OLED Pixel Voltage Sensing Circuit for Aging Compensation
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Solution Overview
Problem
In electronic display devices, particularly those using organic light-emitting diodes (OLEDs), aging of circuit components leads to inconsistent or non-uniform color outputs across pixels, even when receiving the same electrical input, due to changes in electrical properties over time.
Innovation Solution
A sensing system that measures and compensates for variations in pixel properties by determining the voltage associated with light-emitting diodes (LEDs) using a sensing circuit and pixel driving circuit, adjusting data voltages to ensure uniform image presentation across the display as LEDs age.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLED pixels are used to emit light with varying gray levels, then the display can present a range of colors and luminance, but aging of the OLED causes electrical properties to change over time, leading to non-uniform color output across pixels
Solution Approach 1:
The patent implements a feedback mechanism where pixel voltages are sensed and used to generate compensation values that adjust the drive currents. The sensing circuit measures the actual voltage across each OLED pixel, and this information feeds back to the display driver circuitry, which modifies the drive current to compensate for aging effects and maintain uniform color output across all pixels.
Solution Approach 2:
The patent changes the electrical parameters (voltage and current) applied to each pixel based on sensed variations. By measuring the actual voltage across each OLED and calculating compensation values, the system adjusts the drive current parameters to counteract aging-induced parameter drift, thereby maintaining consistent luminance and color characteristics across the display.
2Ease of operation
If the same electrical input is applied to all pixels, then the input signal is simple and consistent, but aging effects cause different pixels to output different gray levels and colors
Solution Approach 1:
The patent applies local quality by providing individualized compensation to each pixel based on its specific characteristics and aging state. Rather than applying a uniform adjustment across the entire display, the system senses and compensates for voltage variations on a per-pixel basis, allowing each pixel to receive tailored drive current adjustments that account for local aging effects and manufacturing variations.
Solution Approach 2:
The system modifies the electrical parameters (drive current magnitude) for each pixel based on sensed voltage variations. By changing the current parameter dynamically for each pixel, the system compensates for aging effects while maintaining simple input signal generation, thus resolving the contradiction between ease of operation and output uniformity.
3Stability of the object's composition
If pixel voltages are sensed to compensate for aging, then color uniformity can be maintained, but additional sensing circuits and control logic are required
Solution Approach 1:
The patent implements multi-functionality by designing the pixel circuit to serve both display and sensing functions. The same pixel circuitry that drives the OLED also performs voltage sensing during specific time periods, eliminating the need for completely separate sensing circuits. The display pixel acts as both the light-emitting element and the sensing element, reducing overall device complexity.
Solution Approach 2:
The pixel circuit performs self-sensing of its own voltage without requiring external sensing components. By utilizing the inherent electrical characteristics of the pixel circuit and OLED combination, the system enables each pixel to monitor its own state, thereby maintaining color uniformity while minimizing additional circuitry complexity.
4Measurement precision
If sensing is performed continuously to track aging, then accurate compensation can be achieved, but power consumption and processing time increase
Solution Approach 1:
The patent implements periodic sensing during specific frame periods rather than continuous sensing. The sensing operation is performed at designated times (e.g., during vertical blanking intervals or specific sub-frames), allowing the system to track aging progression over time while minimizing the impact on display refresh rates and processing time. This periodic approach balances measurement precision with time efficiency.
Solution Approach 2:
The system performs preliminary sensing and compensation calculations during idle periods or before the next display refresh, preparing compensation values in advance. By conducting sensing operations during vertical blanking intervals or other non-display periods, the system maintains accurate voltage measurements without interfering with the active display refresh cycle, thus reducing perceived processing time.
Data Source
AI summary
A display device may include a plurality of pixels configured to display image data on a display. The display device may also include a circuit that measures a first current associated with a light-emitting diode (LED) of a pixel of the plurality of pixels in response to the circuit receiving a first data voltage. The circuit may also measure a second current associated with the LED of the pixel of the plurality of pixels in response to the circuit receiving a second data voltage. The circuit may then determine a voltage associated with the LED based at least in part on the first current and the second current.