Heating Device Zero-Cross Signal Timing Control
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Solution Overview
Problem
Conventional image-forming devices face instability in controlling electricity to heating bodies due to indeterminate internal signal states when switching conduction signals at zero-cross points of AC voltage, leading to potential noise and increased power consumption.
Innovation Solution
A heating device comprising a heating body, a heating switch, a detector, and a control device that detects zero-cross timings of AC voltage and generates a signal with specific high and low level periods and transition timings to control the heating switch, ensuring that at least one transition timing is non-coincident with the zero-cross timing, thereby stabilizing the power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the internal signal is switched at the timing that overlaps with zero-cross point detection, then the conduction signal can be synchronized with zero-cross points, but the internal signal state becomes indeterminate leading to control instability
Solution Approach 1:
The control device generates the internal signal in advance such that its rising and falling transitions are positioned before or after the zero-cross timing, rather than coinciding with it. This preliminary positioning of signal transitions prevents the indeterminate state problem while maintaining synchronization capability
Solution Approach 2:
The control device acts as an intermediary between the zero-cross detection and the heating switch control. It processes the zero-cross timing information and generates an internal signal with appropriately timed transitions, mediating the control signal to avoid direct coincidence with zero-cross points
2Loss of energy
If the conduction signal is switched at zero-cross points, then noise and power consumption are reduced, but control instability occurs due to indeterminate internal signal states
Solution Approach 1:
The internal signal transitions are arranged in advance to occur before or after zero-cross points, allowing the heating switch to be controlled at zero-cross timing without the internal signal being in an indeterminate state, thus maintaining low power consumption while ensuring control stability
Solution Approach 2:
The timing parameters of the internal signal transitions are specifically adjusted to be non-coincident with zero-cross timing. By changing the temporal parameters of the control signal, the system achieves both energy efficiency and operational reliability
Data Source
AI summary
In a heating device, a detector detects AC voltage of the AC power source. A control device detects a zero-cross timing of the AC voltage by using the detector and generate a signal having a high level period of time, a low level period of time, a rising transition changing from a low level to a high level, and a falling transition changing from the high level to the low level. The signal is such a form that at least one of the rising transition and the falling transition is in incoincidence with the zero-cross timing. The control device controls the heating switch to perform a switching action in which the heating switch is rendered on when the zero-cross timing is detected during the high level period of time and rendered off when the zero-cross timing is detected during the low level period of time.