Switch Circuit Pre-Check for Low-Resistance Load Overcurrent
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Solution Overview
Problem
Conventional switch devices allow overcurrent to flow when a load with a low resistance component is connected, potentially damaging the connector and switch.
Innovation Solution
A switch device with a main switch and a sub-switch, along with a processing unit that determines whether the switch current will be less than a threshold value by measuring node voltage when the main switch is turned ON, using a switch circuit with a higher resistance when the sub-switch is ON.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a main switch is provided on the current path from DC power source to load, then power supply control is achieved, but overcurrent may flow when load with low resistance is connected
Solution Approach 1:
The patent applies preliminary action by measuring the resistance value of the load before the main switch is turned ON. The control unit acquires voltage information during a pre-measurement phase (when the main switch is OFF and sub-switch is ON), calculates the resistance value, and determines whether it exceeds the threshold before enabling power supply. This prevents overcurrent from occurring in the first place, rather than reacting after it occurs.
Solution Approach 2:
The patent implements feedback by continuously monitoring the voltage across the load and using this information to control the main switch. The control unit acquires voltage information, calculates resistance values, and uses this feedback to determine whether to turn the main switch ON or OFF, ensuring the load resistance is always above the threshold value. This closed-loop control prevents overcurrent by adjusting the switch state based on real-time measurements.
2Object-affected harmful factors
If resistance measurement is performed to prevent overcurrent, then overcurrent protection is achieved, but additional circuit components and control processing are required
Solution Approach 1:
The patent applies universality by making the existing voltage detection circuit serve multiple functions. The same circuit that detects voltage for normal operation also measures voltage to calculate load resistance for overcurrent protection. The control unit performs dual roles: normal power supply control and resistance measurement for protection. This eliminates the need for separate measurement circuits, reducing overall system complexity while achieving protection functionality.
Solution Approach 2:
The patent implements self-service by using the system's own voltage detection and control capabilities to perform resistance measurement and overcurrent protection. The control unit uses internally available voltage information and its existing processing abilities to calculate resistance values and make protection decisions, without requiring external measurement devices or additional complex control systems. The system protects itself using its own resources.
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
Prevents overcurrent flow by ensuring the switch current remains below a threshold, protecting the switch and connector from damage.
Implementation Method 1
determining whether a switch current that flows via the main switch when the main switch turns ON will be less than a current threshold value, based on the acquired node voltage information
Data Source
AI summary
A load is detachably connected to a device connector of a switch device. A resistance value of a switch circuit when a sub-switch is ON is greater than an ON resistance value of a main switch. A microcomputer acquires node voltage information indicating a node voltage of a connection node located downstream of the main switch and the sub-switch from a voltage detection unit in a state where the main switch is OFF and the sub-switch is ON. The microcomputer determines whether a switch current that flows via the main switch when the main switch turns ON will be less than a current threshold value, based on the acquired node voltage information.