Programmable Voltage Ramp Generator for HDR ADC Resolution

Solution Overview

Problem

High dynamic range solid-state imaging devices face challenges in maintaining relative intensity resolution across varying light intensity ranges due to the use of photoelectric conversion elements with different sensitivities, leading to degradation in analog-to-digital conversion quality.

Innovation Solution

A voltage ramp generator with a resistor network and electronic switches, along with a reference voltage circuit, generates a non-linear voltage ramp that is stable and programmable, enabling effective comparison of pixel output signals across different light conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a large photoelectric conversion element is used, then light sensitivity is improved, but saturation occurs at low light intensities

Engineering Contradiction:

Improvelight sensitivityVSAvoidsaturation resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The pixel circuit is divided into two separate photoelectric conversion elements (large and small) that operate in different light intensity ranges. The large element handles low-light scenarios while the small element handles bright scenes, preventing saturation while maintaining sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between the large and small photoelectric conversion elements based on light intensity conditions. A selection circuit determines which element's output to use, enabling adaptive operation across different lighting conditions.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a small photoelectric conversion element is used, then saturation resistance is improved, but light sensitivity deteriorates

Engineering Contradiction:

Improvesaturation resistanceVSAvoidlight sensitivity

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The pixel circuit is divided into two separate photoelectric conversion elements (large and small) that operate in different light intensity ranges. The large element handles low-light scenarios while the small element handles bright scenes, preventing saturation while maintaining sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between the large and small photoelectric conversion elements based on light intensity conditions. A selection circuit determines which element's output to use, enabling adaptive operation across different lighting conditions.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If digital gain is applied to compensate for sensitivity differences, then high dynamic range performance is improved, but analog-to-digital conversion resolution deteriorates

Engineering Contradiction:

Improvehigh dynamic range performanceVSAvoidanalog-to-digital conversion resolution

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The voltage ramp generator is configured in advance to produce different slope angles corresponding to different photoelectric conversion elements. By pre-setting the ramp characteristics to match the sensitivity ratios of the elements, the system eliminates the need for post-processing digital gain, thereby preserving conversion resolution.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The voltage ramp generator changes its operating parameters (slope angle) based on which photoelectric conversion element is active. This parameter adjustment compensates for sensitivity differences between elements without requiring digital gain multiplication, maintaining full resolution throughout the dynamic range.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240430597A1Voltage ramp generator, analog-to-digital converter and solid-state imaging device

Publication Date: 2024.12.26 SONY SEMICON SOLUTIONS CORP

AI summary

A voltage ramp generator includes a resistor network, electronic switches and at least one reference voltage circuit. The resistor network includes resistor elements electrically connected in series between a first supply node (VDD) and a second supply node (VSS), wherein circuit nodes are formed between neighboring resistor elements. Each electronic switch is operable to connect one of the circuit nodes with a switch arrangement output. The at least one reference voltage circuit supplies a reference voltage to one of the circuit nodes.