Motor Controller Phase Switching Detection
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Solution Overview
Problem
Conventional sensorless driving methods for three-phase motors face challenges in accurately detecting back electromotive force due to unstable floating phase pin voltage, often resulting in insufficient stabilization time, which complicates phase switching detection.
Innovation Solution
A motor controller with a switch circuit, driving circuit, and pulse width modulation circuit that utilizes different frequency pulse width modulation waveforms to stabilize the detection of phase switching time points by switching to a low-frequency waveform during detection, forming a Y-shaped configuration with three-phase coils and generating specific voltage vectors to manage phase switching and reduce current ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the motor controller utilizes the ON time interval of the pulse width modulation signal for detecting the phase switching time point, then the detection process is simplified, but if the ON time interval is too small, the floating phase pin voltage does not have enough time to stabilize, making it difficult to detect the back electromotive force
Solution Approach 1:
The patent dynamically adjusts the pulse width modulation signal frequency based on the detection phase. During back electromotive force detection, the frequency is reduced to extend the ON time interval, allowing sufficient stabilization time for the floating phase pin voltage. During normal motor operation, the frequency returns to its original higher value for efficient motor control. This dynamic frequency adjustment resolves the contradiction by adapting the ON time interval to the specific operational requirements of each phase.
Solution Approach 2:
The patent changes the frequency parameter of the pulse width modulation signal during the detection phase. By lowering the frequency, the ON time interval is extended, providing adequate time for the floating phase pin voltage to stabilize before detection. This parameter change allows the system to maintain both simplified detection methodology and accurate back electromotive force measurement.
2Stability of the object's composition
If the motor controller detects the phase switching time point before the falling edge of the pulse width modulation signal, then the floating phase pin voltage is in its most stable state, but the ON time interval becomes too small, resulting in insufficient stabilization time
Solution Approach 1:
The system dynamically modifies the pulse width modulation signal characteristics during detection phases. By temporarily reducing the frequency, the ON time interval is extended while maintaining the detection timing before the falling edge, thus preserving voltage stability throughout the extended period rather than compromising either stability or duration.
Solution Approach 2:
The patent extends the ON time interval through frequency reduction, providing preliminary stabilization time before the detection moment. This ensures the floating phase pin voltage reaches its stable state well before the actual detection occurs, enhancing both stability and providing adequate duration for the voltage to settle.
3Manufacturing precision
If the motor controller uses a high-frequency pulse width modulation waveform for driving the three-phase motor, then the motor control precision is improved, but the ON time interval becomes too short, making it difficult to detect the back electromotive force
Solution Approach 1:
The patent implements dynamic frequency switching between high-frequency mode for normal motor control and low-frequency mode for back electromotive force detection. During detection, the frequency is reduced to extend the ON time interval, while during normal operation, the high frequency provides precise motor control. This dynamic adjustment resolves the contradiction between control precision and detection capability.
Solution Approach 2:
The system employs periodic switching between high-frequency and low-frequency pulse width modulation modes. High-frequency operation provides precise motor control during normal phases, while periodic low-frequency intervals are introduced specifically for back electromotive force detection, allowing the system to maintain both high control precision and adequate detection time intervals.
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 approach allows for easier detection of back electromotive force and improved phase switching accuracy, reducing the risk of insufficient stabilization time and enhancing the success rate of phase switching detection in three-phase motor control.
Implementation Method 1
The pulse width modulation circuit receives a first pulse width modulation signal for generating a second pulse width modulation signal to the driving circuit
Implementation Method 2
the motor controller compares the floating phase pin voltage Vf with the reference voltage Vr, so as to detect the back electromotive force of the floating phase
Data Source
AI summary
A motor controller comprises a switch circuit and a driving circuit. The switch circuit is coupled to a three-phase motor for driving the three-phase motor. The driving circuit generates a plurality of control signals to control the switch circuit. The motor controller utilizes a first pulse width modulation waveform and a second pulse width modulation waveform for driving the three-phase motor, where the first pulse width modulation waveform and the second pulse width modulation waveform have different frequencies from each other. The motor controller utilizes the second pulse width modulation waveform to detect a phase switching time point, where the frequency of the first pulse width modulation waveform is greater than the frequency of the second pulse width modulation waveform.