AC LED Light Engine with Switchable Arrays
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Solution Overview
Problem
Conventional AC-DC LED drivers are complex and bulky, leading to significant light off-time due to discontinuous LED current at zero crossing of the AC voltage waveform, which is not efficiently addressed by simpler AC LED circuits that turn off at double the line frequency.
Innovation Solution
An AC light engine is developed with multiple LED arrays and switchable constant current sources integrated on a single PCB, allowing direct AC power connection and reducing off-time by dynamically switching LED arrays on and off based on AC voltage levels, using semiconductor chips and direct chip attachment for compact and efficient design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional AC-DC LED drivers are used, then regulated DC power is provided for constant light output, but the circuit becomes complex and bulky
Solution Approach 1:
The patent combines the LED arrays and driver circuitry into a single integrated AC LED circuit module. The driver circuit is directly coupled to the LED arrays on the same circuit board, eliminating the need for separate AC-DC conversion modules. This integration maintains regulated operation while significantly reducing circuit complexity and overall device size.
Solution Approach 2:
The driver circuit is designed to directly accept AC line voltage input and regulate it for LED operation without requiring separate AC-DC conversion stages. The circuit universally handles AC input and provides regulated current to multiple LED arrays, combining multiple functions into a single multi-functional module that reduces overall system complexity.
2Device complexity
If simpler AC LED circuits are used, then circuit complexity is reduced, but light off-time increases due to discontinuous current at zero crossing
Solution Approach 1:
The LED lighting system is divided into multiple independently controllable LED arrays (first, second, third, and fourth arrays). Each array can be selectively activated based on the instantaneous AC voltage level. This segmentation allows the circuit to maintain simplicity while reducing off-time by ensuring that at least one array remains active throughout the AC cycle.
Solution Approach 2:
The circuit dynamically switches between different LED arrays based on the instantaneous AC voltage level. When voltage is high, more arrays are activated; when voltage drops near zero crossing, the circuit transitions to arrays with lower forward voltage requirements. This dynamic switching maintains continuous or near-continuous light output while keeping the circuit relatively simple.
3Loss of time
If multiple LED arrays with different forward voltages are used, then continuous light output is maintained by switching arrays based on voltage levels, but circuit design becomes more complex
Solution Approach 1:
Each LED array is designed with specific forward voltage characteristics suited to different AC voltage levels. The first and second arrays have higher forward voltages and are activated during high-voltage portions of the AC cycle, while the third and fourth arrays have lower forward voltages and are activated during low-voltage portions including near zero crossing. This local optimization of array characteristics reduces the need for complex control circuitry.
Solution Approach 2:
The circuit uses the natural variation in AC voltage levels to automatically determine which LED arrays should be active. Arrays with different forward voltage requirements self-regulate their activation based on the instantaneous voltage, eliminating the need for complex voltage sensing and control logic. The system essentially serves itself by leveraging the inherent properties of the LED arrays and the AC waveform.
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 significantly reduces light off-time from 40% to 10% by enabling a simple and compact AC LED driver that maintains consistent light output with reduced size and complexity, allowing for direct AC line power usage and improved thermal management.
Implementation Method 1
a plurality of LED arrays D1 to Dn connected in series, each LED array having a forward voltage
Data Source
AI summary
An LED array switching apparatus comprises, on a single PCB substrate: a plurality of LED arrays D1 to Dn connected in series, each LED array having a forward voltage; an AC voltage supply coupled to the plurality of LED arrays; and a plurality of constant current sources G1 to Gn, coupled to outputs of LED arrays D1 to Dn, respectively, each of the constant current sources being switchable between a current regulating state and an open state such that as the voltage of the AC voltage supply increases, LED arrays are switched on and lit to form a higher forward voltage LED string, and as the voltage of the AC voltage supply decreases, LED arrays are switched off and removed from the LED string starting with the most recently lit LED array.