Two-Coil Stepper Motor Drive Circuit Impact Detection
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Solution Overview
Problem
Two-coil stepper motors face challenges in accurately detecting and correcting deviations caused by external impacts, as existing technologies struggle to accurately detect impacts regardless of rotor rotation direction, leading to potential time deviation and mechanical instability.
Innovation Solution
A drive circuit for a two-coil stepper motor that includes a detection pulse generation circuit capable of outputting detection pulses to both coils, allowing for simultaneous detection of counter-electromotive currents regardless of rotor direction, and a lock pulse generation circuit to brake the rotor and correct deviations, ensuring accurate impact detection and prevention of time deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If impact compensation means is added to detect and correct rotor deviation, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent makes one of the two drive coils serve dual purposes: it functions as both a drive coil for rotating the rotor and as a detection coil for detecting counter-electromotive force during impact events. This multi-functionality eliminates the need for a separate detection coil, reducing circuit complexity while maintaining impact detection and correction capabilities
Solution Approach 2:
The system uses the existing coil structure and counter-electromotive force generation to detect impacts, rather than requiring external sensors or additional detection mechanisms. The coil itself provides the detection function through the counter-electromotive force it generates during rotor movement, enabling self-diagnosis and self-correction of impact-induced deviations
2Manufacturing precision
If detection and correction mechanisms are implemented, then timekeeping accuracy is improved, but power consumption increases
Solution Approach 1:
The impact detection and correction operates periodically rather than continuously. The control circuit detects counter-electromotive force during specific detection periods when impacts may occur, and only activates correction pulses when deviations are detected. This periodic operation significantly reduces power consumption compared to continuous monitoring while maintaining accurate timekeeping
Solution Approach 2:
The system recovers and utilizes the counter-electromotive force that is naturally generated during rotor movement for detection purposes, rather than discarding it as waste energy. By harvesting this existing electrical signal for impact detection, the system avoids additional power consumption that would result from using external sensors or active detection mechanisms
3Device complexity
If one coil is used for both drive and detection, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies drive pulses with excessive amplitude or duration beyond the minimum required for rotor rotation, creating a distinct baseline counter-electromotive force pattern. During detection periods, any deviations from this expected pattern indicate impacts. The excessive action provides a stronger signal for detection, compensating for the fact that the same coil is used for both drive and detection functions
Solution Approach 2:
The control circuit continuously monitors the counter-electromotive force generated by the coil and compares it against expected values during drive operation. When deviations indicating impacts are detected, the system provides feedback by generating correction pulses to realign the rotor. This closed-loop feedback mechanism ensures accurate impact detection and correction despite using a single coil for dual purposes
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 enables reliable detection and correction of impacts, enhancing the stepper motor's resistance to external influences and maintaining accurate timekeeping, while also improving visibility and design flexibility in analog indication electronic clocks.
Implementation Method 1
a first coil to be magnetically coupled to the first stator magnetic-pole portion and the third stator magnetic-pole portion; a second coil to be magnetically coupled to the second stator magnetic-pole portion and the third stator magnetic-pole portion
Implementation Method 2
capable of outputting detection pulses to at least one of the first coil or the second coil in order to detect a counter-electromotive current that is generated in accordance with a rotational angle of the rotor
Data Source
Figure 1
Figure 2
Figure 3(a)~3(e)
AI summary
Provided is a drive circuit for a two-coil stepper motor, including a rotor (41) that is magnetized to an N-pole and an S-pole, first, second, and third stator magnetic-pole portions (42), a coil A, and a coil B. The drive circuit includes a drive pulse generation circuit (4) configured to output a drive pulse (SP) for driving the coil A and the coil B, a detection pulse generation circuit (6) configured to output a detection pulse (CP) to the coil A and the coil B in order to detect counter-electromotive currents generated in the coil A and the coil B along with a movement of the rotor after the rotor is driven based on the drive pulse, and a detection circuit (30) configured to receive a detection signal (CS) generated based on the detection pulse as input, to thereby detect the movement of the rotor (41) . At least one of the detection pulse to the coil A or the detection pulse to the coil B is output.