Surface-Mount Snubber Circuit for Integrated Electric Compressor Noise Reduction
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Solution Overview
Problem
Integrated electric compressors for on-vehicle air conditioners face challenges in downsizing due to the large size of common mode capacitors and coils, which also contribute to increased radio noise, especially when lead wires are used for wiring, and high-frequency leakage currents occur during motor operation.
Innovation Solution
Incorporating a snubber circuit with a resistor and capacitor between the power source and switching element on a surface-mounted board, reducing radio noise by minimizing the leakage current loop and eliminating the need for lead wires, thereby allowing for a more compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode capacitors and common mode coil are used to reduce radio noise, then radio noise is reduced, but the size of the integrated electric compressor increases
Solution Approach 1:
The patent merges the snubber circuit functionality directly into the control board by surface-mounting the resistor and capacitor components onto the board itself. This eliminates the need for separate common mode capacitors and coils, integrating multiple functions into a single compact unit while maintaining radio noise reduction capabilities.
Solution Approach 2:
The patent replaces the traditional wire-based lead connection system with a surface-mount technology approach. By directly mounting components onto the control board, it eliminates the mechanical lead wire connections that created large leakage current loops, thereby reducing radio noise without increasing size.
2Reliability
If lead wires are used for wiring between driving board and common mode capacitors/coil, then electrical connection is established, but radio noise increases due to increased loop area
Solution Approach 1:
The patent extracts and eliminates the lead wire connections from the system by directly surface-mounting the resistor and capacitor onto the control board. This removes the source of the large leakage current loop area that caused radio noise, while maintaining reliable electrical connection through direct board mounting.
Solution Approach 2:
The patent transitions from a three-dimensional wire-based connection approach to a two-dimensional surface-mount approach on the circuit board. This dimensional change eliminates the loop area problem inherent in wire connections while maintaining electrical connectivity through traces on the board.
3Adaptability or versatility
If the length of lead wire is increased to connect components, then component arrangement flexibility is improved, but voltage fluctuation increases and radio noise worsens
Solution Approach 1:
The patent combines the component mounting and electrical connection functions into a single surface-mount process on the control board. This eliminates the need for separate lead wire connections, providing component arrangement flexibility through standard PCB design practices while avoiding the radio noise problems of wire-based connections.
4Object-affected harmful factors
If common mode capacitors and common mode coil are used to suppress leakage current, then radio noise is reduced, but device complexity increases
Solution Approach 1:
The patent combines the snubber circuit components (resistor and capacitor) directly onto the control board, merging multiple functions into a single integrated unit. This reduces device complexity by eliminating separate common mode capacitors and coils while maintaining the ability to suppress leakage current and reduce radio 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
The snubber circuit effectively reduces radio noise and allows for a smaller integrated electric compressor size by minimizing the leakage current loop and reducing impedance in power wiring, enhancing noise shielding and preventing microcomputer malfunctions.
Implementation Method 1
a snubber circuit which is provided between the power source and the switching element to reduce radio noise and comprises a resistor and a capacitor
Implementation Method 2
a snubber circuit which is provided between the power source and the switching element to reduce radio noise and comprises a resistor and a capacitor
Implementation Method 3
power wiring for applying a voltage from the power source to the first board is preferably formed by a bus bar
Data Source
AI summary
There is provided an integrated electric compressor that can be made small in size while reducing radio noise effectively. In an inverter of the electric compressor, a snubber circuit 21 comprising a resistor R and a capacitor C is provided between input/output terminals 20 of a power source and a switching element 18. The snubber circuit 21 is formed by surface mounting a resistive element constituting the resistor R and a capacitor element constituting the capacitor C on a power board 16. A leakage current from a motor 19 is thus restrained and radio noise is reduced. The resistive element and the capacitor element constituting the snubber circuit 21 are preferably surface mounted on the power board 16 on the side opposite to the side on which a control circuit board is arranged.