Power Control for Image Forming Apparatuses
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Solution Overview
Problem
Image forming apparatuses using electrophotography face challenges in power control due to varying voltage and frequency of AC power supplies, leading to unstable phase control and potential malfunctions, especially in noisy environments where zero-crossing signals are misinterpreted, causing incorrect phase control and device malfunctions.
Innovation Solution
A power control method that generates and detects zero-crossing signals based on AC voltage levels, differentiating between noise-free and noisy conditions to accurately determine phase control parameters, ensuring stable operation even with voltage and frequency variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase control is performed using zero-crossing signals in noisy power supply environments, then power control can be implemented, but zero-crossing signals are misinterpreted due to noise, causing improper phase control and device malfunctions
Solution Approach 1:
The patent introduces an intermediary verification mechanism that mediates between the noisy zero-crossing signal and the phase control execution. The control section verifies whether the detected zero-crossing signal is valid by checking if it meets predetermined criteria before using it for phase control, thus preventing noise-induced misinterpretation while maintaining proper phase control functionality
Solution Approach 2:
The patent implements a feedback mechanism where the control section continuously monitors the zero-crossing signal characteristics and compares them against expected patterns. When noise causes abnormal zero-crossing detection, the feedback loop detects this deviation and prevents improper phase control actions, thereby maintaining reliability in noisy environments
2Temperature
If the heater is energized with high power, then the temperature increases quickly, but inrush currents cause voltage drop and may damage switching devices
Solution Approach 1:
The patent employs periodic action by controlling the heater through cyclic on-off operations based on phase control. Instead of continuous high-power operation, the heater is energized in periodic cycles synchronized with the AC power supply phases, which limits inrush current while maintaining effective heating through cumulative thermal effect
Solution Approach 2:
The patent applies dynamics by making the heater power delivery variable and adaptive. The phase control dynamically adjusts the conduction angle of the switching device, allowing the heater to receive high power when needed for rapid temperature increase while limiting power during other phases to prevent excessive inrush currents and voltage drops
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 method effectively stabilizes phase control, reducing the likelihood of malfunctions and ensuring reliable operation of image forming apparatuses by accurately distinguishing true zero-crossing signals from noise, even in environments with power supply fluctuations.
Implementation Method 1
generating a zero-crossing signal that indicates a first level if an absolute value of AC voltage from the AC power supply is equal to or smaller than a predetermined value, and indicates a second level if the absolute value of the AC voltage is larger than the predetermined value
Implementation Method 2
a phase angle at which a switching device is turned ON in each half cycle of AC is controlled to gradually increase a conduction angle φ at which the switching device is turned ON from 0 to π
Implementation Method 3
a heater to fuse, by heat, a toner image formed on paper to fix the same thereon
Data Source
AI summary
A power control method for performing phase control is provided. The method includes generating a zero-crossing signal that indicates a first level if an absolute value of AC voltage is smaller than a predetermined value, and indicates a second level if the absolute value of the AC voltage is larger than the predetermined value; detecting a zero-crossing width and a non-zero-crossing width, the zero-crossing width being a time width for a case where the absolute value of the AC voltage is smaller than the predetermined value, the non-zero-crossing width being a time width for a case where the absolute value is larger than the predetermined value; detecting a frequency and a voltage value of the AC voltage based on the zero-crossing width and the non-zero-crossing width; and performing phase control depending on the frequency and the voltage value.