Inverter-Integrated Electric Compressor Circuit Board Offset Correction
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Solution Overview
Problem
The op-amp circuit in existing input current detection systems for electric compressors, particularly in vehicular air conditioning equipment, experiences significant detection errors due to temperature changes before and after operation, which affects the accuracy of input current measurement.
Innovation Solution
An inverter-integrated electric compressor with a circuit board that incorporates a current detection circuit and an offset correction circuit, where a first amplifier and a second amplifier are integrated into a single circuit, and both are mounted on the same plane with resistors from the same lot, reducing temperature-related errors by maintaining equal offset values and minimizing temperature unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate amplifier circuits are used for current detection and offset correction, then circuit functionality is achieved, but temperature-related detection errors increase due to temperature unevenness between circuits
Solution Approach 1:
The patent combines the first amplifier (for current detection) and the second amplifier (for offset correction) into a single integrated circuit. This merging ensures both amplifiers experience the same temperature conditions, eliminating temperature differential errors between separate circuits and significantly improving input current detection accuracy under temperature variations.
2Ease of manufacture
If resistors from different manufacturing lots are used, then component availability is improved, but detection accuracy deteriorates due to resistor value variations under temperature changes
Solution Approach 1:
The patent specifies using resistors from the same manufacturing lot for both the current detection circuit and offset correction circuit. This homogeneity ensures consistent temperature characteristics and value stability across all resistors, minimizing detection errors caused by resistor variations under temperature changes while maintaining manufacturability.
3Adaptability or versatility
If amplifiers are mounted on different planes of the circuit board, then layout flexibility is improved, but temperature unevenness increases causing offset value changes
Solution Approach 1:
The patent integrates both amplifiers within the same integrated circuit package, eliminating the need for separate mounting planes. This integration ensures both amplifiers are exposed to identical thermal environments, maintaining stable offset values even when the entire circuit experiences temperature variations during compressor operation.
Data Source
AI summary
To improve the accuracy of detecting a current flowing through an electric compressor after operation of the electric compressor, the electric compressor having a large change in temperature before and after operation. An inverter-integrated electric compressor (1) that compresses and discharges a refrigerant suctioned therein, includes an inverter device (2) provided with a circuit board (60) mounted with an inverter circuit (40), the inverter device (2) being integrally incorporated in an inverter case. The circuit board (60) is provided with a current detection circuit (30) that detects an input current flowing through the inverter circuit (40), and an offset correction circuit (20). The current detection circuit (30) includes a shunt resistor (32) that is serially connected to the inverter circuit (40) and detects a current, and a first amplifier (31) that amplifies and outputs a voltage appearing as a voltage drop in the shunt resistor (32). The offset correction circuit (20) includes a second amplifier (21) that performs an offset correction of the first amplifier (31). The first amplifier (31) and the second amplifier (21) are integrated into a single integrated circuit.