High-Voltage Current Detection Circuit With AD Input Protection
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Solution Overview
Problem
Existing power supply apparatuses for electrophotographic image forming devices face challenges in accurately controlling high voltage output due to limitations in current detection resolution, which can lead to overvoltage application to the CPU, potentially causing damage.
Innovation Solution
A power supplying apparatus comprising a power supply circuit, a current detection circuit, and a controller with an AD converter, determination circuit, and protection circuit to detect currents with high resolution and protect the AD converter from overvoltage, thereby ensuring safe and accurate voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reference voltage of the current detection circuit is increased to improve current detection resolution, then the current detection precision is improved, but the risk of overvoltage damage to the CPU increases
Solution Approach 1:
The patent introduces a protection circuit as an intermediary component between the current detection circuit and the CPU. This protection circuit includes a voltage divider that divides the reference voltage before applying it to the CPU, ensuring the CPU receives a safe voltage level while the current detection circuit can use a higher reference voltage for improved measurement precision.
Solution Approach 2:
The patent segments the voltage supply system into two independent parts: the current detection circuit uses a high reference voltage for precise current measurement, while the CPU receives a divided, lower voltage through the protection circuit. This segmentation allows each component to operate at its optimal voltage level without compromising the other.
2Measurement precision
If a high reference voltage is applied to improve current detection range and resolution, then the detection capability is enhanced, but the CPU may be exposed to damaging overvoltage
Solution Approach 1:
The protection circuit serves as a mediator that allows the current detection circuit to operate with a high reference voltage for enhanced detection capability, while simultaneously protecting the CPU by dividing this voltage to a safe level before it reaches the CPU.
3Measurement precision
If the detection resistor is increased to improve current detection resolution, then the measurement precision is improved, but the voltage applied to the CPU increases beyond safe levels
Solution Approach 1:
The protection circuit with voltage divider acts as an intermediary that decouples the detection resistor value from the CPU voltage. This allows the detection resistor to be increased for better resolution without proportionally increasing the voltage applied to the CPU, as the voltage divider maintains the CPU voltage within safe limits.
Data Source
AI summary
A power supply circuit generates an output voltage. A current detection circuit detects a current flowing through a load. An AD converter reads an output signal from the current detection circuit. A determination circuit determines whether an overvoltage may be applied to an input terminal of the AD converter. A protection circuit protects the input terminal of the AD converter from the overvoltage. Upon determining that the overvoltage may be applied to the input terminal, a controller controls the protection circuit to reduce a voltage applied to the input terminal of the AD converter.