DC Bus Voltage Clamp for Fast Power Tool Shutdown Protection
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Solution Overview
Problem
Existing DC power tools face issues with trapped energy during shutdown, leading to overvoltage conditions due to traditional capacitors occupying space and limiting response speed, which is inefficient and slower.
Innovation Solution
A power tool with a voltage clamp and a controller that activates a transistor to convert trapped energy into heat, using wide bandgap semiconductors like GaN or SiC for faster response and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional DC bus capacitors are used to absorb trapped energy during shutdown, then energy absorption capability is improved, but device volume and response time are worsened
Solution Approach 1:
The patent extracts the energy absorption function from traditional large-volume DC bus capacitors and relocates it to a resonant tank circuit consisting of a resonant inductor and resonant capacitor. This separation allows the main DC bus capacitor to be significantly reduced in size while the resonant circuit handles the trapped energy absorption during shutdown, directly resolving the contradiction between energy absorption capability and device volume.
Solution Approach 2:
The patent changes the operational parameters of the capacitor by introducing a resonant circuit with specific inductance and capacitance values tuned to the shutdown frequency. The resonant capacitor operates at resonant frequency during shutdown conditions, enabling efficient energy absorption with much smaller component values than traditional capacitors would require, thus reducing volume while maintaining reliability.
2Reliability
If traditional DC bus capacitors are used to absorb trapped energy during shutdown, then energy absorption capability is improved, but response speed is worsened
Solution Approach 1:
The patent introduces a dynamic resonant circuit that activates during shutdown conditions to absorb trapped energy. The resonant inductor and capacitor create a dynamic response mechanism that rapidly oscillates at resonant frequency when shutdown occurs, enabling the system to respond much faster to trapped energy conditions than static traditional capacitors, while maintaining effective energy absorption capability.
3Volume of moving object
If power tool size is reduced for compactness, then portability is improved, but space for energy absorption components is worsened
Solution Approach 1:
The patent changes the electrical parameters of the energy absorption system by using a resonant circuit with carefully selected L and C values. This allows the same energy absorption capability to be achieved with dramatically reduced component sizes compared to traditional capacitor-based systems, enabling compact power tool design without sacrificing reliability during shutdown conditions.
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 limits DC bus voltage, saving space and improving response times by converting trapped energy into heat, making the power tool more efficient and compact.
Implementation Method 1
a power dissipating device connected to the DC bus and configured to convert the trapped energy into heat
Data Source
AI summary
A power tool comprising, a motor, a DC bus configured to provide operating power to the motor, a source inductor electrically connected to the DC bus, a voltage clamp provided across the DC bus and configured to be selectively activated, and a controller electrically connected to the voltage clamp. The controller is configured to determine that a voltage across the DC bus is greater than a predetermined threshold and activate the voltage clamp in response to the voltage across the DC bus being greater than the predetermined threshold.