LED Driving Circuit Color Temperature Control via AC Modulation
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Solution Overview
Problem
Conventional LED lighting systems are limited in controlling color temperature and are complex and costly due to the need for separate circuits to handle AC power, with sequential driving schemes only allowing predefined color temperatures.
Innovation Solution
An LED driving circuit and lighting device that modulates AC voltage using a dimmer to control color temperature, featuring rectifying units, dimming level detecting units, and driving modules that inversely proportionally control LED light emitting units to achieve user-selectable color temperature adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate circuit such as SMPS is included to enable AC power driving, then LED can be driven by AC power, but circuit complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the AC power driving function directly into the LED string configuration by connecting an even number of LEDs in series, eliminating the need for separate SMPS circuits. The AC power is directly applied to the LED string with appropriate voltage matching, combining the power conversion and LED driving functions into a single integrated approach.
Solution Approach 2:
The LED string is designed to serve multiple functions: it acts as both the light source and the power conversion element. By selecting LEDs with forward voltage characteristics that match AC power voltage levels, the same LED components perform both illumination and AC-to-DC conversion, reducing overall system complexity.
2Ease of operation
If sequential driving scheme is used with AC power, then LED can be driven regularly, but color temperature control is limited to predefined values
Solution Approach 1:
The LED string is segmented into multiple groups with different forward voltage characteristics and color temperatures. Each group can be independently controlled by applying different voltage levels during the AC cycle, allowing selective activation of specific color temperature groups based on user preference.
Solution Approach 2:
The patent implements dynamic color temperature control by varying the voltage applied to different LED groups throughout the AC power cycle. The dimmer controller dynamically adjusts which LED groups are active and their respective brightness levels, enabling continuous color temperature adjustment rather than fixed predefined values.
3Adaptability or versatility
If multiple LED groups with different forward voltage levels are connected in series, then sequential driving enables AC power operation, but color temperature adjustment capability is restricted
Solution Approach 1:
The patent incorporates a dimmer controller that detects the AC power voltage level and provides feedback control to selectively activate appropriate LED groups. The controller monitors the input voltage and adjusts the driving scheme in real-time, enabling both AC power compatibility and flexible color temperature selection through closed-loop control.
Solution Approach 2:
The system changes operational parameters by varying the forward voltage threshold for activating different LED groups. By adjusting the voltage threshold parameter during the AC cycle, the system can selectively engage LED groups with different color temperatures, transforming a fixed sequential driving scheme into a dynamically adjustable color temperature 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
Enables flexible control of color temperature by modulating AC voltage, allowing for the selection of cool or warm white lighting based on user preference, simplifying the system and reducing manufacturing costs by eliminating the need for complex AC-DC conversion circuits.
Implementation Method 1
a rectifying unit performing a full-wave rectification for an AC voltage to generate and output a driving voltage
Data Source
AI summary
A light emitting diode (LED) driving circuit including a dimmer modulating an AC voltage input depending on a selected dimming level, a rectifying unit performing a full-wave rectification for an AC voltage to generate and output a driving voltage, first and second dimming level detecting units receiving the driving voltage of the rectifying unit to detect the selected dimming level, and outputting first and second dimming level signals depending on the detected dimming level, a first driving module controlling a first LED light emitting unit using the first dimming level signal of the first dimming level detecting unit, and a second driving module controlling a second LED light emitting unit using the second dimming level signal of the second dimming level detecting unit, in which the first and second driving modules control the first and second LED light emitting units, respectively.