Power Converter Noise Suppression via Capacitive Filtering
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Solution Overview
Problem
Existing power conversion apparatuses face high costs and inefficiencies in suppressing noise currents and voltages that propagate through control wiring, leading to malfunctions in control circuits and sensors, and existing noise filters deteriorate electromagnetic noise reduction effects based on wiring length.
Innovation Solution
The power conversion apparatus employs noise-removing components, such as capacitors, strategically placed between signal wiring and connection points to suppress noise, with path electric lengths set to prevent standing waves and noise propagation, and incorporates a shield to prevent re-radiation, ensuring effective noise suppression at a low cost and small size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a reactance element is used in the noise filter, then the noise current suppression is improved, but the apparatus cost increases
Solution Approach 1:
The patent replaces expensive reactance elements with inexpensive capacitors that can be easily manufactured and disposed of. The capacitor-based noise filter achieves effective noise suppression without the high cost of reactance elements, embodying the principle of using cheap components to solve the problem.
Solution Approach 2:
The patent substitutes the electromagnetic reactance element with a capacitor-based electrical component. This substitution changes the noise filtering mechanism from inductive reactance to capacitive coupling, achieving cost reduction while maintaining noise suppression functionality.
2Object-affected harmful factors
If a noise filter (capacitor) is deployed on the board, then the noise current is injected into the board GND, but this causes malfunctions of in-apparatus sensors and circuits
Solution Approach 1:
The patent introduces a series capacitor as an intermediary component between the noise filter capacitor and the board GND. This series capacitor acts as a mediator that blocks the noise current path to the GND while allowing the noise filter to function, thereby preventing sensor and circuit malfunctions caused by GND noise injection.
Solution Approach 2:
The patent segments the GND connection path by introducing a series capacitor that divides the electrical path. This segmentation isolates the noise filter capacitor from directly connecting to the board GND, preventing noise current from reaching sensitive sensors and circuits while maintaining the noise filtering function.
3Adaptability or versatility
If the wiring length after the noise filter is increased, then the noise filter can be placed in more locations, but the electromagnetic-noises reduction effect is tremendously deteriorated
Solution Approach 1:
The patent changes the electrical parameters of the noise filter circuit by adding a series capacitor, which modifies the impedance characteristics and frequency response. This parameter change allows the noise filter to maintain effective noise reduction across varying wiring lengths, overcoming the limitation of placement flexibility versus performance trade-off.
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 enhances immunity performance by significantly reducing noise currents and voltages, preventing malfunctions and maintaining effective noise reduction across varying wiring lengths, thus providing a cost-effective and compact solution for power conversion applications.
Implementation Method 1
a capacitor which blocks a noise current
Implementation Method 2
incorporates a shield to prevent re-radiation
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
There is provided a power conversion apparatus which allows a noise current or voltage to be suppressed at a low cost and in a small size, the noise current or voltage mixing into the power conversion apparatus by propagating through a control wiring connected to an external appliance. The power conversion apparatus includes a housing, connection terminals provided on the housing, a control-circuit unit provided inside the housing, a wiring for establishing the connection between the connection terminals and the control-circuit unit, a first noise-removing unit connected between the wiring and the ground potential of the housing, and a second noise-removing unit connected between the wiring and the ground potential of the housing, and also in parallel to the first noise-removing unit.