Motor Position Sensing Circuit Without Comparator Noise Issues
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Solution Overview
Problem
Existing motor position sensing systems in vehicles are costly and sensitive to variations in battery voltage and magnetic field sensor types, requiring multiple sensors and a comparator, which increases PCB footprint and susceptibility to noise and detection errors.
Innovation Solution
A system comprising a magnetic field sensor, a signal conditioning circuit with an AC-coupling and optional bandpass filter, and a controller that processes AC-coupled signals, eliminating the need for a comparator and reducing sensitivity to battery voltage and sensor type variations, while improving accuracy through active and inactive modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a comparator is used in the signal conditioning circuit, then the system can process magnetic field sensor signals, but the PCB footprint and cost increase
Solution Approach 1:
The patent removes the comparator from the signal conditioning circuit, extracting this component out of the system entirely. The controller directly processes the magnetic field sensor output signal without requiring a comparator, thereby reducing PCB footprint while maintaining signal processing capability
Solution Approach 2:
The controller is designed to perform multiple functions: it directly processes the magnetic field sensor output signal, initializes controller inputs based on stored sensor states, and manages motor position determination. This multi-functionality eliminates the need for dedicated comparator circuitry
2Ease of operation
If traditional signal conditioning is used, then the system can operate, but it is sensitive to battery voltage variations and magnetic field sensor type changes
Solution Approach 1:
The patent changes the signal conditioning approach by removing AC-coupling capacitors and level-shifting circuitry. The controller directly processes the magnetic field sensor output signal across a wide voltage range (4.75V to 5.25V), making the system robust to battery voltage variations and compatible with different magnetic field sensor types without requiring precise voltage matching
3Productivity
If the controller does not initialize inputs to stored sensor states, then the system operates continuously, but pulse counts may be missed affecting motor position accuracy
Solution Approach 1:
The controller performs preliminary action by storing the current state of each magnetic field sensor before entering inactive mode, and then initializing each controller input to the stored state when entering active mode from inactive mode. This preliminary initialization prevents missed pulse counts and ensures accurate motor position determination upon wake-up
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
Reduces PCB footprint and cost, enhances system robustness by minimizing noise interference, and improves motor position detection accuracy by preventing missed pulse counts.
Implementation Method 1
a magnetic field sensor configured to sense the position of a motor and provide an output signal
Implementation Method 2
a signal conditioning circuit configured to condition the output signal to produce an AC-coupled output signal
Implementation Method 3
the bandpass filter is configured to filter out at least some noise or ripple, reducing the likelihood of the noise or ripple causing detection errors by the controller
Data Source
AI summary
A system includes a controller, a magnetic field sensor, and a signal conditioning circuit. The magnetic field sensor is configured to sense a position of a motor and provide an output signal. The signal conditioning circuit is configured to produce an AC-coupled output signal from the output signal. The AC-coupled output signal is an input to the controller. The controller is configured to process the AC-coupled output signal.