Series-Connected LED Light Source Switching for Stable Dimming
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Solution Overview
Problem
Existing light source devices for automobiles using LED light sources face instability in luminous intensity distribution and potential light turn-off due to voltage drops when controlling multiple LED light sources at different duty ratios.
Innovation Solution
A light source device with an electric power unit, light source units, switches, and a switch control circuit that performs on and off control of the switches to maintain stable light output by sequentially turning on and off LED light sources at different duty ratios, preventing light turn-off during voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple LED light sources are controlled at different duty ratios to generate luminous intensity distribution patterns, then lighting functionality is improved, but voltage stability deteriorates causing light turn-off
Solution Approach 1:
The control circuit determines the required total forward voltage before controlling the LED light sources, and preliminarily adjusts the duty ratio of the PWM signal to compensate for voltage drops. This preliminary action ensures that even when multiple LED sources are controlled at different duty ratios, the total forward voltage requirement is met and light turn-off is prevented.
Solution Approach 2:
The control circuit monitors the actual voltage output and uses this feedback to dynamically adjust the PWM duty ratio. When voltage drops are detected during operation with multiple LED sources at different duty ratios, the system automatically increases the duty ratio to compensate, maintaining stable lighting and preventing light turn-off.
2Reliability
If the PWM duty ratio is increased to compensate for voltage drop, then light stability is improved, but energy consumption increases
Solution Approach 1:
Instead of uniformly increasing the PWM duty ratio for all LED light sources, the control circuit applies partial action by selectively adjusting only the duty ratio of specific LED sources that are causing voltage drops. This targeted approach maintains light stability while minimizing unnecessary energy consumption from other LED sources operating at their optimal duty ratios.
3Reliability
If the forward voltage requirement is strictly enforced, then light turn-off is prevented, but luminous intensity distribution flexibility is reduced
Solution Approach 1:
The system dynamically adjusts the PWM duty ratio based on real-time voltage conditions rather than enforcing a fixed forward voltage requirement. This dynamic approach allows the luminous intensity distribution to remain flexible and adaptable to different lighting patterns while automatically compensating for voltage drops to prevent light turn-off.
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 ensures stable light output without restricting luminous intensity patterns, even under varying voltage conditions, improving efficiency and preventing LED light source turn-off.
Implementation Method 1
LED light sources will be light turned on, when current is supplied from a light source drive circuit
Data Source
AI summary
At least one light source unit includes light sources which are series connected, switches which are each connected in parallel with each of the light sources, a light source drive circuit which supplies a current to a structure including the light sources and the switches, and switch control means which carries out on and off control of the switches. Based on light source control information, the light source unit carries out light dimming control of the light sources by performing on and off of the switches, according to a light turned on duty ratio. In addition, each of the light sources is sequentially light turned on from the one with a larger light on duty ratio, and in addition, each of the light sources is sequentially light turned off from the one with a smaller light on duty ratio source.