AC/DC converter, electric motor drive device and refrigeration cycle device
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Solution Overview
Problem
Conventional AC/DC converters for refrigeration cycle devices require four current detectors, leading to increased manufacturing costs, and reducing the number of detectors results in performance deterioration.
Innovation Solution
An AC/DC converter design with a rectifier circuit, charge accumulation unit, switching unit, control unit, and reduced current detection units, utilizing a single current detector between the rectifier circuit and switch unit, and another between the charge accumulation unit and inverter, to detect currents and prevent overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four current detectors are used to detect currents for controlling switching elements, then the reliability of preventing excessive inrush current is improved, but the manufacturing cost increases
Solution Approach 1:
The patent combines the functions of four current detectors into two current detectors by using differential measurement. The first current detector detects the total current from the power supply, and the second current detector detects the current to the load. The control unit calculates the difference between these two detection values to determine the current through each switching element, thereby reducing component count while maintaining protection capability.
Solution Approach 2:
The control unit acts as an intermediary that processes the detection values from two current detectors to derive the current information that would otherwise require four direct detectors. By calculating the difference between the total current and load current, the control unit indirectly obtains the switching element current information needed for protection.
2Ease of manufacture
If the number of current detectors is reduced to lower manufacturing cost, then the manufacturing cost decreases, but the performance deteriorates
Solution Approach 1:
The patent replaces direct physical measurement (mechanical/electrical detection) with mathematical calculation. Instead of using four physical detectors to directly measure each current, the system uses two detectors combined with differential calculation to achieve the same measurement objective, maintaining accuracy while reducing hardware.
Solution Approach 2:
The patent changes the measurement parameters from direct individual current measurements to differential current measurement. By measuring the difference between total current and load current, the system obtains the switching element current information needed for protection, achieving the same functional result with fewer components.
3Adaptability or versatility
If different current ratings are used for various refrigeration cycle device models, then the adaptability to different models is improved, but the device complexity increases
Solution Approach 1:
The patent creates a universal current detection configuration that can be applied across different device models with varying current ratings. The same two-current-detector differential measurement approach works for all models, eliminating the need for model-specific detector configurations and simplifying standardization.
Data Source
AI summary
An AC/DC converter includes: a charge accumulation unit including first and second capacitors connected in series; a switching unit including a switch unit; a control unit; a switch drive unit; and first current and second current detection units. The switch unit includes first and second switching elements connected in series. The switching unit switches between charging and non-charging of each of the first and second capacitors. The switch drive unit causes the first and second switching elements to perform an ON/OFF operation exclusively to each other. A current detector of the first current detection unit is disposed between a rectifier circuit and the switch unit. The control unit detects a current flowing through the switch unit on the basis of based on a difference value between a detection value of a first current detected by the first current detection unit and a detection value of a second current detected by the second current detection unit.