Power Control Apparatus for Image Forming Overheating Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image forming apparatuses, such as laser printers, face challenges in maintaining optimal temperature for fusing units when switching from AC to DC power, leading to potential overheating and degraded image quality due to uncontrollable heating elements.
Innovation Solution
A power control apparatus that includes a DC cutoff circuit and a fusing temperature adjuster, which discontinuously supplies power to the heating element and uses a TRIAC to control temperature, preventing overheating by blocking DC power when DC is input instead of AC, ensuring the heating element operates within a safe temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an AC power switch is used to control the heating element, then the heating element can be controlled when AC power is applied, but the heating element becomes uncontrollable and may overheat when DC power is supplied
Solution Approach 1:
The power control apparatus is designed to handle both AC and DC power types using the same circuit architecture. The controller detects the power type and adjusts the switching strategy accordingly, making the system universally applicable to different power sources without requiring separate control circuits for AC and DC.
Solution Approach 2:
The control method changes based on the detected power type. For AC power, the controller uses zero-crossing detection and triggers the TRIAC at appropriate points in the AC cycle. For DC power, the controller uses pulse-width modulation (PWM) with a chopper circuit to achieve discontinuous power supply. This parameter change in control strategy resolves the contradiction between controllability and adaptability.
2Productivity
If continuous power is supplied to the heating element, then the fusing unit can maintain high temperature for efficient printing, but the heating element may overheat and cause malfunction
Solution Approach 1:
The power control apparatus implements periodic interruption of power supply to the heating element. For AC power, it uses phase-angle control with TRIAC to supply power in controlled cycles. For DC power, it uses a chopper circuit with PWM to create periodic on-off cycles. This periodic action maintains average power delivery for efficient printing while preventing continuous overheating.
Solution Approach 2:
The system incorporates temperature sensing feedback to monitor the heating element temperature. The controller adjusts the duty cycle of the PWM signal or the phase angle of TRIAC triggering based on the feedback temperature signal, dynamically balancing printing efficiency with overheating prevention.
3Ease of operation
If a TRIAC is used to control AC power to the heating element, then temperature control is achieved, but the TRIAC cannot function properly when DC power is supplied
Solution Approach 1:
The system introduces a chopper circuit as an intermediary between the DC power source and the heating element. This chopper circuit converts DC power into pulsating DC that can be controlled similarly to AC power. The TRIAC or equivalent switching device then operates on this conditioned power, enabling temperature control functionality to be maintained across different power types.
Solution Approach 2:
The control system dynamically adapts its operation mode based on the detected power type. When AC power is detected, the system operates in phase-angle control mode using TRIAC. When DC power is detected, the system switches to PWM control mode using a chopper circuit. This dynamic adaptation maintains ease of operation across different power types.
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 effectively prevents overheating and maintains the fusing unit at a proper temperature, ensuring stable and safe printing operations regardless of the power type, thereby extending the life of the fusing unit and maintaining image quality.
Implementation Method 1
a fusing unit provided to fuse operation fuses an image on the surface of the printing medium by heating the paper to which the image has been transferred to a proper temperature
Implementation Method 2
DC cutoff circuit and a fusing temperature adjuster, which discontinuously supplies power to the heating element and uses a TRIAC to control temperature
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A power control apparatus and an image forming apparatus is provided to prevent a heating element from overheating when DC power is supplied and to perform normal operation regardless of the type of input power. The power control apparatus includes a power supply to supply power to a load, an alternating current (AC) power switch to discontinuously switch on AC power between the power supply and the load, and a direct current (DC) cutoff circuit to block supply of DC power through the AC power switch to prevent supply of the DC power to the load via the AC power switch when the DC power is input through the power supply.