LED Light Emitting Device Series-Parallel Circuit Luminance Control
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Solution Overview
Problem
In light emitting devices with LEDs connected in series-parallel configurations, luminance unevenness and reduced luminous efficiency occur due to electrode wiring patterns and the use of Zener diodes or resistors, which also complicate packaging and increase energy loss.
Innovation Solution
A light emitting device configuration featuring a substrate with LEDs connected in series-parallel, a resin frame with low optical transmittance surrounding the LEDs, and a fluorescent-material-containing resin layer, along with connection electrodes that reduce the need for conventional electrode wiring patterns, enhancing packaging density and minimizing light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zener diodes are connected in inverse-parallel to LEDs to protect from excessive voltage, then reliability is improved, but device complexity increases and packaging becomes more difficult
Solution Approach 1:
The patent extracts the protection function from the main LED circuit by using separate protective elements (resistors or Zener diodes) connected in parallel with each LED or LED string. This separation allows the protective function to be added without fundamentally changing the LED circuit configuration, reducing the complexity increase compared to integrating protection directly into the LED structure.
Solution Approach 2:
The patent divides the protection scheme into discrete protective elements that can be individually connected to specific LEDs or LED strings. This segmentation allows flexible packaging arrangements where protective elements are distributed throughout the package rather than requiring a single complex protection circuit, making packaging more manageable.
2Reliability
If resistors are connected in parallel to LEDs as bypass resistors to prevent LED disconnection effects, then reliability is improved, but energy loss increases due to large current requirements
Solution Approach 1:
The patent optimizes the resistance value parameters of bypass resistors to balance their protective function with energy loss. By carefully selecting resistance values that are low enough to provide adequate bypass current for reliability but high enough to minimize power dissipation, the patent resolves the contradiction between reliability improvement and energy loss.
3Reliability
If electrode wiring patterns are deposited between adjoining LEDs to electrically connect them, then electrical connectivity is improved, but luminance unevenness increases and luminous efficiency decreases due to light absorption
Solution Approach 1:
The patent extracts the electrical connection function from the light-emitting area by depositing electrode wiring patterns in the spaces between adjoining LEDs rather than over the LED surfaces. This spatial separation ensures that electrodes provide necessary electrical connectivity while minimizing their presence in the light path, thereby reducing light absorption and maintaining luminance uniformity.
Solution Approach 2:
The patent transitions the electrode wiring from a two-dimensional planar pattern to a three-dimensional arrangement that utilizes the vertical space and inter-LED gaps. By positioning electrodes in the spaces between LEDs and using vertical connection paths, the patent achieves electrical connectivity without electrodes blocking the horizontal light path, thus maintaining luminous 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
This configuration improves luminous efficiency by reducing light absorption and luminance unevenness, while also extending the device's lifespan and reliability through parallel protective elements.
Implementation Method 1
a fluorescent-material-containing resin layer made of a resin containing fluorescent materials, the fluorescent-material-containing resin layer being provided adjacent to an inner side of the resin frame so as to cover the plurality of light emitting elements
Data Source
AI summary
A light emitting device includes: a ceramic substrate; a plurality of LED chips; a printed resistor(s) connected in parallel with the plurality of LED chips; a dam resin made of a resin having a low optical transmittance; a fluorescent-material-containing resin layer; and an anode-side electrode and a cathode-side electrode, (a) which are provided on a primary surface of the ceramic substrate so as to face each other along a first direction on the primary surface and (b) which are disposed below at least one of the dam resin and the fluorescent-material-containing resin layer. With the configuration in which a plurality of LEDs, which are connected in a series-parallel connection, are provided on a substrate, it is possible to provide a light emitting device which can achieve restraining of luminance unevenness and an improvement in luminous efficiency.