LED Lighting System PWM Current Amplitude Control
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Solution Overview
Problem
Existing lighting systems using pulse width modulation (PWM) struggle with independent control of LED brightness and color, especially in maintaining color mix at low intensities and matching between LEDs with different shades, due to limitations in PWM resolution and duty cycle management.
Innovation Solution
A lighting system with a microprocessor that independently controls the current and duty cycle of LEDs, using digital-to-analog converters and PWM signals to manage amplitude and timing, allowing for pulse-by-pulse adjustments in brightness and color, enabling flexible control of LED driving and color mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM duty cycle is reduced to control LED intensity, then LED brightness decreases, but color mixing accuracy deteriorates at low intensities
Solution Approach 1:
The patent segments the control of LED parameters by separating intensity control (via PWM duty cycle) from color control (via current amplitude). This allows independent optimization of each parameter, enabling accurate color mixing even at low intensities where traditional PWM-only control fails.
Solution Approach 2:
The patent changes the control parameter from单一的PWM duty cycle to a combination of PWM duty cycle and current amplitude. By adjusting current amplitude independently, the system maintains color accuracy across the full intensity range, particularly at low intensities where duty cycle alone is insufficient.
2Measurement precision
If PWM frequency is increased to improve dimming resolution, then brightness control precision improves, but power consumption and heat generation increase
Solution Approach 1:
The patent changes the control approach from relying solely on high-frequency PWM to using current amplitude modulation. This allows achieving fine dimming resolution through current control rather than requiring extremely high PWM frequencies, thereby reducing power consumption and heat generation.
3Adaptability or versatility
If multiple LEDs with different shades are used to expand color range, then color versatility improves, but color matching between LEDs becomes difficult
Solution Approach 1:
The patent applies local quality control by independently adjusting the current amplitude for each LED based on its specific characteristics. This allows each LED to be optimized for its particular shade and efficiency, enabling accurate color matching across LEDs with different specifications.
Solution Approach 2:
The patent uses current amplitude as an additional control parameter to compensate for variations in LED characteristics. By independently tuning current amplitude for each LED, the system achieves consistent color output across LEDs with different shades and efficiencies.
4Device complexity
If traditional PWM control is used to simplify circuitry, then device complexity decreases, but independent control of brightness and color is lost
Solution Approach 1:
The patent makes the current source multi-functional by enabling it to perform both intensity control (through PWM gating) and color control (through amplitude modulation). This eliminates the need for separate control circuits while achieving independent brightness and color control.
Solution Approach 2:
The patent introduces dynamic current amplitude control that can be adjusted independently of PWM duty cycle. This dynamic parameter allows the system to independently control both brightness and color, transforming the static PWM-only control into a flexible two-dimensional control system.
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 provides maximum flexibility in LED control, allowing for accurate color mixing and intensity adjustment across the full range, maintaining color consistency at low intensities and ensuring compatibility between LEDs with different shades, using common low-cost components.
Implementation Method 1
at least one device for emitting light in response to receiving electrical power
Data Source
AI summary
A lighting system is provided with a device for emitting light in response to receiving electrical current, a microprocessor and a current source. The microprocessor is programmed to provide a color control signal and an intensity control signal that are independently controllable relative to each other. The current source is adapted to provide the electrical current to the device at an amplitude based on the color control signal and at an on-off timing based on the intensity control signal.