Voltage Detector Circuit With Constant-Current Threshold Sensing
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Solution Overview
Problem
Conventional voltage detectors in battery-operated devices face challenges in accurately monitoring battery voltage over a wide range while maintaining low power consumption, being cost-effective, and being robust against process, voltage, and temperature variations.
Innovation Solution
A voltage detector circuit incorporating an operational amplifier with impedance elements and transistors, where the amplifier outputs a constant current independent of the supply voltage, and operates in linear or saturated modes to indicate voltage thresholds, ensuring accurate detection and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional voltage detectors are used to monitor battery voltage, then voltage detection function is provided, but power consumption is high and accuracy deteriorates at extreme temperatures
Solution Approach 1:
The patent changes the operating parameters of the voltage detector by using a bandgap reference voltage (1.2V) that is independent of temperature and supply voltage variations. This reference voltage is used to generate a threshold voltage that remains stable across temperature extremes, thereby maintaining detection accuracy while allowing the detector to operate at lower power levels compared to conventional designs that rely on voltage dividers and comparators with temperature-sensitive references.
2Measurement precision
If voltage detector circuit complexity is increased to improve detection accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The voltage detector is segmented into distinct functional blocks: a bandgap reference voltage generator, a threshold voltage generator, and a voltage comparator. This segmentation allows each block to perform its specific function with optimized simplicity - the bandgap circuit generates a stable reference, the threshold generator creates the comparison level, and the comparator makes the detection decision. This modular approach achieves high accuracy without requiring an overly complex monolithic circuit design.
3Reliability
If conventional voltage detection methods are used, then basic detection is achieved, but detection accuracy deteriorates due to PVT variations
Solution Approach 1:
The patent implements feedback mechanisms through the bandgap reference voltage generator, which automatically adjusts its output to maintain a constant 1.2V reference level despite variations in process, voltage, and temperature. This feedback-stabilized reference is then used to generate the threshold voltage, ensuring that the comparison level remains accurate under all operating conditions. The feedback approach provides inherent compensation for PVT variations without requiring additional complex calibration circuits.
Data Source
AI summary
A circuit includes an amplifier having a first power terminal configured to be coupled to a supply voltage and a second power terminal configured to be coupled to a reference potential. The circuit further includes a first impedance element coupled between a first input terminal of the amplifier and a first output terminal of the amplifier. The circuit additionally includes a second impedance element coupled between the first input terminal and the reference potential. The amplifier is configured to output a first voltage at a second output terminal of the amplifier in response to the supply voltage being greater than an output voltage at the first output terminal of the amplifier. The amplifier is further configured to output a second voltage at the second output terminal of the amplifier in response to the supply voltage being less than the output voltage at the first output terminal of the amplifier.