Motor Controller Zero Point Detection Noise Reduction
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Solution Overview
Problem
Conventional motor controllers face challenges in reducing motor noise due to back electromotive force during motor rotation, with P-type pulse width modulation mode being difficult to design and N-type mode having complex zero-point detection methods, limiting the effective use of both modes.
Innovation Solution
A motor controller with an H-bridge switch circuit, pre-driver, phase detecting unit, control unit, and comparator, which facilitates zero-point detection of motor current by comparing voltages across motor terminals, allowing for efficient detection and phase switching to reduce noise and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If P-type pulse width modulation mode is used to drive the motor, then the zero point detection method is simple (comparing terminal S voltage), but the driving method is difficult to design
Solution Approach 1:
The patent segments the control into two independent parts: the pre-driver generates PWM signals for the H-bridge switches, while the comparator independently detects zero points by monitoring terminal voltages. This segmentation allows P-type PWM's simple detection method to be used without complicating the overall control design.
Solution Approach 2:
The patent introduces a pre-driver as an intermediary component between the control unit and the H-bridge circuit. The pre-driver handles the complex PWM generation and switch control, while the control unit focuses on zero point detection through voltage comparison. This intermediary simplifies the design burden on the main control unit.
2Ease of manufacture
If N-type pulse width modulation mode is used to drive the motor, then the driving method is easy to design, but the zero point detection method is complicated (comparing terminal VCC voltage)
Solution Approach 1:
Instead of detecting zero points by comparing against VCC voltage (the conventional N-type method), the patent inverts the approach by comparing terminal voltages against each other or against a reference derived from the H-bridge state. This allows using the simpler P-type detection methodology while maintaining N-type PWM's design simplicity.
3Device complexity
If phase switching is performed without considering back electromotive force, then the control is simple, but mechanical noise increases due to motor current at switching time
Solution Approach 1:
The patent performs preliminary zero point detection before phase switching occurs. By continuously monitoring terminal voltages and detecting when current reaches zero, the system prepares for optimal switching moments, eliminating noise without requiring complex real-time control adjustments during switching.
Solution Approach 2:
The patent implements feedback by using the comparator to continuously monitor terminal voltages and generate detection signals that feed back to the control unit. This feedback mechanism provides real-time information about motor current status, enabling noiseless switching while maintaining relatively simple control logic.
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
Enables effective detection of the zero point of motor current, allowing for reduced motor noise and improved motor control efficiency by combining the advantages of N-type and P-type pulse width modulation modes.
Implementation Method 1
the comparator is configured to detect the zero point of the motor current by comparing a voltage of the first terminal with a voltage of the terminal S or by comparing a voltage of the second terminal with the voltage of the terminal S
Data Source
AI summary
A motor controller configured to reduce the motor noise by detecting the zero point of the motor current is disclosed. The motor controller comprises a switch circuit, a pre-driver, a phase detecting unit, a control unit, a comparator, a first resistor, and a second resistor. The switch circuit is an H-bridge circuit. The switch circuit includes a first upper-side switch, a second upper-side switch, a first lower-side switch, and a second lower-side switch. When the motor controller performs the last pulse width modulation driving with respect to the first lower-side switch before phase switching, the second upper-side switch is turned off and the first lower-side switch is kept turning on, so as to facilitate the detection of the zero point of the motor current.