Variable-Resolution A/D Converter for Lower-Power Image Sensing

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Solution Overview

Problem

Existing A/D converters in image sensors face challenges in reducing power consumption while maintaining performance, particularly in portable devices where resolution and processing time need to be improved, and circuit size minimized.

Innovation Solution

The A/D converter switches resolution from m bits to n bits by partially stopping clock signals or gray code counters at predetermined times, using a comparison unit with a ramp waveform reference voltage and time quantization to decode phase information from multiple clock signals, allowing for dynamic resolution adjustment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the frequency is raised to improve resolution, then measurement precision is improved, but power consumption increases

Engineering Contradiction:

ImproveresolutionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies dynamics by making the counter operation dynamic rather than static. The counter is selectively operated or stopped based on the input signal characteristics and required resolution. This allows the system to adapt its operational state (running or stopped) to match the actual measurement needs, thereby reducing unnecessary power consumption while maintaining required measurement precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameter of the counter from a fixed state to a variable state. By controlling whether the counter operates or stops based on signal conditions and resolution requirements, the system dynamically adjusts its power consumption and measurement precision parameters to optimize performance for different operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the processing time is reduced to improve productivity, then productivity is improved, but measurement precision deteriorates

Engineering Contradiction:

Improveprocessing timeVSAvoidresolution

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies partial action by selectively operating the counter only when necessary rather than continuously. The counter is stopped during periods when high-resolution measurement is not required, performing only the necessary counting operations. This reduces overall processing time and power consumption while maintaining measurement precision when actually needed.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of manufacture

If the circuit size is reduced to improve ease of manufacture, then ease of manufacture is improved, but device complexity increases

Engineering Contradiction:

Improvecircuit sizeVSAvoidcircuit complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent applies universality by designing the counter and control circuitry to perform multiple functions. The same counter structure is used for both high-resolution and low-resolution operations, and the control logic manages different operational modes (operated vs. stopped states). This multi-functionality reduces the need for separate circuits for different resolution modes, thereby reducing overall circuit size while managing complexity through unified design.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8749420B2A/D converter, A/D conversion method, and program

Publication Date: 2014.06.10 SONY GROUP CORP

AI summary

An A/D converter switches resolution of m bits to resolution of n bits smaller than the m bits at a predetermined time.