Method and system for determining whether a portable device is charging

摘要

A method and system for detecting a charging current supplied to a portable device through a USB charger. The method includes the steps of connecting a charging circuit to a portable device, allowing the portable device to draw charging current from the charging circuit, measuring the current drawn from the charging circuit, comparing the measured current with a threshold value, making one or more system level decisions regarding charging of the portable device if the detected charging current is below the threshold current.

主权项

1. A battery charging system for detecting charging current supplied to a portable device, the system comprising:
a charging circuit including:
a power switch connecting the portable device to a power supply;a current detector connected to the power switch for detecting the charging current drawn from the power supply;a comparator connected to the current detector for comparing the detected charging current with a threshold current;an emulation circuit for performing a handshake protocol;a timer for controlling a time window within which the handshake protocol has to complete; and wherein the charging circuit is configured to determine whether a selected handshake protocol is completed by the emulation circuit within the time window and wherein the charging circuit is further configured to reset the portable device and discard the selected handshake profile if the handshake protocol has not been completed within the time window and select a new handshake profile.