OLED Pixel Degradation Compensation via Anode Voltage Sensing
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Solution Overview
Problem
Existing display devices face challenges in compensating for pixel degradation, which leads to reduced luminance due to the degradation of organic light emitting diodes (OLEDs) and thin film transistors (TFTs), making it difficult to maintain desired voltage levels and increase power consumption.
Innovation Solution
A method that involves sensing currents and voltages through specific transistors and capacitors to estimate the voltage of the anode electrode of the OLED, determining a degradation compensation value, and generating compensation data to adjust the driving current, thereby compensating for pixel degradation without direct measurement of the driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power voltage is set at the time of shipment to provide a driving current of the pixel, then the pixel can be driven initially, but a voltage greater than the desired voltage is supplied even before OLED and TFT are degraded, which increases power consumption
Solution Approach 1:
The patent performs preliminary sensing of the anode electrode voltage and calculates degradation compensation values before actual degradation occurs. By establishing the initial voltage state and computing compensation factors in advance, the system prepares correction data that will be applied later to maintain optimal voltage levels without excessive power consumption.
Solution Approach 2:
The patent implements a feedback mechanism where the sensed anode electrode voltage is continuously monitored, degradation compensation values are calculated based on the voltage deviation from desired levels, and compensation data is generated to adjust subsequent driving voltages. This closed-loop control ensures the pixel receives only the necessary voltage to maintain luminance, avoiding unnecessary power consumption.
2Illumination intensity
If degradation compensation is implemented, then pixel luminance can be maintained, but the driving current cannot be measured directly, making compensation difficult
Solution Approach 1:
The patent introduces the anode electrode voltage as an intermediary parameter that can be sensed indirectly through existing sensing lines and transistors. Instead of directly measuring the driving current, the system measures the voltage at the anode electrode, which correlates with the driving current and luminance output. This intermediary measurement approach enables degradation detection without requiring direct current measurement capabilities.
Solution Approach 2:
The patent replaces the direct electrical current measurement approach with a voltage sensing approach. By substituting current measurement with voltage measurement across the anode electrode, the system utilizes standard voltage sensing circuitry already present in the display device, avoiding the need for specialized current measurement mechanisms.
Data Source
AI summary
A method of compensating for degradation of a display device includes sensing a first sensing current flowing through a sensing line connected to a pixel, which includes a programming period for writing a data voltage of a predetermined color to a storage capacitor of the pixel, sensing a sensing voltage of the sensing line, which includes a period for charging a line capacitor connected to the sensing line, estimating a voltage of an anode electrode of an organic light emitting diode using a second sensing current estimated from the first sensing current and the sensing voltage, and determining a degradation compensation value using the voltage of the anode electrode.