Motor Driver PWM Timing at Commutation to Reduce Fan Noise
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Solution Overview
Problem
Conventional motor drivers generate unpredictable pulse width modulation signal frequencies, leading to noise and vibration in motors used for cooling heat-generating components in electronic devices.
Innovation Solution
A motor driver circuit comprising a motor position detecting circuit, commutation control circuit, and pulse width modulation calculating circuit that sets pulse width modulation signals at commutation time points, aligning signal intervals with phase control signals to maintain a low current level during dead time and ensure stable motor operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional motor drivers set pulse width modulation signals according to commutation messages, then the motor can be driven to rotate, but the frequencies of the pulse width modulation signals change unexpectedly causing noise
Solution Approach 1:
The patent applies preliminary action by setting the pulse width modulation signal frequency based on the commutation signal frequency in advance. Specifically, the control circuit determines the PWM frequency according to the detected commutation signal frequency before generating the PWM output, ensuring that the PWM frequency remains synchronized with the motor's rotational state and preventing unexpected frequency changes that cause noise
Solution Approach 2:
The patent implements feedback by continuously monitoring the commutation signal frequency and using it to adjust the pulse width modulation signal frequency. The control circuit receives feedback from the commutation signal and dynamically sets the PWM frequency accordingly, creating a closed-loop control system that maintains stable operating frequencies and eliminates noise caused by frequency drift
2Productivity
If pulse width modulation signals are generated without aligning with commutation time points, then the motor driver can operate continuously, but current levels fluctuate causing instability during dead time
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the pulse width modulation signal timing with the commutation signal timing. The control circuit calculates and sets the PWM signal start time and duration based on the commutation signal characteristics before the actual PWM generation, ensuring that PWM pulses are properly aligned with commutation events and maintaining stable current levels during dead time periods
Solution Approach 2:
The patent implements periodic action by generating pulse width modulation signals with regular periodic intervals that are synchronized to the motor's commutation cycle. The control circuit produces PWM pulses at consistent periodic intervals aligned with each commutation event, ensuring predictable and stable current flow patterns throughout continuous motor operation
Data Source
AI summary
A motor driver of setting pulse width modulation at commutation time points of a motor is provided. A commutation control circuit outputs a phase control signal and a commutation starting signal according to a preset phase angle and a commutation signal of the motor. A pulse width modulation calculating circuit determines a starting time point of each of a plurality of cycles of a pulse width modulation signal according to the commutation starting signal. The pulse width modulation calculating circuit determines time of each of the plurality of cycles of the pulse width modulation signal according to the phase control signal. The pulse width modulation calculating circuit determines widths of a plurality of pulse waves of the pulse width modulation signal according to a target rotational speed of the motor. A motor driver circuit drives the motor according to the pulse width modulation signal.