LED Illumination Device with Dynamic Series-Parallel Switching
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Solution Overview
Problem
LED lighting systems powered from AC sources experience inefficiencies due to varying supply voltage, leading to intermittent operation and noticeable flicker, as they are switched ON/OFF at AC frequency, with increased power dissipation in resistors when trying to maintain light output.
Innovation Solution
A system comprising at least three groups of LEDs connected by controllable switches, capable of being switched into series, parallel, or combinations thereof, with a controllable current source to maintain constant LED current, utilizing a controller that adjusts switch states and current settings based on rectified AC voltage thresholds to ensure continuous light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LEDs are connected in series to AC power mains with a current limiting resistor, then the circuit is simple and cheap to implement, but the LEDs can only produce light during one half of the AC current period, resulting in noticeable flicker and reduced productivity
Solution Approach 1:
The LED array is divided into multiple strings that can be independently controlled. By segmenting the LED array into multiple strings and using controllable switches for each string, the system can activate different strings at different times during the AC cycle, thereby eliminating flicker and improving light output continuity while maintaining circuit simplicity.
2Productivity
If the supply voltage amplitude is increased to increase the duty cycle and reduce flicker, then the LEDs can operate more continuously, but the power dissipated in the series resistor increases, leading to greater energy loss
Solution Approach 1:
The system dynamically adjusts the connection configuration of LED strings based on the instantaneous AC voltage level. By using controllable switches to reconfigure LED strings between series and parallel arrangements in real-time, the system maintains optimal duty cycle and reduces power dissipation in resistors without requiring excessive voltage amplitude increases.
Solution Approach 2:
The system changes the electrical parameters (voltage and current distribution) across different LED strings based on the AC voltage level. By adjusting which strings are active and how they are connected (series or parallel), the system optimizes the duty cycle and minimizes energy loss without requiring a fixed high voltage amplitude.
3Productivity
If multiple LED strings are used to improve light output during both AC half periods, then continuous light production is achieved, but the device complexity increases with additional switches and control mechanisms
Solution Approach 1:
The controllable switches are designed to perform multiple functions: they control individual LED strings, enable reconfiguration between series and parallel arrangements, and facilitate flicker elimination. This multi-functionality reduces the need for separate control mechanisms and minimizes overall device complexity while achieving continuous light output.
4Illumination intensity
If LEDs are arranged in parallel to produce more light at the same voltage drop, then more current is required, but this increases power supply costs and energy loss
Solution Approach 1:
The system dynamically switches between series and parallel LED string configurations based on the AC voltage level. During high voltage periods, LEDs are arranged in series to reduce current and power loss. During low voltage periods, they are arranged in parallel to maintain light output. This dynamic reconfiguration optimizes the balance between illumination intensity and energy 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 system ensures continuous LED operation with reduced flicker and consistent light output by dynamically adjusting the connection configuration and current supply in response to varying AC voltage, minimizing power loss and maintaining constant LED current.
Implementation Method 1
a rectifier (23) rectifying an AC input voltage and providing a rectified AC output voltage
Implementation Method 2
a first group of light emitting diodes (D1), a second group of light emitting diodes (D2), and a third group of light emitting diodes (D3)
Data Source
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AI summary
A light generating device (20) comprises: -a rectifier (23) rectifying an AC input voltage and providing a rectified AC output voltage (Vin); -a controllable current source (40); -a switch matrix (30) comprising a plurality of controllable switches (S1-SN); -a plurality of n LEDs (D1, D2,... Dn) connected to output terminals of the switch matrix (30); -a controller (50) controlling said switches and controlling the current generated by the current source dependent on the momentaryvalue of the rectified voltage (Vin). The controller is capable of operating in at least three different control states. In a first control state all LEDs are connected in parallel. In a second control state all LEDs are connected in series. In a third control state at least two of said LEDs are connected in parallel while also at least two of said LEDs are connected in series.