensation value by comparing a current data signal, herein referred to as “current data DATA” and the previous data. In addition, the data compensator50calculates a final data compensation value by using the hysteresis compensation value with a luminance/color coordinate compensation value previously stored in a driving IC, in a luminance correction process. The data compensator50changes the current data DATA by applying the calculated data compensation value to the current data DATA and then outputs the changed current data DATA as compensation data DATA′. The compensation data DATA′ output from the data compensator50is supplied to the data driver20via the timing controller40.

Here, the hysteresis compensation value may be set to a value corresponding to the difference between the current data DATA and the previous data. For example, as the difference between the current data DATA and the previous data is large, the degree of the hysteresis is large, and thus a larger compensation value may be set.

The luminance/color coordinate correction value is a value specified and stored for each module. For example, the luminance/color coordinate correction value is obtained by detecting luminance and color coordinate characteristics for each panel display in the luminance correction process of the OLED display device during manufacturing and testing. In this case, the luminance and color coordinate characteristics of the panel mainly result from a process tolerance of the panel, such as a threshold voltage of a driving transistor or mobility variation. Therefore, the process tolerance of the panel is reflected in the luminance/color coordinate correction value. Thus, if the compensation data DATA′ is generated by applying the luminance/color coordinate value, the hysteresis of the driving transistor can be more effectively compensated by reflecting the process tolerance of the display panel.

As described above, the hysteresis of the driving transistor is compensated by comparing the current and previous data signals, and the compensation data DATA′ is generated by applying the luminance/color coordinate compensation value together with the hysteresis compensation value. Accordingly, the compensation of the hysteresis of the driving transistor can be optimized by reflecting the process tolerance of the panel together with the hysteresis of the driving transistor.

The detailed configuration and operation of the data compensator50of some embodiments will be described in detail with reference toFIGS. 2 and 3.

FIG. 2is a configuration view illustrating an example of a data compensator shown inFIG. 1.FIG. 3is a flowchart illustrating an example of a method of calculating a final data compensation value by applying a luminance/color coordinate correction value to a hysteresis compensation value lookup table.

Referring toFIG. 2, the data compensator50according to this embodiment calculates a data compensation value using a hysteresis compensation value and a luminance/color coordinate compensation value, and outputs compensation data DATA′ by adjusting the current data DATA using the data compensation value.

The data compensator50includes a storage unit52, a hysteresis compensation value lookup table (hereinafter, referred to as a hysteresis compensation value LUT)54, a compensation value calculator56and an operator58.

The storage unit52is used to temporarily store a previous data signal. If the current data DATA is input, the storage unit52outputs the temporarily stored previous data to the compensation value calculator56according to a control signal supplied from the timing controller40, and temporarily stores the input as current data DATA.

The hysteresis compensation value look up table (LUT)54is an LUT in which a hysteresis compensation value corresponding to the compared result of the current data DATA and the previous data is stored. For example, a hysteresis compensation value corresponding to the difference between the current data DATA and the previous data may be stored in the hysteresis compensation value LUT54.

The compensation value calculator56receives the previous data together with the current data DATA, and extracts a hysteresis compensation value from the hysteresis compensation value LUT54by comparing the current data DATA and the previous data signal. For example, the compensation value calculator56may calculate a difference between the current data DATA and the previous data and extract a hysteresis compensation value from the hysteresis compensation value calculator LUT54, which corresponds to the difference between the current data DATA and the previous data. The compensation value calculator56may include a subtractor for calculating a difference between the current data DATA and the previous data.

The compensation value calculator56receives a luminance/color coordinate correction value55, which has been previously determined during the luminance correction process of the panel. The compensation value calculator56uses luminance/color coordinate correction value55along with the hysteresis compensation value, thereby calculating the data compensation value. For example, the compensation value calculator56may calculate the data compensation value by summing the hysteresis compensation value and the luminance/color coordinate compensation value55. In some embodiments, the compensation value calculator56may include an adder for adding up the hysteresis compensation value and the luminance/color coordinate compensation value. However, the compensation value calculator56is not necessarily limited to the addition when calculating the data compensation value using the hysteresis compensation value and the luminance/color coordinate compensation value55. For example, the compensation value calculator56may calculate the data compensation value by applying an additional offset value to the hysteresis compensation value in proportion to the luminance/color coordinate compensation value55.

In some embodiments, the compensation value calculator56predicts a process tolerance of the panel with reference to the luminance/color coordinate compensation value55, and adjusts the hysteresis compensation value so that the hysteresis compensation is more effective by using the process tolerance of the panel.

As shown inFIG. 3, the process300starts at block302. The process next moves to decision state304, wherein the compensation value calculator56determines whether the luminance/color coordinate compensation value is a (+) or (−) offset value and apply the additional offset value to hysteresis compensation value extracted from the hysteresis compensation value LUT54according to the decided result. If the compensation value calculator56determines the luminance/color coordinate correction value is a (+) offset value, the process300moves to block306, wherein the (+) offset value is applied to the hysteresis compensation value extracted from the hysteresis compensation value LUT54. If the compensation value calculator56determines the luminance/color coordinate correction value is a (−) offset value, the process300moves to block308, wherein the (−) offset value is applied to the hysteresis compensation value extracted from the hysteresis compensation value LUT54.

The offset range of the luminance/color coordinate compensation value may be determined based on a center value among the luminance/color coordinate compensation values. Referring back toFIG. 2, for example, when the luminance/color coordinate compensation value55has a value of 8 bits in a range of 00000000 to 11111111, the center value may be set to 00001111, and the (+) or (−) offset direction may be determined based on the center value.

In some embodiments, in the calculating of the data compensation value, if the luminance/color coordinate compensation value is within the (+) offset range, the (+) offset value is applied to the hysteresis compensation value. If the luminance/color coordinate compensation value is within the (−) offset range, the (−) offset value is applied to the hysteresis compensation value. However, the present development is not limited thereto.

The method of calculating the data compensation value may be modified based on the design, such as the type of a transistor, or other components. For example, in a case where a relatively low driving current flows with the same data voltage due to a high threshold voltage of the transistor, and therefore, luminance decreases, the offset value may be applied so that a higher driving current can flow through the transistor. In a case where a relatively high driving current flows with the same data voltage due to a low threshold voltage of the transistor, and therefore, luminance increases, the offset value may be applied so that a lower driving current can flow through the transistor.

Next, the operator58outputs compensation data DATA′ by operating the current data DATA and the data compensation value. In some embodiments, for example, the operator58may be set as an adder for adding up the current data DATA and the data compensation value.

A driving method of the OLED display device, in which hysteresis is compensated using the data compensator according to this embodiment, will be described. The driving method includes storing previous data in the storage unit52, comparing the previous data and current data DATA and extracting a hysteresis compensation value corresponding to the compared result, calculating data compensation value by operating the hysteresis compensation value with a luminance/color coordinate compensation value55, generating and outputting compensation data DATA′ obtained by changing the current data DATA through application of the data compensation value, generating a data signal by providing the compensation data DATA′ to the data driver20, and supplying the data signal to the pixels.

Specifically, the hysteresis compensation value may be obtained by calculating a difference between the previous data and the current data DATA and extracting a hysteresis compensation value corresponding to the difference from the hysteresis compensation value LUT54in which the hysteresis compensation value is stored.

The data compensation value may be obtained by adding the hysteresis compensation value and the luminance/color coordinate compensation value55or by applying an additional offset value, either (+) or (−), to the hysteresis compensation value in proportion to the luminance/color coordinate compensation value55. In this case, the additional offset value may be set by detecting the range and degree of the luminance/color coordinate compensation value, based on the reference value the luminance/color coordinate compensation value.

Meanwhile, the compensation data DATA′ is generated using the data compensation value and the current data DATA. For example, the compensation data DATA′ may be generated by adding up the data compensation value and the current data DATA. The compensation data DATA′ is used to generate an actual data signal, and thus the OLED display device displays an image corresponding to the compensation data DATA′.

While the present development has been described in connection with certain exemplary embodiments, it is to be understood that the development is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.