Dual-Voltage Comparator Circuit for Faster Pixel AD Conversion

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Solution Overview

Problem

In solid-state image pickup devices, the limited area for circuit housing in pixels makes it difficult to produce a comparator that satisfies requirements, leading to decreased determining speed and increased power consumption, especially when performance is enhanced.

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 a data storage unit to store time codes when the compared result signal inverts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the comparator is designed to enhance performance in limited pixel area, then the determining speed may deaccelerate or power consumption may increase

Engineering Contradiction:

Improvecomparator performanceVSAvoiddetermining speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The comparator is divided into two functional segments: a differential input circuit operating at first power supply voltage for accurate comparison, and a positive feedback circuit operating at lower second power supply voltage for accelerated transition. This segmentation allows each part to optimize its function independently, resolving the contradiction between performance and speed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the power supply voltage parameter between different circuit stages. The differential input circuit uses first power supply voltage for accurate comparison, while the positive feedback circuit uses lower second power supply voltage for fast transition. This parameter change enables the circuit to achieve both high reliability and high speed without compromise.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the comparator is designed to enhance performance in limited pixel area, then power consumption may increase

Engineering Contradiction:

Improvecomparator performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The comparator operates in periodic cycles: during the comparison phase, the differential input circuit operates at first power supply voltage for accurate determination; during the transition phase, the positive feedback circuit operates at lower second power supply voltage for rapid switching. This periodic operation reduces average power consumption while maintaining performance.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If a single power supply voltage is used for the entire comparator, then circuit simplicity is maintained but determining speed and power efficiency are compromised

Engineering Contradiction:

Improvecircuit configurationVSAvoiddetermining speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

4Use of energy by moving object

If a single power supply voltage is used for the entire comparator, then power efficiency is maintained but determining speed decreases

Engineering Contradiction:

Improvepower efficiencyVSAvoiddetermining speed

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10498321B2Comparator, AD converter, solid-state image pickup device, electronic device, method of controlling comparator, data writing circuit, data reading circuit, and data transferring circuit

Publication Date: 2019.12.03 SONY GROUP CORP

AI summary

An imaging device for improving the determining speed of the comparator and reducing power consumption. The comparator includes a differential input circuit that operates with a first power supply voltage, the differential input circuit that outputs a signal when an input signal is higher than a reference signal in voltage, a positive feedback circuit that operates with a second power supply voltage lower than the first power supply voltage and accelerates transition speed when a compared result signal indicating a compared result between the input signal and the reference signal in voltage, is inverted, based on the output signal of the differential input circuit, and a voltage conversion circuit that converts the output signal of the differential input circuit into a signal corresponding to the second power supply voltage.