AC Brushless Motor Control Circuit for Stable Controller Power
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Solution Overview
Problem
In high voltage brushless motor systems, the rectification of alternating current to direct current results in unstable voltage during modulation or commutation processes, leading to damage in electronic devices due to unstable power supply, particularly affecting the weak current part of the printed circuit board assembly and preventing real-time detection of bus voltage for under-voltage protection.
Innovation Solution
The implementation of a motor control circuit with a power module connected to both a first and second rectifier circuit, where the second rectifier circuit includes a rectifier unit, filter unit, voltage regulator, and voltage converter to stabilize the direct current supply to the controller and driver circuit, preventing interference from bus voltage fluctuations and ensuring stable power to the weak current part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single rectifier circuit is used to power both the motor control system and the controller, then the device complexity is reduced, but the voltage stability deteriorates due to freewheeling current interference during motor commutation
Solution Approach 1:
The power supply system is segmented into two independent rectifier circuits: a first rectifier circuit for the motor control system and a second rectifier circuit for the controller. This segmentation isolates the controller's power supply from the motor's freewheeling current interference, ensuring stable voltage for sensitive electronic components while maintaining overall system functionality.
2Device complexity
If the rectifier circuit directly outputs rectified voltage without additional regulation, then the device complexity is reduced, but the voltage fluctuation increases during motor commutation
Solution Approach 1:
A voltage regulator is introduced as an intermediary component between the second rectifier circuit and the controller. This regulator acts as a buffer that maintains stable output voltage despite fluctuations in the rectified input voltage, protecting the controller from voltage instability during motor commutation without requiring complex circuit redesign.
3Device complexity
If real-time voltage detection is not implemented, then the device complexity is reduced, but the reliability decreases due to inability to provide under-voltage protection
Solution Approach 1:
A voltage detection module is implemented to provide real-time feedback on the voltage status of the controller's power supply. This feedback mechanism enables the system to detect voltage abnormalities and trigger under-voltage protection, significantly improving system reliability by preventing controller damage during voltage fluctuations while maintaining relatively simple circuit architecture.
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 configuration effectively stabilizes the power supply to the weak current part, preventing damage from voltage fluctuations and enabling real-time under-voltage protection, thus ensuring the reliable operation of the brushless motor and associated electronic components.
Implementation Method 1
it is necessary to rectify an alternating current into a direct current
Implementation Method 2
a filter unit, a voltage regulator and a voltage converter to stabilize the direct current supply
Implementation Method 3
a filter unit, a voltage regulator and a voltage converter to stabilize the direct current supply
Data Source
AI summary
An alternating current power tool includes a function element, a brushless motor, and a motor control circuit. The motor control circuit includes a power module, a first rectifier circuit, a driver circuit, a controller, and a second rectifier circuit. The power module is used for receiving an alternating current. The first rectifier circuit is used for receiving the alternating current received by the power module and operatively outputting a direct current bus voltage. The second rectifier circuit is electrically connected to the power module and used for receiving the alternating current received and outputting a direct current to supply power to at least the controller.