OLED Data Driving Circuit Feedback Brightness Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
OLED displays face challenges in achieving desired brightness due to varying threshold voltages of transistors in pixels and the inability to measure and control the real current flowing in each pixel, leading to inconsistent light emission.
Innovation Solution
A data driving circuit is developed, comprising a voltage digital-analog converter, current digital-analog converter, voltage control unit, buffer unit, and selection unit, which generates and adjusts gradation voltages based on feedback pixel current to ensure desired current flow, thereby controlling pixel brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transistors are provided in each pixel to supply current corresponding to data signal, then the OLED display can emit light, but the transistors have different threshold voltages causing inconsistent brightness
Solution Approach 1:
The patent implements a feedback mechanism where the actual current flowing through each pixel is measured and fed back to the data driving circuit. The circuit then adjusts the data signal to compensate for transistor threshold voltage variations, ensuring consistent brightness across all pixels despite manufacturing variations.
Solution Approach 2:
The patent replaces the conventional voltage-based current control mechanism with a current-based feedback control mechanism. Instead of relying on transistor voltage thresholds to control current, the system directly measures and controls the actual current flow, substituting indirect voltage control with direct current control.
2Measurement precision
If additional lines are added to measure and control pixel current, then current control precision improves, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent makes the data line serve multiple functions: it carries the data signal from the data driving circuit to the pixel, and simultaneously serves as the feedback path to return the actual pixel current to the data driving circuit. This multi-functionality eliminates the need for separate measurement lines, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent merges the data signal transmission function and the current feedback function into a single data line. By combining these two functions that were previously performed by separate pathways, the overall device complexity is reduced while achieving both data transmission and precise current measurement.
3Reliability
If feedback control is implemented to adjust gradation voltage, then brightness consistency improves, but control circuit complexity increases
Solution Approach 1:
The data driving circuit performs self-adjustment by automatically comparing the actual pixel current feedback with the expected current and autonomously correcting the data signal to compensate for threshold voltage variations. This self-service capability reduces the need for external control circuits while maintaining brightness consistency.
Data Source
AI summary
A data driving circuit including: a voltage digital-analog converter adapted to generate a first gradation voltage corresponding to external data; a current digital-analog converter adapted to generate a gradation current corresponding to the external data; a voltage control unit adapted to receive a feedback pixel current from a pixel via a data line and to generate a second gradation voltage by increasing or decreasing a level of the first gradation voltage in accordance with the feedback pixel current; a buffer unit adapted to selectively supply the first or second gradation voltage to the data line; and a selection unit adapted to selectively connect the data line to either the buffer unit or the voltage control unit. With this configuration, an image is displayed with a desired brightness.