Pixel Circuit With Dual Drive Paths for Color Accuracy
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Solution Overview
Problem
Inorganic light-emitting devices like micro-LEDs experience variations in luminous efficiency based on emitted light wavelength, leading to deviations in color coordinates and white balance due to high voltages, affecting image quality.
Innovation Solution
A pixel circuit design with independent duty ratios for each color, utilizing two compensation circuits to alternately drive light-emitting elements during different periods, ensuring operation within maximum efficiency regions while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If voltage is increased to achieve maximum luminous efficiency for certain colors, then luminous efficiency is improved, but color coordinates and white balance deviate from target values, resulting in deterioration of image quality
Solution Approach 1:
The pixel circuit is divided into two separate circuits: a first circuit for driving light-emitting elements of first colors (e.g., red, green) and a second circuit for driving light-emitting elements of second colors (e.g., blue). Each circuit independently controls its driving transistor and EM switch transistor, allowing separate optimization of driving voltages and duty ratios for different color wavelengths, thus achieving maximum luminous efficiency for each color while maintaining accurate color coordinates and white balance.
2Illumination intensity
If voltage is increased to drive light-emitting elements at high luminance, then luminous efficiency is improved, but image quality deteriorates due to color deviation
Solution Approach 1:
Each color channel (first color and second color light-emitting elements) is driven by a dedicated circuit with independently optimized parameters. The first circuit uses voltage and duty ratio settings optimized for first colors, while the second circuit uses settings optimized for second colors. This localized optimization allows each color to operate at high luminance within its maximum efficiency region while maintaining overall image quality through color-specific parameter tuning.
3Loss of energy
If duty ratio is increased to improve luminous efficiency, then energy efficiency is improved, but image quality deteriorates due to color coordinate deviation
Solution Approach 1:
The pixel circuit dynamically switches between first and second driving transistors based on the color of the light-emitting element being driven. The control circuit selectively activates either the first EM switch transistor or the second EM switch transistor, enabling dynamic adaptation of driving parameters (voltage and duty ratio) to match the specific wavelength requirements of different color light-emitting elements, thereby optimizing luminous efficiency while maintaining accurate color coordinates.
Data Source
Figure 1~2A
Figure 2B~3
Figure 4
AI summary
A pixel circuit can include a light-emitting element, a first driving transistor, a second driving transistor, a first emission switch transistor configured to electrically connect the first driving transistor to the light-emitting element in response to a light emission signal, and a second emission switch transistor configured to electrically connect the second driving transistor to the light-emitting element in response to the light emission signal. Also, the pixel circuit can include a first circuit configured to charge a first data voltage during a first driving period and transfer the light emission signal to the first emission switch transistor during a second driving period, and a second circuit configured to transmit the light emission signal to the second emission switch transistor during the first driving period and charge a second data voltage during the second driving period.