Charging Power Supply Circuit for Ripple-Free DC Current Detection
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Solution Overview
Problem
Existing electrophotographic image forming apparatuses with AC charging systems face errors due to ripple voltage caused by AC current flowing into the current detector, especially when sampling rates are insufficient, leading to inaccurate detection of the DC current and surface potential of the image bearer.
Innovation Solution
A power supply device with an AC voltage generation circuit, a DC voltage generation circuit, and a DC current detection circuit, which includes a reduction circuit to minimize AC current inflow and a reverse waveform applicator circuit to cancel ripple voltage, ensuring accurate detection of the DC current and surface potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a current detector is provided in the low voltage section to detect DC current inexpensively, then the detection cost is reduced, but ripple voltage from AC current causes detection errors
Solution Approach 1:
An AC current reducer circuit is introduced as an intermediary component between the AC voltage generation circuit and the DC current detection circuit. This mediator reduces the AC current that would otherwise flow into the detection circuit and cause ripple voltage, thereby maintaining detection accuracy while keeping the detector in the low voltage section
Solution Approach 2:
The power supply device is segmented into distinct functional sections: AC voltage generation, AC current reduction, DC voltage generation, and DC current detection. By separating the AC current reduction function into its own circuit stage, the detection circuit can operate independently in the low voltage section without being affected by AC ripple
2Measurement precision
If the sampling rate is increased to reduce detection errors from ripple voltage, then measurement precision improves, but CPU occupancy increases
Solution Approach 1:
The AC current is reduced before the DC current detection and sampling process. By preliminarily reducing the AC current component that causes ripple voltage, the detection can proceed with lower sampling rates without sacrificing accuracy, thus reducing CPU occupancy
Data Source
AI summary
A power supply device that applies a voltage in which a direct-current (DC) voltage and an alternating-current (AC) voltage are superimposed on each other to a charging member that charges an image bearer, includes: an AC voltage generation circuit that generates the AC voltage; a DC voltage generation circuit that generates the DC voltage; a DC current detection circuit provided on an output terminal side of the DC voltage generation circuit, which detects an output DC current flowing into the image bearer; and a reduction circuit that reduces an inflow of an AC current to the DC current detection circuit.