Voltage Generating Apparatus for Image Forming Devices
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Solution Overview
Problem
Existing voltage generating apparatuses for electrophotographic image forming devices face challenges in rapidly raising output voltage while minimizing overshooting and undershooting, particularly due to bottlenecks in charging electrolytic capacitors and increased ripples in transformer output voltage control.
Innovation Solution
A voltage generating apparatus that employs a step-up transformer with a switch circuit and signal generation unit to control the output voltage by adjusting the frequency or duty ratio of the switching control signal until a threshold value is reached, then transitions to supply voltage control to stabilize the output voltage near the target value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the DC voltage on the primary side of the transformer is changed to raise the output voltage, then the output voltage can be adjusted, but the charging speed is limited by the electrolytic capacitor charging time
Solution Approach 1:
The patent applies preliminary action by pre-charging the electrolytic capacitor to a predetermined voltage before the main output voltage raising operation. This preparation step allows the system to quickly raise the output voltage without being bottlenecked by the slow capacitor charging process during the actual voltage transition.
Solution Approach 2:
The patent segments the voltage control process into two distinct phases: a first control period using PWM signal duty ratio adjustment for rapid voltage raising, and a second control period using DC voltage adjustment for stable voltage maintenance. This segmentation allows each phase to optimize for its specific function.
2Reliability
If the pulse width modulation signal is thinned out to control the output voltage, then the output can be regulated, but ripples increase in size for high output performance transformers
Solution Approach 1:
The patent applies dynamics by making the control method adaptive based on operating conditions. The system dynamically switches between two control approaches: using PWM duty ratio adjustment during the first control period for rapid response, and using DC voltage adjustment during the second control period for ripple-free stable operation. This dynamic adaptation eliminates the harmful ripples associated with PWM thinning.
3Adaptability or versatility
If the frequency of the pulse width modulation signal is changed to adjust the output voltage, then voltage control is achieved, but the desired output voltage may not be obtained depending on transformer characteristics
Solution Approach 1:
The patent applies parameter changes by switching between two different control parameters: PWM signal duty ratio during the first control period and DC voltage magnitude during the second control period. This dual-parameter approach provides both the flexibility needed for rapid voltage transitions and the precision required for accurate voltage regulation, overcoming the limitations of frequency-only control.
4Speed
If an integrator circuit is arranged on the input side of the PWM pulse output circuit to raise the PWM on-duty width, then the output voltage can be increased, but startup time (integration time) is required
Solution Approach 1:
The patent applies preliminary action by pre-charging the electrolytic capacitor before the main voltage raising operation. This eliminates the need for integration-time-based duty width adjustment during startup, as the capacitor is already prepared to deliver the required voltage immediately when the voltage raising operation begins.
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 allows for high-speed raising of the output voltage while reducing overshooting and undershooting, achieving stable voltage control and minimizing ripples, thus shortening the time to reach the target voltage.
Implementation Method 1
a step-up transformer 1
Data Source
AI summary
Until an output voltage of a converter reaches a threshold value, a control part performs switching control, and after the output voltage reaches the threshold value, the control part performs supply voltage control while the state of a switching control signal at the time when the output voltage reaches the threshold value is maintained. Switching control is a control method in which the output voltage is adjusted by adjusting the frequency or duty ratio of the switching control signal that drives a driving part. Supply voltage control is a control method in which the output voltage is adjusted by adjusting the supply voltage that is applied to the primary side of the converter.