Charge Sharing Circuit for LED Brightness Uniformity
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Solution Overview
Problem
In LED arrays, LEDs in a line scan exhibit different conduction periods and actual brightness levels due to varying voltages, leading to inconsistent light emission, especially at low brightness levels where these differences are more pronounced.
Innovation Solution
A display system with a driving device that includes a charge balance line and a charge sharing circuit, which establishes or disrupts electrical connections between drive lines and a charge balance line based on control outputs, ensuring equal voltage levels across drive lines and facilitating charge sharing among them to synchronize LED conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If LEDs in a line are set to have the same expected brightness level, then the display can maintain uniform brightness control, but the LEDs would become conducting at different time points due to different voltages, resulting in different conduction periods and actual brightness levels
Solution Approach 1:
The patent applies preliminary action by establishing electrical connections between drive lines and the charge balance line before the LEDs become conducting. This allows voltage equalization to occur in advance, ensuring that all LEDs in a line experience substantially the same voltage and conduction period, thereby eliminating brightness inconsistencies without requiring complex real-time adjustments during the conduction phase
2Illumination intensity
If the expected brightness level of the LEDs in the line is low, then the display can represent dimmer scenes, but the conduction periods of the LEDs become short and length differences among conduction periods are more noticeable, worsening brightness consistency
Solution Approach 1:
For low brightness levels, the patent establishes electrical connections between drive lines and the charge balance line before the short conduction period begins. This preliminary voltage equalization ensures that even during the brief conduction window, all LEDs experience substantially uniform voltage and conduction duration, making brightness consistency maintainable at low intensity levels where conventional approaches would show noticeable variations
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures consistent brightness across LEDs by minimizing voltage differences and extending conduction periods, thereby alleviating the issue of inconsistent light emission in LED arrays.
Implementation Method 1
the charge sharing circuit is operable, based on the control output, to establish or not establish an electrical connection between the drive line and the charge balance line
Implementation Method 2
ensuring equal voltage levels across drive lines and facilitating charge sharing among them to synchronize LED conduction
Data Source
AI summary
A display system includes a light emitting array and a driving device. The light emitting array includes multiple scan lines, multiple drive lines and multiple light emitting elements. The driving device includes a controller, a charge balance line and a charge sharing circuit. The controller generates a control output. The charge sharing circuit is coupled to the drive lines, the charge balance line and the controller, and receives the control output from the controller. With respect to each of the drive lines, the charge sharing circuit is operable, based on the control output, to establish or not establish an electrical connection between the drive line and the charge balance line.