Frequency Converted Dimming Circuit for Flicker-Free LED Control
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Solution Overview
Problem
Solid state lighting systems face challenges in dimming control due to rapid response times and flickering issues when using phase cut AC signals, as conventional dimming circuits struggle to accurately detect and respond to variations in pulse width, leading to inconsistent light output and potential flicker.
Innovation Solution
The implementation of frequency converted dimming circuits that convert input waveforms with varying duty cycles to output waveforms with higher frequencies, reducing flicker perception and allowing for effective dimming control of LEDs by maintaining the integrated duty-cycle value, thereby addressing the limitations of direct pulse width control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase cut AC signals are used for dimming control, then dimming capability is achieved, but flicker and inconsistent light output occur due to rapid LED response times
Solution Approach 1:
The patent applies periodic action by using pulse width modulation (PWM) to switch the LED on and off at high frequency. The dimming control is achieved through periodic switching where the LED is turned on for a specific pulse width and off for the remainder of the period, creating an average dimming effect that is consistent and free from flicker while maintaining reliable light output.
2Ease of operation
If pulse width variations are used to control dimming level, then dimming is achieved, but detection precision is insufficient leading to inaccurate dimming control
Solution Approach 1:
The patent implements feedback by using a microcontroller to precisely measure the pulse width of the dimming signal and adjust the PWM duty cycle accordingly. The system continuously monitors the incoming signal characteristics and provides feedback control to maintain accurate dimming levels, compensating for any variations in the input signal and ensuring precise dimming control.
3Reliability
If high frequency PWM is used to eliminate flicker, then flicker is reduced, but device complexity increases due to additional circuitry
Solution Approach 1:
The patent applies universality by using a single microcontroller to perform multiple functions: detecting the dimming signal pulse width, generating the PWM output signal, and controlling the LED driver circuit. This multi-functional approach eliminates the need for separate dedicated circuits for each function, reducing overall device complexity while maintaining high frequency PWM operation for flicker elimination.
Data Source
AI summary
There is provided a lighting control circuit comprising a duty cycle detection circuit, an averaging circuit, a waveform generator and a comparator circuit. The duty cycle detection circuit generates a first periodic waveform having a duty cycle and frequency corresponding to an input waveform duty cycle and frequency. The averaging circuit generates a first signal having a voltage level corresponding to the duty cycle of the first periodic waveform. The waveform generator outputs a second periodic waveform having a frequency different from the input waveform frequency. The comparator circuit compares the second periodic waveform with the first signal to generate an output waveform having a duty cycle corresponding to the input waveform duty cycle and a frequency corresponding to the frequency of the second periodic waveform. Also, there are provided methods.