Motor Control Circuit Reducing Phase Switching Noise
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Solution Overview
Problem
Conventional motor control circuits generate loud noise when the coil phase changes in motor speed control, particularly in fan motors, limiting their usage due to noise issues.
Innovation Solution
A motor control circuit comprising a Hall element, a separated signal generating circuit, a comparator, and a coil switching circuit, which generates a motor speed control signal with square pulses where the width of pulses near the center is greater than those farther from the center, reducing noise by comparing phase signals and using pulse width modulation to control motor speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional motor control circuits use standard pulse width modulation to control motor speed, then the motor speed can be effectively controlled, but loud noise occurs when the coil phase changes
Solution Approach 1:
The patent applies periodic action by using non-uniformly distributed pulse sequences instead of uniform periodic pulses. The pulse widths are deliberately varied within each phase cycle, with wider pulses near the center of the phase and narrower pulses at the edges, creating a periodic but non-uniform modulation pattern that reduces noise during phase transitions while maintaining effective motor speed control
Solution Approach 2:
The patent changes the temporal parameters of the control signal by using variable pulse widths within each phase cycle. Instead of using equal-width pulses, the system employs pulses with different widths depending on their position within the phase cycle, thereby altering the signal characteristics to reduce noise during coil phase changes while preserving speed control functionality
2Device complexity
If the motor speed control signal uses uniform square pulses, then the control circuit is simple, but noise is generated during phase switching
Solution Approach 1:
The patent modifies the pulse parameter distribution within each phase cycle without fundamentally changing the control circuit architecture. By varying the pulse widths in a specific pattern (wider near phase center, narrower at edges) while maintaining the overall square pulse format, the system reduces phase switching noise while keeping the control circuit relatively simple
3Use of energy by moving object
If standard PWM modulation is used to decrease motor speed, then energy consumption is reduced, but the noise problem during phase change persists
Solution Approach 1:
The patent combines energy-efficient PWM modulation with non-uniform periodic pulse distribution. The pulse sequences are arranged periodically within each phase cycle but with varying widths, maintaining the energy-saving benefits of PWM while addressing the noise issue through strategic pulse width variation that reduces electromagnetic interference during phase transitions
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 effectively reduces noise during motor phase changes, enhancing the operational quietness and performance of fan motors by modulating the motor speed control signal, thereby improving their usability in quiet environments.
Implementation Method 1
Hall element 12 detects signals generated by the motor (not shown in the figure), such as the phase switching signal generated during the rotation of the motor, and generates a phase signal wherein the phase thereof is consistent with the rotation phase of the motor
Implementation Method 2
The comparator is coupled to the Hall element and the separated signal generating circuit and compares the first phase signal and the separated signal to generate a first control signal
Implementation Method 3
When receiving the motor speed control signal from driving circuit 10, coil switching circuit 14 outputs the motor speed control signal to the coil 20 in the motor accordingly and thereby switches the current directions in two neighboring phases of the coil 20, maintaining rotation of the motor
Implementation Method 4
a pulse width modulation (PWM) generator 16 is provided to modulate the motor speed control signal into a plurality of small periodic square pulses as shown in FIG. 3. According to the equivalence principle, the amplitude of the equivalent motor speed control signal is smaller than that of the original motor speed control signal as shown in FIG. 4 and thus the motor speed is decreased
Data Source
AI summary
A motor control circuit and method thereof serving a coil for controlling the motor. The motor control circuit comprises a separated signal generating circuit generating a separated signal and a comparator comparing a first phase signal from a Hall element or a second phase signal from a phase signal generating circuit with the separated signal. Thus, a motor speed control signal is generated to control the motor. The noise is reduced during controlling the motor.