Zero-crossing Detection Circuit for Brushless Motor Noise Rejection
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Solution Overview
Problem
Existing zero-crossing detection circuits in brushless motors suffer from detection errors and vibration due to hysteresis characteristics, leading to reduced motor efficiency and uneven rotation.
Innovation Solution
A zero-crossing detection circuit with a first comparison circuit, a second comparison circuit having a hysteresis function, and a logic circuit that accurately determines the zero-crossing point by processing input signals and removing noise influences, achieving high accuracy with a simple and compact configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hysteresis characteristics are used to prevent chattering near the zero-crossing, then the stability of the output signal is improved, but the measurement precision of the zero-crossing position deteriorates
Solution Approach 1:
The patent divides the zero-crossing detection function into two separate comparison circuits: a first comparison circuit that provides hysteresis to prevent chattering and ensure output stability, and a second comparison circuit that detects the actual zero-crossing position with high precision. This segmentation allows each circuit to specialize in one aspect, resolving the contradiction between stability and precision.
Solution Approach 2:
The patent introduces a timing circuit as an intermediary between the two comparison circuits. The timing circuit generates a detection window that enables the second comparison circuit to accurately capture the zero-crossing position without being affected by the hysteresis of the first comparison circuit. This intermediary mechanism协调s the conflicting requirements of stability and precision.
2Device complexity
If a simple comparison circuit is used for zero-crossing detection, then the device complexity is reduced, but the reliability of noise rejection deteriorates
Solution Approach 1:
The patent segments the noise rejection function into two independent comparison circuits with different characteristics. The first comparison circuit with hysteresis filters out noise and prevents chattering, while the second comparison circuit detects the precise zero-crossing point. This segmentation achieves reliable noise rejection without requiring a single complex circuit design.
Solution Approach 2:
The patent changes the operational parameters of the two comparison circuits: the first circuit uses hysteresis voltage to reject noise and stabilize output, while the second circuit operates without hysteresis to achieve precise zero-crossing detection. By adjusting these parameters differently in each circuit, the system achieves both noise rejection and detection accuracy.
Data Source
AI summary
Provided is a zero-crossing detection circuit capable of detecting zero-crossing with high accuracy without being influenced by noise. The zero-crossing detection circuit includes a first comparison circuit, a second comparison circuit having a hysteresis function, and a logic circuit. The first comparison circuit is configured to output a zero-crossing detection result of a first input signal and a second input signal. The second comparison circuit is configured to output a comparison result of the first input signal and the second input signal. The logic circuit includes a unit configured to determine whether to reflect the zero-crossing detection result to output of the logic circuit based on the zero-crossing detection result and the comparison result.