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Automatic connect/disconnect control of USB port according to system power source condition

IP.com Disclosure Number: IPCOM000014672D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-20
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Abstract

Disclosed is a circuit design and its control method to connect/disconnect USB port from system control s/w.

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  Automatic connect/disconnect control of USB port according to system power source condition

Disclosed is a circuit design and its control method to connect/disconnect USB
port from system control s/w.

This method is to connect/disconnect USB port
dynamically while system operation, according to
system condition.

This method can be used, for example, to achieve
longer battery operation time by controlling USB
connection according
to system power source in mobile computing system.

Figure 1 shows a typical implementation of this
method into mobile computing system, from H/W on
the right side to user on the left side. Power line
and signal lines of USB port (1) are switched using
analog switching circuit, such as FET or Q-switch.
On/Off of these switches are controlled from a
system logic, like GPIO (general purpose
input/output) signal of system ASIC (2). This
signal is controlled by system control S/W, such as
BIOS or ASL(ACPI Source Language) (3). System
control S/W can determine the system condition such
that power source is either AC adapter or battery,
through system's EC (embedded controller).

When system power source is battery, system control
S/W can automatically switch off the USB port
switch, so that USB device is regarded to be
disconnected from system. When power source is
changed to AC adapter, system control S/W can
automatically switch on the USB port, so that USB
device is regarded to be connected to system. USB
device supports plug/unplug operation while
operation therefore this switching is regarded as
USB device's plug/unplug and handled as such, and
it does not hang up the system's operation.

The...