Power Tool Protection Circuit Prevents Unintended Restart
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Solution Overview
Problem
Power tools, such as blowers, can inadvertently restart when power is restored after an interruption, causing discomfort or damage due to forgotten switch states during low battery conditions or sudden power supply disruptions.
Innovation Solution
A power tool design incorporating a main control switch and a power supply protection circuit that ensures the power supply path is only completed when the main control switch is in the on state and an external power source meets the power supply requirement, using capacitors and bipolar transistors to control the power supply and blocking switches to prevent unintended restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the power tool is designed to allow easy restart after power interruption, then the ease of operation is improved, but unintended restarts causing safety hazards and discomfort occur
Solution Approach 1:
The power supply protection circuit performs preliminary detection of the main control switch state before allowing power restoration. The circuit includes a detection unit that checks whether the main control switch is in the on-state before completing the power supply path, preventing unintended restarts while maintaining ease of operation when properly switched on
Solution Approach 2:
The power supply protection circuit acts as an intermediary between the power source and the power system. It includes a power supply path with a controllable switch that mediates power delivery, only completing the circuit when the main control switch is confirmed to be in the on-state, thus preventing unauthorized restarts
2Ease of operation
If the LOCK_ON switch is provided to maintain closed state, then the ease of operation is improved, but the operator may forget to open it causing unintended restarts
Solution Approach 1:
The power supply protection circuit provides feedback by continuously monitoring the state of the main control switch. When the switch is in the off-state, the circuit prevents power delivery even if power is restored, giving the operator feedback that the system is protected against unintended restarts. This layered protection works alongside LOCK_ON switches to ensure reliability
Solution Approach 2:
The protection circuit performs preliminary verification of the main control switch state before allowing any power restoration. This preliminary action creates an additional safety layer that works independently of the LOCK_ON switch mechanism, ensuring that even if the operator forgets to open LOCK_ON, the system won't restart unless the main control switch is intentionally turned on
3Productivity
If the power supply path is always available, then the productivity is improved, but safety hazards from sudden reactivation occur
Solution Approach 1:
The power supply protection circuit implements preliminary detection of switch state before completing the power supply path. The detection unit checks whether the main control switch is in the on-state, and only then allows power to be delivered to the power system. This ensures productivity is maintained when properly switched on while preventing sudden reactivation hazards
Solution Approach 2:
The protection circuit serves as an intermediary layer in the power supply path, including a controllable switch that mediates between the power source and power system. This intermediary only completes the power path when verification confirms the main control switch is on, balancing productivity with safety by preventing unauthorized power delivery
Data Source
AI summary
A power tool includes a power connection terminal, a power system, a main control switch, and a power supply protection circuit. A power supply path is disposed between the power connection terminal and the power system. The main control switch and the power supply protection circuit are configured to control the power supply path to be completed or broken. During the use of the tool, the power tool is not restarted if the main control switch is turned on before an external power source that meets a power supply requirement is connected.