Open Loop LED Driver for Brightness Accuracy
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Solution Overview
Problem
Existing closed loop LED drivers face challenges in achieving accurate brightness control and matching between multiple LED strings due to stringent hardware requirements, including high-resolution digital-to-analog converters and fast current drivers, leading to errors in pulse width modulation and increased complexity.
Innovation Solution
An open loop LED driver architecture that directly controls LED current using a driver device without a closed loop amplifier, employing an analog comparator and pulse width modulation control to terminate current when the accumulated charge matches the target charge, resulting in faster pulse edges and improved brightness accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop amplifier is used for LED current control, then brightness control accuracy can be improved, but device complexity and hardware requirements increase
Solution Approach 1:
The patent removes the closed-loop amplifier from the LED driver circuit, extracting only the essential open-loop control components (current source, integrator, and comparator) needed for accurate brightness control. This eliminates unnecessary hardware complexity while maintaining the core functionality of precise current control through direct integration of LED current and charge comparison.
Solution Approach 2:
The patent applies local quality by implementing precise control only where needed - using an integrator to accumulate LED current and a comparator to directly compare accumulated charge with target charge. This localized precision approach replaces the need for a complex closed-loop amplifier, achieving accurate brightness control through targeted functional components rather than comprehensive system complexity.
2Manufacturing precision
If high-resolution digital-to-analog converters and fast current drivers are used, then pulse width modulation accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive, high-resolution digital-to-analog converters and fast current drivers with simpler, lower-cost components. The open-loop architecture uses basic digital logic and standard current sources, treating the control system as a disposable or low-cost solution that achieves sufficient accuracy through software-based charge integration and comparison rather than expensive hardware precision components.
Solution Approach 2:
The patent substitutes mechanical/electrical precision components (high-resolution DACs, fast current drivers) with a software-based control algorithm. The integrator and comparator implement pulse width modulation accuracy through digital computation and logical comparison, replacing the need for precision analog hardware with a more flexible, lower-cost digital implementation.
3Reliability
If closed loop amplifier is used, then brightness matching between multiple LED strings can be improved, but implementation complexity increases
Solution Approach 1:
The patent implements a universal open-loop control architecture that can be replicated across multiple LED string channels using identical, simple components. Each channel uses the same integrator-comparator structure, enabling easy manufacturing and consistent brightness matching across multiple strings without requiring complex, channel-specific closed-loop amplifier designs. This multi-functional approach allows the same simple circuit to serve multiple purposes across different LED channels.
Solution Approach 2:
The patent segments the control function into independent, identical modules for each LED string - each with its own simple integrator and comparator. This segmentation allows independent optimization and manufacturing of each channel while ensuring consistent performance across all strings, reducing implementation complexity compared to interconnected closed-loop systems that require synchronized operation across multiple channels.
4Speed
If fast current drivers are used, then pulse edges become sharper, but power consumption and heat generation increase
Solution Approach 1:
The patent uses periodic PWM control with controlled pulse widths to achieve sharp effective pulse edges without requiring continuously fast current drivers. The integrator accumulates current over the pulse duration, and the comparator terminates the pulse at the precise moment when accumulated charge equals target charge, creating sharp effective edges through timed periodic action rather than requiring high-speed driver circuitry that would consume excessive power.
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 simplifies implementation, enhances brightness accuracy, and improves matching between multiple LED strings by eliminating the need for high-frequency counter clocks and reducing errors in pulse width modulation, while maintaining efficient power delivery.
Implementation Method 1
A light-emitting diode (LED) display is a video display that uses a light-emitting diode in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current.
Data Source
AI summary
Light emitting diode display panels with an open loop amplifier resulting in better brightness accuracy and matching between multiple light emitting diode strings.