High-Voltage Generation Apparatus for Rapid Polarity Switching
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Solution Overview
Problem
High-voltage generation apparatuses face challenges in rapidly switching between positive and negative polarities during continuous printing in electrophotographic color image forming, leading to increased temperature-related misregistration and density variations, which disrupt productivity due to the time required to form and detect patch images.
Innovation Solution
A high-voltage generation apparatus with a transformer, driving unit, rectification unit, detection unit, and feedback control unit that adjusts the slew rate and startup period to rapidly reach target voltages without overshoot or undershoot, allowing for quick polarity switching by varying the on-duty width of PWM signals based on the magnitude of the target voltage and load potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the high voltage is switched between positive and negative polarities during continuous printing, then color misregistration and density variation are reduced, but the switching time of 50-100ms causes productivity reduction
Solution Approach 1:
The patent applies preliminary action by pre-charging a capacitor with opposite polarity before voltage switching is needed. When polarity switching is required, the pre-charged capacitor is rapidly connected to the output, immediately establishing the opposite polarity without waiting for the transformer to ramp up voltage. This eliminates the 50-100ms switching delay while maintaining the calibration benefits.
Solution Approach 2:
The patent implements periodic action by alternately charging capacitors with opposite polarities in advance during periods when voltage switching is not immediately needed. The capacitors are charged periodically at lower priority times, then rapidly discharged when polarity switching is required, enabling fast switching while distributing the energy preparation work over time.
2Manufacturing precision
If the patch image is formed and detected between sheets to maintain image quality, then color misregistration and density are corrected, but the time required for patch formation and detection reduces productivity
Solution Approach 1:
The patent performs preliminary action by pre-charging the capacitor with opposite polarity before the patch image formation period. This allows the voltage switching to occur instantaneously during the patch formation window, eliminating the voltage ramping time from the patch formation process and enabling quality calibration without time loss.
3Manufacturing precision
If the secondary transfer bias is switched to negative polarity to prevent back smudging, then recording material quality is maintained, but the voltage switching time of 50-100ms causes productivity reduction
Solution Approach 1:
The patent applies preliminary action by pre-charging a capacitor with negative polarity before the recording material reaches the transfer nip portion. When switching is needed to prevent back smudging, the pre-charged capacitor is rapidly connected, immediately establishing the negative bias without the 50-100ms delay, thus maintaining material quality while preserving productivity.
4Productivity
If the high voltage is raised quickly to reach target voltage, then productivity is improved, but voltage overshoot or undershoot occurs reducing stability
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors to the exact target voltage level before switching is needed. When switching occurs, the pre-charged capacitor immediately establishes the correct target voltage without overshoot or undershoot, as the capacitor voltage cannot change instantaneously and provides a stable starting point for the voltage transition.
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
Enables rapid and efficient switching between polarities, reducing the time required to form patch images and maintain image quality, thereby enhancing productivity and stability during continuous printing.
Implementation Method 1
a transformer T1 and a boosting circuit unit 23... an output unit 39 for outputting a voltage obtained by boosting an input voltage by the transformer T1
Implementation Method 2
a rectification unit configured to rectify an output voltage from the transformer to output a direct-current voltage
Data Source
AI summary
A high-voltage generation apparatus raises, when switching from a state where a voltage having a predetermined polarity is output to a state where a voltage having a polarity opposite to the predetermined polarity is output, the voltage having the predetermined polarity in change amounts corresponding to the voltage having the predetermined polarity and a target voltage having the opposite polarity in a transient-state period elapsed until the voltage reaches the target voltage.