Relay Welding Detection Circuit for Reliable Power Converters
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Solution Overview
Problem
Existing power conversion devices that determine relay welding reliability rely on short-lived photocouplers, leading to low detection circuit reliability.
Innovation Solution
A power conversion device using a welding detector with resistors and capacitors to apply an inspection signal and determine relay welding, reducing reliance on short-lived components and enhancing detection accuracy through signal delay and software-controlled determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photocouplers are used in the detection circuit to determine relay welding, then the detection function is achieved, but the reliability decreases due to the short life of photocouplers
Solution Approach 1:
The patent replaces the optical detection system (photocouplers) with an electrical detection system using resistors and capacitors. The welding detector applies an inspection signal through a capacitor and resistors to the relay terminal, and a determiner detects the signal response to determine welding status. This substitution eliminates the use of photocouplers with short lifetimes, thereby improving detection circuit reliability.
Solution Approach 2:
The patent changes the detection parameter from optical signal transmission (using photocouplers) to electrical signal response characteristics (using RC circuits). By measuring the time constant or amplitude response of the capacitor-resistor network when an inspection signal is applied, the system determines relay welding status without relying on short-lived optical components.
2Measurement precision
If multiple photocouplers are used to detect relay welding, then detection coverage is improved, but the overall system reliability decreases due to component failure
Solution Approach 1:
The patent replaces multiple photocoupler-based detection circuits with a single electrical detection circuit using resistors and capacitors. The welding detector applies an inspection signal through a capacitor to the relay terminal, and the determiner analyzes the electrical response to detect welding. This substitution maintains detection accuracy while eliminating the reliability issues associated with multiple short-lived photocoupler components.
3Device complexity
If a simple detection circuit is used, then device complexity is reduced, but detection reliability decreases due to component limitations
Solution Approach 1:
The patent uses a simple electrical circuit comprising a capacitor, resistors, and a signal source to replace complex optical detection systems. The welding detector applies an inspection signal through a capacitor and resistors to the relay terminal, and the determiner detects the electrical response. This simple circuit configuration using long-lived electrical components achieves both low complexity and high reliability.
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
Significantly reduces the decrease in reliability of the determiner by using long-lived components and simplifies the circuit configuration, improving the ability to detect relay welding accurately.
Implementation Method 1
the applied inspection signal is delayed by the first resistor, and a signal is input to the determiner such that the determiner can easily determine whether or not the relay is welded based on the signal delay
Data Source
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AI summary
A power conversion device (100) includes a power converter (11, 12), a relay (21, 22, 23, 24, 25), and a welding detector (30). The welding detector includes a first resistor (R301, R31, R32, R33) connected to a terminal of the relay on a first side, a capacitor (C101, C201, C11, C21, C41, C51, C61, C71, C81, C91) and a second resistor (R101, R201, R11, R21, R41, R51, R61, R71, R81, R91), both of which are connected to a terminal of the relay on a second side, an application unit (33) configured to apply an inspection signal to the relay via the capacitor and the second resistor, and a determiner (31) connected between the capacitor and the second resistor, the determiner configured to detect a signal based on application of the inspection signal by the application unit to determine whether or not the relay is welded.