Heater Controller Flicker Reduction via Dynamic Control Switching
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Solution Overview
Problem
Existing heater control technologies, such as phase control and turn-on/off pattern control, fail to effectively improve frequency characteristics and reduce flicker when transitioning between these methods, leading to suboptimal performance in halogen heater systems used in image forming apparatuses.
Innovation Solution
A heater controller comprising a detector, determination circuit, limiting circuit, and selection circuit that dynamically adjusts the turn-on ratio of the heater based on temperature differences and previous control cycles, selecting between phase control and half-wave control patterns to minimize flicker and maintain effective frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If phase control technology is used to suppress inrush current, then inrush current is reduced, but frequency characteristics cannot be effectively improved during transition period
Solution Approach 1:
The patent dynamically switches between phase control and turn-on/off pattern control based on the operational state. During transition periods when the heater is first energized or after prolonged operation, phase control is used to suppress inrush current. Once the heater reaches steady-state operation, the system transitions to turn-on/off pattern control to optimize frequency characteristics and eliminate flicker. This dynamic adaptation resolves the contradiction by applying the appropriate control method at different operational stages.
Solution Approach 2:
The patent changes the control parameters by switching between two distinct control strategies: phase control (which adjusts the phase angle of AC voltage application) and turn-on/off pattern control (which controls the duty cycle and timing of heater activation). This parameter change allows the system to optimize for inrush current suppression during transitions while achieving superior frequency characteristics during steady-state operation.
2Object-generated harmful factors
If turn-on/off pattern control is used to reduce flicker, then flicker is reduced, but frequency characteristics cannot be effectively improved during transition period
Solution Approach 1:
The system dynamically selects the control method based on operational conditions. During transition periods (heater startup or recovery from prolonged shutdown), phase control is applied to maintain stable frequency characteristics. Once steady-state is achieved, turn-on/off pattern control is applied to minimize flicker by avoiding the 8.8 Hz frequency range where human eyes are most sensitive. This dynamic selection resolves the contradiction between flicker reduction and frequency characteristic stability.
3Object-generated harmful factors
If combined phase control and turn-on/off pattern control are used, then both inrush current and flicker are addressed, but frequency characteristics and flicker cannot be reduced effectively during transition period
Solution Approach 1:
The patent segments the control process into distinct phases: an initial transition period using phase control, and a steady-state period using turn-on/off pattern control. By dividing the operational timeline into these segments and applying different control strategies to each, the system avoids the problem of combined control failing during transitions. The segmentation ensures that each control method is applied in its optimal operational context.
Solution Approach 2:
The system performs preliminary action by using phase control during the transition period before switching to turn-on/off pattern control. This preliminary phase control establishes stable frequency characteristics during heater startup or recovery, preparing the system for the subsequent flicker-reduction phase. This sequential approach ensures that frequency characteristics are stabilized before attempting flicker minimization.
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 solution reduces flicker and improves frequency characteristics by limiting turn-on ratios during transition periods, ensuring consistent and efficient heater control, thereby minimizing light fluctuations and enhancing the performance of image forming apparatuses.
Implementation Method 1
A halogen heater is used as a fixing heater used for an electro-photographic image forming apparatus
Implementation Method 2
The detector detects a temperature of a heating object, the heating object is heated by the heater
Data Source
AI summary
A heater controller and heater control method is disclosed. The hater controller includes a detector, a determination circuit, a limiting circuit, a selection circuit, and a driving circuit. The detector detects a temperature of the heating object, which is heated by the heater. The determination circuit determines turn-on ratio for the heater for every control cycle of AC voltage, based on the surface temperature of the heating object and a target temperature of the heating object. The limiting circuit limits the turn-on ratio of current control cycle when the control method of previous control cycle is phase control. The selection circuit selects control pattern to control the heater, based on the turn-on ratio, and the driving circuit applies a heater driving signal to the heater.