Opposed Power Switch Module With Thermal Vias and Safety Cutoff
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Solution Overview
Problem
Conventional power tools with brushless DC motors are susceptible to unintentional motor activation in case of controller or power switch failure, posing a risk to users due to the lack of a reliable power contact switch mechanism.
Innovation Solution
An electronic module with a power contact switch and flyback diode is integrated into the control module, ensuring power is cut off to the motor when the trigger is not actuated, even if electronic components fail, and providing a current path for back-EMF during motor braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a separate power contact switch is integrated into the control module, then device complexity is reduced, but safety reliability deteriorates due to susceptibility to unintentional motor activation
Solution Approach 1:
The patent extracts the power contact switch function from the integrated control module and implements it as a separate mechanical switch assembly. This separation allows the mechanical switch to provide reliable power cutoff independent of the electronic control system, preventing unintentional motor activation while maintaining overall device integration. The mechanical switch is positioned to physically disconnect power before it reaches the motor, creating a safety barrier that operates independently of the controller or power switches.
2Temperature
If heat sinks are mounted on the circuit board, then thermal management is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the heat sinks with the circuit board by directly mounting them onto the board structure, creating an integrated thermal management solution. The heat sinks are positioned to receive heat from power components (such as power switches) and dissipate it to the surrounding air. This integration eliminates the need for separate thermal management assemblies and simplifies the manufacturing process while effectively managing heat from high-power components.
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
This solution ensures safe operation by preventing unintentional motor activation and providing a secondary safety mechanism to ensure power is disconnected when the trigger is not engaged, enhancing user safety and reliability.
Implementation Method 1
Thermal vias are disposed through the circuit board between corresponding ones of the heat sinks and the power switches
Implementation Method 2
An electronic module with a power contact switch and flyback diode is integrated into the control module, ensuring power is cut off to the motor when the trigger is not actuated, even if electronic components fail, and providing a current path for back-EMF during motor braking
Data Source
AI summary
An electronic module is provided including a circuit board defining a longitudinal axis and having a first surface and a second surface. A module housing is provided having a bottom surface and side walls extending from the bottom surface to form an open face through which the circuit board is received. Power switches configured as an inverter circuit to drive an electric motor are mounted on the second surface of the circuit board facing the bottom surface of the module housing, and a series of heat sinks are discretely mounted on the first surface of the circuit board facing the open face opposite the power switches. Potting material is disposed in the distance between the circuit board and the bottom surface of the module housing to cover the power switches. Thermal vias are disposed through the circuit board between corresponding ones of the heat sinks and the power switches.