AC Threshold Detection Circuit Using Band-Pass Filtering
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Solution Overview
Problem
Existing AC voltage detection circuits suffer from start-up and switch-off delays due to signal averaging and filtering, are complex with high power consumption, and are susceptible to noise and impedance issues, requiring additional components like zero-crossing detectors and timers.
Innovation Solution
A circuit arrangement with a band-pass filter connected between the AC-input port and the threshold detection circuit, using a comparator to directly compare AC line voltage to a reference voltage, eliminating the need for signal smoothing and reducing complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal averaging and filtering are used in AC voltage detection circuits, then measurement precision is improved, but response speed deteriorates due to start-up and switch-off delays
Solution Approach 1:
The patent extracts and removes the signal averaging and filtering components from the detection circuit. By eliminating these components, the circuit achieves fast response speed without the start-up and switch-off delays that characterize conventional filtered detection circuits, while still maintaining adequate measurement precision through direct voltage comparison.
2Speed
If additional components like zero-crossing detectors and timers are added to achieve fast voltage threshold detection, then response speed is improved, but device complexity increases
Solution Approach 1:
The patent removes unnecessary components such as zero-crossing detectors and timers from the circuit. By using a simplified approach with a voltage divider and direct comparator, the circuit achieves fast detection speed without the complexity of additional components, directly addressing the contradiction between speed and complexity.
Solution Approach 2:
Instead of adding components to achieve fast detection, the patent inverts the approach by subtracting components. The fast detection capability is achieved through a minimalist circuit design that uses only essential components, turning the conventional wisdom of adding complexity for performance improvement on its head.
3Reliability
If additional components are added to the circuit for noise filtering and threshold detection, then reliability is improved, but power consumption increases
Solution Approach 1:
The patent extracts and removes power-consuming components from the circuit while maintaining detection reliability through the efficient use of a voltage divider and comparator. This minimalist approach reduces power consumption while preserving the essential noise filtering and threshold detection functions.
4Measurement precision
If impedance-matching components are added to the DC-circuit for precise voltage detection, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent removes complex impedance-matching components from the DC-circuit. By using a simple voltage divider configuration, the circuit achieves adequate voltage detection precision without the need for complex impedance matching networks, thereby reducing overall circuit complexity while maintaining functional precision.
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 provides fast and reliable AC voltage threshold detection, robust against noise and impedance, with minimal power consumption and cost-effective design, allowing for precise voltage monitoring and safe switch-off.
Implementation Method 1
a band-pass filter connected between the AC-input port and said first voltage input
Implementation Method 2
a first comparator element for comparing a voltage at the first voltage input to a reference voltage and for outputting a detection signal at the first detection output if said voltage at the first voltage input crosses said reference voltage
Data Source
Figure 1~2
Figure 3a~4b
Figure 4a~4c
AI summary
The invention relates to a circuit arrangement (300; 400; 500), which comprises an AC-input port (310; 410; 510) for connecting an AC voltage (100) and a threshold detection circuit (330; 430; 530) for detecting a crossing of a first voltage threshold by the AC voltage (100). The threshold detection circuit (330; 430; 530) includes a first voltage input (331 a; 431 a; 531 a), a first detection output (334a; 434a; 534a) and a first comparator element (335a; 435a; 535a) for comparing a voltage at the first voltage input (331a; 431a; 531a) to a reference voltage and for outputting a detection signal at the first detection output (334a; 434a; 534a). The circuit arrangement is characterized by a band-pass filter (320; 420; 520) connected between the AC-input port (310; 410; 510) and the first voltage input (331a; 431a). Additionally this invention relates to an electrical device, preferably a AC-DC power supply including a rectification unit, preferably a bridge rectifier. It also relates to a method of detecting a crossing of a threshold by an AC voltage.