AC Switch Relay and Semiconductor Parallel Control for Overcurrent Protection
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Solution Overview
Problem
Conventional power supply devices with AC switches having relay contacts and semiconductor switches face issues with semiconductor switch failure due to excessive current during load short-circuits, as they exceed the safety operation region or current conduction capacity, leading to size and cost increases when using higher current capacity semiconductor switches.
Innovation Solution
A power supply device with a control unit that manages an AC switch with a relay contact and a semiconductor switch in parallel, where the control unit closes only the relay contact when an excessive current is detected during the current conduction mode, preventing the semiconductor switch from conducting the excessive current, thus protecting it from failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a semiconductor switch is used in the AC switch, then the turn-on speed is extremely fast and highly frequent current ON/OFF operation is suitable, but the current conduction capacity is insufficient when excessive current flows during load short-circuit
Solution Approach 1:
The AC switch is segmented into two parallel paths: one with a semiconductor switch for fast switching and another with a relay contact for high current capacity. This segmentation allows each component to handle different aspects of the switching requirement, resolving the contradiction between speed and reliability.
Solution Approach 2:
The patent combines a semiconductor switch and a relay contact in parallel within the AC switch. The semiconductor switch provides fast turn-on capability while the relay contact provides high current conduction capacity. By merging these two components, the system achieves both fast switching and reliable high-current handling.
2Reliability
If a relay contact is used in the AC switch, then the conduction resistance is smaller, but the turn-on time is longer and highly frequent current ON/OFF operation is not suitable
Solution Approach 1:
The AC switch is divided into two parallel paths: one with a relay contact for low conduction resistance and another with a semiconductor switch for fast switching. This segmentation allows each component to excel at its strength while compensating for its weakness through the parallel configuration.
Solution Approach 2:
The patent merges a relay contact and a semiconductor switch in parallel within the AC switch. The relay contact provides low conduction resistance while the semiconductor switch provides fast turn-on capability. This combination resolves the contradiction between low resistance and fast switching.
3Reliability
If the semiconductor switch capacity is increased to handle excessive current, then the current conduction capacity is sufficient, but the size and cost of the device increase
Solution Approach 1:
Instead of using a single oversized semiconductor switch, the patent segments the current handling function between a standard-capacity semiconductor switch and a relay contact. This segmentation allows the use of a smaller, more cost-effective semiconductor switch while still achieving the required overall current conduction capacity.
Solution Approach 2:
The patent combines a standard-capacity semiconductor switch with a relay contact in parallel to achieve high current conduction capacity without requiring an oversized semiconductor switch. This merging approach reduces both size and cost compared to using a single high-capacity semiconductor switch.
Data Source
AI summary
This power supply device includes: an AC path from an input end to an output end; a current sensor configured to detect a current flowing through the AC path; a conversion unit connected to the AC path and being capable of bidirectional power conversion; a storage battery connected to the AC path via the conversion unit; an AC switch provided between the input end and a point at which the conversion unit is connected to the AC path, the AC switch including parallel body of a relay contact and a semiconductor switch; and a control unit configured to control the conversion unit and the AC switch. When the control unit executes a current conduction mode for the first time, and when the current sensor detects an excessive current during the current conduction mode, the control unit closes only the relay contact while keeping the semiconductor switch opened.