LED Driver PWM Duty Cycle Compensation for Brightness Matching
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Solution Overview
Problem
Conventional LED controllers in multi-string LED systems face limitations in maintaining uniform brightness across LED strings due to driver mismatches, leading to insufficient current and brightness matching.
Innovation Solution
The implementation of a feedback configuration that adjusts the duty cycle of PWM drive signals for each LED string based on error signals generated from comparisons between measured and target current or duty cycle values, using compensation circuits and error determination circuits to ensure matching brightness levels across channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional LED controllers are used without feedback compensation, then the device complexity is low, but the brightness matching precision between LED strings is insufficient
Solution Approach 1:
The patent implements feedback compensation by measuring the actual current through each LED string and comparing it with the target current. The error signal is then used to adjust the PWM duty cycle dynamically, ensuring brightness matching between multiple LED strings despite driver mismatches. This closed-loop feedback mechanism directly resolves the contradiction by improving precision through additional control complexity.
Solution Approach 2:
The patent replaces manual calibration or mechanical adjustment methods with an automated electronic feedback system. The error determination circuit and PWM adjustment mechanism automatically compensate for brightness mismatches, eliminating the need for complex manual calibration procedures while achieving high precision brightness matching.
2Manufacturing precision
If feedback compensation circuits are added to adjust PWM duty cycles, then the brightness matching precision is improved, but the device complexity increases
Solution Approach 1:
The patent divides the control system into independent compensation circuits for each LED string, where each circuit processes its own current feedback and adjusts its PWM duty cycle independently. This segmentation allows the system to achieve high current matching precision for each channel without requiring a monolithic complex control architecture, as each segment handles a specific task autonomously.
Solution Approach 2:
The compensation circuits are designed to be self-regulating, where each circuit automatically adjusts its own PWM duty cycle based on its measured current feedback. The error determination circuits compare actual current with target current and autonomously generate correction signals, eliminating the need for centralized complex control logic and reducing overall system complexity.
3Stability of the object's composition
If PWM duty cycles are dynamically adjusted based on error signals, then the brightness uniformity across LED strings is improved, but the control system complexity increases
Solution Approach 1:
The patent dynamically changes the PWM duty cycle parameter based on real-time current measurements and error signals. By adjusting this single critical parameter, the system achieves brightness uniformity across all LED strings without needing to redesign the entire control architecture or add multiple complex control variables, thus maintaining relatively simple control system structure.
Data Source
AI summary
An LED (Light Emitting Diode) controller comprises a first LED driver to generate a first PWM (Pulse Width Modulation) drive signal to turn on or turn off, respectively, a first current through a first LED string. Additionally, the LED controller comprises a compensation circuit to generate the first PWM drive signal responsive to a first duty set signals. The first duty set signal is indicative of a first duty cycle set for the first PWM drive signal. The compensation circuit receives a first feedback signal indicative of the first current, generates a first error signal indicative of a difference between a first predetermined target value and the first feedback signal, and generates the first PWM drive signal to have the first duty cycle corresponding to the first duty set signal and further adjusted by the first error signal.