Solid-State Image Sensor Power Supply Circuit Noise Reduction
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Solution Overview
Problem
Conventional solid-state image capturing apparatuses suffer from horizontal line noise due to external source voltage noise, and using a boosting circuit to mitigate this issue increases chip area and current consumption.
Innovation Solution
A solid-state image capturing apparatus with a power supply circuit that steps down external source voltage to generate a stable pixel source voltage using a driver transistor operating in a saturated state, accompanied by a bias level generating circuit to maintain a constant bias level and control the driver transistor, thereby reducing noise influence and avoiding the need for a boosting circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If external source voltage is directly supplied to pixels, then device complexity is reduced, but noise from external systems is superimposed on the source voltage causing horizontal line noise
Solution Approach 1:
A power supply circuit is introduced as an intermediary between the external source voltage and the pixels. This circuit includes a driver transistor that generates a pixel source voltage from the external source voltage, and a bias level generating circuit that creates a constant bias level independent of external voltage fluctuations. The bias level is fed back to control the driver transistor, forming a feedback loop that isolates the pixel circuitry from external noise while maintaining voltage regulation.
2Object-affected harmful factors
If a boosting circuit is used to eliminate external noise influence, then noise immunity is improved, but layout area and current consumption increase
Solution Approach 1:
Instead of using a boosting circuit that increases voltage, the invention changes the approach by using a power supply circuit that regulates and stabilizes the voltage level. The driver transistor operates with a controlled bias level that is independently generated, allowing the system to maintain noise immunity through voltage stabilization rather than voltage amplification. This parameter change from voltage boosting to voltage regulation enables achieving noise immunity with reduced layout area and lower current consumption.
3Object-affected harmful factors
If a power supply circuit with driver transistor is used to generate stable pixel source voltage, then noise influence is reduced, but device complexity increases
Solution Approach 1:
The power supply circuit incorporates a feedback mechanism where the bias level generating circuit continuously monitors and adjusts the driver transistor operation. The bias level is generated based on reference voltage and feedback from the circuit operation, creating a self-regulating system that maintains stable pixel source voltage despite external noise. This feedback loop automatically compensates for voltage fluctuations and maintains noise immunity without requiring complex external control circuits.
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
The solution provides a stable voltage level to pixels and vertical driving circuits without increasing layout area or current consumption, effectively eliminating noise influence and improving picture quality.
Implementation Method 1
a driver transistor for generating a pixel source voltage from the external source voltage, the driver transistor being operative in a saturated state
Data Source
AI summary
A solid-state image capturing apparatus according to the present invention includes: a pixel array in which a plurality of pixels are arranged; a driving circuit for driving each pixel of the pixel array; and a power supply circuit for stepping down an external source voltage supplied from an external power source to generate a pixel source voltage to be supplied to each pixel of the pixel array, where the power supply circuit includes a driver transistor for generating a pixel source voltage from the external source voltage and the driver transistor is operative in a saturated state.