Under Voltage Lockout Circuit with Dynamic Comparator
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Solution Overview
Problem
Conventional under voltage lockout circuits face challenges in reducing power consumption and accuracy due to static current and resistor-based designs, which lead to increased power loss and variability in start-up voltage and current.
Innovation Solution
The proposed under voltage lockout circuit incorporates a current generating circuit, a reference voltage generating circuit, an oscillator, a voltage divider, and a dynamic comparator, where the dynamic comparator only activates to output a power-on-reset signal when the detection voltage exceeds the reference voltage, and all components are activated in a sequential order to minimize static current consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistors are used to divide power supply voltage and a comparator is used to compare voltages, then the start-up voltage accuracy is improved, but the start-up current and power consumption increase due to static current and full-time operation
Solution Approach 1:
The patent employs a dynamic comparator that operates periodically rather than continuously. The comparator is enabled only during specific phases when voltage comparison is needed, while remaining disabled during other phases to eliminate static current consumption. This periodic operation maintains measurement precision when needed while dramatically reducing average power consumption.
Solution Approach 2:
The patent uses a dynamic comparator architecture that can transition between active and inactive states. The comparator's operation is controlled by enable signals that activate it only when required for voltage comparison, allowing the system to adapt its power consumption dynamically based on operational requirements while maintaining accuracy when active.
2Use of energy by moving object
If a latch path with MOSFET and resistor is used to reduce operating current loss, then power consumption is reduced, but the start-up voltage varies due to threshold voltage variation in the manufacturing process
Solution Approach 1:
The patent introduces a reference voltage circuit as an intermediary that provides a stable reference for comparison. This reference voltage is generated independently of MOSFET threshold variations and serves as a mediator to establish accurate start-up voltage detection, compensating for the variations introduced by the latch path components.
Solution Approach 2:
The patent creates a copied version of the voltage signal through the dynamic comparator architecture, where the comparison is performed against a reference voltage. This copying mechanism allows the system to evaluate the voltage condition without being directly affected by threshold voltage variations in the latch path, improving start-up voltage accuracy.
Data Source
AI summary
An under voltage lockout circuit includes a reference circuit, an oscillator, a voltage divider, and a dynamic comparator. The reference circuit generates a reference voltage signal and a current source activation signal. The oscillator is activated to generate a clock signal after receiving the current source activation signal. The voltage divider samples an operating voltage signal to generate a detection voltage signal after receiving the clock signal. The voltage divider includes a switched-capacitor circuit for adjusting a ratio of the detection voltage signal to the operating voltage signal. The dynamic comparator receives the clock signal, the detection voltage signal and the reference voltage signal, and compares the reference voltage signal with the detection voltage signal only after receiving the clock signal. When the reference voltage signal is higher than the detection voltage signal, the dynamic comparator outputs a power-on-reset pulse signal.