LED Drive Circuit Using Digital-to-Analog Current Control
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Solution Overview
Problem
Existing LED control systems rely on pulse width modulation, which can cause flicker and generate EMI noise, and lack high-resolution color and intensity control, especially when scaling to control multiple LEDs.
Innovation Solution
A system that uses a microprocessor to generate digital signals converted into direct current (DC) drive currents, allowing for precise control of LED brightness and color through various conversion circuits such as summing, digital-to-analog, frequency-to-voltage, and counting circuits, reducing flicker and EMI noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse width modulation is used to control LED intensity, then LED brightness control is achieved, but flicker and EMI noise are generated
Solution Approach 1:
The patent replaces pulse width modulation (a time-based switching method) with analog voltage control that directly modulates the LED forward current. This substitution eliminates the switching action that causes flicker and EMI, while maintaining continuous brightness control capability through variable voltage levels applied to the LED junction.
Solution Approach 2:
The invention changes the control parameter from digital pulse width (time domain) to analog voltage level (amplitude domain). By varying the forward voltage applied to the LED, the current through the LED junction is directly controlled, achieving brightness modulation without the discontinuous switching that generates harmful electromagnetic interference and flicker.
2Measurement precision
If digital control signals are used for LED intensity control, then control resolution is improved, but conversion circuit complexity increases
Solution Approach 1:
The patent introduces an operational amplifier as an intermediary device that simplifies the conversion process. The op-amp receives digital control signals and directly converts them to proportional analog voltages that drive the LED, eliminating the need for complex multi-stage DAC circuits while maintaining high control resolution through the op-amp's precise voltage scaling capability.
3Manufacturing precision
If multiple LEDs are controlled individually, then color and intensity precision is improved, but system complexity increases
Solution Approach 1:
The patent combines multiple LED control channels into a single integrated circuit architecture. By using operational amplifiers that can handle multiple input signals and controlling multiple LEDs through shared control logic, the system achieves individual LED control precision while reducing overall system complexity through functional integration and resource sharing.
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 system provides high-resolution color and intensity control for LEDs, reduces flicker and EMI noise, and is scalable to manage multiple LEDs, making it suitable for various lighting applications.
Implementation Method 1
A first converter is included for converting the digital signal to one or more analog voltages. A second converter converts the one or more analog voltages into corresponding one or more drive currents, with each of the drive currents applied to at least one of the plurality of LEDs to cause the at least one of the plurality of LEDs to emit light.
Implementation Method 2
The microprocessor is programmed to provide a plurality of digital signals to a summing circuit, which generates an analog voltage signal having a level dependent upon the digital signals.
Implementation Method 3
The microprocessor is programmed to provide a digital signal to a frequency-to-voltage converter, which generates an analog voltage signal having a level dependent upon the digital signal.
Implementation Method 4
The microprocessor is programmed to provide a digital signal to a counting circuit, which generates an analog voltage signal having a level dependent upon the digital signal.
Data Source
AI summary
A system and method is disclosed for illuminating a plurality of emitters such as light emitting diodes (LEDs). The system comprises a plurality of LEDs and a circuit to provide a digital signal. An LED drive circuit is included comprising a first converter for converting the digital signal to one or more analog voltages. The LED drive circuit further comprises a second converter that converts the one or more analog voltages into corresponding one or more drive currents. Each of the drive currents is applied to at least one of the plurality of LEDs to cause the at least one of the plurality of LEDs to emit light. The intensity of emission of the LEDs is related to the level of the applied drive current.