AC LED Dimmer PWM Control for Harmonic Reduction
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Solution Overview
Problem
Conventional AC LED dimmers using Triacs have limited dimming ranges due to drive voltage and R/C phase controller characteristics, produce harmonics during switching, and suffer from flickering issues due to insufficient operating margins.
Innovation Solution
An AC LED dimmer employing a rectifier for full-wave rectification, a voltage converter for stepped-up voltage generation, a pulse width modulation controller for generating a pulse width modulation signal, and a switch for bidirectional control under PWM signal control, which adjusts the duty cycle to dim the AC LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a Triac-based phase control scheme is used to dim AC LED, then the dimming function is achieved, but the dimming range is limited due to drive voltage and R/C phase controller characteristics
Solution Approach 1:
The patent changes the control parameter from phase angle (traditional Triac control) to duty cycle (PWM control). By using PWM signaling with adjustable duty cycle, the system achieves broader dimming range without being constrained by Triac drive voltage limitations or R/C phase controller characteristics. The controller adjusts the duty cycle of PWM signals to control LED brightness, enabling flexible dimming from 0% to 100%.
Solution Approach 2:
The patent replaces the mechanical/electronic Triac switching system with a PWM-based control system. Instead of using Triacs that physically switch AC phases, the system uses PWM signals to control the average power delivered to the LED, achieving dimming through electronic control rather than mechanical switching limitations.
2Ease of operation
If a Triac is used for AC voltage switching, then dimming control is achieved, but harmonics are produced during switching operation
Solution Approach 1:
The patent uses periodic PWM signals to control the LED. By switching the LED on and off in periodic pulses with adjustable duty cycles, the system achieves smooth dimming control. The periodic nature of PWM allows for precise control of average power while avoiding the abrupt switching harmonics generated by Triacs, as the PWM frequency can be optimized to minimize harmonic content.
3Ease of manufacture
If traditional R/C phase controller is used, then Triac driving is achieved, but flickering occurs due to insufficient operating margins
Solution Approach 1:
The patent implements a feedback control mechanism where the controller monitors the actual LED output and adjusts the PWM duty cycle accordingly. This feedback loop ensures stable operation by compensating for variations in LED characteristics and operating conditions, eliminating flickering that occurs in traditional R/C phase controllers due to insufficient operating margins. The feedback mechanism maintains consistent dimming performance across different operating conditions.
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 broader dimming range, reduces harmonics, and minimizes flickering, achieving a more efficient and linear dimming function compared to traditional Triac-based dimmers.
Implementation Method 1
a rectifier for full-wave rectification of the AC voltage
Implementation Method 2
a voltage converter for stepped-up voltage generation
Implementation Method 3
a pulse width modulation controller for generation of a pulse width modulation signal for dimming the AC LED
Implementation Method 4
a switch for bidirectional switching under control of the pulse width modulation signal
Data Source
AI summary
The disclosure relates to an AC LED dimmer and dimming method thereof. The AC LED dimmer includes a rectifier receiving AC voltage from an AC voltage source and full-wave rectifying the AC voltage; a direct current (DC)/DC converter receiving the full-wave rectified voltage from the rectifier, generating a full-wave rectified stepped-up voltage, and generating a pulse enable signal; a pulse width modulation controller receiving the full-wave rectified stepped-up voltage and generating a pulse width modulation signal to dim an AC LED in response to the pulse enable signal; a switch driving the AC LED under control of the pulse width modulation signal, and an electromagnetic interference (EMI) filter to be connected between the AC voltage source and the switch to eliminate electromagnetic interference from the AC voltage source. Accordingly, the dimmer can perform an efficient and linear dimming function and suppress harmonics.