Automatic connect/disconnect control of USB port according to system power source condition
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2003-Jun-20
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).