Electric Power Tool Battery Over-discharge Protection
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Solution Overview
Problem
Existing electric power tools face challenges in preventing over-discharging of rechargeable batteries when switching between motor-driven and illumination modes, as the discharge characteristics change, leading to potential voltage drops and control circuit failures.
Innovation Solution
An electric power tool with a control circuit that sets and stores reference voltage values for each load, including a motor and illumination LEDs, to manage power supply and prevent over-discharging by comparing battery voltage with specific reference values for different operational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single reference voltage value is used for protecting the rechargeable battery when the motor is driven, then the motor operation is protected from over-discharging, but the battery may become over-discharged when only the illumination means is activated due to different discharge characteristics
Solution Approach 1:
The patent segments the battery protection mechanism by creating separate reference voltage values for different operational modes (motor-driven mode and illumination mode). The control circuit identifies the current operational mode and selects the appropriate reference voltage value, ensuring each mode has its own optimized protection threshold based on its specific discharge characteristics.
Solution Approach 2:
The patent implements a dynamic reference voltage selection mechanism where the reference voltage value changes based on the operational mode. The control circuit dynamically switches between different reference voltage values stored in the storage unit, allowing the protection threshold to adapt to the current load conditions and discharge characteristics.
2Power
If the discharge characteristics change from illumination mode to motor-driven mode, then the battery can support higher power output, but a voltage drop may occur that causes the control circuit to fail
Solution Approach 1:
The patent applies preliminary action by setting the reference voltage values in advance for each operational mode, considering the voltage drop that occurs during mode transitions. The control circuit uses these pre-calculated reference values to anticipate and compensate for voltage drops, ensuring the control circuit continues to operate reliably during transitions from illumination mode to motor-driven mode.
3Power
If the reference voltage value is set based on motor-driven discharge characteristics, then high power operation is protected, but the illumination means may be deactivated prematurely due to lower load current
Solution Approach 1:
The patent applies local quality by setting different reference voltage values tailored to each operational mode's specific requirements. The illumination mode has a higher reference voltage value appropriate for its lower current draw, while the motor-driven mode has a lower reference voltage value suitable for high power operation. This localized optimization ensures each mode operates with its own appropriate protection threshold.
Data Source
AI summary
An electric power tool that receives driving power from a rechargeable battery includes loads and a control circuit that controls supply of the driving power from the rechargeable battery to the loads. The control circuit sets and stores for each of the loads a reference voltage value of the rechargeable battery used for stopping or issuing a notification in order to obviate over-discharging of the rechargeable battery.