TRIAC Dimmer Compatible LED Driver Circuit
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Solution Overview
Problem
Existing TRIAC dimmers are not compatible with LED drivers, resulting in unsatisfactory dimming performance due to LED not being a pure resistive load, leading to varying maximum and minimum brightness under different AC input voltages and TRIAC dimmer manufacturing deviations, with limited dimming range and poor line regulation.
Innovation Solution
A TRIAC dimmer compatible LED driver is developed, comprising a TRIAC dimmer, rectifier, switching converter, feedback circuit, and controller with a dimming signal generator, processor, and switch control circuit, which generates a dimming signal with regulated duty cycle and control signal to adjust the switching converter based on feedback, ensuring uniform maximum and minimum brightness and extended dimming range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional TRIAC dimmer is used to control LED brightness, then the dimmer can adjust the conduction phase to control power supply, but the LED dimming performance becomes unsatisfactory because LED is not a pure resistive load
Solution Approach 1:
The patent introduces an intermediary circuit between the TRIAC dimmer and LED that includes a rectifier to convert AC chopped voltage to DC chopped voltage, a switching converter to generate driving signals, and a controller with feedback circuit to process dimming signals and regulate LED current. This intermediary system adapts the TRIAC dimmer's AC control signal to properly drive the LED load, resolving the incompatibility between TRIAC dimmers and non-resistive LED loads.
2Illumination intensity
If the conduction phase of AC chopped voltage is adjusted to control LED brightness, then the brightness can be varied, but the maximum and minimum brightness vary under different AC input voltages and TRIAC dimmer manufacturing deviations
Solution Approach 1:
The patent implements a feedback circuit that senses the current flowing through the LED and feeds it back to the controller. The controller compares the feedback signal with the processed dimming signal and adjusts the switching converter's duty cycle accordingly. This closed-loop feedback mechanism compensates for variations in AC input voltage and TRIAC dimmer characteristics, maintaining consistent maximum and minimum brightness across different operating conditions.
Solution Approach 2:
The patent dynamically adjusts the duty cycle of the switching converter based on the processed dimming signal and feedback signal. By changing the duty cycle parameter in response to varying AC input voltages and dimming requirements, the system maintains stable LED brightness output despite external parameter variations.
3Device complexity
If a simple rectifier and switching converter are used, then the circuit complexity is reduced, but the dimming range is limited and line regulation is poor
Solution Approach 1:
The patent employs a dynamic control system where the controller processes the dimming signal to generate a processed dimming signal with adjusted duty cycle, and the switching converter dynamically adjusts its switching duty cycle based on feedback. This dynamic adaptation enables a wide dimming range from near-zero to maximum brightness while maintaining good line regulation, achieving high adaptability without excessive circuit 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 achieves uniform maximum and minimum brightness of LEDs across different AC input voltages and TRIAC dimmers, extending the dimming range and improving line regulation, ensuring consistent LED brightness and efficiency.
Implementation Method 1
The rectifier rectifies the AC chopped voltage Vtr to generate a DC chopped voltage Vbus
Implementation Method 2
A flyback converter comprising a switch S1, a transformer T1 and a diode D2 receives the DC chopped voltage Vbus, and converts it into a driving signal to drive LEDs
Data Source
AI summary
The present invention provides a controller used in a TRIAC dimmer compatible LED driver and method thereof. The controller comprises a dimming signal generator, a dimming signal processor and a switch control circuit. The dimming signal generator receives an AC chopped voltage from a TRIAC dimmer and generates a dimming signal with regulated duty cycle in accordance with the AC chopped voltage. The dimming signal processor is coupled to the dimming signal generator and generates a processed dimming signal in accordance with the dimming signal. The duty cycle of the processed dimming signal is a sum of a predetermined duty cycle and the duty cycle of the dimming signal. Based on the processed dimming signal and a feedback signal indicative of the current flowing through LED, the switch control circuit generates a control signal to control at least one switch in a switching converter.