Ramp ADC Comparator Gating in CMOS Image Sensors
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Solution Overview
Problem
Current imaging devices, particularly CMOS image sensors, face challenges in efficiently converting analog pixel output signals to digital signals due to high power consumption and noise filtering limitations in their analog-to-digital converter circuits.
Innovation Solution
The implementation of an analog-to-digital converter circuit that includes a comparator, counter, and control circuit, which uses a ramp signal and enable signals to optimize conversion efficiency, and incorporates a pixel bias circuit and amplify circuit to reduce power consumption and filter noise effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional analog-to-digital converter circuits are used in CMOS image sensors, then conversion function is provided, but power consumption is high
Solution Approach 1:
The patent implements periodic action by enabling the analog-to-digital converter circuit only during specific conversion periods using enable signals. The converter operates in alternating active and idle states, where during idle periods the circuit is disabled to save power, and during active periods it performs conversion tasks. This periodic operation mode resolves the contradiction by reducing overall power consumption while maintaining necessary conversion efficiency during active operation windows.
2Object-affected harmful factors
If conventional analog-to-digital converter circuits are used, then conversion is performed, but noise filtering is insufficient
Solution Approach 1:
The patent introduces an intermediary approach by using the ramp signal generator and controlled conversion process as a mediator between the analog pixel signal and digital output. The ramp signal acts as a reference that enables noise-resistant conversion through controlled comparison. Additionally, the enable signal mechanism serves as an intermediary control that coordinates the operation of multiple circuit components, allowing noise filtering through synchronized operation without requiring complex additional filtering circuits.
3Productivity
If conversion speed is increased, then productivity improves, but power consumption increases
Solution Approach 1:
The patent applies periodic action by implementing intermittent conversion operations controlled by enable signals. Instead of continuous high-speed conversion that would consume excessive power, the converter operates at high speed only during necessary conversion windows and remains idle otherwise. This creates a periodic pattern of high-speed conversion followed by low-power idle states, resolving the contradiction between conversion speed and power consumption by separating the temporal aspects of speed and energy usage.
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 solution enhances the conversion efficiency of analog pixel output signals to digital signals while minimizing power consumption and noise, thereby improving the overall performance of imaging devices.
Implementation Method 1
Each photosensitive element produces charge that is proportional to intensity of light which the photosensitive element receives
Data Source
AI summary
An integrated circuit includes a ramp signal generator circuit, a comparator, a counter and a control circuit. The ramp signal generator circuit is configured to generate a ramp reference signal. The comparator configured to compare a pixel output signal and the ramp reference signal thereby generating a comparator output signal. The counter is coupled to the comparator, and configured to be enabled or disabled in response to the comparator output signal. The control circuit coupled to the comparator, and configured to enable or disable the comparator by a first enable signal, the first enable signal generated in response to at least the comparator output signal.