Brushless DC Motor Driver Circuit Reducing Vibration Noise
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Solution Overview
Problem
Conventional brushless DC motor driver circuits experience increased vibration and shock noise at higher rotation speeds due to ineffective reconstruction of magnetic fields during phase-switching, leading to abrupt torque changes.
Innovation Solution
A brushless DC motor driver circuit comprising a magnetic field detecting circuit, counters, and a signal processor that generates linearly varying driving voltages based on detected magnetic field signals, allowing smoother torque changes and reduced noise by adjusting the phase switching rate through varying magnetic flux densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopper amplifier architecture is used to detect Hall sensor signals, then the offset voltage problem is solved, but the torque changing rate increases and vibration or shock noise increases at higher rotation speeds
Solution Approach 1:
The patent applies dynamics by making the sampling frequency variable rather than fixed. The sampling frequency is dynamically adjusted based on the rotor's rotational speed, allowing the system to maintain effective magnetic field reconstruction at higher speeds while using lower frequencies at lower speeds, thus reducing vibration and noise without sacrificing measurement precision
Solution Approach 2:
The patent changes the parameter of sampling frequency based on rotational speed conditions. By adjusting the sampling frequency parameter dynamically according to the motor's operating speed, the system optimizes the balance between accurate Hall signal detection and minimizing torque ripple-induced vibration and noise
2Measurement precision
If chopper amplifier is used to amplify Hall sensor signals, then offset voltage is compensated, but the magnetic field variation cannot be effectively reconstructed at higher rotation speeds
Solution Approach 1:
The system dynamically adjusts the sampling frequency according to the detected rotational speed. At higher rotation speeds, the sampling frequency is increased to capture the faster magnetic field variations, ensuring effective reconstruction of the magnetic field waveform while maintaining measurement accuracy across the full speed range
3Device complexity
If fixed sampling frequency is used in Time-Voltage Digital/Analog Converter, then circuit design is simplified, but torque changing rate increases and vibration or shock noise increases
Solution Approach 1:
The patent implements a dynamic sampling frequency adjustment mechanism that modifies the sampling rate based on the motor's rotational speed. This dynamic approach reduces torque changing rate and associated vibration and shock noise, while the control logic for frequency adjustment is integrated into the existing T/D-A converter framework to minimize additional circuit complexity
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 reduces vibration and shock noise by generating linearly rising and falling signals to smoothly control the motor's torque, enhancing operational stability and noise reduction.
Implementation Method 1
The brushless dc motor is also called the Hall motor or the DC Servo Motor, which utilizes a permanent magnet as its rotor and utilizes the Hall effect to detect the position of the rotor
Data Source
AI summary
The present invention discloses a brushless dc motor driver circuit capable of reducing vibration or shock noise and a method thereof. The brushless dc motor driver circuit of the present invention comprises a Time-Voltage Digital/Analog Converter. The Time-Voltage Digital/Analog Converter further comprises: at least one magnetic field detecting circuit, at least one counter, and a signal processor. The Time-Voltage Digital/Analog Converter is connected to a driver circuit of a brushless dc motor and detects the periodically varying magnetic field of the brushless dc motor. Based on the rising time and the falling time of the preceding magnetic field variation, the Time-Voltage Digital/Analog Converter calculates the elapsed time from the current phase-change point and generates a linearly rising signal and a linearly falling signal. Then, those two sets of analog signals are used to drive the brushless dc motor. Thereby, the vibration or shock noise of the brushless dc motor is reduced. Besides, the phase switching rate of the brushless dc motor can be modified via adjusting a first magnetic flux density and a second magnetic flux density of the Time-Voltage Digital/Analog Converter.