DC Bus Overcurrent Protection Circuit With Freewheeling Path
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Solution Overview
Problem
Existing overcurrent protection circuits in DC bus applications are prone to damaging sensitive components due to high fault currents and prolonged protection times, which can lead to heat damage and reduced component lifetime.
Innovation Solution
An overcurrent protection circuit is designed with a main protection branch, freewheeling switch branches, a detection unit, and a control unit. This configuration allows for quick overcurrent detection and protection by disconnecting the faulty current path and providing a freewheeling loop to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quick fuse is used for overcurrent protection, then the protection time is extended to several seconds or tens of seconds, but the fault current remains tens of times larger than rated current causing damage to sensitive components
Solution Approach 1:
The protection circuit is divided into multiple independent modules: detection unit, control unit, and protection switch branch. Each module performs a specific function, allowing the system to detect overcurrent conditions and respond rapidly to isolate faults before heat damage occurs to sensitive components.
Solution Approach 2:
The detection unit continuously monitors current conditions before fault occurs, and the control unit is pre-configured to immediately activate the protection switch branch when overcurrent is detected. This preliminary monitoring and pre-configured response enables the system to act instantly upon fault detection, preventing heat damage before it can accumulate.
2Reliability
If quick fuse is used for overcurrent protection, then the protection time is extended to several seconds or tens of seconds, but sensitive components are damaged by high fault currents
Solution Approach 1:
The protection switch branch acts as an intermediary between the fault condition and the sensitive components. When overcurrent is detected, the protection switch rapidly opens to insert itself into the current path, blocking fault current from reaching sensitive components and preventing damage while maintaining system reliability.
Solution Approach 2:
The invention replaces the mechanical fuse operation with an electronically controlled protection switch branch. The control unit uses electronic detection and control signals to activate the protection switch, enabling much faster response times compared to mechanical fuse operation, thus protecting component integrity before heat damage can occur.
3Reliability
If quick fuse is used for overcurrent protection, then the protection time is extended to several seconds or tens of seconds, but component lifetime is reduced
Solution Approach 1:
The detection unit continuously provides feedback on current conditions to the control unit. When overcurrent is detected, the control unit immediately activates the protection switch branch to isolate the fault. This closed-loop feedback system enables rapid response to fault conditions, protecting components from cumulative heat stress and extending their operational lifetime while maintaining reliable overcurrent protection.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
The invention discloses an overcurrent protection circuit, coupled to a DC bus between first and second DC ends, the DC bus including positive bus and negative bus, and the circuit including: a main protection branch connected in series with the positive or negative bus, and including first and second protection switches connected in series and connected to a first node; a freewheeling switch branch having two ends, one end being connected to the first node, the other end being connected to an opposite bus to the main protection branch; a detection unit coupled to the DC bus for detecting a voltage or a current of the DC bus to output an overcurrent detection signal; and a control unit coupled to the detection unit and the main protection branch, and configured to control the main protection branch according to the overcurrent detection signal.