Ground Fault Shutdown Circuit for Dual-Battery Power Switches
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Solution Overview
Problem
Conventional power supply systems struggle to effectively turn off switches in the event of a ground fault, which can lead to damage from power surges and potential CPU malfunction.
Innovation Solution
A control circuit is introduced, featuring a third switch connected to the gates and sources of the first and second switches, which turns on to short them off in case of a ground fault, thereby protecting the switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CPU and voltage/current detectors are used to detect ground fault and control switch shutdown, then the system can identify ground faults, but the shutdown signal may arrive too late to prevent power surge damage to the switches
Solution Approach 1:
The patent connects the third switch directly to the gate terminals of the first and second switches through resistors, establishing a pre-configured shutdown path. When ground fault occurs, the third switch can immediately discharge the gate capacitance without waiting for CPU processing, achieving preliminary action that prevents power surge damage
2Measurement precision
If conventional voltage and current detectors are used to monitor for ground faults, then ground fault detection is possible, but the CPU may be damaged by ground fault before it can send shutdown signals
Solution Approach 1:
The third switch acts as an intermediary protective device that operates independently of the CPU. It directly monitors the ground reference voltage and can trigger switch shutdown without CPU intervention, protecting the CPU from ground fault damage while maintaining detection capability
3Stability of the object's composition
If the third switch is always on to provide ground reference, then the reference voltage is continuously available, but power is wasted and the switches cannot be properly controlled
Solution Approach 1:
The third switch transitions from a static always-on state to a dynamic on/off state controlled by ground fault detection. It normally remains off to conserve energy and allow proper switch control, but activates when ground fault is detected to provide stable ground reference and trigger protective shutdown
Solution Approach 2:
The system periodically monitors the ground reference voltage through the third switch and resistive divider network. This periodic detection allows the third switch to remain off during normal operation (saving energy) while being ready to activate immediately when ground fault conditions are detected
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
The control circuit ensures that the first and second switches are turned off promptly in the event of a ground fault, preventing damage from power surges and maintaining system integrity without relying on the CPU.
Implementation Method 1
a voltage at the third gate and third source of the third switch is the same, turning on the third switch and shorting the first gate, first source, the second gate and the second source of the first switch and the second switch so as to turn off the first switch and the second switch
Data Source
AI summary
A power supply system and a control circuit for a power supply system are provided. The power supply system includes a first battery, a second battery, a first switch and a second switch are operable to control power supply from the first and second battery by turning on and off. The control circuit includes a third switch. A drain of the third switch is connected to the gates of the first and second switches and a source of the third switch is connected to the source of the first and the second switches. In the event of a ground fault, a voltage at the gate and source of the third switch is the same, turning on the third switch voltage wherein a voltage at the gates and sources of the first and second switches are made equal, turning off the first and second switches.