Segmented Current Generator for Low-Power Bio-Impedance Monitoring
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Solution Overview
Problem
Existing bio-signal monitoring systems face challenges in achieving high accuracy while minimizing power consumption, particularly in implantable devices, due to high power requirements for accurate measurements and complex architectures that lead to intolerable measurement errors and increased form factor.
Innovation Solution
A current generator using a plurality of current cells connected in parallel, with a summer to sum their outputs and generate pseudo-sinusoidal alternating current through switchable sequences at multiple quantization levels, allowing for low power consumption and high accuracy biopotential monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a purely sinusoidal current source is used to achieve high measurement accuracy, then measurement precision is improved, but power consumption increases significantly
Solution Approach 1:
The current source is segmented into multiple current cells (first subset for positive alternations, second subset for negative alternations) that can be independently controlled. This segmentation allows the system to generate pseudo-sinusoidal waveforms with reduced harmonic distortion while consuming less power compared to a traditional sinusoidal current source, as not all current cells need to operate at full power simultaneously.
Solution Approach 2:
The patent employs periodic switching of current cells according to a sequence to generate pseudo-sinusoidal alternating current. By periodically activating and deactivating current cells in a controlled manner, the system achieves accurate biopotential measurement with reduced power consumption, as the current cells are not continuously operating at maximum capacity.
2Use of energy by moving object
If multi-level quantized signal with quadrature demodulation is used to reduce power consumption, then power consumption is reduced, but measurement accuracy deteriorates due to phase variations and harmonic folding
Solution Approach 1:
The system dynamically adjusts the switching sequences of current cells to generate pseudo-sinusoidal waveforms that minimize harmonic distortion. By dynamically controlling which current cells are active and their switching timing, the system achieves both low power consumption and high measurement accuracy without the need for complex quadrature demodulation, thereby avoiding phase variation errors and harmonic folding issues.
Solution Approach 2:
The patent changes the waveform parameters by generating pseudo-sinusoidal current instead of using square-wave or multi-level quantized signals. This parameter change eliminates the need for quadrature demodulation, reduces phase variation sensitivity, and prevents odd harmonic folding into the baseband, thereby improving measurement accuracy while maintaining low power consumption.
3Use of energy by moving object
If complex architecture with multi-level demodulation amplifier is used to achieve low power consumption, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for complex multi-level demodulation amplifiers by using pseudo-sinusoidal current generation. The simplified current source architecture directly generates the measurement signal without requiring complex demodulation stages, thereby reducing device complexity while maintaining low power consumption and high measurement accuracy.
Solution Approach 2:
Instead of using complex demodulation to extract signals from square-wave or multi-level quantized current, the patent inverts the approach by directly generating pseudo-sinusoidal current that naturally provides the measurement signal. This inversion simplifies the overall architecture by eliminating the need for complex multi-level demodulation amplifiers while achieving the same measurement objectives.
Data Source
AI summary
A current generator is disclosed. An example current generator includes a plurality of current cells connected in parallel, each current cell being connected to a switch. The current generator further includes a first summer configured to sum the output of each current cell of a first subset of the plurality of current cells and a second summer configured to sum the output of each current cell of a second subset of the plurality of current cells. The current generator also includes a combiner configured to combine the outputs of the first and second summers. Further, each switch is switchable according to a sequence to generate a summed output of the current cells at a plurality of quantization levels to generate positive and/or negative alternations of a pseudo-sinusoidal, alternating current.