Comparator-Counter ADC Switching Speed by Luminance

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Solution Overview

Problem

Photoelectric conversion apparatuses face high power consumption due to fixed operation of the counter circuit regardless of incident light luminance, which is inefficient and wasteful.

Innovation Solution

The analog-to-digital conversion circuit employs a comparator circuit and counter that switch between high-speed and low-speed operation periods based on luminance, adjusting resolution and operating frequency to optimize power usage, with the counter circuit performing count processing in parallel with comparison processing and switching between different resolutions and frequencies accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the counter circuit operates at fixed high speed regardless of luminance, then measurement precision is maintained, but power consumption increases

Engineering Contradiction:

ImproveAD conversion precisionVSAvoidcounter circuit power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The counter circuit dynamically adjusts its operating speed based on luminance conditions. During first period (low luminance), the counter operates at high speed to maintain precision. During second period (high luminance), the counter operates at low speed to reduce power consumption. This dynamic adaptation resolves the contradiction between maintaining measurement precision and reducing power consumption.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The operating parameters of the counter circuit (clock frequency, counting speed) are changed based on luminance levels. The control circuit switches between high-speed mode and low-speed mode, altering the counter's operational parameters to match lighting conditions, thereby achieving both precision maintenance and power savings.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the counter circuit operates at high speed continuously, then conversion speed is maintained, but power consumption increases

Engineering Contradiction:

ImproveAD conversion speedVSAvoidcounter circuit power consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The counter circuit operates periodically at different speeds based on luminance conditions. During first period, high-speed conversion occurs; during second period, low-speed conversion occurs. This periodic variation in operational speed allows the system to maintain high productivity when needed while reducing power consumption during periods when high speed is not critical.

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If resolution is reduced to save power, then power consumption decreases, but measurement precision deteriorates

Engineering Contradiction:

Improvecounter circuit power consumptionVSAvoidAD conversion resolution

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The system applies different quality levels (resolutions) locally based on luminance conditions. In low-luminance regions, high resolution is maintained for precision. In high-luminance regions, lower resolution is acceptable and is applied to reduce power consumption. This local differentiation resolves the contradiction between power savings and precision maintenance.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces power consumption while maintaining image quality by adjusting resolution based on luminance, effectively managing power usage without significant degradation in image quality, especially in high-luminance regions where resolution changes are less noticeable.

Implementation Method 1

compares a magnitude relation between the potential of a reference signal having a time-varying potential and the potential of a pixel signal

Methodology Applied

Scientific EffectElectrical potential comparison: Electric Field

Implementation Method 2

measures the time duration from the time when AD conversion starts up to the time when the magnitude relation between the potentials of the reference and pixel signals is inverted

Methodology Applied

Scientific EffectTime measurement through counting:

Implementation Method 3

converting a pixel signal based on electric charges generated in each pixel into digital data

Methodology Applied

Scientific EffectAnalog-to-digital conversion:

Data Source

PatentUS11627269B2Analog-to-digital conversion circuit using comparator and counter, photoelectric conversion apparatus using comparator and counter, and photoelectric conversion system using comparator and counter

Publication Date: 2023.04.11 CANON KK

AI summary

An analog-to-digital conversion circuit includes a comparator circuit configured to perform processing of comparison between an analog signal and a ramp signal, and a counter configured to perform count processing in parallel with the comparison processing by the comparator circuit. The analog-to-digital conversion circuit acquires digital data, which is a count value corresponding to the comparison processing, and subjects the analog signal to analog-to-digital conversion. A period from the start to the end of the analog-to-digital conversion of the one analog signal includes a first period and a second period following the first period. The first and the second periods are switched based on an output of the counter. The count processing is performed at a high speed during the first period and performed at a low speed during the second period.