Halogen Heater Phase Control for Flicker and Inrush Current
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Solution Overview
Problem
Conventional heater on/off control in image forming apparatuses experiences increased inrush current and disturbance voltage when transitioning from heater-off to heater-on, making it difficult to maintain a low-flicker level stably, especially when all half-waves are allocated to heater-on during the initial period.
Innovation Solution
An image forming apparatus that includes a fixing unit with a heater, an alternating-current power source, a half-wave control unit, a measuring unit, a determining unit, and a phase control unit. The apparatus performs half-wave control based on a predetermined cycle and measures the heater-off period to determine if phase control is necessary, shifting the phase of the alternating voltage only for a specific period after switch-on and before half-wave control to minimize flicker and inrush current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If half-wave control is used to reduce flicker, then flicker level is improved, but inrush current increases when transitioning from heater-off to heater-on
Solution Approach 1:
The patent applies preliminary action by measuring the heater-off period in advance and determining whether phase control is needed before the heater transitions from off to on state. This allows the system to prepare appropriate control strategies (phase control followed by half-wave control, or direct half-wave control) to prevent inrush current while maintaining low flicker levels.
Solution Approach 2:
The patent implements dynamics by making the heater control strategy adaptive based on the measured heater-off period. The determining unit dynamically selects between different control modes (phase control + half-wave control, or only half-wave control), and the phase control duration is dynamically adjusted based on the heater-off period, allowing the system to optimize performance for each specific operating condition.
2Power
If phase control is performed for a longer period to reduce inrush current, then disturbance voltage is reduced, but flicker increases
Solution Approach 1:
The patent applies parameter changes by using the heater-off period as a key parameter to determine the duration of phase control. The measuring unit measures the heater-off period, and the determining unit uses this parameter to decide whether phase control is needed and how long it should last. This dynamic parameter adjustment optimizes the balance between reducing inrush current/disturbance voltage and minimizing flicker.
3Productivity
If all half-waves are allocated to heater-on during initial period, then heating efficiency is improved, but inrush current undesirably flows
Solution Approach 1:
The patent applies preliminary action by measuring the heater-off period and determining the appropriate control strategy before the heater transitions from off to on state. This allows the system to prepare phase control measures in advance to prevent inrush current while maintaining heating efficiency through subsequent half-wave control.
Solution Approach 2:
The patent implements periodic action through half-wave control, where the heater is controlled in periodic half-wave cycles after the initial phase control period. This maintains high heating efficiency by utilizing the periodic nature of AC power while avoiding continuous operation that would cause sustained inrush current.
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
This solution reduces flicker and disturbance voltage by minimizing the duration of phase control based on the measured heater-off period, ensuring a stable low-flicker level and reducing inrush current.
Implementation Method 1
a heater provided in the fixing unit; an alternating-current power source that applies an alternating voltage to the heater
Data Source
AI summary
An image forming apparatus includes a halogen heater in a fixing unit; an AC source applying an alternating voltage to the halogen heater; a half-wave control unit that performs the heater half-wave control to control the halogen heater on the half-wavelength basis, according to a heater-on/off pattern set for each control cycle having a predetermined length; a heater-off-time measuring unit that measures heater-off period of time; a phase-control-execution determining unit that determines, based on the measured heater-off period of time, whether the heater phase control is to be performed on the alternating voltage, the phase control being performed by shifting phase of the alternating voltage; and a phase control unit that performs, when the phase control is determined to be performed, the phase control only for a period of time depending on the measured heater-off period of time after switch-on of the heater and before execution of the half-wave control.