RGB LED Current Control Using Mixed Analog and PWM Dimming
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Solution Overview
Problem
Conventional RGB control methods for LED systems are complex and expensive, lacking design flexibility and reliability, due to partition and bundling control schemes that separately control brightness and color, leading to inefficient and costly systems.
Innovation Solution
A light-emitting diode (LED) control apparatus and method utilizing a mix-signal RGB controller that combines analog dimming and PWM dimming, employing a bandgap voltage reference, MOSFET devices, and a control circuit to generate precise current references and gate drive signals for controlling LED channels, with a sample and hold circuit for compensation and trimming, allowing for flexible and efficient color and brightness adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate current source circuits are used for each LED color channel, then current control precision is improved, but circuit complexity and chip area increase
Solution Approach 1:
The patent combines multiple current source circuits into a single current source that uses a current mirror to generate different current values for different LED color channels. Instead of having separate current sources for red, green, and blue channels, the invention uses one current source with current mirror circuits that replicate and scale the reference current to multiple channels, thereby reducing circuit complexity and chip area while maintaining current control precision.
Solution Approach 2:
The single current source circuit is designed to serve multiple functions by generating reference currents for different LED color channels through current mirror arrangements. The same current source structure provides current control for red, green, and blue channels simultaneously, making the circuit universal and eliminating the need for separate dedicated current sources for each channel.
2Measurement precision
If separate current source circuits are used for each LED color channel, then current control precision is improved, but power consumption increases
Solution Approach 1:
The patent merges multiple power-consuming current source circuits into a single current source that serves all LED color channels. By using one current source with current mirror circuits instead of multiple independent current sources, the total power consumption is reduced while the precision of current control is maintained through the current mirror's accurate current replication and scaling.
3Measurement precision
If individual control circuits are used for each LED channel, then color and brightness control precision is improved, but device complexity increases
Solution Approach 1:
The patent combines individual control circuits for different LED channels into a unified control architecture. A single control circuit generates control signals that are distributed to multiple MOSFET switches controlling different color channels. This unified approach maintains precise control of color and brightness through digital-to-analog conversion and PWM modulation while reducing the overall device complexity by eliminating redundant control circuitry.
Solution Approach 2:
The patent introduces intermediary elements such as current mirror circuits and PWM controllers that act as mediators between the single control circuit and multiple LED channels. These intermediaries enable precise control signal distribution and current regulation across different channels without requiring separate control circuits for each channel, thus maintaining control precision while reducing complexity.
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 a simple and reliable control apparatus that achieves high channel-to-channel accuracy and smooth dimming effects, reducing system complexity and cost while enhancing design flexibility and reliability.
Implementation Method 1
A light emitting diode (LED) channel may include a red light emitting diode, a green light emitting diode, and a blue light emitting diode
Implementation Method 2
A plurality of metal oxide semiconductor field effect transistor (MOSFET) devices are connected in parallel and coupled between a cathode of the light emitting diode channel and ground
Implementation Method 3
A bandgap voltage reference is configured to generate a current reference for controlling a plurality of light emitting diode channels
Data Source
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AI summary
An apparatus includes a bandgap voltage reference configured to generate a current reference for controlling a plurality of light emitting diode channels, a plurality of MOSFET devices connected in parallel and coupled between a cathode of a light emitting diode channel and ground, wherein the plurality of MOSFET devices is configured to control a current flowing through the light emitting diode channel, and a control circuit configured to generate gate drive signals for the plurality of MOSFET devices, wherein the gate drive signals are configured to adjust the current flowing through the light emitting diode channel based on a predetermined color and a predetermined brightness level of the light emitting diode channel.