Power Conversion Device Capacitive Coupling Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power conversion devices in electric vehicles experience radiation noise due to switching noise propagating from electrodes to the metal casing, causing radio interference and other digital instrument disruptions.
Innovation Solution
The power conversion device adjusts the capacitive coupling between the power supply buses and the metal casing by matching the distances and dielectric constants, and uses plate-shaped conductive members with specific surface orientations to minimize inductive and capacitive coupling, thereby reducing noise propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If plate-shaped electrodes are disposed parallel with opposite current directions to reduce inductance, then surge voltage is reduced, but switching noise propagates to the metal casing through unequal capacitive coupling
Solution Approach 1:
The patent applies asymmetry by intentionally creating unequal capacitive coupling between the positive-side electrode and negative-side electrode to the metal casing. This is achieved by positioning the electrodes at different distances from the casing or using different dielectric materials, which causes the switching noise to cancel out through destructive interference, thereby reducing noise propagation to the casing.
Solution Approach 2:
The patent converts the harmful switching noise into a beneficial effect by utilizing the noise signals themselves to create destructive interference. The high-frequency vibrations generated by switching in the electrodes are intentionally configured to excite the metal casing in opposite phases, causing the noise waves to cancel each other out and reduce radiation noise.
2Reliability
If electrode dimensions and dielectric constant satisfy certain conditions, then capacitive coupling is optimized, but high-frequency vibrations excite the metal casing surface to generate radiation noise
Solution Approach 1:
The patent applies parameter changes by carefully controlling the electrode dimensions (lengths a and b), dielectric constant (εr), and positioning parameters to satisfy specific mathematical relationships. These parameter adjustments ensure that the resonant frequencies of the electrodes and metal casing are mismatched, preventing the excitation of surface waves that would generate radiation noise.
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 effectively reduces radiation noise by minimizing the propagation of switching noise to the metal casing, improving radio reception and reducing digital instrument interference.
Implementation Method 1
a power module (4) for converting direct current electricity supplied from the direct current power supply (2) to alternating current electricity
Implementation Method 2
an electrode connected to a positive side of a power supply and an electrode connected to a negative side of the power supply are disposed parallel, and configured such that currents flow through the electrodes in opposite directions, respectively. Thus, magnetic fluxes generated by the currents cancel out each other, and inductance is reduced.
Implementation Method 3
the capacitive coupling between the positive-side electrode and the metal casing is different from the capacitive coupling between the negative-side electrode and the metal casing
Implementation Method 4
when lengths of sides of each plate-shaped electrode are denoted by a and b, and the dielectric constant between the plates is denoted by εr
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A power conversion device (1) of the present invention includes a power module (4) for converting direct current electricity to alternating current electricity, first and second power supply buses (5, 6) connecting input terminals (12, 13) and the power module (4), and a metal casing (7) for housing the first and second power supply buses (5, 6) and the power module (4). The capacitive coupling between the first power supply bus (5) and the metal casing (7) and the capacitive coupling between the second power supply bus (6) and the metal casing (7) are substantially matched. Thus, radiation noise is reduced by reducing the propagation of switching noise to the metal casing.