Opposed Power Switch Layout With Discrete Heat Sinks for Safe Motor Cutoff
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Solution Overview
Problem
Conventional power tools with brushless DC motors are susceptible to unintentional motor activation due to failures in the controller or power switches, posing a risk to users, especially in integrated switch and control modules where space constraints limit the placement of separate power contact switches.
Innovation Solution
An electronic module with a circuit board and module housing that includes power switches configured as an inverter circuit, heat sinks, and a potting material to secure components, along with a power contact switch and flyback diode, which ensures safe power cutoff even if the controller or power switches fail, using a user-actuated input unit to control the motor activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an integrated switch and control module is used to save space, then the device complexity is reduced and space is saved, but the reliability decreases due to increased susceptibility to unintentional motor activation from controller or power switch failures
Solution Approach 1:
A separate power contact switch is introduced as an intermediary safety component between the battery and motor circuit, independent of the integrated controller. This mediator ensures that even if the controller or power switches fail, the motor cannot activate unintentionally, thus resolving the reliability concern while maintaining the integrated module's space efficiency.
2Reliability
If a separate power contact switch is added to improve safety, then the reliability increases, but the device complexity and space requirements increase
Solution Approach 1:
The power contact switch is integrated into the existing control module assembly, combining the safety function with the controller and power switches in a single compact unit. This merging approach maintains the benefits of integration while adding the necessary safety component, avoiding increased space requirements and complexity.
3Measurement precision
If the controller continuously monitors and controls power switches, then the motor operation precision is improved, but the loss of time increases due to potential controller failures causing unintentional activation
Solution Approach 1:
The power contact switch is designed to be actuated in advance by the trigger mechanism, establishing a predetermined mechanical connection that physically disconnects power when the trigger is released. This preliminary mechanical action ensures immediate safety cutoff without requiring controller intervention or monitoring, eliminating the time loss associated with electronic failure detection and response.
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 provides a safe and reliable power control mechanism that prevents unintentional motor activation by ensuring power is cut off when the trigger is not actuated, even in case of component failures, enhancing user safety and reducing the risk of accidents.
Implementation Method 1
a series of heat sinks are discretely mounted on the first surface of the circuit board facing the open face opposite the power switches
Implementation Method 2
Thermal vias are disposed through the circuit board between corresponding ones of the heat sinks and the power switches
Implementation Method 3
Potting material is disposed in the distance between the circuit board and the bottom surface of the module housing to cover the power switches
Data Source
AI summary
An electronic module is provided including a circuit board a first conductive track, second conductive tracks, third conductive tracks mounted on a first surface of the circuit board; at least one first heat sink mounted on the first conductive track; second heat sinks mounted respectively on the second conductive tracks; motor terminals formed through the third conductive tracks; and power switches mounted on the second surface of the circuit board configured as an inverter circuit to supply power from a power supply to an electric motor. High-side power switches are located opposite the at least one first heat sink and in thermal communication therewith, and low-side power switches are located opposite the second heat sinks and in respective thermal communication therewith.