Motor Driving Circuit Leading Angle Control for BEMF Noise
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Solution Overview
Problem
Existing motor driving circuits face challenges in preventing noise during rapid changes in output rotation speed, particularly due to misjudgment of the back electromotive force (BEMF) zero point and prolonged phase current discontinuity, which leads to noise and errors in sensorless motor control.
Innovation Solution
A motor driving circuit and method that includes a rotation speed request generator, motor driving signal generating unit, inverter circuit, position detecting circuit, current detecting module, rotation speed signal lookup module, automatic leading angle controller, and modulation signal generating circuit, which adjusts the leading angle to ensure the current zero-crossing point occurs ahead of the BEMF zero point, reducing noise and discontinuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the BEMF zero point measurement is performed by stopping transmission of output drive signal and waiting for current to completely flow through coil, then measurement accuracy is improved, but during rapid switching variation of rotation speed, the BEMF zero point may be misjudged when phase current has not completely flowed out
Solution Approach 1:
The patent applies preliminary action by outputting the driving voltage at a maximum leading angle when rotation speed changes, which causes the phase current zero point to appear earlier. This preliminary adjustment ensures that the current has sufficiently decayed before BEMF zero point measurement begins, preventing misjudgment during rapid speed changes while maintaining measurement accuracy
2Reliability
If the driving voltage is output directly at a maximum leading angle when rotation speed changes, then the phase current zero point can appear earlier to avoid misjudgment, but a duration of the phase current discontinuity may be too long, thereby causing noise
Solution Approach 1:
The patent applies dynamics by implementing an automatic leading angle controller that dynamically adjusts the leading angle based on rotation speed. During rapid speed changes, the leading angle is increased to ensure current decay, but during normal operation, the leading angle is reduced to minimize phase current discontinuity duration and noise. This dynamic adjustment resolves the contradiction between reliability and noise generation
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 and ensures accurate BEMF zero point detection by determining the lead angle through a lookup table, making the current zero-crossing point appear earlier and adjusting it to align with the BEMF zero point, thereby minimizing errors and discontinuous regions.
Implementation Method 1
The position detecting circuit is configured to receive a plurality of back electromotive force (BEMF) signals from the plurality of phase circuits and generate a position reference signal for indicating a back electromotive force (BEMF) zero point of the motor
Data Source
AI summary
A motor driving circuit includes a rotation speed request generator, a motor driving signal generating unit, an inverter circuit, a position detecting circuit, a current detecting module, a rotation speed signal lookup module, an automatic leading angle controller, and a modulation signal generating circuit. When the rotation speed request signal indicates that a rotation speed of a motor is adjusted to a current rotation speed, the rotation speed signal lookup module queries a lookup table and generates a leading angle indication signal for indicating a current leading angle as a adjusting angle, and the automatic leading angle controller generates a phase adjusting signal, and the modulation signal generation circuit roughly adjusts a modulation waveform with the adjusting phase. The modulation signal generating circuit performs a fine adjustment on the modulation waveforms according to a phase difference, thereby making the current zero-crossing point near the BEMF zero point.