Off-line LED Driver with Integrated Digital Optical Feedback
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Solution Overview
Problem
Existing off-line LED drivers lack efficiency, fail to provide temperature compensation, and do not offer dimming arrangements or protection for LEDs, with isolated drivers being overly complex due to the need for secondary side signals to be coupled across isolation barriers.
Innovation Solution
An off-line LED driver with integrated digital optical feedback that uses a switch mode power converter with either non-isolated or isolated topology, where the controller is coupled only to primary side signals, allowing for high power factor and low Total Harmonic Distortion (THD) input current shaping, and operates in both current mode/DC voltage and PWM modes for temperature compensation and dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolated topology is used for off-line LED driver, then safety isolation is achieved, but device complexity increases due to secondary side signal coupling requirements
Solution Approach 1:
The patent extracts the optical feedback function from the secondary side and implements it on the primary side through a light sensor that directly detects LED optical output. This eliminates the need for complex signal coupling across the isolation barrier while maintaining safety isolation, as the controller processes only primary side signals including the optically-derived feedback signal.
Solution Approach 2:
The patent introduces an optical intermediary (light sensor detecting optical output) as a mediator between the LED and controller. This optical path serves as an intermediate channel that provides feedback information without requiring direct electrical coupling across the isolation barrier, thereby simplifying the signal transmission while maintaining isolation.
2Illumination intensity
If multiple LED system parameters are measured for high quality optical system, then optical output quality is improved, but device complexity becomes almost impossible due to signal coupling requirements
Solution Approach 1:
The patent enables the system to self-measure multiple parameters (optical output, forward voltage, current) using sensors and measurements taken directly on the primary side. The controller processes these self-generated signals without requiring external signal coupling, allowing comprehensive parameter measurement while maintaining manageable complexity.
Solution Approach 2:
The patent merges multiple measurement functions (optical detection, voltage sensing, current sensing) into a unified primary-side control architecture. All measurements are combined and processed by a single controller that uses synthesized feedback signals, eliminating the need for separate signal coupling paths for each parameter and thereby reducing overall system complexity.
3Device complexity
If non-isolated topology is used for off-line LED driver, then device complexity is reduced, but efficiency and power delivery capability deteriorate
Solution Approach 1:
The patent segments the power conversion function into distinct stages (rectification, power factor correction, LED driving) with dedicated control for each stage. This segmentation allows the non-isolated topology to maintain simplicity while achieving high efficiency through optimized control of each segment, including synthesized feedback that coordinates all stages for maximum overall efficiency.
4Illumination intensity
If synthesized digital optical feedback is implemented, then optical output quality is improved, but measurement and control difficulty increases
Solution Approach 1:
The patent implements synthesized digital optical feedback by using a light sensor to detect LED optical output and feeding this information back to the controller. The controller synthesizes this optical feedback with voltage and current measurements to create a comprehensive feedback signal that automatically adjusts driving parameters, thereby improving optical output quality while the automated feedback loop reduces the difficulty of manual measurement and control.
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
The solution provides a high-quality luminous output with efficient energy delivery, temperature compensation, and dimming capabilities, ensuring safe and effective LED operation while simplifying the driver design by eliminating the need for secondary side signal coupling across isolation.
Implementation Method 1
a switch mode power converter configured to maintain a high quality of desired lumen output
Implementation Method 2
controls the optical output of a luminous system of variable number of LED by providing electrical energy
Implementation Method 3
in addition to LED current and forward voltage drop sense, provides feedback to a switch mode power converter
Data Source
AI summary
The present invention creates an LED driver in which all feedback signals are derived from a power stage media, and presents an isolated off-line LED driver with an accurate primary side controller only to power one or more LEDs. The present invention further provides an effective off-line LED driver comprising AC current shape controller with a minimum number of components. The present invention further provides a high quality luminous system based on LED drivers with the integrated synthesized optical feedback to compensate for imperfections of the LEDs as sources of light.