Silicon OLED Pixel Island Driving Circuit for High PPI Low-Gray-Scale
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Solution Overview
Problem
Silicon-based OLEDs face challenges in achieving high pixel per inch (PPI) while maintaining low-gray-scale display due to small pixel current and threshold voltage uniformity issues, making it difficult to achieve high PPI and low-gray-scale display simultaneously.
Innovation Solution
A display substrate with a pixel island driving mode that includes a light emission control circuit connected between the first power supply end and the driving transistor's first electrode, and resistors between pixel islands to manage current, allowing for fixed maximum voltage during low-gray-scale display and adjusting pulse width modulation to achieve different gray scales without increasing subpixel area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase PPI, then pixel current becomes too small to achieve low-gray-scale display, but increasing pixel size reduces PPI
Solution Approach 1:
The patent introduces a light emission control circuit as an intermediary component between the power supply and the pixel circuit. This control circuit includes a switch transistor that can precisely regulate the current supplied to each pixel, enabling effective control of pixel current even at high PPI where individual pixel currents are very small. The intermediary control circuit acts as a current amplifier and regulator, solving the contradiction between small pixel current and low-gray-scale display capability.
Solution Approach 2:
The patent changes the control parameter from direct pixel-level current control to pulse width modulation (PWM) at a higher level. By controlling the duty cycle of the light emission control signal, the system can achieve precise gray scale control without requiring large currents. This parameter change from amplitude control to temporal control allows high PPI and low-gray-scale display to coexist.
2Reliability
If pixel circuit components are increased to improve threshold voltage uniformity, then pixel area increases, but increasing pixel area reduces PPI
Solution Approach 1:
The patent merges the light emission control function with the pixel driving function by integrating the light emission control circuit at the pixel island level. Multiple subpixels share common light emission control circuits, reducing the need for separate control components in each pixel. This merging approach maintains threshold voltage uniformity through shared control while minimizing the area occupied by control circuitry, thus preserving high PPI.
Solution Approach 2:
The light emission control circuit serves multiple functions simultaneously: it controls the timing of light emission, regulates current distribution, and provides gray scale control through PWM. This multi-functionality reduces the need for separate dedicated components for each function, minimizing the overall pixel area while maintaining reliability and uniformity.
3Illumination intensity
If PWM duration is extended to improve low-gray-scale display, then power consumption increases, but shortening PWM duration reduces display quality
Solution Approach 1:
The patent employs periodic pulse width modulation where the light emission control signal operates in repeated cycles with variable duty cycles. For low-gray-scale display, the PWM duration within each period is precisely controlled to provide just enough illumination while maintaining energy efficiency. The periodic nature allows the system to achieve good display quality through temporal averaging rather than continuous high-power operation.
Solution Approach 2:
The light emission control circuit ensures continuous useful action by maintaining the pixel in a ready state with minimal power consumption, and only activating full current flow during the necessary PWM duration for light emission. This continuous readiness with on-demand activation balances display quality and power consumption by eliminating idle power waste while maintaining instantaneous display performance.
Data Source
AI summary
A display substrate, a driving method therefor, and a display device are provided. The display substrate includes: a base substrate, provided with multiple pixel islands discretely provided, the pixel islands including multiple subpixels distributed in an array; a plurality of pixel circuits, arranged in the subpixels respectively, each of the pixel circuits including a driving transistor and a light-emitting component, a first electrode of the driving transistor being electrically connected to a first power supply end, a second electrode of the driving transistor being electrically connected to an anode of the light-emitting component, and a cathode of the light-emitting component being electrically connected to a second power supply end; and multiple light emission control circuits, each arranged at a gap between adjacent pixel islands, the light emission control circuit being electrically connected between the first power supply end and the first electrode of the driving transistor.