Parallel LED Driving System with PWM Current Balance
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Solution Overview
Problem
Existing LED driving systems face inefficiencies and high costs due to linear operation of switches, leading to thermal and reliability issues in large screen applications, and require numerous inductors and controllers.
Innovation Solution
A LED driving system with parallel output lines, a main switch, and a controller that generates control signals based on current sense signals to regulate current through each LED string, using a power converter with a main switch operating in on and off states to provide driving voltage, and output switches operating in series with LED strings and capacitors to balance current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear current sources are used to balance LED current between different LED strings, then current balance is achieved, but efficiency is low and thermal issues occur
Solution Approach 1:
The patent changes the operating parameters of the switches from linear mode to switching mode (on/off states). The output switches S1-S6 are controlled to operate in switching mode with duty cycles between 0-100%, fundamentally changing how current is regulated. This parameter change enables high efficiency while maintaining current balance through PWM control rather than linear dissipation.
Solution Approach 2:
The patent replaces the linear current source mechanism with a switching current source mechanism. Instead of using linear regulators that dissipate excess current as heat, the system uses synchronous rectification with switches operating in on/off states, controlled by PWM signals. This substitution eliminates the thermal issues and efficiency losses associated with linear operation.
2Loss of energy
If n LED drivers are used to drive n LED strings, then efficiency is higher, but device complexity and cost increase due to numerous inductors and controllers
Solution Approach 1:
The patent merges multiple independent LED driver circuits into a single integrated driving system. One controller U1 manages all six LED strings through a shared power stage with inductor L1 and capacitor C1. The output switches S1-S6 are controlled by PWM signals from the same controller, consolidating what would traditionally require six separate drivers into one unified system, thereby reducing component count and complexity.
Solution Approach 2:
The single controller U1 performs multiple functions: it generates PWM signals for all output switches S1-S6, manages the power stage, and balances current across all LED strings. The shared inductor L1 and capacitor C1 serve the entire system rather than individual strings. This multi-functionality allows one controller to replace what would traditionally require six controllers, reducing system complexity while maintaining high efficiency.
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 achieves higher efficiency and lower costs by reducing power loss and minimizing external components, providing balanced current to LED strings with reduced thermal issues and improved reliability.
Implementation Method 1
an energy storage component coupled between the input port and the switch node
Implementation Method 2
each output line having a capacitor coupled in parallel with the LED string
Data Source
AI summary
A LED driving system comprising: an input port to receive an input signal; a switch node to provide a switching signal; an energy storage component coupled between the input port and the switch node; a main switch coupled between the switch node and ground; n output lines coupled in parallel, and each output line having a first and second terminals, and wherein the first terminal is coupled to the switch node, and the second terminal is coupled the reference ground, and wherein each output line having an output switch, a diode and a LED string coupled in series between the first and second terminals, and wherein each output line having a capacitor coupled in parallel with the LED string; and a controller providing a control signal to the main switch and providing corresponding n control signals to the corresponding n output switches in the corresponding n output lines.