AC Power Loss Detection Using Zero-Crossing and Amplitude Signals
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Solution Overview
Problem
Existing devices lack a reliable method to quickly and accurately detect AC power loss, leading to potential failure when a short-term back power source is depleted during an outage.
Innovation Solution
Detect zero-crossings of AC power and compare the zero-crossing count and amplitude to expected values to trigger shutdown actions before the back power source is depleted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device waits for complete AC power loss before taking action, then the detection method is simple, but the short-term back power source is depleted without performing critical actions
Solution Approach 1:
The system performs preliminary detection of AC power loss by monitoring zero-crossings and amplitude, then takes critical actions (opening relays, saving state, sending alerts) during the shutdown period before the back power source is depleted. This preliminary action approach ensures critical functions are executed proactively rather than reactively after power loss occurs.
Solution Approach 2:
The system continuously monitors AC power parameters (zero-crossings, amplitude) and provides feedback to the controller. When deviations from expected values are detected, the system adjusts its behavior by initiating shutdown actions. This closed-loop feedback mechanism enables reliable detection and response to power loss conditions.
2Measurement precision
If the device uses complex detection methods to accurately detect AC power loss, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The system uses the existing AC power signal itself to detect power loss conditions by monitoring its own zero-crossings and amplitude characteristics. The controller leverages the natural properties of the AC signal without requiring external reference signals or complex comparison circuits, enabling the system to self-diagnose power loss conditions using readily available information.
Solution Approach 2:
The system detects AC power loss by monitoring changes in key parameters of the AC signal, specifically the zero-crossing count and amplitude. When these parameters deviate from expected values (e.g., fewer than expected zero-crossings over a measurement period, or amplitude below threshold), the system identifies power loss. This parameter-based detection approach provides accurate measurement without complex circuitry.
Data Source
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AI summary
Power losses may be detected by detecting zero-crossings of the AC power and determining a zero-crossing count of zero-crossings detected over a count period of time. A determination is made as to when the zero-crossing count is less than an expected zero-crossing count over the count period of time. When the zero-crossing count is less than the expected zero-crossing count over the count period of time, the amplitude of the AC power is compared to the expected amplitude. When the amplitude of the AC power is less than the expected amplitude by at least a threshold margin, one or more shut down actions are performed during the shutdown period of time to prepare the circuit for loss of AC power.