AC-Line Filter Leakage Current Reduction via Rectifier Segmentation
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Solution Overview
Problem
Conventional EMI filters in electric appliances face a tradeoff between minimizing leakage current and effectively attenuating high-frequency noise, as the capacitance value required to reduce leakage current interferes with noise attenuation capabilities.
Innovation Solution
An EMI filter devoid of grounding capacitors is used, with a grounding capacitor placed between the rectifier and ground electrode, allowing it to be exposed to a rectified signal rather than the AC current, thereby reducing leakage current while enabling higher capacitance values for effective noise attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitance value of the grounding capacitor is increased to improve EMI attenuation, then the effectiveness of noise attenuation is improved, but the leakage current increases
Solution Approach 1:
The patent divides the grounding capacitor function into two separate components: an EMI filter capacitor (first capacitor) for noise attenuation and a grounding capacitor (second capacitor) for leakage current discharge. This segmentation allows each capacitor to be optimized independently - the first capacitor can have higher capacitance for better EMI attenuation without being constrained by leakage current limitations of the second capacitor.
Solution Approach 2:
The patent introduces a rectifier as an intermediary component between the EMI filter and the grounding capacitor. The rectifier converts AC input to DC, and the grounding capacitor is connected to this rectified output rather than directly to the AC input. This intermediary placement allows the grounding capacitor to discharge leakage currents from rectified signals while being electrically isolated from the high-frequency AC noise, enabling higher capacitance values without excessive leakage current.
2Object-generated harmful factors
If the capacitance value of the grounding capacitor is minimized to reduce leakage current, then the leakage current is minimized, but the EMI attenuation capability is reduced
Solution Approach 1:
The patent divides the grounding capacitor function into two separate components: an EMI filter capacitor (first capacitor) for noise attenuation and a grounding capacitor (second capacitor) for leakage current discharge. This segmentation allows each capacitor to be optimized independently - the first capacitor can have higher capacitance for better EMI attenuation without being constrained by leakage current limitations of the second capacitor.
3Object-generated harmful factors
If a grounding capacitor is placed at the AC input to discharge leakage current, then leakage current is controlled, but the capacitor is exposed to high-frequency AC noise requiring lower capacitance
Solution Approach 1:
The patent introduces a rectifier as an intermediary component between the EMI filter and the grounding capacitor. The rectifier converts AC input to DC, and the grounding capacitor is connected to this rectified output rather than directly to the AC input. This intermediary placement allows the grounding capacitor to discharge leakage currents from rectified signals while being electrically isolated from the high-frequency AC noise, enabling higher capacitance values without excessive leakage current.
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 leakage current while maintaining effective noise attenuation, allowing for higher capacitance values to be used without compromising performance, achieving reduced radio-frequency voltage levels and limited leakage current.
Implementation Method 1
A filter can also be provided to attenuate at least a portion of the electromagnetic interference ('EMI') conducted along the AC power line
Implementation Method 2
A rectifier is disposed electrically between the filter and the heating element to convert the AC electric current into a rectified signal
Implementation Method 3
a grounding capacitor is provided to establish a capacitive, conductive path between an output of the rectifier and a ground electrode
Implementation Method 4
a heating element that generates heat in response to being electrically energized by electric energy
Data Source
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AI summary
Provided is a power supply apparatus, and an appliance including the power supply apparatus, which includes a filter that attenuates a noise component of an AC electric current. The filter lacks a capacitor establishing a conductive path for conducting a high-frequency alternating signal, a leakage current, or both to a ground electrode. A rectifier is also included, and is disposed electrically between the filter and a load that is to be energized by operation of the power supply circuit. The rectifier converts the AC electric current into a rectified signal. The power supply apparatus also includes a grounding capacitor that establishes a capacitive, conductive path between an output of the rectifier and a ground electrode that is to be electrically connected to earth ground. The grounding capacitor is electrically separated from the filter by the rectifier, and extends electrically between the ground conductor and at least one of: (i) a positive DC bus conductor from the rectifier, and (ii) a DC bus return to the rectifier.