Protective Circuit Layout for Switch Surge Suppression
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Solution Overview
Problem
Conventional energy storage apparatuses face challenges in protecting switches from surges generated during rapid current changes, particularly when large inductance loads are involved, which can lead to switch failure due to excessive voltage.
Innovation Solution
A protective circuit is implemented with a switch on the power line, a first protective element (capacitor and Zener diode) in parallel to absorb surges, and a second protective element (freewheel diode) to return surges to the load, effectively suppressing surge voltage and preventing switch failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switch is used to cut off current between an energy storage device and a load, then current control is achieved, but a large surge occurs when the switch is opened causing potential switch failure
Solution Approach 1:
A protective element is connected in parallel to the switch beforehand to cushion the surge voltage that occurs when the switch is opened. This protective element absorbs the voltage spike before it can damage the switch, ensuring reliable operation during current cutoff events.
Solution Approach 2:
The protective element acts as an intermediary between the switch and the surge voltage. It provides a parallel path for the surge current, mediating the interaction between the switch opening action and the resulting voltage spike, thereby protecting the switch from direct exposure to harmful voltages.
2Strength
If the switch withstands large surge voltage, then switch protection is improved, but the protective element may fail to absorb the surge effectively
Solution Approach 1:
The protective element is designed with specific electrical parameters (breakdown voltage, capacitance) that change its behavior based on the applied voltage. Under normal operating conditions, it remains non-conductive, but when surge voltage exceeds its breakdown voltage, it transitions to a conductive state, absorbing the surge energy and protecting the switch.
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 solution effectively absorbs and returns surges, reducing the voltage applied to the switch, thereby protecting it from failure and ensuring reliable operation during current cutoff events.
Implementation Method 1
a first protective element that is connected in parallel to the switch and absorbs a surge generated when the switch is opened and discharge current is cut off
Implementation Method 2
A plurality of Zener diodes are connected in series so that the output terminal side of the vehicle generator becomes a cathode and the ground (GND) side becomes an anode. A breakdown voltage of the Zener diode is set to be equal to or less than a breakdown voltage of the MOS transistor
Implementation Method 3
a second protective element that is connected in parallel to the load and returns the surge, which is generated when the switch is opened and discharge current is cut off, to the load
Data Source
AI summary
A protection circuit 60 is provided with: switches 61, 62 positioned on a power line PL of an electricity storage element 22 and a load 12; first protection elements 63, 64, 65 connected in parallel with the switches 61, 62 and absorbing surge caused when the switches 61, 62 open and cut off discharge current; and a second protection element 66 connected in parallel with the load and flowing, back to the load, the surge caused when the switches 61, 62 open and cut off the discharge current.