LED Light Source Control Unit Using Parametric Current Calculation
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Solution Overview
Problem
Conventional light output control methods for light-emitting diodes (LEDs) face challenges in achieving high responsiveness and accuracy due to temperature variations and sensitivity to disturbances, particularly in applications requiring rapid adjustments, such as endoscopes, where precise control of light output is essential.
Innovation Solution
A light source apparatus with a control unit that employs a curved surface function to determine the necessary current for the LED based on temperature and target light output, using a mathematical formula that includes coefficients to accurately calculate the current amount, allowing for real-time control with a reduced number of processes and maintaining high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a data table with relationship among light output, temperature, and current is prepared for feedforward control, then light output control accuracy is improved, but the amount of data required and processing complexity increase significantly
Solution Approach 1:
The patent transforms the complex three-variable relationship (light output, temperature, current) into a simplified mathematical model with temperature-dependent parameters. Instead of storing exhaustive data tables, the system uses parametric equations where only key parameters (α0, α1, α2 coefficients) need to be stored, dramatically reducing data requirements while maintaining control accuracy.
Solution Approach 2:
The patent replaces the mechanical/data-intensive approach of storing and searching large data tables with a mathematical computation system. The control current is calculated through mathematical formulas (Equations 1-3) that compute the relationship in real-time, substituting data retrieval and processing with efficient mathematical operations.
2Measurement precision
If data reading and complement processing is performed from a large data table, then accurate current determination is achieved, but responsiveness to light output adjustment decreases
Solution Approach 1:
The patent replaces data table reading and complement processing operations with direct mathematical computation. The arithmetic processing unit calculates the control current using Equations 1-3, which provides both accuracy and speed by eliminating the need to search and process large data tables, achieving real-time responsiveness.
Solution Approach 2:
The patent performs preliminary action by pre-calculating and storing only the essential temperature-dependent parameters (α0, α1, α2 coefficients) rather than complete data tables. This preliminary parameter storage enables rapid real-time computation of control current through simple mathematical operations, achieving both accuracy and responsiveness.
3Stability of the object's composition
If feedback control using a photosensor is implemented to stabilize LED light output, then light output stability is improved, but temperature sensitivity and disturbance effects on the photosensor reduce control accuracy
Solution Approach 1:
The patent introduces temperature as an intermediary variable that mediates between the LED operating conditions and the control current. By measuring temperature and using it to calculate the appropriate control current through the mathematical model, the system compensates for temperature effects on both the LED and photosensor, achieving accurate control without being subject to photosensor temperature sensitivity.
Solution Approach 2:
The patent replaces the photosensor-based feedback mechanism with a temperature-based feedforward control system. Instead of relying on the photosensor to detect light output and adjust current (which suffers from temperature sensitivity), the system uses temperature sensors and mathematical models to predict and control the required current, eliminating the photosensor's temperature sensitivity problem.
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 approach enables high responsiveness and accurate control of light output, ensuring consistent irradiance in applications like endoscopes and maintaining color balance in multi-wavelength LED systems, while reducing the need for extensive data tables and improving quick responsiveness.
Implementation Method 1
a temperature detector that detects a temperature of an installation location of the light-emitting element
Implementation Method 2
a light-emitting element such as a light-emitting diode (LED) varies in an actual amount of light emission
Data Source
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AI summary
Provided is a light source apparatus capable of performing light output control with high responsiveness. The light source apparatus (1) includes a light-emitting element (12), a temperature detector (19), a drive circuit (21), a control unit (22), and a target light output receiving unit (31). The control unit (22) includes: a first storage unit (26) in which a control function for obtaining a third variable correlated with a current supplied to the light-emitting element from a first variable correlated with the temperature and a second variable correlated with the light output is recorded, and an arithmetic processing unit (25) substitutes the temperature T and the target value Φ into the first variable and the second variable in the control function to determine the amount of current supplied to the light-emitting element (12) which is the third variable.