Brushless Power Tool Current Control for Stable AC Output
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Solution Overview
Problem
Existing power tools powered by AC supply face instability due to commercial power fluctuations, limiting their high-power applications, and existing solutions fail to provide a stable output effectively.
Innovation Solution
A power tool design incorporating a brushless motor with a drive circuit, detection device, and controller that adjusts the motor current based on load parameters to maintain stability, using an AC power module, rectifier, EMI module, and electrolytic capacitor to ensure smooth and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power tool is connected with commercial AC power to provide high power, then the power output is improved, but the output stability deteriorates due to commercial power fluctuations
Solution Approach 1:
The patent employs a feedback control mechanism where a detection device continuously monitors the load parameter of the brushless motor and sends signals to the controller. The controller adjusts the drive circuit's output based on this feedback, maintaining stable motor operation despite AC power fluctuations. This closed-loop control system resolves the contradiction by dynamically compensating for power variations while maintaining high power output capability.
Solution Approach 2:
The controller dynamically adjusts the drive parameters (such as PWM duty cycle) of the brushless motor based on detected load conditions and power fluctuations. By changing these control parameters in real-time, the system maintains stable motor performance and output stability even when commercial AC power varies, thus resolving the contradiction between high power output and stability.
2Reliability
If a DC power supply is used to power the tool, then the output stability is improved, but the available power is limited
Solution Approach 1:
The patent designs a universal power system that can accept both AC and DC power inputs while maintaining stable operation through the same feedback control mechanism. The controller adapts its operation based on the detected power source type and load conditions, enabling the tool to achieve both high power output (when connected to AC) and stable operation (through feedback control), thus resolving the limitation of DC-powered tools.
3Power
If the motor current is increased to handle high load, then the power output is improved, but the risk of overheating and damage increases
Solution Approach 1:
The detection device continuously monitors the motor's load parameter (current) and provides feedback to the controller. When the current approaches dangerous levels, the controller automatically adjusts the drive circuit to reduce current intake, preventing overheating and damage. This feedback mechanism allows the system to operate at high power levels safely by dynamically controlling current within safe thresholds.
Solution Approach 2:
The system dynamically adjusts the motor current based on real-time load detection and power supply conditions. Rather than operating at a fixed high current level, the controller modulates the current dynamically through PWM control, allowing the motor to deliver high power when needed while automatically reducing current to prevent overheating, thus resolving the contradiction between power output and overheating risk.
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 stable output and improved efficiency by adjusting the motor current and voltage, enhancing the power tool's performance and adaptability to varying power conditions, thus overcoming the limitations of commercial power fluctuations.
Implementation Method 1
using an AC power module, rectifier, EMI module, and electrolytic capacitor to ensure smooth and efficient operation
Implementation Method 2
a brushless motor including several windings, a drive circuit for driving the brushless motor
Data Source
AI summary
A power tool includes a brushless motor including several windings, a drive circuit for driving the brushless motor, a detection device for detecting the brushless motor so as to obtain a load parameter corresponding to a load of the brushless motor, and a controller for outputting a first control signal to reduce current of the brushless motor in a first slope when the load parameter exceeds a first preset range.