Dynamic Delay Overcurrent Protection Circuit
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Solution Overview
Problem
Existing overcurrent protective devices either require frequent replacement like fuses or have delayed protective actions, leading to inefficiencies in responding to varying overcurrent magnitudes, and they often increase in size and cost due to the need for high withstand voltage elements, while also consuming excessive power in signal transmission circuits.
Innovation Solution
An overcurrent protective device with a detector and controller that dynamically adjusts the delay time for overcurrent interruption based on current magnitude, using a bias circuit to reduce the control circuit's voltage requirements and incorporating a signal transmission circuit with switches and resistors to manage power consumption and prevent erroneous signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuse is used for overcurrent protection, then the protection response is timely and simple, but the fuse requires frequent replacement and is not maintenance-free
Solution Approach 1:
The patent replaces the mechanical fuse system with an electronic protective device using a field-effect transistor as a switch, controlled by a detector and controller that monitor current and automatically interrupt overcurrent without requiring physical replacement of components
Solution Approach 2:
The protective device automatically detects overcurrent conditions through the detector, processes the signal through the controller, and interrupts the current through the field-effect transistor without requiring human intervention or component replacement, making the system self-service and maintenance-free
2Device complexity
If a constant delay time is used for overcurrent protection, then the circuit configuration is simple, but the protection is not timely for large magnitude overcurrents
Solution Approach 1:
The patent implements a dynamic delay mechanism where the delay time varies based on the magnitude of overcurrent detected. The controller adjusts the delay period according to the overcurrent magnitude, providing shorter delays for larger currents and longer delays for smaller currents, optimizing protection timing for different fault conditions
Solution Approach 2:
The system changes the delay time parameter dynamically based on the detected overcurrent magnitude. The controller receives the limitation signal and generates a turn-off signal after a delay period that is determined by the magnitude of the overcurrent, allowing the protection response time to adapt to different fault severity levels
3Strength
If high withstand voltage elements are used in the control circuit, then the device can handle high voltage, but the device size and cost increase
Solution Approach 1:
The patent introduces a bias circuit as an intermediary between the high voltage power supply and the control circuit. The bias circuit generates a bias voltage that is lower than the power supply voltage, allowing the control circuit to operate at reduced voltage levels while still protecting against high voltage conditions through the field-effect transistor switch
Data Source
AI summary
The present overcurrent protective device comprises an input terminal configured to receive a power supply voltage, an output terminal, a switch, a detector, and a controller. The switch is provided between the input terminal and the output terminal. The detector is configured to output a limitation signal without delay when a current flowing through the switch exceeds a prescribed tolerance value. The controller is configured to receive the limitation signal and control the switch to prevent the current from exceeding the tolerance value. The detector is configured output a turn-off signal to the controller when a first state continues for a delay time determined depending on the current's magnitude. The first state is a state where the current is smaller than the tolerance value and the current exceeds a first threshold value smaller than the tolerance value. The controller turns off the switch in response to the turn-off signal.