OLED Residual Voltage Sensing Circuit for Luminance Compensation
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Solution Overview
Problem
Organic Light Emitting Diode (OLED) displays face challenges in maintaining consistent light emission efficiency over time, leading to decreased luminance and color shifts due to varying light emitting efficiencies of subpixels of different colors, which existing technologies fail to effectively address.
Innovation Solution
A method and apparatus that include a pixel driving circuit with a sensing sub-circuit to measure residual voltage signals at the anode of light emitting elements after an initial voltage is applied and allowed to discharge, transmitting these signals to an integrated circuit for compensation in subsequent image display phases, ensuring data signals are adjusted based on residual voltage differences to maintain consistent luminance and color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If OLED display operates over time, then light emission continues, but light emitting efficiency decreases causing luminance degradation and color shifts
Solution Approach 1:
The patent implements a sensing circuit that measures the residual voltage at the anode of the light emitting element after a sensing period. This residual voltage serves as feedback information about the element's current state. The measured voltage is transmitted to a data driving integrated circuit that uses it to calculate compensation values, which are then applied to adjust the data signals for subsequent display periods, creating a closed-loop feedback system that continuously corrects for efficiency degradation
Solution Approach 2:
The patent changes the electrical parameters (voltage and time) applied to the light emitting element during the sensing period. An initial voltage signal is applied for a first period of time, then allowed to discharge for a second period of time. The residual voltage measured at the end of the second period reflects the element's charge-holding capability, which correlates with its light emitting efficiency. This parameter-based sensing enables non-destructive measurement of element state
2Illumination intensity
If sensing circuit measures residual voltage to compensate for efficiency changes, then luminance consistency is maintained, but device complexity increases
Solution Approach 1:
The sensing circuit shares the same data line and integrated circuit infrastructure with the normal display operation. The data line serves both to drive the display during image display phases and to transmit sensing data during sensing phases. The integrated circuit performs both normal data processing and compensation calculations using the same hardware resources, reducing the need for completely separate sensing circuitry
Solution Approach 2:
The patent merges the sensing function with the existing pixel driving circuit by integrating the sensing transistor and sensing capacitor into the same pixel structure that contains the driving transistor and storage capacitor. The sensing operation is combined with the display operation in time-division multiplexing, where sensing phases alternate with image display phases, allowing both functions to coexist within the same hardware framework
Data Source
AI summary
A method for image display in a display apparatus is provided. The method includes displaying an image in a respective subpixel in an image display phase. In a sensing phase subsequent to the image display phase, the method further includes providing an initial voltage signal to an anode of a respective light emitting element in the respective subpixel for a first period of time; allowing the anode of a respective light emitting element to discharge for a second period of time, upon discontinuation of the initial voltage signal; obtaining a residual voltage signal at the anode of the respective light emitting element at an end of the second period of time by a sensing sub-circuit of a respective pixel driving circuit; and transmitting the residual voltage signal to an integrated circuit.