Microcontroller PWM LED Driver Circuit Topology
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Solution Overview
Problem
Current LED driver circuits, particularly those using analogue electronic components, face challenges in accurately controlling current and voltage, leading to inefficiencies in power management, thermal management, and limitations in dimming resolution, communication capabilities, and compatibility with multiple LED strings, necessitating a more efficient and programmable solution.
Innovation Solution
A controlled illumination apparatus utilizing a microcontroller with data acquisition and processing means to adjust the duty cycle of PWM signals based on temperature and other parameters, optimizing driving current, modulation frequency, and duty cycle to enhance energy efficiency and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analogue electronic components are used for LED driver circuits, then current and voltage control can be achieved, but the circuit complexity increases due to the need for auxiliary electronic circuitry (capacitors, resistors, etc.) and the accuracy is strongly correlated with component precision
Solution Approach 1:
The patent replaces the mechanical/electronic system of analogue components (resistors, capacitors, transistors) with a digital microcontroller-based system. The microcontroller executes firmware to generate PWM signals and control LED current, eliminating the need for complex analogue driver circuits while improving control accuracy through software-based regulation.
Solution Approach 2:
The patent changes the control parameter from direct analogue voltage/current control to pulse-width modulation (PWM) duty cycle control. By varying the duty cycle of PWM signals generated by the microcontroller, the system achieves precise LED current control without requiring precision analogue components, thus reducing circuit complexity while maintaining or improving control accuracy.
2Adaptability or versatility
If a separate power supply is used for microcontroller and LED string, then multiple LED's can be driven in series with higher voltage, but the device complexity and cost increase
Solution Approach 1:
The patent makes the single power supply serve multiple functions: it powers both the microcontroller and the LED string simultaneously. The microcontroller is designed to operate within the voltage range provided by this single supply, and the PWM output stage is configured to drive the LED string from the same supply voltage, eliminating the need for separate power supplies while maintaining the ability to drive multiple LED strings in series.
Solution Approach 2:
The patent merges the power supply function into a single unified source that serves both the control circuitry (microcontroller) and the load (LED string). This consolidation reduces the number of power supply components, simplifies the overall circuit architecture, and lowers cost while preserving the capability to drive multiple LED strings through proper PWM control and voltage scaling.
3Adaptability or versatility
If microcontroller-based PWM control is implemented, then programmable luminosity levels and communication capabilities are achieved, but the switching speed and dimming resolution are limited by A/D conversion time and instruction cycle duration
Solution Approach 1:
The patent uses pre-calculated PWM duty cycle values stored in lookup tables or computed based on predefined luminosity levels. Instead of performing A/D conversions and complex calculations in real-time for each dimming level change, the system prepares control parameters in advance, significantly reducing the processing time required for switching and dimming operations while maintaining programmable luminosity control.
Solution Approach 2:
The patent implements a periodic PWM control scheme where the microcontroller updates LED duty cycles at fixed time intervals synchronized with the PWM frequency. This periodic operation allows the system to maintain high switching speeds by using timer-based interrupt routines that execute at predetermined frequencies, eliminating the need for continuous A/D conversions and ensuring consistent dimming resolution at high update rates.
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 provides improved energy consumption optimization, accurate constant current regulation, and enhanced thermal management, enabling efficient operation of LED strings with programmable luminosity levels and reduced hardware requirements.
Implementation Method 1
LEDs have very low dynamic resistance, with the same voltage drop for widely varying currents
Implementation Method 2
The light output of an LED is proportional to the forward current
Data Source
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AI summary
The invention proposes a method for operating a controlled illumination apparatus, the illumination apparatus comprising at least one PWM controlled LED, the method comprising the following steps: - carrying out a duty cycle sweep of the PWM signal driving the at least one LED while sensing at least one parameter indicative of the power consumption of the at least one LED in order to compute a curve reflecting the duty-cycle dependency of the power efficiency of the at least one LED.