Sine-Cosine Position Circuit With Three-Comparator Interpolation
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Solution Overview
Problem
Existing position determination systems using sine and cosine analogue signals are limited by the need for numerous precision comparators, which restricts accuracy and increases circuit size due to offset voltage limitations.
Innovation Solution
A circuit for position determination using two analogue sine signals in quadrature, requiring only three precision comparators, achieves segmentation and interpolation through a first and second segmentation circuit, with a capacitor charging current generation mechanism to produce a pulse-width modulated position signal, allowing for precise phase angle determination with reduced component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital interpolation with N states is implemented, then position determination accuracy is improved, but the number of precision comparators increases to N-1, limiting attainable N due to offset voltage and restricting accuracy
Solution Approach 1:
The circuit segments the periodic sine and cosine signals into multiple intervals using only three precision comparators. By dividing the signal period into segments and processing each segment separately with simple threshold comparisons, the system achieves high-resolution position determination without requiring N-1 comparators for N states.
Solution Approach 2:
The invention transitions from digital interpolation in the time domain to analogue time-interval measurement in the frequency domain. By measuring the time interval between comparator trigger events rather than comparing multiple discrete voltage levels, the system achieves high accuracy with minimal comparators.
2Measurement precision
If numerous precision comparators are used to achieve high accuracy, then position determination precision is improved, but circuit size increases significantly
Solution Approach 1:
The circuit segments the periodic sine and cosine signals into multiple intervals using only three precision comparators. By dividing the signal period into segments and processing each segment separately with simple threshold comparisons, the system achieves high-resolution position determination without requiring N-1 comparators for N states.
3Measurement precision
If precision comparators are used, then measurement accuracy is improved, but the offset voltage of comparators limits the attainable number of states N
Solution Approach 1:
The invention replaces the mechanical/voltage-based comparison system with a time-based measurement system. Instead of comparing multiple voltage levels simultaneously (which is sensitive to comparator offset voltage), the system measures the time interval between trigger events, which is much less sensitive to offset voltage and achieves higher reliability.
Data Source
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AI summary
It consists of a circuit for a first segmentation, which generates a third signal (s3) from a time dependence function of that one of a first and a second signal which has a higher voltage at the moment and generates a fourth signal from that one which has a lower voltage at the moment and of a circuit for a second segmentation, which consists of a circuit (21) for a charging current generation the charging current having such time dependence that in each charging cycle a voltage across a capacitor (22) increases linearly during intervals of equal time duration and which time intervals are defined by border points situated on a sine curve, the capacitor (22), of an adaptive timer (23) which discharges the capacitor (22) each time when the voltage across it has reached the instantaneous voltage of the third signal (s3) and of a comparator (24), to whose input terminals the capacitor voltage (Uc) and the fourth signal (s4) are conducted and at whose output the position signal (so) appears. The proposed circuit needs just three precision comparators, therefore it is smaller than a known circuit with the same 10-bit accuracy.