Step Motor Detection Circuit for Electronic Watch
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Solution Overview
Problem
Existing electronic watches with step motors for analog displays face challenges in accurately detecting rotor rotation fluctuations, leading to unstable high-speed driving and reduced battery life due to inefficient power usage, especially under disturbances like external magnetic fields.
Innovation Solution
An electronic watch with a driving interval switch circuit that adjusts detection conditions between normal and high-speed driving intervals, using a detection resistor with lower resistance and stricter threshold settings during high-speed driving to quickly judge non-rotation and optimize driving force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed detection condition is used for step motor rotation detection, then the detection method is simple, but the rotation state cannot be detected accurately under disturbances like external magnetic fields
Solution Approach 1:
The patent applies dynamics by switching between two different detection conditions based on the driving mode. During fast-forward driving, the first detection condition is used which detects reverse induced power at a timing after a predetermined period from driving pulse output. During normal driving, the second detection condition is used which detects reverse induced power at a different timing. This dynamic switching allows accurate rotation detection under different operating conditions, resolving the contradiction between simple detection and accurate detection under disturbances.
Solution Approach 2:
The patent changes detection parameters (detection timing) based on driving mode. By adjusting when the reverse induced power is detected relative to the driving pulse output, the system optimizes detection accuracy for each mode. This parameter change enables accurate rotation state detection under external magnetic field disturbances while maintaining simple detection methodology.
2Reliability
If more driving power is supplied to the step motor during fast-forward operation, then high-speed driving stability is improved, but battery life is reduced
Solution Approach 1:
The patent uses feedback by detecting the reverse induced power generated by the step motor during rotation and using this information to control the driving pulses. The rotation detection circuit monitors the actual rotation state and provides feedback to the driving control, allowing the system to supply only the necessary driving power for stable fast-forward operation rather than excessive power, thus extending battery life while maintaining stability.
Solution Approach 2:
The step motor generates reverse induced power during rotation that is detected and used to determine subsequent driving pulse timing. This self-generated signal serves the dual purpose of indicating rotation status and controlling the driving rhythm, eliminating the need for separate sensing mechanisms and enabling efficient power management that extends battery life.
3Device complexity
If a predetermined fixed delay period is used before outputting the next driving pulse, then the detection timing is simple, but the fast-forward operation speed is limited
Solution Approach 1:
The patent applies dynamics by making the delay period before outputting the next driving pulse variable rather than fixed. During fast-forward operation, the system uses a first predetermined period, while during normal driving, it uses a second predetermined period. This dynamic adjustment of timing allows higher operation speeds during fast-forward mode while maintaining simple detection timing methodology, resolving the contradiction between simplicity and speed.
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 stable high-speed driving at low power consumption by quickly detecting rotation speed decreases and strengthening the driving force, thereby optimizing step motor performance and extending battery life.
Implementation Method 1
assuming that reverse induced power excited by rotation of the rotor is a current or a voltage
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
Anelectronicwatch (1) includes: a step motor (30) ; a driving pulse generator circuit (5) configured to output a driving pulse (SP) for driving the step motor; a detection pulse generator circuit (10) configured to output a detection pulse for detecting rotation of the step motor; a correction pulse generator circuit (6) configured to output a correction pulse (FP) ; a pulse selection circuit (7) configured to select and output the driving pulse, the detection pulse, and the correction pulse (FP); a driver circuit (20) configured to supply to the step motor the outputs from the pulse selection circuit (7); and a rotation detection circuit (40) configured to receive a detection signal generated by the detection pulse (CP) to judge rotation of the step motor. The electronic watch (1) further includes a driving interval switch circuit (4) configured to switch a driving interval of the driving pulse (SP) between a normal driving interval and a high-speed driving interval. The rotation detection circuit (40) is capable of changing a detection condition by the driving interval switch circuit (4).