USB Host Interface Power Control for Overcurrent Prevention
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Solution Overview
Problem
Information processing apparatuses with USB interfaces face issues where external devices cannot be used after returning from a power-saving state due to overcurrent generation, caused by the overcurrent preventing mechanism activating when external devices maintain a high potential during the transition from a power-saving state to a normal state.
Innovation Solution
The apparatus includes a USB host interface with a switching mechanism and an overcurrent preventing mechanism, where a controller outputs signals to turn off and then restore the power supply, allowing the removal of the electrical connection cutoff when returning to the normal state, ensuring the USB host interfaces can supply power to external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overcurrent preventing mechanism is activated to protect against overcurrent during power-saving state transitions, then device safety is improved, but the USB host interface cannot supply power to external devices after returning from power-saving state
Solution Approach 1:
The controller outputs a first signal before the second signal to preemptively turn off the power supply during the transition from power-saving state to normal state. This preliminary action prevents the overcurrent condition that would trigger the cutoff mechanism, allowing the electrical connection to remain intact and the USB device to remain usable after power restoration.
Solution Approach 2:
The system dynamically controls the power supply state through sequential signaling. The switching mechanism transitions the power supply from off to on state in a controlled sequence, adapting the electrical connection state to match the power-saving state transitions and preventing premature overcurrent detection.
2Use of energy by moving object
If the power supply is turned off during power-saving state to reduce energy consumption, then energy efficiency is improved, but external devices cannot be used after returning from power-saving state due to overcurrent
Solution Approach 1:
The controller preemptively outputs the first signal to turn off the power supply before the actual power-saving state transition completes. This ensures that when the apparatus returns from power-saving state, the power supply is already in the correct state and can be safely restored without triggering overcurrent protection, maintaining both energy efficiency and power supply reliability.
3Reliability
If the electrical connection is cut off by the overcurrent preventing mechanism to prevent damage, then device protection is improved, but the USB host interface loses connectivity to external devices
Solution Approach 1:
The controller outputs the first signal in advance to turn off the power supply before the overcurrent condition can develop. This preliminary action prevents the overcurrent preventing mechanism from activating and cutting off the electrical connection, thereby maintaining USB interface connectivity while still protecting the device through controlled power management.
Data Source
AI summary
According to an aspect of the present disclosure, an image forming apparatus checks a connection status of devices to an USB host interface, and then turns off once a GPIO controlling a Vbus of interfaces to which USB devices are not connected, and then turns on the GPIO (that is, writing an enable signal “1” after writing a disable signal “0”), and then remove a cutoff state of electrical connection with the USB devices by a overcurrent preventing mechanism.