Battery Pack Interface Circuit for Series Tool Communication
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Solution Overview
Problem
When multiple battery packs are connected in series in an electric power tool, the differing reference voltages between the integrated circuits and the tool's controller prevent direct communication, rendering the autostop function and other control signals unusable, leading to potential over-discharge and damage to the battery packs.
Innovation Solution
Incorporating a voltage level-shifter or DC-to-DC converter between the tool's controller and the battery pack integrated circuits to align the signal voltage levels, enabling effective communication and implementing the autostop function, while also addressing the issue of reverse voltage damage through bypass circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple battery packs are connected in series to provide higher voltage, then the power output of the electric tool is improved, but the reference voltage difference between integrated circuits prevents signal communication
Solution Approach 1:
A voltage level-shifter circuit is introduced as an intermediary component between the controller and the integrated circuits of series-connected battery packs. This level-shifter converts signal voltage levels from one reference potential to another, enabling reliable communication while maintaining the series connection configuration for higher power output.
2Power
If battery packs are connected in series to achieve high voltage operation, then the voltage level for power-intensive operations is improved, but the signal voltage from integrated circuits becomes incompatible with the controller
Solution Approach 1:
The voltage level-shifter dynamically adjusts the signal voltage parameters (voltage level and reference potential) to match between the controller and battery pack integrated circuits. This parameter transformation enables compatibility while maintaining the high voltage series connection configuration.
3Device complexity
If integrated circuits directly communicate with the controller in series-connected battery packs, then the device complexity is reduced, but the differing reference voltages cause communication failure
Solution Approach 1:
The voltage level-shifter serves as a mediating component that bridges the reference voltage difference between the controller and battery pack integrated circuits. This intermediary ensures reliable signal transmission without requiring complex communication protocols or additional synchronization circuits.
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
Enables seamless communication between battery pack integrated circuits and the tool's controller, preventing over-discharge and extending battery life, and allows the use of lower-voltage battery packs to power higher-voltage tools, enhancing flexibility and safety.
Implementation Method 1
a voltage level-shifter adapted to shift the voltage level of signals between the controller and the integrated circuits of the battery packs
Implementation Method 2
DC-to-DC converter adapted to convert DC voltage between the controller and the integrated circuits of the battery packs
Data Source
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AI summary
An electric power tool (70; 100) is powered by a plurality of battery packs (10) connected in series. The electric power tool comprises a controller (152; 252) adapted to receive signals outputted from the integrated circuits located in each of the battery packs. A first voltage level-shifter (156b; 256b) is disposed between the controller of the electric power tool and one of the integrated circuits of the battery packs. The first voltage level-shifter is adapted to shift the voltage level of the signal outputted from the respective integrated circuit to the tool controller to an acceptable level for the controller.