Precision current-to-digital converter
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Solution Overview
Problem
Conventional delta-sigma modulator-based current sensing circuits require high power consumption and dynamic range, especially when measuring high impedance sensors, necessitating front-end signal-conditioning stages that draw current and affect sensor performance.
Innovation Solution
Incorporating a capacitive summation circuit within the primary feedback loop of the delta-sigma modulator to reduce the number of nodes requiring high dynamic range, thereby enabling direct connection to high impedance sources without pre-amplifiers and achieving high input impedance with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a front-end signal-conditioning stage is used to convert high impedance sensor current signal to low impedance output signal, then the current sensing circuit can achieve proper signal conditioning for digitization, but the circuit draws current from the sensor and negatively affects sensor performance while increasing power consumption
Solution Approach 1:
The invention removes the front-end signal-conditioning stage from the system architecture. By integrating the capacitive summation circuit directly into the delta-sigma modulator, the patent eliminates the separate pre-amp stage that was drawing current from the sensor and consuming excessive power, while still achieving proper signal conditioning through the capacitive elements within the modulator loop.
Solution Approach 2:
The patent combines the signal conditioning function with the delta-sigma modulator by placing the capacitive summation circuit within the modulator's feedback loop. This merging eliminates the need for a separate front-end conditioning stage, reducing power consumption and current draw from the sensor while maintaining signal conditioning capability through the integrated capacitive network.
2Measurement precision
If the required resolution becomes higher, then the measurement precision improves, but the high dynamic range enforced at the input nodes results in relatively high power implementation
Solution Approach 1:
The invention applies local quality by concentrating the high dynamic range requirement to only the output node of the capacitive summation circuit rather than distributing it across multiple input nodes. This localized approach allows high resolution (greater than 15-bit) to be achieved while minimizing the overall power consumption by restricting the high dynamic range enforcement to a single critical point in the signal path.
3Productivity
If conventional DSM-based current sensing circuits are used for high impedance sensors, then the circuit can process the signal, but it requires additional front-end components that increase device complexity
Solution Approach 1:
The patent merges the signal processing capability directly into the delta-sigma modulator by integrating the capacitive summation circuit within the modulator loop. This eliminates the need for separate front-end signal-conditioning components, reducing device complexity while maintaining full signal processing capability for high impedance sensors.
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 achieves greater than 15-bit resolution and sub-MHz bandwidth with significantly reduced power consumption by enforcing high dynamic range only at a single node, minimizing input referred noise and eliminating the need for front-end pre-amplifiers, thus improving the efficiency and performance of current sensing systems.
Implementation Method 1
a first capacitance connected between the output of the first amplifier and the input of the first amplifier
Implementation Method 2
at least one second capacitance being arranged in the first feedback path and configured to capacitively couple the quantized signal to the first node
Data Source
AI summary
A current sensing system and delta sigma modulator architecture are discloses for sensing and digitizing a current input signal from a high impedance signal source with improve power efficiency. The delta sigma modulator integrates a signal condition stage within the delta sigma modulator feedback loop by utilizing a capacitive summation stage. For given gain, resolution, and bandwidth requirements, the delta sigma modulator architecture achieves reduced power consumption by advantageously reducing the number of nodes in the system that require a high dynamic range. Additionally, the delta sigma modulator has very high input impedance such that the input of the delta-sigma modulator can be connected directly to a high impedance signal source, without the need for a front-end pre-amplifier stage, or the like.