Window Comparator Circuit for Single-Comparator Tri-State Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional window comparator circuits for optical pointing devices, such as computer mice, require multiple electronic components and struggle to accurately perform tri-state comparisons due to the need for two comparators, leading to inefficiencies and residual offset issues.
Innovation Solution
A method utilizing a single output comparator successively to minimize residual offsets and reduce electronic components, with a symmetrical window around a differential voltage of 0V, allowing for easy programming of window voltage adjustments through capacitive ratio adaptation, and using a single reference voltage for the window function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two comparators are used to perform window comparison with hysteresis, then tri-state detection capability is achieved, but device complexity increases due to too many electronic components
Solution Approach 1:
The patent combines the functions of two separate comparators into a single comparator by implementing a window comparison mechanism that uses one comparator to evaluate whether an input signal falls within a defined window range bounded by upper and lower threshold voltages. This merging reduces the number of electronic components while maintaining tri-state detection capability (indicating whether the signal is above, within, or below the window range).
Solution Approach 2:
The single comparator is designed to perform multiple functions: it compares the input signal against both upper and lower threshold voltages, implements hysteresis to prevent chatter at boundaries, and generates tri-state output. This multi-functional design eliminates the need for separate comparators while achieving the same detection capability.
2Measurement precision
If two comparators are used to define tri-state comparison function, then detection accuracy is improved, but manufacturing precision becomes difficult due to matching issues
Solution Approach 1:
By merging the comparison functions into a single comparator, the patent eliminates the need to match two separate comparators. The single comparator inherently provides consistent comparison behavior against both upper and lower thresholds, removing the manufacturing precision issues associated with matching multiple comparators while maintaining accurate tri-state detection.
Solution Approach 2:
The patent introduces threshold voltage generation circuitry as an intermediary that provides stable upper and lower reference voltages to the single comparator. This intermediary mechanism ensures consistent comparison references without requiring precise matching of multiple active comparator components, thereby improving manufacturability while maintaining measurement precision.
3Adaptability or versatility
If multiple comparators are used in the comparator array, then window function capability is achieved, but the number of electronic components increases excessively
Solution Approach 1:
The patent merges the window function capability that would traditionally require multiple comparators into a single comparator implementation. By using one comparator to evaluate the input signal against dynamically generated upper and lower thresholds, the system achieves window comparison functionality with minimal components, maintaining adaptability while reducing complexity.
Solution Approach 2:
The patent implements dynamic threshold voltage generation where the upper and lower comparison thresholds are generated adaptively based on the input signal and hysteresis requirements. This dynamic approach allows a single comparator to achieve the versatility of multiple fixed-threshold comparators, enabling window function capability without the component overhead.
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The method performs a tri-state comparison of two input signals (VINN, VINP) in a window comparator circuit (1). In a first phase, a first input voltage is stored on a first capacitor (C1n), a ground voltage is stored on a second capacitor (C2n), an offset voltage (Offset) is stored on a third capacitor (C2p), and a second input voltage is stored on a fourth capacitor (C1p). A comparison in a comparator (2) is performed between the first adapted input voltage and the second adapted input voltage added to the adapted offset voltage, to provide a first output signal (OUT1). In a second phase, the first input voltage is stored on the first capacitor, the offset voltage is stored on the second capacitor, the ground voltage is stored on the third capacitor, and the second input voltage is stored on the fourth capacitor. A comparison in the comparator is performed between the first adapted input voltage added to the adapted offset voltage and the second adapted input voltage, to provide a second output signal (OUT2). Finally a control of the state of the first and second output signals is performed to determine if the comparison of the first and second input signals is in a low state or in a high state if the first and second output signals have a same low or high output level, or in an intermediate state if the first and second output signals have a different output level.