LED Color Temperature Adjustment via Analog Current Steering
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Solution Overview
Problem
Existing LED lighting systems struggle to precisely adjust color temperature in correlation with dim level changes, often resulting in premature light turn-off due to high processor consumption at lower current levels and inability to mimic the color temperature shift of dimmed incandescent lamps.
Innovation Solution
The use of a differential amplifier and current sensor to steer current flow between groups of LEDs with different Correlated Color Temperatures (CCTs), allowing for precise control of CCT adjustment based on dim level inputs through a reference voltage threshold, ensuring accurate color temperature changes during dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If processor-based PWM circuitry is used to control current distribution among LED strings, then color temperature adjustment is enabled, but precision is compromised particularly at lower current levels
Solution Approach 1:
The patent replaces processor-based PWM control with an analog differential amplifier circuit that directly controls current distribution. This substitution of digital/mechanical control with analog circuitry eliminates processing delays and precision losses, providing continuous and precise current steering to LED strings based on dimmer input voltage levels.
Solution Approach 2:
The differential amplifier acts as an intermediary between the dimmer control voltage and the LED driver circuits. It compares the dimmer voltage against reference voltages and generates appropriate control signals to steer current between warm and cool LED strings, enabling precise color temperature adjustment without processor intervention.
2Use of energy by moving object
If current is reduced for high dim levels, then power consumption decreases, but processor consumption becomes a relatively large portion causing premature light turn-off
Solution Approach 1:
The patent eliminates the processor from the control loop, replacing it with analog differential amplifier circuits. This removes the processor's fixed power consumption overhead, allowing the system to operate efficiently at all dim levels without the processor consuming a disproportionate share of the reduced current at high dim levels.
Solution Approach 2:
The differential amplifier circuits automatically adjust current distribution between LED strings based on the dimmer input voltage, without requiring processor intervention. The circuit self-regulates to maintain proper operation across the full dimming range, preventing premature light turn-off.
3Adaptability or versatility
If multiple LED strings with different CCTs are used, then color temperature adjustment is achieved, but device complexity increases
Solution Approach 1:
The differential amplifier serves as a simple intermediary that accepts a single dimmer control voltage and automatically distributes appropriate current to warm or cool LED strings based on the control voltage level. This eliminates the need for complex digital processing or multiple control circuits, maintaining simplicity while enabling color temperature adjustment.
Solution Approach 2:
The patent combines the dimming control and color temperature adjustment functions into a single analog control circuit. The differential amplifier simultaneously manages both brightness control and CCT selection based on the dimmer input voltage, merging multiple functions into one simple circuit rather than requiring separate control systems.
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 enables precise color temperature adjustment in LED lighting systems, eliminating premature light turn-off and providing a high-precision, cost-effective method to mimic the color temperature shift of incandescent lamps, ensuring consistent light output across varying brightness levels.
Implementation Method 1
a differential amplifier (more specifically an Instrumentation Amplifier) to steer the current flow from the first group of LEDs to the second group of LEDs
Implementation Method 2
a current sensor to provide a sensor output signal to a first input of the differential amplifier, the sensor output signal having a first voltage corresponding to the current provided to the light source
Implementation Method 3
a first group of light emitting diodes (LEDs) that emits a first light and a second group of LEDs that emits a second light. The first light has a first Correlated Color Temperature (CCT), and the second light causes the illumination light to have a warmer CCT
Data Source
AI summary
A lighting device includes a light source that emits an illumination light. The light source includes a first group of light emitting diodes (LEDs) that emits a first light and a second group of LEDs that emits a second light. The first light has a first Correlated Color Temperature (CCT), and the second light causes the illumination light to have a warmer CCT. The lighting device further includes a differential amplifier to adjust a current flow through the second group of LEDs. The second light is switched on when a current provided to the light source is below a threshold corresponding to the adjustable reference voltage. The lighting device also includes a current sensor to provide a sensor output signal to a second input of the differential amplifier, the sensor output signal having a second voltage corresponding to the current provided to the light source.