Linear LED Dimmer Circuit for Low-Illuminance Power Factor
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Solution Overview
Problem
Conventional phase-cut mode Triac dimmers for LED lighting suffer from power factor reduction and increased harmonics during low-illuminance dimming, leading to power loss and transformer failure, while failing to meet the dimming range requirements of applications like hospital operating rooms.
Innovation Solution
A linear dimmer for LED lighting that includes a bridge rectifier circuit and a constant current control circuit using a field effect transistor, fixed, and variable resistances to maintain a high power factor even at low illuminance, effectively addressing noise from AC input wires and reducing power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phase-cut mode Triac dimmer is used for LED lighting, then dimming function is achieved, but power factor is reduced and harmonics increase during low-illuminance dimming
Solution Approach 1:
The patent replaces the phase-cut mode Triac dimming mechanism with a linear mode converter that uses pulse width modulation (PWM) control. This substitution eliminates the harmful phase-cutting method that causes power factor reduction and harmonics, while maintaining effective dimming control through a different technical approach that is compatible with LED lighting characteristics.
Solution Approach 2:
The patent changes the fundamental operating parameters of the dimming system by using a linear mode converter with PWM control instead of phase-cut mode. This parameter change allows the system to maintain high power factor and low harmonics while achieving the desired dimming range, resolving the contradiction between illumination control and electrical quality.
2Illumination intensity
If phase-cut mode Triac dimmer is used for LED lighting, then dimming control is achieved, but power loss in transmission line increases
Solution Approach 1:
The patent substitutes the phase-cut mode Triac dimmer with a linear mode converter that uses PWM control. This replacement eliminates the power loss in transmission line that occurs with phase-cut mode, while maintaining effective illuminance control through a more efficient switching mechanism that reduces energy waste.
3Ease of manufacture
If phase-cut mode Triac dimmer is used for LED lighting, then simple installation is achieved, but transformer failure may occur
Solution Approach 1:
The patent replaces the phase-cut mode Triac dimmer with a linear mode converter that uses PWM control. This substitution maintains the simplicity of installation while eliminating the harmful effects on transformers, as the linear mode converter produces clean switched-mode power that does not cause transformer failures.
4Illumination intensity
If digital mode dimming (analog 0-10V, DALI) is used for LED lighting, then dimming control is achieved, but separate line or wireless signal path is required
Solution Approach 1:
The patent integrates dimming control functionality directly into the power supply circuit through PWM control of the linear mode converter. This multi-functional approach combines power conversion and dimming control in a single integrated system, eliminating the need for separate dimming signal lines or wireless communication paths while maintaining full dimming control capability.
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 maintains a high power factor during low-illuminance dimming, reducing power loss and enhancing the reliability and lifespan of LED lighting systems, while allowing for a miniaturized and cost-effective design.
Implementation Method 1
a rectifier circuit unit full-wave rectifying a commercial alternating current (AC) power supplied from an input stage (AC line), and outputting a rectified current power
Implementation Method 2
a current control circuit unit connected to an output stage of the rectifier circuit unit, and controlling the rectified current power output by the rectifier circuit unit to a predetermined current magnitude
Data Source
AI summary
The present invention relates to a linear dimmer for an LED lighting, which controls an illumination in an LED lighting apparatus, the linear dimmer including: a rectifier circuit unit full-wave rectifying a commercial alternating current (AC) power supplied from an input stage (AC line), and outputs a rectified current power; and a current control circuit unit connected to an output stage of the rectifier circuit unit, and controlling the rectified current power output by the rectifier circuit unit to a predetermined current magnitude, and outputting the predetermined current power to an LED lighting.