LED Luminescence Apparatus AC Power Factor Correction
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Solution Overview
Problem
LED luminescence apparatuses using AC power face issues with power factor and total harmonics distortion (THD) due to distorted waveforms, leading to inefficiencies and challenges in controlling brightness, especially when driven by phase control type dimmers.
Innovation Solution
The apparatus includes a rectifying unit, multiple LEDs connected in series, and switches with a switch control unit that senses currents through resistors to adjust gate terminal voltages, controlling current rising and falling periods to overlap and maintain constant current flow, thereby improving power factor and THD ratios and enabling efficient dimming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If AC power is used to drive LEDs through a rectifying circuit, then the LED luminescence apparatus can operate with AC power supply, but the waveform distortion causes poor power factor and high total harmonics distortion
Solution Approach 1:
The patent divides the LED string into multiple groups and uses multiple switches to control current flow through different segments sequentially. This segmentation allows the apparatus to maintain sinusoidal current waveform while operating from AC power, resolving the contradiction between AC power compatibility and power quality
Solution Approach 2:
The patent employs periodic switching of multiple switches in sequence, where each switch conducts for a specific portion of the AC cycle. This periodic action creates a sinusoidal current waveform that maintains good power factor and low THD while enabling AC power operation
2Adaptability or versatility
If the LED driving current waveform is distorted, then the LED luminescence apparatus can operate with non-ideal AC voltage, but very large deviations occur in the luminescence efficiency of the LEDs
Solution Approach 1:
The patent uses periodic switching of multiple switches to maintain sinusoidal current waveform through the LEDs even when input voltage is non-ideal. This periodic control ensures consistent luminescence efficiency by preventing current distortion that would cause deviations in LED performance
Solution Approach 2:
The patent incorporates current sensing and control mechanisms that monitor the actual current waveform and adjust switch timing accordingly. This feedback ensures the current remains sinusoidal and maintains consistent LED luminescence efficiency despite variations in input voltage quality
3Ease of operation
If phase control type dimmer is used to control brightness, then dimming function can be implemented, but the high impedance of LED luminescence apparatus makes it difficult to control
Solution Approach 1:
The patent divides the LED string into multiple controllable segments and uses multiple switches with different conduction angles. This segmentation creates variable impedance characteristics that can be matched to phase control dimmers, enabling easy brightness control while maintaining system compatibility
4Reliability
If multiple switches are used in multistage driving, then power factor and THD can be improved, but control of current rising and falling periods becomes complex
Solution Approach 1:
The patent uses a systematic periodic switching scheme where multiple switches are turned on and off in sequence during each AC cycle. The controller manages the current rising and falling periods of each switch in a coordinated periodic manner, achieving good power factor and low THD while maintaining controllable complexity through regular switching patterns
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 configuration reduces deviations in luminescence efficiency, prevents overcurrent issues, and satisfies electromagnetic interference (EMI) standards by providing a sinusoidal-like LED driving current, while allowing for effective dimming even during low output voltage periods.
Implementation Method 1
a rectifying unit rectifying an AC voltage and generating a rectified voltage
Implementation Method 2
a plurality of LEDs connected in series to an output terminal of the rectifying unit
Implementation Method 3
LED (Light Emitting Diode) luminescence apparatus
Data Source
AI summary
An LED luminescence apparatus is provided, which includes a rectifying unit rectifying an AC voltage and generating a rectified voltage; a plurality of LEDs connected in series to an output terminal of the rectifying unit; a plurality of switches having drain terminals connected to cathodes of the plurality of LEDs, respectively; and a switch control unit sensing current through a plurality of resistors connected to source terminals of the plurality of switches, respectively, comparing the sensed current with a set reference current, and outputting a voltage corresponding to a difference between the sensed current and the set reference current to a gate terminal of each of the plurality of switches.