LED Driving Apparatus Suppressing THD and EMI
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Solution Overview
Problem
LED driving systems using AC power sources face challenges in suppressing total harmonic distortion (THD) and electromagnetic interference (EMI) due to the need for precise control of LED arrays' on/off states and voltage management.
Innovation Solution
The proposed solution involves a driving apparatus with a rectifier to rectify AC signals and a series of driving units connected to LED arrays, where transistors and sensing resistors are used to manage current paths based on voltage levels, allowing for efficient control of LED arrays and minimizing harmonic distortion and EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If AC voltage is rectified and used to control LED array on/off states, then LED illumination control is achieved, but total harmonic distortion (THD) and electromagnetic interference (EMI) increase
Solution Approach 1:
The LED array is divided into multiple independently controllable LED strings, each with its own driving unit. This segmentation allows selective activation of specific strings based on voltage levels, enabling precise control while distributing the control burden and reducing harmonic distortion and EMI compared to controlling the entire array as a single unit.
Solution Approach 2:
The patent implements dynamic control where the state of each LED string changes based on real-time voltage level detection. The driving units dynamically adjust their on/off states according to the rectified voltage magnitude, creating an adaptive system that responds to varying power conditions while maintaining controlled THD and EMI levels.
2Illumination intensity
If multiple LED arrays are controlled with precise voltage management, then illumination quality improves, but device complexity increases
Solution Approach 1:
The control apparatus is segmented into multiple independent driving units, each responsible for a specific LED string. Each driving unit contains its own voltage detection and control circuitry, allowing distributed intelligence that simplifies the overall control logic while enabling precise illumination management across multiple arrays.
Solution Approach 2:
Each driving unit operates autonomously, detecting its own voltage conditions and controlling its associated LED string without requiring complex centralized control. This self-service approach reduces the complexity of the overall control system while maintaining precise voltage management and illumination quality across all LED arrays.
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 approach effectively suppresses THD and EMI while providing greater flexibility in operating voltage management for LED arrays, enhancing the performance and reliability of LED driving systems.
Implementation Method 1
a rectifier configured to rectify an alternating current (AC) signal and supply a rectified signal or voltage to the light emitting unit
Data Source
AI summary
An LED driving apparatus controls a light emitting unit including first to k-th LED arrays, a rectifier for rectifying an AC signal, and first to (k−1)-th driving units respectively corresponding to the first to (k−1)-th LED arrays. Each driving unit includes an input terminal connected to a first terminal of the LED array, a sensing terminal connected to a second terminal of the LED array, an output terminal connected to a next driving unit, a transistor between the input terminal and the sensing terminal, and a sensing resistor between the sensing terminal and the output terminal. The rectified signal or voltage is applied to the first driving unit.