Dual-Threshold Voltage Detection to Prevent False Reset Signals
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Solution Overview
Problem
Conventional voltage detectors can incorrectly output a reset signal when the input voltage does not reach the reset threshold during power-on, and they fail to operate reliably in high-voltage applications due to unstable reference voltages and transient voltage fluctuations.
Innovation Solution
The improved voltage detector incorporates a first and second voltage detection circuit, along with a logic holder circuit, where the second detection voltage is lower than the first and higher than the minimum operating voltage, allowing the logic holder to retain the logic state of the first detection signal when the second input voltage is below its detection voltage, preventing incorrect reset signals and ensuring stable operation across varying power supply conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage detector uses a single detection circuit with a fixed detection threshold, then the circuit structure is simple, but it cannot reliably distinguish between transient voltage fluctuations and actual power-on conditions, leading to incorrect reset signals
Solution Approach 1:
The voltage detection function is divided into two separate detection circuits: a first voltage detection circuit that detects when the power supply voltage rises above a first threshold (indicating potential power-on), and a second voltage detection circuit that detects when the voltage falls below a second threshold (indicating actual power-on completion). This segmentation allows each circuit to be optimized for its specific detection range, improving reliability while keeping individual circuits simple.
Solution Approach 2:
A logic holder circuit is introduced as an intermediary between the two detection circuits and the reset signal output. The logic holder receives signals from both detection circuits and integrates their logic states to determine the final reset signal output. This intermediary component resolves the contradiction by coordinating the simple structures of individual detection circuits to achieve complex, reliable detection functionality.
2Speed
If the voltage detector operates with transient voltage fluctuations during power supply stabilization, then the response time is fast, but the reference voltage becomes unstable causing incorrect detection
Solution Approach 1:
The detection system dynamically adapts its reference voltages based on operating conditions. The first voltage detection circuit uses a first reference voltage optimized for detecting initial power-on when voltage is rising, while the second voltage detection circuit uses a second reference voltage optimized for detecting power-on completion when voltage may be fluctuating. This dynamic adaptation allows fast response during transient conditions while maintaining detection stability through condition-appropriate reference levels.
Solution Approach 2:
The system changes detection parameters (reference voltages and detection thresholds) based on the detected voltage range and operational phase. During initial power-on with transient fluctuations, the first detection circuit uses parameters optimized for rising edge detection. Once the voltage stabilizes above the second threshold, the second detection circuit takes over with parameters optimized for stable operation, thus maintaining both speed and reliability across different operational phases.
3Reliability
If the voltage detector requires the power supply voltage to stabilize before detection, then the reference voltage is stable, but the detection is delayed until voltage stabilization occurs
Solution Approach 1:
The first voltage detection circuit is designed to operate and provide detection functionality before the power supply voltage fully stabilizes. It uses a reference voltage and detection threshold specifically optimized for the transient power-on phase, allowing it to detect the initial voltage rise and prepare the logic holder circuit. This preliminary action eliminates detection delay while maintaining reliability because the first detection circuit is specifically designed for accurate operation during transient conditions.
Solution Approach 2:
The detection system maintains continuous useful action through the handoff between the first and second detection circuits. The first detection circuit continuously monitors during the power-on transient phase, and as the voltage stabilizes, the second detection circuit continuously monitors for the completion condition. This continuous monitoring across both circuits eliminates gaps in detection functionality, ensuring no detection delay occurs while maintaining reference voltage stability through appropriate circuit selection.
Data Source
AI summary
A voltage detector includes a first input terminal, a second input terminal, a first voltage detection circuit, a second voltage detection circuit, and a logic holder circuit. The first input terminal receives a first input voltage. The second input terminal receives a second input voltage. The first voltage detection circuit outputs a first detection signal that switches a logic state thereof when the first input voltage falls below a first detection voltage. The second voltage detection circuit outputs a second detection signal that switches a logic state thereof when the second input voltage falls below a second detection voltage. The logic holder circuit retains the logic state of the first detection signal when the second detection signal indicates that the second input voltage is below the second detection voltage.