Three-Phase Power Converter Control for Body Diode Overcurrent
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Solution Overview
Problem
Existing electric-power conversion apparatuses face issues with excessive current flow in semiconductor switching devices, leading to deterioration of body diodes, which is exacerbated by the need for additional reflux diodes that contradict downsizing and cost-saving requirements.
Innovation Solution
An electric-power conversion apparatus with phase current detection and switching control that turns on or off specific groups of switching devices to suppress excessive currents, preventing diode deterioration without requiring additional reflux diodes or expanding semiconductor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an additional reflux diode is connected with the semiconductor switching device to protect the body diode from excessive current, then the body diode is protected from deterioration, but the device complexity and cost increase
Solution Approach 1:
The semiconductor switching device utilizes its own body diode to protect against excessive current by turning off all switching devices when overcurrent is detected, allowing the current to flow through the body diode in a controlled manner, thereby eliminating the need for additional external protection diodes
Solution Approach 2:
The body diode, which is normally a parasitic element, is made to serve a dual function: its original rectification function and an additional protection function against excessive current, thereby eliminating the need for separate protection components
2Reliability
If the semiconductor size of the FET is expanded to increase the allowable current of the body diode, then the tolerance against excessive current is raised, but the downsizing and cost-saving goals are compromised
Solution Approach 1:
The invention changes the operational parameters of the switching device by implementing a control strategy that monitors phase currents and turns off all switching devices when overcurrent is detected, thereby protecting the body diode without requiring physical enlargement of the semiconductor device
3Productivity
If all switching devices are turned off to suppress excessive current, then the excessive current is suppressed, but the body diode may still be damaged by the excessive current
Solution Approach 1:
The control device detects excessive current in advance by monitoring phase currents and turns off all switching devices before the excessive current can damage the body diode, preventing deterioration through proactive protection
Solution Approach 2:
The system continuously monitors the current flowing through each phase and provides feedback to the control device, which adjusts the switching device states accordingly to prevent excessive current from damaging the body diode
Data Source
AI summary
Provided is an electric-power conversion apparatus including respective arms of three phases each having switching devices that are connected with a DC power source and an external connection point that is connected with a winding of an electric rotating machine. A phase current detection unit detects a current of each of the three phases, and a switching control apparatus that controls the electric rotating machine by turning on or off the positive-polarity switching devices and the negative-polarity switching devices and that determines that an excessive current has occurred, in the case where a current detected by the phase current detection unit exceeds a predetermined threshold value, and then turns on any one of a group of all the positive-polarity switching devices and a group of all the negative-polarity switching devices and turns off the other one thereof.