LED Light Source with Reversed Current Flow Order
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Solution Overview
Problem
Existing LED light sources connected to low-frequency AC voltage have low LED utilization due to differing current-carrying durations among LED loads, leading to inefficient use of LED packages, where most packages are not used to their full capacity.
Innovation Solution
A control mechanism that reverses the order of current flow among LED loads at each zero crossing of the AC supply voltage, ensuring all loads carry equal average currents, allowing for cheaper LED packages as utilization is improved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If LED loads are connected in series to AC supply voltage, then the circuit can be directly supplied from mains voltage, but different LED loads conduct current during time lapses of substantially different duration resulting in low LED utilization
Solution Approach 1:
The patent applies periodic action by switching between two operating states at each zero-crossing of the AC supply voltage. In the first operating state, LED loads conduct in a first order (1st, 2nd, 3rd, 4th). In the second operating state, LED loads conduct in a reversed order (4th, 3rd, 2nd, 1st). This periodic reversal ensures that all LED loads conduct current for equal durations over complete cycles, equalizing their average currents and improving LED utilization while maintaining direct AC supply connection.
2Reliability
If all LED packages have the same power capacity to meet worst case requirements, then reliability is ensured, but most LED packages are not used to their full capacity resulting in higher costs
Solution Approach 1:
By implementing periodic reversal of current flow order through switching between two operating states, the patent ensures that all LED loads receive equal average current over complete cycles. This equalization allows LED packages to be selected based on average power requirements rather than worst-case peak requirements, enabling the use of cheaper LED packages while maintaining reliability through the balancing effect of the periodic switching.
3Power
If the first LED load carries higher average current than the Nth LED load, then the first LED load meets its current requirements, but the Nth LED load is underutilized
Solution Approach 1:
The patent applies inversion by reversing the conduction order of LED loads in the second operating state compared to the first operating state. In the first state, current flows through LED loads in order 1-2-3-4; in the second state, current flows in reversed order 4-3-2-1. This inversion equalizes the average current through each LED load over complete cycles, ensuring all packages are utilized equally and eliminating the disparity where the first load carried higher current than the Nth load.
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 LED utilization by ensuring all loads carry equal average currents, reducing the cost of LED packages and improving overall efficiency.
Implementation Method 1
a rectifier coupled to the input terminals for rectifying the low-frequency AC supply voltage
Implementation Method 2
The LED loads are LED arrays comprising series arrangements and possibly parallel arrangements of individual LEDs
Data Source
AI summary
LED light source comprising a string of LED loads (LED1-LED4) supplied by a rectified mains voltage. The number of LED loads carrying current is increased as the momentary amplitude of the rectified mains voltage increases, and is decreased as the momentary amplitude of the rectified mains voltage decreases. The order in which the LED loads start carrying a current and the order in which the LED loads stop carrying a current is reversed for each half period of the mains.