Image Sensor ADC Comparator Using Capacitive Non-Inverting Comparison
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Solution Overview
Problem
Conventional analog-to-digital converters (ADCs) in image sensors face high power consumption and introduce undesirable distortions due to comparator artifacts, particularly during inversion operations.
Innovation Solution
The implementation of a comparator configuration in an image sensor that includes capacitors and transistors to manage pixel and reference signals, reducing power consumption and artifacts by controlling the input dynamic range and using a single-type amplifier to minimize current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional ADC comparators are used to perform analog-to-digital conversion, then the conversion function is achieved, but power consumption becomes excessively large
Solution Approach 1:
The patent changes the voltage parameter of the comparator by applying different voltage levels (first voltage level during integration, second voltage level during comparison) to reduce power consumption while maintaining conversion accuracy. This dynamic voltage scaling allows the system to consume less power during operation without sacrificing the reliability of the ADC conversion process.
2Reliability
If inversion operations are performed in the comparator, then the comparison function is achieved, but undesirable artifacts and signal distortions are introduced
Solution Approach 1:
The patent extracts and removes the inversion operation from the comparator circuit to eliminate the source of artifacts. By avoiding the inversion operation entirely, the system prevents the generation of undesirable signal distortions and comparator artifacts, thereby improving signal accuracy without compromising the comparison function.
Solution Approach 2:
Instead of performing an inversion operation that causes artifacts, the patent uses a non-inverting comparison approach. The comparator directly compares the integrated signal with the reference signal without inverting the input, thereby eliminating the harmful artifacts while maintaining the essential comparison functionality.
3Adaptability or versatility
If the comparator processes a wide dynamic range of input signals, then the ADC conversion range is improved, but power consumption increases
Solution Approach 1:
The patent employs dynamic voltage adjustment in the comparator, switching between different voltage levels based on the operational phase (integration vs. comparison). This dynamic approach allows the comparator to maintain a wide input dynamic range during comparison while consuming less power during the integration phase, effectively balancing adaptability with energy efficiency.
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 configuration effectively reduces power consumption and minimizes signal distortions, enhancing the accuracy and efficiency of image sensor operations.
Implementation Method 1
a first capacitor configured to receive the pixel signal
Implementation Method 2
a second capacitor configured to receive a reference signal
Implementation Method 3
a third capacitor coupled between a gate of the second transistor and a first line supplied with a first voltage
Data Source
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AI summary
Provided is an image sensor including: a pixel section configured to include a plurality of pixels arranged therein; and an AD conversion unit configured to perform analog-to-digital (AD) conversion on a pixel signal on the basis of a result of comparison between a first voltage of a signal, which is obtained by adding, via capacitances, the pixel signal of the pixel and a reference signal that linearly changes in a direction opposite to the pixel signal, with a second voltage serving as a reference.