Current-to-Digital Converter with Auxiliary Current for Low-Noise Settling
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Solution Overview
Problem
Current amplifiers in optical front ends, particularly in computed tomography applications, face a challenge in achieving a favorable noise-power tradeoff, as reducing thermal noise often requires increasing signal power or using expensive low-threshold voltage transistors, which is not efficient in terms of power consumption and area.
Innovation Solution
A current-to-digital converter circuit with an integrator amplifier, quantizer circuit, and controlled current source is designed to provide an auxiliary current that helps maintain the output voltage within a valid range, improving settling accuracy and reducing power consumption by supplying charge only when needed, thus enhancing the noise-power tradeoff.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the signal power is increased to improve the signal-to-noise ratio, then the noise performance is improved, but the power consumption increases
Solution Approach 1:
The patent implements periodic action by using a controlled current source that supplies auxiliary current only during specific periods when the integrator output voltage approaches the reference voltage level, rather than continuously. This periodic supplementation of charge allows the system to maintain low noise performance while significantly reducing average power consumption compared to continuous high-power operation.
Solution Approach 2:
The system employs self-service through feedback control where the quantizer circuit continuously monitors the integrator output voltage and automatically triggers the controlled current source when needed. This self-regulating mechanism ensures the output voltage remains within the valid range without requiring external intervention or continuous high-power operation, thereby improving noise performance efficiently.
2Measurement precision
If expensive low threshold voltage transistors are used to reduce thermal noise, then the noise performance is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces expensive low-threshold voltage transistors with standard transistors combined with a controlled current source that provides temporary auxiliary current. This approach uses cheaper, more manufacturable components while achieving the same noise performance through dynamic current supplementation rather than relying on expensive specialized transistors.
Solution Approach 2:
The system changes the operating parameters dynamically by adjusting the auxiliary current from the controlled current source based on the integrator output voltage level. This parameter modulation allows standard transistors to achieve performance comparable to expensive low-threshold voltage transistors, thereby reducing manufacturing costs while maintaining noise performance.
3Measurement precision
If the amplifier is designed for low noise, then the noise performance is improved, but the settling time increases
Solution Approach 1:
The controlled current source provides periodic auxiliary current supplementation only when the integrator output voltage approaches the reference voltage level, as detected by the quantizer circuit. This periodic intervention accelerates the settling process during critical moments without requiring the amplifier to operate at continuously high power, thereby reducing settling time while maintaining low noise performance.
Solution Approach 2:
The system implements feedback control where the quantizer circuit monitors the integrator output voltage and provides feedback to control the current source. This feedback mechanism ensures that auxiliary current is supplied precisely when needed to accelerate settling, optimizing both noise performance and settling time by intervening only during critical settling phases.
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 proposed solution achieves improved noise performance with significantly reduced power consumption and without the need for expensive transistors, enabling faster and more accurate signal settling, with settling time improved by a factor of 4 to 20.
Implementation Method 1
optical front ends which detect optical energy by means of an optical sensor, e.g. a photodiode, and convert said energy into a voltage signal
Implementation Method 2
The integrator amplifier has an input which is adapted to receive a current signal and an output which is adapted to provide a voltage signal as a function of an integration of the current signal
Data Source
AI summary
A current to digital converter circuit has an integrator amplifier with an input adapted to receive a current signal and an output adapted to provide a voltage signal as a function of an integration of the current signal, a quantizer circuit with an input which is coupled to the output of the integrator amplifier and with an output adapted to provide a binary result signal as a function of a comparison of the voltage signal with at least a first reference voltage signal, a digital-to-analog converter circuit which is coupled in a switchable manner as a function of the binary result signal to the input of the integrator amplifier, and a controlled current source which is coupled to the output of the integrator amplifier via a first switch which is controlled as a function of the binary result signal such that an auxiliary current is supplied to the output of the integrator amplifier.