Fixing Unit Heater Control via Segmented Power Supply
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image forming apparatuses with high-output heaters experience significant harmonic current issues due to phase control, leading to excessive heat generation in switching elements.
Innovation Solution
The apparatus employs a controller to manage the switching element's conduction state on a half-cycle basis, dividing the power supply period into a first and second power supply period, with the sum of these periods ranging from 1/6000 to 1/40 of a cycle, to minimize harmonic current while maintaining target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If phase control is used to supply power to a high-output heater, then quick responsiveness of temperature control is achieved, but harmonic current becomes large
Solution Approach 1:
The power supply period within each half-cycle is divided into multiple segments (first power supply period, second power supply period, and third power supply period). This segmentation allows the controller to supply power in controlled intervals rather than continuously, reducing the abrupt current changes that generate harmonic current while maintaining temperature control responsiveness.
Solution Approach 2:
The controller implements periodic power supply action by dividing each half-cycle into multiple power supply periods with specific duration ratios. The first power supply period has a duration of 1/30 to 1/1000 of a cycle, followed by a second power supply period with duration of 1/6000 to 1/40 of a cycle, and optionally a third power supply period. This periodic structure reduces harmonic current by avoiding continuous phase control while maintaining effective heating.
2Object-generated harmful factors
If the abrupt current change is made moderate to reduce harmonic current, then harmonic current is reduced, but the switching element generates heat
Solution Approach 1:
The controller ensures continuous useful action by providing multiple power supply periods (first, second, and third) within each half-cycle. Even though each individual period is short, the cumulative effect maintains continuous heating action. This allows the use of shorter power supply periods that reduce harmonic current while maintaining effective temperature control, thereby reducing stress and heat generation on switching elements.
Solution Approach 2:
The controller changes the parameter of power supply duration by dividing each half-cycle into multiple periods with specific duration ratios. The first power supply period has duration of 1/30 to 1/1000 of a cycle, the second has duration of 1/6000 to 1/40 of a cycle, and the third has duration of 1/30 to 1/1000 of a cycle. These parameter changes optimize the balance between reducing harmonic current and minimizing switching element heat generation.
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 approach effectively reduces harmonic current while minimizing the heat influence on switching elements, enhancing the apparatus's efficiency and reliability.
Implementation Method 1
a heater represented by, for example, a ceramic heater is used as a heat source
Implementation Method 2
phase control is carried out in many cases in order to realize quick responsiveness of the control
Data Source
AI summary
An image forming apparatus includes a fixing unit, a switching element, and a controller. The controller controls the switching element on a half-cycle basis of an alternating current. A period in which the electric power is supplied to the heater within a period of a half-cycle of the alternating current is divided into at least one first power supply period and a second power supply period longer than one first power supply period. A length of a sum of the at least one first power supply period is a length from 1/6000 to 1/40 of one cycle of the alternating current. A sum of electric power supplied in the at least one first power supply period and electric power supplied in the second power supply period is determined depending on a difference between a temperature and a target temperature of the fixing unit.