High Current RGB LED Interface Circuit
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Solution Overview
Problem
Existing RGB LED systems face challenges in efficiently and cost-effectively interfacing high power RGB LEDs with standard low power controllers, requiring expensive solutions and wasting precision constant current drive capabilities, while also needing separate constant current regulators for each color.
Innovation Solution
A differential amplifier circuit with current sense resistors and transistors is used to amplify the output from a standard low power controller, allowing for precise constant current regulation and on/off control of high power LEDs using time division multiplexing, eliminating the need for separate high power current regulators for each color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a low current RGB controller is used to drive high current RGB LEDs, then the controller can be used with standard low power LEDs, but separate 200mA capable constant current regulators must be added for each color
Solution Approach 1:
The patent merges the functions of multiple separate constant current regulators into a single shared regulator. The differential amplifier shares a common high-current transistor that can drive multiple LED colors sequentially through time-division multiplexing, eliminating the need for separate 200mA regulators for each color channel.
Solution Approach 2:
The patent employs periodic switching of LED colors at frequencies above human visual detection threshold. The controller alternates between driving red, green, and blue LEDs in rapid succession, creating the perception of simultaneous color mixing while using a single shared current regulator.
2Measurement precision
If separate 200mA capable constant current regulators are added for each color, then precise constant current regulation is achieved, but the unit cost increases
Solution Approach 1:
The patent makes the low-current controller's precision constant current capability serve a dual purpose. Instead of being wasted on low-power LEDs only, the controller's precise current regulation is used to control the shared high-current regulator through the differential amplifier, achieving both precision and cost-effectiveness.
3Device complexity
If a shared constant current regulator is used for multiple LED colors, then component count and cost are reduced, but the controller's low current CCR pins are only used for on/off control
Solution Approach 1:
The patent makes the controller's CCR pins universally functional. Instead of being limited to simple on/off control, the CCR pins continue to provide precise constant current regulation by controlling the shared high-current regulator through the differential amplifier's feedback mechanism.
4Stability of the object's composition
If time division multiplexing is used to control LED colors, then stable color mixing is achieved, but the switching frequency must be above human detection threshold
Solution Approach 1:
The patent ensures continuous perception of stable color by maintaining switching frequencies above the human visual threshold. The rapid alternation between color channels creates the illusion of simultaneous illumination, providing continuous stable color output without visible flicker or separation.
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 a cost-effective and efficient method for controlling high power RGB LEDs, achieving stable color mixing and reduced unit costs by utilizing existing low power controller capabilities and minimizing the need for additional current regulators, while maintaining precise current control.
Implementation Method 1
a differential amplifier includes a first differential amplifier transistor and a second differential amplifier transistor... a base of a first differential amplifier transistor is electrically coupled to one of a plurality of driver outputs... a base of a second differential amplifier transistor is electrically coupled to a supply voltage through one or more current sense resistors
Implementation Method 2
a base of a second differential amplifier transistor is electrically coupled to a supply voltage through one or more current sense resistors... one or more current sense resistors are coupled to a current path of each of a respective current path of LEDs
Implementation Method 3
a current regulator includes a current regulator transistor in which a base of the current regulator transistor is coupled to a differential amplifier... provides accurate and temperature stable constant current regulation
Implementation Method 4
each of a plurality of switches are field effect transistors... the switch being in an 'ON' state allows current to flow through the switch and the respective LED and the switch being in an 'OFF' state does not allow current to flow
Data Source
Figure 1~2
Figure 3
Figure 4A
AI summary
An electrical circuit for an illumination device for automotive and other applications is described. The hardware includes a printed circuit board having multiple light emitting diodes (LEDs) each with its own current path; a controller having multiple driver outputs for controlling the LEDs such that the outputs outnumbers the number of LEDs; and a current regulator coupled to one of the controller's driver outputs and to the respective current path of each of the LEDs.