Switchable Output Resistance in Dual-Polarity Power Supplies
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Solution Overview
Problem
Existing power supply apparatuses for electro-photographic image forming devices require a positive and negative power supply connected in parallel, leading to reduced output voltage due to interference between the power supply circuits, necessitating excessive voltage generation and increased manufacturing costs.
Innovation Solution
A power supply apparatus with a resistance switching circuit that controls the output resistance by switching a second resistor in and out of the output resistance circuit, allowing for independent control of the output resistance based on the polarity of the applied voltage, thereby minimizing interference and optimizing voltage delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a positive power supply and a negative power supply are connected in parallel, then both polarities can be supplied to the load, but the power supply circuits interfere with each other causing reduced output voltage
Solution Approach 1:
The patent applies dynamics by making the output resistance of the power supply circuits adjustable rather than fixed. A resistance switching circuit is introduced that can dynamically change the output resistance value between different states (high resistance and low resistance) depending on the operating conditions. This dynamic adjustment allows the system to optimize performance for different polarity outputs while minimizing interference between the power supply circuits.
Solution Approach 2:
The patent changes the parameter of output resistance to resolve the contradiction. By switching the output resistance between different values based on which power supply circuit is active (positive or negative), the system can maintain stable output voltage. When one power supply is operating, its output resistance is increased to reduce interference from the other circuit, thereby maintaining voltage stability while providing both polarity capabilities.
2Reliability
If excessive voltage is generated to compensate for voltage reduction, then the required output voltage can be achieved, but the circuit size increases and manufacturing cost increases
Solution Approach 1:
Instead of increasing the voltage generation capability (which would require larger transformers and more complex circuits), the patent changes the resistance parameter of the power supply circuits. By adjusting the output resistance dynamically, the system can maintain the required output voltage level without needing to generate excessive voltage, thereby avoiding increased circuit size and manufacturing cost.
3Reliability
If the output resistance is increased to reduce interference, then voltage stability improves, but the voltage drop across the resistance increases
Solution Approach 1:
The patent resolves this contradiction by making the output resistance dynamic rather than static. The resistance switching circuit adjusts the output resistance value based on which power supply circuit is active. When one power supply is operating, the output resistance is increased to reduce interference and improve voltage stability. When voltage delivery is needed, the resistance is decreased. This dynamic adjustment allows the system to optimize both voltage stability and power delivery capability at different times.
Data Source
AI summary
A resistance switching circuit includes a resistor forming an output resistance of a first power supply. The resistance switching circuit switches between a state in which the resistor forms part of an output resistance and a state in which the resistor does not form part of the output resistance. A control circuit is configured to in a case where a DC voltage with a first polarity is applied to a load from a first power supply, control the resistance switching circuit such that the resistor does not form part of the output resistance, and in a case where a DC voltage with a second polarity is applied to the load from a second power supply, control the resistance switching circuit such that the resistor forms part of the output resistance.