Comparator Circuit With Low-Voltage Feedback for Fast Image Sensing
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Solution Overview
Problem
In solid-state image pickup devices, the area housing circuits is limited in pixels, making it difficult to produce a comparator that satisfies requirements, leading to decreased determining speed and increased power consumption.
Innovation Solution
A comparator with a differential input circuit operating at a first power supply voltage, a positive feedback circuit operating at a lower second power supply voltage to accelerate transition speed, and a voltage conversion circuit to convert signals, along with an AD converter, solid-state image pickup device, electronic device, method of controlling the comparator, data writing and reading circuits, and data transferring circuits to improve determining speed and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the comparator is designed to improve determining speed, then the transition speed increases, but power consumption increases
Solution Approach 1:
The comparator is divided into two separate circuits: a differential input circuit that operates continuously at high voltage for fast response, and a positive feedback circuit that operates intermittently at low voltage to accelerate transitions. This segmentation allows each circuit to be optimized for its specific function, achieving fast determining speed while reducing overall power consumption.
Solution Approach 2:
The power supply voltage to the positive feedback circuit is dynamically changed based on the operation state. When a comparison is needed, the voltage is switched from a low second voltage to a high first voltage to accelerate the transition. When no comparison is active, the voltage returns to the low second voltage to reduce power consumption. This dynamic voltage adjustment resolves the contradiction between speed and power consumption.
2Area of stationary object
If the comparator area is reduced to fit in pixel, then area efficiency improves, but determining speed decreases
Solution Approach 1:
By segmenting the comparator into differential input and positive feedback circuits with different voltage requirements, the design achieves compact area while maintaining fast determining speed through the low-voltage positive feedback acceleration mechanism.
Solution Approach 2:
The invention changes the voltage parameter dynamically - using high first voltage for fast transitions when needed, and low second voltage for normal operation. This parameter change allows the compact comparator to achieve high determining speed only when required, reducing average power consumption while maintaining small area.
3Use of energy by moving object
If the power supply voltage is reduced to lower power consumption, then energy efficiency improves, but transition speed decreases
Solution Approach 1:
The positive feedback circuit dynamically switches between low second voltage (for power saving) and high first voltage (for fast transition acceleration). This dynamic voltage control allows the system to achieve low power consumption during normal operation while maintaining the capability for fast transitions when comparisons are performed.
Solution Approach 2:
The high voltage is applied periodically only when a comparison operation is initiated, rather than continuously. This periodic high-voltage application accelerates transitions only when needed, achieving fast transition speed on demand while maintaining low average power consumption during non-comparison periods.
Data Source
AI summary
An imaging device for improving the determining speed of a comparator and reducing power consumption. The comparator imaging device includes a differential input circuit that operates with a first power supply voltage, the differential input circuit outputs a signal when an input signal is higher than a reference signal in voltage, and a positive feedback circuit that operates with a second power supply voltage lower than the first power supply voltage. The positive feedback circuit accelerates transition speed when a compared result signal indicating a compared result between the input signal and the reference signal in voltage, is inverted, on the basis of the output signal of the differential input circuit. The imaging device further includes a voltage conversion circuit that converts the output signal of the differential input circuit into a signal corresponding to the second power supply voltage.