Micro-LED Pixel Circuit for Accurate Grayscale Pulse-Width Control
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Solution Overview
Problem
Inorganic micro-LEDs pose challenges in applying current-based grayscale driving methods due to variations in emission wavelengths with current changes, making it difficult to achieve accurate grayscale expression compared to organic LEDs.
Innovation Solution
A pixel circuit and display panel design utilizing time-division sensing and driving methods, incorporating transistors and capacitors to generate bias and grayscale voltages, which control the magnitude and pulse width of the driving current for inorganic micro-LEDs, ensuring accurate grayscale expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current-based grayscale driving method is applied to inorganic micro-LEDs, then driving simplicity is improved, but grayscale expression accuracy deteriorates due to emission wavelength variations with current changes
Solution Approach 1:
The grayscale control function is segmented into two independent parts: magnitude control (via bias voltage affecting current) and duration control (via pulse width modulation). This separation allows each parameter to be optimized independently, resolving the contradiction between simple current-based driving and accurate grayscale expression.
Solution Approach 2:
The patent introduces dynamic control parameters (bias voltage and pulse width) that can be adjusted independently to compensate for micro-LED characteristics. By making the driving parameters dynamic rather than static, the system can adapt to wavelength variations while maintaining grayscale accuracy.
2Measurement precision
If time-division sensing and driving method is implemented, then grayscale control accuracy is improved, but device complexity increases due to additional transistors and capacitors
Solution Approach 1:
The pixel circuit components (transistors and capacitors) are designed to serve multiple functions: sensing transistor characteristics, storing bias and grayscale voltages, controlling current magnitude, and regulating pulse width. This multi-functionality reduces the need for separate dedicated components, mitigating the complexity increase.
Solution Approach 2:
The patent merges the sensing function and driving function into a single integrated pixel circuit. The same transistors and capacitors used for voltage storage also serve as sensing elements, combining multiple functions into unified circuit blocks to manage complexity.
3Manufacturing precision
If bias voltage and grayscale voltage are separately controlled, then driving current precision is improved, but control complexity increases
Solution Approach 1:
The patent adds a temporal dimension to voltage control by introducing pulse width modulation alongside bias voltage control. Grayscale is expressed through the combination of voltage magnitude (bias) and time duration (pulse width), transforming a one-dimensional control problem into a two-dimensional solution space that achieves higher precision.
Data Source
AI summary
A display panel includes sub-pixels each including a light-emitting element and a pixel circuit including a first transistor and a second transistor; a timing control unit to generate bias data based on first characteristic information of the first transistor, and generate correction data based on second characteristic information of the second transistor; and a data sensing driving unit configured to receive the bias data and the correction data, and output a bias voltage and a grayscale voltage to the pixel circuit. The pixel circuit includes the first transistor to output a driving current to the light-emitting element; a first driving circuit to control a magnitude of the driving current based on the bias voltage; and a second driving circuit including the second transistor and configured to control a pulse width of the driving current based on the grayscale voltage.