Light Emitting Display Device Driving Transistor Voltage Compensation
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Solution Overview
Problem
In light emitting display devices, the variation in threshold voltage of driving transistors across pixels and degradation of light emitting elements lead to inconsistent luminance, as the same data voltage applied to pixels results in varying currents due to differences in threshold voltages, and external compensation methods may fail to adequately address degradation when the sensing voltage range of the analog-to-digital converter is not appropriately set.
Innovation Solution
A light emitting display device with a display panel connected to data lines, scan lines, and reference voltage lines, utilizing an analog-to-digital converter to convert sensed voltages into sensing data, and a voltage supply unit that provides specific voltage ranges for degradation compensation, ensuring the reference voltage is equal to or less than the low voltage in the degradation compensation mode to prevent the source voltage of the driving transistor from exceeding the sensing voltage range of the analog-to-digital converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the same data voltage is applied to all pixels, then the data driving is simplified, but the luminance varies per pixel due to threshold voltage differences and light emitting element degradation
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the data voltage based on sensed threshold voltage and mobility information. The data driver modifies the data voltage parameter in response to sensing results, transforming the static voltage application into a dynamic adaptive process that compensates for pixel-to-pixel variations and degradation.
Solution Approach 2:
The patent implements feedback through a sensing mechanism that measures the actual voltage at the source electrode of the driving transistor and uses this information to adjust the data voltage. The feedback loop includes: sensing the source voltage, converting to digital data, comparing with reference, and adjusting the data voltage accordingly to maintain uniform luminance.
2Adaptability or versatility
If the sensing voltage range of the analog-to-digital converter is set to cover all compensation scenarios, then complete compensation capability is achieved, but the source voltage may exceed the sensing range during degradation compensation
Solution Approach 1:
The patent segments the voltage sensing range into multiple sub-ranges corresponding to different compensation modes (threshold voltage compensation, mobility compensation, and degradation compensation). Each mode has its own optimized voltage range, allowing the system to select the appropriate range for each compensation scenario, preventing out-of-range errors while maintaining comprehensive compensation capability.
Solution Approach 2:
The patent makes the sensing voltage range dynamic by adjusting it based on the current compensation mode. The data driver dynamically selects the appropriate voltage range for the analog-to-digital converter depending on whether threshold voltage compensation, mobility compensation, or degradation compensation is being performed, ensuring optimal sensing accuracy for each scenario.
Data Source
AI summary
A light emitting display device and a method for driving the same are disclosed, in which a source voltage of a driving transistor for compensating for degradation of a light emitting element may be prevented from getting out of a sensing voltage range of an analog-to-digital converter. The light emitting display device comprises a display panel connected to data lines, scan lines and reference voltage lines and provided with pixels, each pixel including a light emitting element; an analog-to-digital converter (ADC) converting voltages sensed from the pixels through the reference voltage lines into sensing data; and a voltage supply unit supplying a reference voltage to the reference voltage lines. The voltage supply unit supplies a third low voltage and a third high voltage to the ADC in a degradation compensation mode for compensating for degradation of the light emitting element. In the degradation compensation mode, the reference voltage is equal to or higher than the third low voltage.