LED Driver Master-Slave Voltage Regulation for Current Imbalance
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Solution Overview
Problem
Parallel LED strings face current imbalance issues due to manufacturing tolerances, aging, and temperature variations, leading to luminous intensity and color variations, and existing solutions like ballast resistors and linear current regulators suffer from inefficiencies and complexity.
Innovation Solution
A common master power converter provides the majority of the driver voltage, with separate slave power converters regulating residual voltage to balance current in each LED string, using semiconductor switches or magnetic amplifiers for efficient voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If parallel LED strings are used to increase system power, then the number of LEDs that can be driven increases, but current imbalance occurs due to manufacturing tolerances and aging
Solution Approach 1:
The patent divides the LED string control into multiple independent segments by introducing separate current regulation circuits for each parallel LED string. Each string is regulated by its own circuit that independently controls the forward current, preventing current imbalance caused by manufacturing tolerances and aging. This segmentation allows each LED string to be precisely controlled while maintaining parallel configuration for high power application.
2Manufacturing precision
If ballast resistors are added in series with each LED string to minimize current differences, then current balance improves, but power loss increases significantly
Solution Approach 1:
The patent replaces the passive mechanical approach of using ballast resistors with an active electronic current regulation system. Instead of relying on resistive elements to balance current (which cause significant power loss), the invention employs controlled rectifiers or current regulators that actively adjust the forward current of each LED string based on feedback, achieving current balance with minimal power loss.
3Manufacturing precision
If linear current regulators are used for each LED string to ensure good current sharing, then current balance improves, but power loss on the regulator increases
Solution Approach 1:
The patent changes the operating parameters of the current regulation system by using switched-mode power supply techniques instead of linear regulation. The controlled rectifiers operate in a switching mode that converts electrical energy efficiently, changing the regulation mechanism from continuous linear conduction to pulsed switching action. This parameter change enables precise current sharing while dramatically reducing the power loss in the regulation circuits.
4Measurement precision
If separate voltage sources are provided for each LED string with independent sensing and control, then current control precision improves, but device complexity and cost increase
Solution Approach 1:
The patent merges the voltage source functions into a single common power supply that feeds multiple parallel LED strings. Instead of providing separate voltage sources for each string, the invention uses one unified power supply with distributed controlled rectifiers or current regulators that independently control each string's current. This merging approach maintains precise current control through individual string regulation while significantly reducing the overall device complexity and component count.
Data Source
AI summary
An LED driver for a plurality of LED light strings has a common node and a plurality of driver output nodes for connection of a plurality of LED light strings. A master power circuit is provided and has a master output connected with the common node. A plurality of slave power circuits are provided which each have a slave output connected with a respective one of the driver output nodes.