Series-Connected LED Cells for Direct AC Drive
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Solution Overview
Problem
Light emitting diodes (LEDs) are prone to damage when directly connected to an AC power source due to repeated on-off cycles, making them unsuitable for general illumination using household AC power.
Innovation Solution
A light emitting device with multiple LEDs connected in series on a single substrate, featuring a buffer layer, n-layer, active layer, and p-layer, with wires connecting them in series or parallel, allowing for direct AC power driving, and electrodes forming ohmic contacts to reduce junction resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a light emitting diode is connected directly to an AC power source, then it can be used for general illumination, but the light emitting diode may be easily damaged due to repeated on-off cycles
Solution Approach 1:
The invention divides a single light emitting diode into multiple light emitting cells (first light emitting cell and second light emitting cell) connected in series. This segmentation allows the device to handle AC power by having cells oriented in opposite directions, so that when one cell is off during reverse bias, the other can still operate or the structure prevents damage from repeated on-off cycles.
Solution Approach 2:
The patent employs light emitting cells with opposite orientations (first light emitting cell and second light emitting cell facing opposite directions) connected in series. This inversion strategy ensures that during AC cycling, when one cell would be reverse-biased and turned off, the other cell is forward-biased and conducting, thereby distributing the stress and preventing repeated on-off damage to a single cell.
2Area of stationary object
If multiple light emitting cells are formed on a single substrate, then space occupation is reduced, but an etching process is required to separate the cells
Solution Approach 1:
The invention merges multiple light emitting cells onto a single substrate without requiring etching to separate them. The cells are formed in adjacent regions with different orientations, and the substrate itself serves as the common base. This combining approach eliminates the need for additional etching processes while maintaining compact space utilization.
Solution Approach 2:
The patent applies local quality by forming light emitting cells with different orientations (first light emitting cell and second light emitting cell) in different regions of the same substrate. Each region has locally optimized cell orientation to handle AC power cycles, while the overall substrate structure remains intact without requiring separation etching.
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
Enables the use of LEDs for general illumination with a household AC power source while eliminating the need for an etching process to separate cells, ensuring reliable operation and reduced space occupation.
Implementation Method 1
A light emitting diode is a electroluminescence device having a structure in that an n-type semiconductor of which major carriers are electrons and a p-type semiconductor of which major carriers are holes are joined together, and emits predetermined light through recombination of these electrons and holes
Implementation Method 2
The electrodes form ohmic contacts with the p-layers, thereby reducing junction resistances
Data Source
AI summary
Disclosed are a light emitting device having a plurality of light emitting cells connected in series and a method of fabricating the same. The light emitting device includes a buffer layer formed on a substrate. A plurality of rod-shaped light emitting cells are located on the buffer layer to be spaced apart from one another. Each of the light emitting cells has an n-layer, an active layer and a p-layer. Meanwhile, wires connect the spaced light emitting cells in series or parallel. Accordingly, arrays of the light emitting cells connected in series are connected to be driven by currents flowing in opposite directions. Thus, there is provided a light emitting device that can be directly driven by an AC power source.