AFE Power Supply Switching for Noise and Efficiency
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Solution Overview
Problem
Image forming apparatuses face challenges in providing high-quality power supply to analog front-end (AFE) circuits while minimizing noise and power consumption, especially in sleep mode, due to the limitations of series path regulators and DC-DC converters.
Innovation Solution
An image forming apparatus with a switching circuit that switches between a series path regulator for low-noise power supply during AFE usage and a DC-DC converter for high power efficiency during non-use, ensuring low noise and reduced power consumption in sleep mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a DC-DC converter is used to supply power to the reading unit, then power conversion efficiency is improved, but ripple noise increases causing image quality deterioration
Solution Approach 1:
The patent dynamically switches between two power supply methods (series path regulator and DC-DC converter) based on operational conditions. During image reading operations, the series path regulator is used to minimize noise. During non-reading operations or sleep mode, the DC-DC converter is used to maximize power efficiency. This dynamic adaptation resolves the contradiction by optimizing the power supply method according to real-time operational needs.
Solution Approach 2:
The patent segments the power supply function into two distinct paths: a series path regulator for noise-sensitive operations and a DC-DC converter for power-efficient operations. The switching circuit divides the power supply task between these two segments, allowing each to operate in its optimal performance regime without compromising the other.
2Loss of energy
If power to the AFE is turned off in sleep mode, then power consumption is reduced, but a potential difference occurs causing current flow and latch-up phenomenon
Solution Approach 1:
The patent introduces a potential equalization circuit as an intermediary between the AFE and other circuits. This circuit includes a resistor connected between the AFE power supply terminal and ground, which maintains a minimal current path to prevent potential differences. The resistor acts as a mediator that allows the AFE to be effectively powered down while maintaining electrical continuity to prevent latch-up phenomena.
3Object-affected harmful factors
If a series path regulator is used to supply power to the AFE, then noise is reduced improving image quality, but power conversion efficiency decreases increasing power consumption
Solution Approach 1:
The system dynamically selects the power supply method based on operational mode. During active image reading, the series path regulator is engaged despite its lower efficiency because noise reduction is the priority. During sleep mode or non-reading operations, the DC-DC converter takes over to minimize power consumption. This dynamic switching resolves the contradiction by prioritizing different parameters at different times.
Data Source
AI summary
An image forming apparatus that ensures high-quality power supply to an AFE (analog front-end) and reduces the amount of power consumed by the AFE in sleep mode. The AFE, which converts an analog signal into a digital signal, and another circuit different from the AFE are incorporated in an SOC (system-on-a-chip). A switch circuit switches power to the AFE between first DC power supply from a 5-V/3.3-V_LDO and second DC power from a 24-V/3.3-V_DC-DC converter. When the AFE is in use, the switch circuit is controlled such that the first DC power is supplied from the 5-V/3.3-V_LDO to the AFE, and when the AFE is not in use, the switch circuit is controlled such that the second DC power is supplied from the 24-V/3.3-V_DC-DC converter to the AFE.