Heating Device Zero-Crossing Signal Error Processing
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Solution Overview
Problem
The gradual drop in voltage after AC power supply is turned off can lead to erroneous detection of power supply abnormalities in heating devices, causing unnecessary error processing, especially when the power supply is in an OFF state.
Innovation Solution
A heating device with a zero-crossing signal generating unit that produces a square pulse signal synchronized with AC voltage zero-crossings, allowing a control device to detect abnormalities in power supply frequency and waveform, and perform error processing only when the zero-crossing signal level indicates an actual abnormality, thereby avoiding false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control device detects abnormality based on zero-crossing signal width alone, then abnormality detection is simplified, but false detection occurs when AC power supply is in OFF state
Solution Approach 1:
The control device monitors the level of the zero-crossing signal at the detection timing and uses this feedback information to distinguish between power supply OFF state and actual abnormalities. When the level is the first level (indicating OFF state), no error processing is performed even if the width condition is met. This feedback mechanism resolves the contradiction by adding a simple level check that prevents false detection without significantly complicating the overall detection process.
2Reliability
If error processing is performed whenever zero-crossing signal width is small, then power supply abnormalities are detected, but erroneous error processing occurs during power supply OFF state
Solution Approach 1:
The control device performs a preliminary check of the zero-crossing signal level before executing error processing. By checking the level in advance (before the error processing action), the system can determine whether the small width is due to power supply OFF state (first level) or actual abnormality (second level). This preliminary action prevents the harmful effect of erroneous error processing while maintaining reliable abnormality detection.
Data Source
AI summary
A heating device including: a heat generating unit configured to receive an AC voltage from a power supply; a zero-crossing signal generating unit configured to generate a zero-crossing signal which is a square pulse signal synchronizing with a zero-crossing timing of the AC voltage, the zero-crossing signal being a first level at the zero-crossing timing and being a second level at other timings; and a control device configured to perform a detecting process in which an abnormality in a frequency or an output wave of the power supply or is detected, and an error processing, in a case where the abnormality in the frequency of the power supply or the abnormality in the output waveform of the power supply is detected and the level of a zero-crossing signal at a detection timing of detecting the abnormality is the second level.