Intermittent Rotation Sensing to Cut Vehicle Off-State Current
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Solution Overview
Problem
Existing rotation detection devices consume excessive current when the ignition switch is off due to continuous power supply to the rotation detection unit, even when no rotation is occurring, leading to increased dark current consumption.
Innovation Solution
The rotation detection device intermittently supplies power to the rotation sensor unit when the ignition switch is off, adjusting the intermittent interval based on the presence or absence of rotation information, and stores this information for transfer to the controller when the switch is turned on again, using a configuration with multiple power supply units to manage voltage and reduce current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power is continuously supplied to the rotation sensor unit when the ignition switch is off, then rotation information can be detected without interruption, but current consumption increases due to dark current
Solution Approach 1:
The power supply to the rotation sensor unit is made periodic rather than continuous. The control unit supplies power at specific intervals by activating the second power supply unit based on predetermined conditions, such as when rotation is detected or when the ignition switch transitions from off to on. This periodic power supply reduces dark current consumption while ensuring rotation information is captured when needed.
2Measurement precision
If the rotation sensor unit operates continuously, then accurate rotation detection is maintained, but the device complexity increases due to requiring multiple power supply units with different resolutions
Solution Approach 1:
The rotation sensor unit is designed to function under multiple power supply conditions. It can operate with either the first power supply unit (connected to the battery via the ignition switch) or the second power supply unit (connected to the battery directly). The sensor unit maintains its detection capability across different power supply modes, eliminating the need for separate detection circuits for each mode and thereby reducing overall device complexity.
Data Source
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AI summary
Provided is a rotation detection device including: a power supply unit configured to output constant power supply; a rotation sensor unit configured to output a detection signal that depends on rotation of a vehicle; and a controller configured to calculate on-time rotation information on the vehicle, which is information at a time when an ignition switch is on, to control a motor, in which the rotation detection device further includes a calculation unit configured to calculate off-time rotation information on the vehicle by intermittently supplying a power supply voltage to the rotation sensor unit when the ignition switch is off, update a set value of an intermittent interval so that the set value becomes smaller when the off-time rotation information contains information indicating rotation of a motor for the vehicle, and update the set value of the intermittent interval so that the set value becomes larger when the off-time rotation information does not contain information indicating rotation of the motor for the vehicle.