Dynamic Reference Selection for Parallel Light Source Current Equalization
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Solution Overview
Problem
In liquid crystal display (LCD) devices, the varying voltage drops across light sources connected in parallel lead to unequal current distribution, affecting luminance uniformity and display quality, as current mirror circuits can only operate effectively if the voltage drop of the reference light source is the highest, limiting adjustments and causing uneven luminance.
Innovation Solution
A method and apparatus that dynamically select the light source with the highest total forward voltage as the reference current level, allowing for equalization of current levels across light sources through a current control system involving a power supply, current selection, and current control parts, including switching elements and diodes, to ensure stable operation of the current mirror circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reference light source is used in the current mirror circuit, then the circuit structure is simple, but the luminance uniformity deteriorates when voltage drops vary among light sources
Solution Approach 1:
The patent applies the dynamics principle by making the reference light source selection dynamic rather than fixed. The current mirror circuit automatically selects which light source serves as the reference based on real-time voltage drop measurements, allowing the system to adapt to variations in light source characteristics and maintain current balance across all parallel-connected light sources.
2Ease of operation
If the current mirror circuit operates with a fixed reference light source, then the control mechanism is simple, but the current distribution among light sources becomes unequal when voltage drops differ
Solution Approach 1:
The patent implements feedback by continuously monitoring the voltage drops across parallel-connected light sources and using this information to adjust the reference light source selection. The current mirror circuit receives feedback signals from voltage detection circuits, processes this information, and automatically adjusts which light source serves as the reference to maintain equal current distribution, thereby achieving precise current control despite variations in light source characteristics.
3Illumination intensity
If a dynamic reference light source selection is implemented, then the luminance uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by designing a current control system that automatically selects the reference light source without requiring external intervention or complex control algorithms. The system uses inherent voltage drop measurements from the parallel-connected light sources to self-determine which light source should serve as the reference, enabling the circuit to maintain luminance uniformity through autonomous operation while minimizing additional complexity.
Data Source
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AI summary
A light source apparatus includes a plurality of light source parts (300,310,320,330,340), a power supply part (100), a current selection part (500) and a current control part (700). The plurality of the light source parts (300,310,320,330,340) are connected in parallel and the power supply part provides power to a first terminal (311,321,331,341) of each of the light source parts. The current selection part selects the current level of one of the light source parts as a reference current level. The current control part adjusts the levels of the currents (I1,I2,I3,I4) flowing through the light source parts to be substantially equal to the reference current level. Selection of the light source part that provides the reference current level is dynamically changed.