Halogen Heater Current Feedback Circuit for Inrush Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power supply control devices for image forming apparatuses using halogen heaters face issues with high inrush current during cold start, which can lead to IGBT destruction and extended warm-up times, particularly due to the need to restrict input voltage, thereby increasing the First Copy Output Time (FCOT).
Innovation Solution
A power supply control device with a current feedback circuit capable of switching between different methods for generating current feedback signals, using a higher feedback signal during an initial period after halogen heater startup to suppress inrush current, and switching to a lower feedback signal once the heater reaches a sufficient temperature, thereby preventing IGBT destruction and maintaining efficient warm-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If input voltage is restricted for a predetermined time during cold start to suppress inrush current, then IGBT destruction is prevented, but warm-up time is extended
Solution Approach 1:
The patent applies dynamics by making the current feedback signal dynamically adjustable based on heater temperature. The control unit switches between a first current feedback signal (with higher gain) during cold start and a second current feedback signal (with lower gain) during normal operation, allowing the system to adapt its characteristics to different operational states and resolve the contradiction between protection and performance.
Solution Approach 2:
The patent changes the parameter of current feedback signal characteristics based on heater temperature. By monitoring temperature and switching between different feedback signal configurations, the system modifies its control parameters to prevent inrush current during cold start while enabling full performance during normal operation, thus resolving the time-loss contradiction.
2Reliability
If duty cycle is reduced initially to suppress inrush current, then IGBT destruction is prevented, but first copy output time is extended
Solution Approach 1:
The patent uses feedback by continuously monitoring heater temperature and adjusting the current feedback signal accordingly. The control unit receives temperature information and dynamically switches between different current feedback signals, enabling the system to protect the IGBT during cold start while rapidly transitioning to full performance mode, thereby preventing extension of first copy output time.
Solution Approach 2:
The system dynamically adjusts the current feedback characteristics based on real-time temperature conditions, allowing it to provide maximum protection when needed and maximum performance when safe, resolving the contradiction between reliability and productivity.
3Reliability
If current feedback gain is increased to suppress inrush current, then IGBT protection is improved, but heater response speed is reduced
Solution Approach 1:
The patent changes the current feedback signal parameters based on heater temperature. During cold start, a first current feedback signal with higher gain is used to suppress inrush current and protect the IGBT. Once the heater reaches a predetermined temperature, the control unit switches to a second current feedback signal with lower gain, restoring full heater response speed and eliminating the speed reduction issue.
Solution Approach 2:
The control period is segmented into distinct phases: cold start phase with high-gain feedback for protection, and normal operation phase with low-gain feedback for performance. This segmentation allows each phase to have optimized characteristics without compromising the other, resolving the contradiction between protection and response speed.
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 suppresses inrush current during cold starts without extending the warm-up time, ensuring the reliability of the power supply control device and reducing the FCOT, thus improving the performance of image forming apparatuses.
Implementation Method 1
a rectifier circuit performing full-wave rectification of the AC power to output full-wave rectified power
Implementation Method 2
a constant current control circuit performing pulse-width modulation of the amount of the heater current according to a difference between a target amount of the heater current and the current amount indicated by the current feedback signal
Implementation Method 3
Image forming apparatuses utilizing electrophotography have heat sources for heat-fixing toner onto recording sheets. Among various types of such heat sources, halogen heaters are widely used
Data Source
AI summary
A power supply control device including a chopper circuit generating a heater current for a halogen heater, a current feedback circuit generating a current feedback signal indicating a current amount based on an amount of the heater current, and a constant current circuit performing pulse-width modulation of the heater current amount according to a difference between a target heater current amount and the current amount indicated by the current feedback signal. The current feedback circuit switches between methods at least including a first method and a second method for generating the current feedback signal. The current feedback signal indicates a greater current amount with the first method than with the second method, and the current feedback circuit uses the first method during a period with a predetermined time length starting from when the halogen heater is turned on, and uses the second method after elapse of the period.