Two-Coil Stepper Motor Drive Circuit with Dynamic Force Adjustment
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Solution Overview
Problem
Bi-directional rotation stepper motors require excessive drive force due to varying loads, leading to high power consumption and reduced battery life in electronic watches, as they need to account for maximum load conditions continuously.
Innovation Solution
A drive circuit for a two-coil stepper motor that includes a rotor, stator magnetic-pole portions, coils, a drive pulse generation circuit, a detection pulse generation circuit, and a rotation detection circuit, which outputs detection pulses to the coils to accurately determine rotor rotation, allowing for reduced drive force usage and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stepper motor is always driven with the drive force corresponding to the maximum load, then the stepper motor can rotate even when the maximum load is applied, but the stepper motor continuously consumes more power than necessary
Solution Approach 1:
The patent applies dynamics by making the drive force adjustable rather than fixed. The drive circuit dynamically changes the drive force level based on actual operating conditions - using high drive force when load exceeds a threshold and low drive force when load is within normal range. This resolves the contradiction by allowing the system to maintain reliability under maximum load while reducing power consumption during normal operation.
Solution Approach 2:
The patent changes the drive force parameter based on detected rotation status. When the rotor fails to rotate (indicating high load), the circuit switches to high drive force mode; when rotation succeeds, it switches to low drive force mode. This parameter adaptation allows the system to balance between ensuring rotation capability and minimizing power consumption.
2Measurement precision
If the detection pulse is output to both coils, then the success or failure of the rotor rotation can be determined with high accuracy, but the device complexity increases
Solution Approach 1:
The patent applies multi-functionality by using the same detection pulse generation circuit and detection resistor for both coils. The detection circuit processes signals from both coils through a unified path, allowing rotation detection accuracy to be improved while avoiding the complexity increase that would result from separate detection circuits for each coil.
Solution Approach 2:
The patent merges the detection functions for both coils into a single integrated detection circuit. By combining the detection paths and using common components (detection resistor, comparison circuit), the system achieves high rotation detection accuracy without duplicating circuit elements, thus preventing complexity increase.
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 high-speed bi-directional rotation with low power consumption, accurately detecting rotor rotation and reducing false detection, thereby extending battery life and improving reliability in electronic watches.
Implementation Method 1
a first coil, which is to be magnetically coupled to the first stator magnetic-pole portion and the third stator magnetic-pole portion; a second coil, which is configured to be magnetically coupled to the second stator magnetic-pole portion and the third stator magnetic-pole portion
Implementation Method 2
a detection pulse generation circuit, which is configured to output, to at least one of the first coil or the second coil, a detection pulse for detecting a counter-electromotive current generated in at least one of the first coil or the second coil
Data Source
AI summary
Provided is a drive circuit for a two-coil stepper motor, including: a rotor; a stator including first, second, and third stator magnetic-pole portions; a coil A to be magnetically coupled to the first stator magnetic-pole portion and the third stator magnetic-pole portion; a coil B to be magnetically coupled to the second stator magnetic-pole portion and the third stator magnetic-pole portion; a drive pulse generation circuit configured to output a drive pulse; a detection pulse generation circuit configured to output a detection pulse for detecting counter-electromotive currents generated in the coil A and the coil B; and a rotation detection circuit configured to receive a detection signal generated due to the detection pulse as input to determine whether or not the rotor has rotated.