LED Control Device PWM Duty Cycle Adjustment
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Solution Overview
Problem
Motor vehicle light-emitting diode (LED) systems face challenges in maintaining a constant luminous flux over time due to temperature effects, which can lead to excessive glare and non-compliance with legal luminous flux limits, especially in direction indicators.
Innovation Solution
A light-emitting diode control device using pulse width modulation (PWM) to vary the duty cycle, ensuring a substantially constant average luminous flux is maintained by adjusting the pulse duty factor over time, thereby compensating for temperature-induced flux decreases and reducing glare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light-emitting diode is supplied with increased electrical power from the start to ensure minimum luminous flux after temperature increase, then the minimum luminous flux requirement is met, but the luminous flux becomes excessively high immediately after switching on, causing dazzling to other road users
Solution Approach 1:
The patent applies pulse width modulation (PWM) to periodically switch the LED on and off during the initial phase, creating a dimmed state that reduces average luminous flux. The duty cycle is varied over time, starting low and increasing to full power, which allows the LED to meet minimum flux requirements after warm-up while avoiding excessive initial brightness that would dazzle other road users
2Object-affected harmful factors
If the light-emitting diode is supplied with normal electrical power, then the initial luminous flux is acceptable, but the luminous flux decreases sharply over time due to temperature effects, potentially falling below legal minimum requirements
Solution Approach 1:
The patent implements dynamic control of the LED power supply through PWM, where the duty cycle continuously adapts based on temperature conditions. During initial operation, the duty cycle is reduced to prevent glare. As the LED warms up and temperature stabilizes, the duty cycle increases to maintain adequate luminous flux output, ensuring continuous compliance with legal minimum requirements throughout the operational lifecycle
3Reliability
If pulse width modulation with varying duty cycle is applied, then the average luminous flux is maintained at desired levels, but the control device complexity increases
Solution Approach 1:
The control device utilizes the LED's inherent thermal characteristics and the natural temperature-luminous flux relationship to automatically adjust the PWM duty cycle. The system monitors temperature changes and autonomously modulates the duty cycle accordingly, eliminating the need for complex external control circuits or additional sensors, thereby maintaining reliable luminous flux control while minimizing added device complexity
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 effectively maintains a desired luminous flux over longer periods while minimizing glare and ensuring compliance with legal luminous flux requirements, reducing the risk of dazzling other road users.
Implementation Method 1
a light source in the form of a light-emitting diode (LED)
Implementation Method 2
the light-emitting diode is in an active state or on state of the motor vehicle light - in the sense of or by pulse width modulation - Is dimmable, the duty cycle is varied in the active state of the motor vehicle light
Implementation Method 3
the luminous flux generated by a light-emitting diode decreases sharply over time due to a temperature effect
Data Source
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AI summary
The subject matter of the invention is a motor vehicle light system with a motor vehicle light which comprises, as a light source, at least one light emitting diode, and which is configured with a light emitting diode control device in such a way that, in an active state of the motor vehicle light, the light emitting diode can be dimmed in the sense of pulse width modulation, wherein the pulse duty factor is varied.