Synchronous LED String Driver Circuit Topology
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Solution Overview
Problem
Existing LED string driving technologies face challenges in efficiently managing current across multiple LED strings with varying forward voltage drops, leading to power surges and increased costs due to the need for multiple stages of power conversion and balancing elements, which are not suitable for DC-operated LEDs.
Innovation Solution
A synchronous driving architecture that connects LED strings in series with an electronically controlled switch, powered by a PFC stage and a switching bridge, with optional capacitors to manage current swings and prevent power surges, allowing for synchronized control of current through all strings using a single power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple power sources are supplied for each LED string to control current, then balanced overall luminance is achieved, but system cost increases significantly
Solution Approach 1:
The patent combines multiple LED strings in series within a single string configuration, allowing them to share a common current from a single power source. This merging approach eliminates the need for separate power sources for each string while maintaining balanced luminance output across all LEDs in the string.
Solution Approach 2:
The single power source is designed to universally drive multiple LED strings through the series configuration, performing the function of multiple dedicated power sources simultaneously. This multi-functional approach reduces system complexity and cost while achieving the same current control objective.
2Illumination intensity
If a controlled dissipative element is placed in series with each LED string to balance voltage, then current equality is achieved, but energy waste increases
Solution Approach 1:
The patent extracts and eliminates the dissipative balancing element from the circuit configuration. By using series-connected LED strings with a common current path, the need for additional dissipative components is removed entirely, preventing the energy waste that would otherwise occur in those elements.
Solution Approach 2:
The patent converts the potential harm of voltage mismatches between strings into a benefit by using the series configuration to naturally equalize current. The voltage differences are absorbed by the series connection itself rather than requiring active dissipation, turning a potential problem into an inherent advantage of the circuit topology.
3Illumination intensity
If binning is performed to sort LEDs by electrical characteristics, then current balance is improved, but manufacturing cost increases
Solution Approach 1:
The patent enables the LED string system to self-regulate current distribution through its series configuration. The inherent electrical characteristics of the LEDs work together in the series circuit to naturally balance current flow, eliminating the need for external binning processes and associated manufacturing costs.
4Device complexity
If a single power source is used for multiple LED strings, then system cost is reduced, but current balance control becomes difficult
Solution Approach 1:
The patent creates an equipotential current path by connecting LED strings in series, ensuring that the same current flows through all strings. This topological approach to achieving equipotential conditions simplifies control, as the series configuration inherently enforces current equality without requiring complex control circuits.
Data Source
AI summary
A light emitting diode (LED) based luminaire driving arrangement constituted of: a switched driver; a plurality of LED based luminaires arranged to receive power from the switched driver; at least one electronically controlled switch in series with at least one of the plurality of LED based luminaires and arranged to alternatively pass current through the at least one LED based luminaire when closed and prevent the flow of current through the at least one LED based luminaire when opened; and at least one synchronous driver in communication with the at least one electronically controlled switch, the at least one synchronous driver arranged to close the at least one electronically controlled switch only when the switched driver is actively supplying power.