Voltage Reference Circuit for Low-Current High-Impedance Detection
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Solution Overview
Problem
Existing voltage detectors are unsuitable for continuous, non-invasive monitoring of high-impedance source voltages due to high quiescent current consumption, which reduces the source output voltage and prevents the use of wireless rectifying antennas and wearable energy harvesters with high source impedances, and they fail to provide a low quiescent power consumption while maintaining a high maximum input voltage and low detection threshold.
Innovation Solution
A voltage reference circuit with a series connection of current controlling elements that allow current to flow as a non-linear function of voltage, featuring a semiconductor device operating in subthreshold mode, and a reset input to reduce current consumption when not required, enabling a voltage detector with low quiescent power consumption and a wide input voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing voltage detectors are used to monitor input voltage, then voltage detection function is provided, but quiescent current consumption is high which reduces source output voltage and prevents use with high-impedance sources
Solution Approach 1:
The voltage detector employs dynamic power management by switching between active and low-power states. The detector activates only when voltage transition is detected, otherwise remaining in a low-power state, thereby reducing average quiescent current consumption while maintaining reliable voltage detection functionality.
Solution Approach 2:
The detector modifies its operational parameters by adjusting detection thresholds and activation conditions based on input voltage characteristics. This allows the detector to adapt its current consumption profile to match the impedance characteristics of the connected source, enabling compatibility with high-impedance sources like wireless rectifying antennas and wearable energy harvesters.
2Measurement precision
If voltage detector is activated to provide detection signal, then detection threshold is met, but quiescent current increases sharply dragging input voltage down and switching detector off again
Solution Approach 1:
The voltage detector incorporates feedback mechanisms that monitor the input voltage level and adjust detection operations accordingly. When activation causes voltage droop, the feedback system modulates the detection signal or extends the active state duration to prevent premature shutdown, thereby maintaining both detection precision and input voltage stability.
Solution Approach 2:
The detector performs preliminary voltage assessment before full activation to predict potential voltage droop. This preliminary action allows the system to prepare compensatory measures, such as adjusting detection thresholds or extending activation timing, to prevent the cyclic on-off behavior caused by voltage dragging.
3Reliability
If voltage detector monitors high-impedance sources continuously, then always-awake input monitoring is achieved, but power consumption increases
Solution Approach 1:
The voltage detector implements periodic sampling of the input voltage rather than continuous monitoring. By strategically spacing measurement intervals and using low-power comparison circuits, the detector maintains reliable always-awake functionality for high-impedance sources while minimizing average power consumption to levels suitable for energy-harvesting applications.
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 allows for continuous monitoring of high-impedance sources with minimal quiescent current, capturing power pulses effectively while preventing damage from high input voltages, and achieving low power consumption and a low detection threshold, enabling efficient energy harvesting from a wide range of input voltages.
Implementation Method 1
featuring a semiconductor device operating in subthreshold mode
Data Source
AI summary
A voltage detector (200) for monitoring an input signal and outputting a detection signal at an output when a voltage of the input signal meets a first threshold having: an input configured for receiving the input signal; a voltage reference circuit for receiving an input voltage and producing a reference voltage having a maximum value independent of the input voltage; and a trigger configured to compare the input signal and the reference voltage and to output a detection signal to the output when the voltage of the input signal reaches the first threshold. The voltage reference circuit comprises a reset input connected to either the input or the output and is configured to reduce the reference voltage when a predetermined reset signal is received. The voltage reference circuit may include: an input for receiving the input voltage; a first current controlling element (210), such as a diode, which allows current to flow as an increasing, non-linear function of voltage at least within a first range of voltages; a second current controlling element (240), such as a transistor, which allows current to flow as an increasing, non-linear function of voltage at least with a second range of voltages; and an output at which the output reference voltage is produced. The first current controlling element and the second current controlling element are connected in series between the input and a common reference, with the second current controlling element between the first current controlling element and a common reference, the output comprises a node between the two current controlling elements, the first and second range of voltages overlap and the second current controlling element is configured to vary the function by which it allows current to flow in dependence on the input voltage.