Display Device PWM Signal Cycle Control for Brightness Balance
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Solution Overview
Problem
Existing organic EL display devices lack a simplified drive circuit and struggle to control light emitting brightnesses of red, green, and blue pixels across a wide range, including high to low brightness, while maintaining balance among light emitting brightnesses, and fail to address local brightness irregularities between pixels.
Innovation Solution
The display device incorporates signal lines and a drive circuit that supplies video signals and PWM signals to pixels with a drive transistor, capacitive element, and reset switching element, allowing for multiple brightness display modes by adjusting the PWM signal cycle and inflection points to achieve optimal grayscale characteristics and balance among pixel brightnesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gamma correction memories and complex correction circuits are used to suppress display non-uniformity, then display uniformity is improved, but device complexity increases
Solution Approach 1:
The patent extracts the gamma correction function from complex correction memories and circuits, implementing it instead through a simplified PWM signal generation mechanism that directly controls the light emission period based on video signal levels, thereby achieving uniformity correction without complex hardware
Solution Approach 2:
The patent replaces the mechanical/electrical correction system (gamma correction memories and correction circuits) with a signal processing approach using PWM modulation, where the light emission characteristics are controlled by varying the pulse width rather than through complex voltage correction circuits
2Adaptability or versatility
If multiple brightness display modes are implemented, then adaptability is improved, but control precision over pixel brightness balance deteriorates
Solution Approach 1:
The patent implements dynamic control of PWM signal parameters (cycle and inflection points) that can be adjusted according to different brightness display modes, allowing the system to adapt to various viewing conditions while maintaining precise control over pixel brightness balance through real-time parameter modification
Solution Approach 2:
The patent changes the parameters of the PWM signal (cycle duration and inflection point positions) to achieve different brightness display modes, where each mode uses optimized parameter settings to maintain uniform pixel brightness characteristics across the display
3Use of energy by moving object
If PWM signal cycle is shortened for low brightness mode, then power consumption is reduced, but grayscale characteristic control becomes more difficult
Solution Approach 1:
The patent modifies the PWM signal parameters (specifically the cycle duration and inflection points) to match the grayscale characteristics required for each brightness mode, ensuring that even with shorter cycles in low brightness mode, the grayscale transitions remain precise and visually accurate
Data Source
AI summary
In an image display device, each pixel includes a drive transistor for driving a light emitting element, a capacitive element which is connected between a signal line and a control electrode of the drive transistor, and a reset switching element. The reset switching elements of all pixels are turned off within a light emission period, and a PWM signal is supplied to a signal line from a drive circuit. A cycle of the PWM signal in a low brightness display mode is shorter than a cycle of the PWM signal in a standard brightness display mode. Due to such a constitution, the constitution of a drive circuit can be simplified, and it is possible to control light emission brightnesses of respective pixels of red, green and blue over a wide range from high brightness to low brightness while taking a balance among the light emission brightnesses.