LED Dimmer Circuit Stabilizes Brightness via DC Voltage Conversion
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Solution Overview
Problem
LEDs experience flickering due to unstable TRIAC pulses from TRIAC dimmers and low PWM frequencies, which affect brightness control, as they are more sensitive to current variations compared to traditional light bulbs.
Innovation Solution
Converting TRIAC or PWM pulses to DC voltage and using this DC voltage to control the on and off operation of a control transistor, thereby stabilizing the lighting of the LED array by adjusting the conduction angle and duty ratio independently of AC waveform fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If TRIAC dimmer is used to control LED brightness, then brightness adjustment is achieved, but flickering occurs due to unstable TRIAC pulses
Solution Approach 1:
The patent introduces an intermediary circuit that converts unstable TRIAC pulses into stable DC voltage. This DC voltage serves as a mediator between the unstable TRIAC dimmer output and the LED array, eliminating flickering while preserving brightness control functionality. The conversion process stabilizes the control signal without requiring changes to the existing TRIAC dimmer or LED array.
2Illumination intensity
If PWM control is used for LED dimming, then brightness control is achieved, but flickering appears when PWM frequency is low
Solution Approach 1:
The patent replaces the direct PWM control mechanism with a DC voltage-based control system. Instead of using high-frequency PWM signals that can cause flickering at low frequencies, the system converts control signals into DC voltage levels that directly control LED brightness through a control transistor. This substitution eliminates the flickering issue inherent in low-frequency PWM control while maintaining effective brightness adjustment.
3Loss of energy
If TRIAC pulse conduction angle is narrow, then power consumption is reduced, but flickering is more likely to appear
Solution Approach 1:
The patent changes the parameter of the control signal from narrow TRIAC pulses to DC voltage levels. By converting narrow TRIAC pulses into proportional DC voltages, the system maintains low power consumption (achieved through narrow conduction angles) while eliminating flickering. The DC voltage level corresponds to the desired brightness level, allowing energy-efficient operation without the flickering problems associated with narrow-pulse TRIAC control.
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
This approach prevents flickering and ensures consistent LED brightness by making the lighting uniform and reducing current fluctuations, even when TRIAC pulse stability is low or PWM frequency drops.
Implementation Method 1
initially convert a pulse for dimming control to DC (direct current) voltage
Data Source
AI summary
A TRIAC dimmer gates an AC waveform from an AC power source in proportion to a control signal and outputs a TRIAC pulse having part of the waveform missing. The TRIAC pulse is rectified and is applied to an LED array and the drive current flowing to the LED array is detected at a current detection resistor. The drive current value and a predetermined value are compared at a comparator and in accordance with the comparison result thereof the control transistor is turned off. Then, the TRIAC pulse is converted to a DC voltage signal and in accordance with the obtained DC voltage signal the drive current value or the predetermined value input by the comparator are changed. Furthermore, instead of the TRIAC pulse, a PWM pulse supplied from an external source may also be utilized.