LED Dimming Circuit with Matched Forward Voltage and Series Resistance
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Solution Overview
Problem
Conventional lighting systems using solid state light sources for applications like roadway lighting face inefficiencies due to energy wastage in resistive elements during dimming, requiring multiple types of lights for specific installations and lacking flexibility in light distribution patterns and color temperatures.
Innovation Solution
A lighting system comprising multiple sets of solid state light sources with matched forward voltage drops, connected in parallel to a constant current source and controlled by a circuitry that adjusts current through each set using resistors and shunt paths, allowing for variable dimming and color temperature adjustments while maintaining constant forward voltage, enabling flexible light distribution patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If resistive elements are used for dimming solid state light sources, then the brightness can be adjusted, but significant amounts of energy are wasted due to power dissipation
Solution Approach 1:
The patent changes the electrical parameters by introducing series resistance that selectively modifies the current distribution among parallel LED strings. By adjusting the resistance value, the system controls the forward voltage drop across individual LED strings, thereby dimming specific strings without requiring energy-dissipating resistive elements in series with each LED. This parameter-based control achieves brightness adjustment with minimal energy loss.
Solution Approach 2:
The patent introduces a series resistance as an intermediary element between the constant current source and the parallel LED strings. This intermediary resistance selectively regulates the current flowing to specific LED strings by creating a voltage drop, thereby controlling their brightness. The series resistance acts as a mediator that enables dimming control without directly dissipating energy in the same way conventional resistive dimming does.
2Adaptability or versatility
If multiple types of lights are installed for different installations, then specific illumination patterns and color temperatures can be achieved, but the device complexity and installation requirements increase
Solution Approach 1:
The patent creates a universal lighting system where a single luminaire housing contains multiple sets of solid state light sources with different correlated color temperatures. Each set can be independently controlled through series resistance, allowing the same physical device to provide multiple illumination patterns and color temperatures suitable for different installation requirements. This eliminates the need for maintaining separate light types for different applications.
Solution Approach 2:
The patent segments the light sources into multiple independent sets, each with different correlated color temperatures and controlled by separate series resistance elements. This segmentation allows individual control of each light set's brightness and color temperature contribution, enabling the system to produce various illumination patterns by selectively dimming or activating specific segments.
3Ease of operation
If series resistance is added to dim LED strings, then current control is achieved, but the forward voltage drop varies with current changes
Solution Approach 1:
The patent exploits the parameter relationship between resistance, current, and voltage drop. By introducing series resistance, the system deliberately changes the voltage drop parameter across individual LED strings to achieve current control. The series resistance creates a variable voltage drop that compensates for current variations, allowing stable dimming control while accepting that the overall forward voltage of the string changes with current level.
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 solution reduces energy wastage, allows for adjustable light output characteristics, and simplifies the need for multiple light types by enabling selective dimming and color temperature control, enhancing the flexibility and efficiency of lighting systems.
Implementation Method 1
a first set of one or more electrically coupled solid state light sources having a first forward voltage drop across the first set of solid state light sources
Implementation Method 2
at least one resistor electrically coupled to at least one of the first set and the second set of solid state light sources; and a set of control circuitry that is operably coupled to control a resistance electrically coupled in series with said at least one of the first set and the second set of solid state light sources
Data Source
AI summary
A light having a first set of electrically coupled solid state light sources having a first forward voltage drop and a second set of electrically coupled solid state light sources having a second forward voltage at least approximately matching the first forward voltage drop. The first set and second sets of solid state light sources are electrically coupled in parallel to a constant current source. A resistor is electrically coupled to at least one of the first and second sets of solid state light sources. Control circuitry is operably coupled to control a resistance electrically coupled in series with said at least one of the first set and the second set of solid state light sources to adjust a respective current therethrough and thereby dim said at least one of the first set and the second set of solid state light sources while maintaining the respective forward voltage drops.