Harmonics Correction Circuit for Aircraft LED Lighting
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Solution Overview
Problem
Aircraft electrical systems are negatively impacted by unwanted harmonics, which generate adverse electromagnetic field effects and disrupt other systems, and existing solutions like constant current drivers are limited in maintaining optimal voltage levels.
Innovation Solution
A harmonics correction circuit that aligns input and output waveforms by using a differential amplifier, ballast resistance, and a transistor feedback path to adjust current and voltage, ensuring a sinusoidal current waveform and improving power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a constant current driver is used to maintain reference voltage at peak input voltage, then harmful harmonic effects are avoided, but the solution is limited in maintaining optimal voltage levels and cannot adapt to varying voltage conditions
Solution Approach 1:
The patent transitions from a static constant current driver to a dynamic harmonics correction circuit that continuously adjusts its operation based on real-time detection of input voltage waveform characteristics. The circuit dynamically modifies its current draw to counteract harmonics, adapting to varying voltage conditions while maintaining power factor correction.
Solution Approach 2:
The invention implements a feedback mechanism where the harmonics correction circuit detects the input voltage waveform shape and uses this information to adjust its operation. The circuit monitors the AC voltage input and dynamically responds by drawing appropriate current to eliminate harmonics, creating a closed-loop control system that adapts to changing conditions.
2Reliability
If LED strings draw square current waveforms, then LED operation is maintained, but total harmonic distortion increases and power factor deteriorates
Solution Approach 1:
The patent converts the harmful square waveform current drawn by LED strings into a beneficial sinusoidal waveform by using the harmonics correction circuit. The circuit draws a compensating current that, when combined with the LED current, creates a sinusoidal total current draw from the AC source, thereby eliminating harmonics while maintaining LED operation.
Solution Approach 2:
The invention changes the current waveform parameter from square to sinusoidal by introducing the harmonics correction circuit. The circuit modifies the current draw characteristics to match the sinusoidal shape of the AC voltage input, transforming the waveform parameters to achieve power factor correction and harmonic elimination.
3Object-affected harmful factors
If existing harmonics correction solutions are used, then some harmonic reduction is achieved, but power factor of 1.00 and less than 1% total harmonic distortion cannot be achieved
Solution Approach 1:
The patent replaces conventional harmonics correction approaches with an improved circuit implementation using differential amplifiers and transistors. This substitution of the correction mechanism enables precise control of the compensating current, achieving superior performance with power factor of 1.00 and THD less than 1%.
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 effectively eliminates power harmonics and achieves a power factor of 1.00 with less than 1% total harmonic distortion, outperforming commercial designs, and adapts to various voltage and frequency conditions.
Implementation Method 1
the correction circuit includes a differential circuit (such as a differential amplifier) that receives the two waveforms as inputs
Implementation Method 2
provides an output current of the differential circuit to a transistor that is disposed in a feedback path to the differential circuit. As the output current of the differential circuit varies, the resistance of the transistor varies
Implementation Method 3
the correction circuit further includes a ballast resistance (e.g., a ballast resistor) in the feedback path to provide an upper limit on the amount of current that passes through the transistor
Implementation Method 4
the waveform at the output of the LED string is reflected as a voltage at a sense resistor, which is electrically coupled to a node through which the current as measured at the output of the group of LEDs passes
Data Source
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AI summary
The present disclosure is generally directed to a harmonics correction method and apparatus. In an embodiment, the method and apparatus are carried out in a light-emitting diode ("LED") lighting unit that includes a set or string of LED lights. According to an embodiment, the LED lighting unit is a line-replaceable unit ("LRU").