Blue-Green LED Drive Timing for Stable Chromaticity

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Solution Overview

Problem

Existing light sources using blue and green LED elements require separate driver ICs, leading to increased cost and complexity, and struggle to maintain desired chromaticity under varying luminance and temperature conditions.

Innovation Solution

A light source design incorporating a switch and timing controller to alternately drive blue and green LED elements with a single drive circuit, optimizing forward voltage differences and adjusting current values and periods to achieve desired chromaticity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate driver ICs are used for blue and green LED elements, then each LED can be driven independently with optimal current control, but device complexity and cost increase

Engineering Contradiction:

Improvecurrent control precisionVSAvoiddriver circuit quantity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the driving functions for both blue and green LED elements into a single driver IC. The driver IC includes a current control unit that can selectively supply current to either the blue LED element or the green LED element, eliminating the need for separate driver ICs while maintaining independent control capability for each LED type.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The driver IC is designed with multi-functional capability to drive different types of LED elements (blue and green) using a single device. The current control unit can adapt its output characteristics based on which LED element needs to be driven, making the driver IC universal for both LED types.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Device complexity

If blue and green LED elements are driven simultaneously with fixed current, then circuit design is simplified, but chromaticity stability deteriorates under varying temperature and luminance conditions

Engineering Contradiction:

Improvecontrol circuit simplicityVSAvoidchromaticity stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent implements dynamic current control where the current control unit adjusts the current supplied to LED elements based on operating conditions such as temperature and luminance requirements. The current values can be dynamically changed to maintain optimal chromaticity under varying conditions, transitioning from static to dynamic control.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the electrical parameters (current values) supplied to different LED elements based on operating conditions. By adjusting current parameters dynamically rather than using fixed current, the system maintains stable chromaticity across varying temperature and luminance conditions.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If forward voltage differences between green and blue LED elements are not optimized, then device fabrication is simpler, but driving efficiency and chromaticity control worsen

Engineering Contradiction:

Improvedevice fabrication simplicityVSAvoiddriving efficiency

Core Design Contradiction:

Ease of manufactureVSPower

Solution Approach 1:

The patent applies local quality optimization by specifically designing the LED elements with particular forward voltage characteristics. The green LED element is designed with a forward voltage lower than that of the blue LED element, creating localized electrical property differences that enable more efficient driving and better chromaticity control when using the single driver IC.

Inventive Principle:

Principle #3Local quality

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 design allows for cost-effective production of light sources with stable chromaticity by using a single drive circuit, reducing complexity and cost while maintaining desired color output across varying conditions.

Implementation Method 1

a first light-emitting element and a second light-emitting element that are located on the substrate; A light emission peak wavelength of the first light-emitting element is 430 nm or greater and less than 490 nm. A light emission peak wavelength of the second light-emitting element is 490 nm or greater and less than 570 nm

Methodology Applied

Scientific EffectLight emission from LED elements: Light Emitting Diode

Implementation Method 2

a light-emitting device including a substrate, and a first light-emitting element and a second light-emitting element that are located on the substrate

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12581582B2Light source and driving method of light source

Publication Date: 2026.03.17 NICHIA CORP

AI summary

A light source including a light-emitting device including a substrate, and a first light-emitting element and a second light-emitting element that are located on the substrate. The light source further includes a drive circuit to supply a current to drive the light-emitting device, a switch configured to switch between a first state of supplying a current to only the first light-emitting element and a second state of supplying a current to only the second light-emitting element, and a timing controller configured to control a timing of an operation of the switch. A light emission peak wavelength of the first light-emitting element is 430 nm or greater and less than 490 nm. A light emission peak wavelength of the second light-emitting element is 490 nm or greater and less than 570 nm. A forward voltage of the second light-emitting element is less than a forward voltage of the first light-emitting element.