Comparator Circuit Power Reduction via Segmented Comparison
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Solution Overview
Problem
Existing image capturing apparatuses do not sufficiently reduce power consumption during the analog-to-digital conversion period, particularly for the comparators, as the current consumption of the first amplifier is not effectively minimized in previous designs.
Innovation Solution
The apparatus includes a pixel, an analog-to-digital conversion unit with an offset imparting unit, a first comparator, and a second comparator, where the second comparator is in a non-operating state until the signal level of the first comparison result signal changes, and the current consumption per unit time of the first comparison is lower than that of the second comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the second comparator operates continuously during the analog-to-digital conversion period, then the comparison accuracy is maintained, but the current consumption per unit time increases
Solution Approach 1:
The comparison process is divided into two stages: first comparison (during the entire analog-to-digital conversion period) and second comparison (only after the first comparison result signal changes). This segmentation allows the second comparator to remain inactive during the initial period, reducing current consumption while maintaining overall comparison accuracy through the two-stage approach.
Solution Approach 2:
The first comparison is performed preliminarily during the analog-to-digital conversion period to prepare the comparison result. This preliminary action allows the second comparator to be activated only when needed, rather than operating continuously, thus reducing energy consumption while ensuring accuracy is maintained when the second comparison is performed.
2Use of energy by moving object
If the second comparator is in a non-operating state until the first comparison result signal changes, then the current consumption per unit time is reduced, but the device complexity increases
Solution Approach 1:
The comparator functionality is segmented into two distinct comparators with different operational roles. The first comparator operates continuously to generate the control signal, while the second comparator operates selectively. This segmentation manages the complexity by distributing functions across two components rather than requiring a single complex comparator with dynamic control logic.
Solution Approach 2:
The first comparison result signal acts as an intermediary control signal that mediates between the continuous operation requirement and the energy saving goal. It automatically controls when the second comparator should be activated, eliminating the need for complex control logic while achieving both energy reduction and functional requirements.
3Use of energy by moving object
If the current consumption of the first comparator is reduced, then the overall power consumption decreases, but the comparison speed may be affected
Solution Approach 1:
The comparison function is segmented between two comparators with different current consumption characteristics. The first comparator operates at lower current consumption continuously, while the second comparator operates at higher current consumption only when needed. This segmentation allows the system to achieve low average power consumption while maintaining comparison speed capability when the second comparator is activated.
Solution Approach 2:
The second comparator operates periodically rather than continuously, activating only after the first comparison result signal changes. This periodic operation pattern allows the system to reduce average power consumption significantly while ensuring that comparison speed requirements are met during the active periods when the second comparator is operating at higher current.
Data Source
AI summary
An image capturing apparatus includes a comparison circuit unit including a first comparator and a second comparator. The second comparator is kept in a non-operating state until the signal level of a first comparison result signal from the first comparator changes and is brought into an operating state in correspondence with a change in the signal level of the first comparison result signal.