Method and system for determining whether a portable device is charging
View Patent ↗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.
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.
2. The system of claim 1 , wherein if no suitable handshake profile can be implemented, accepting a charging profile that provides less than optimum charging current.
3. The system of claim 1 , wherein the charging circuit is further configured, after the handshake protocol has been completed, to make one or more system level decisions regarding charging of the portable device if the detected charging current is below the threshold current,
wherein the one or more system level decisions comprising: resetting the portable device; offering another handshake profile; alerting the portable device; or continuing charging the portable device.
4. The system of claim 1 , wherein the charging circuit further comprising a profile database for storing multiple charging profiles.
5. The system of claim 4 , wherein the profile database stores handshake protocols and associated time window values for each charging profile.
6. The system of claim 1 further comprising a power supply coupled to the power switch.
7. The system of claim 1 further comprising a host coupled to the charging circuit and the portable device through one or more data pins.
8. The system of claim 1 wherein the charging circuit is a universal serial port (USB) charging port.
9. A battery charging system for measuring charging current supplied to a portable device and the system comprising:
a power supply;
a power switch connecting the power supply to the portable device;
a current sensing module connected to the power switch for detecting the charging current drawn from the power supply;
a current threshold database for storing one or more threshold current values;
a comparator connected to the current sensing module for comparing the detected charging current with a corresponding threshold current value;
a profile database for storing one or more handshake protocols for connecting the portable device;
a timer for controlling a time window within which a handshake protocol has to complete; and
an emulation circuit for:
applying a handshake protocol to connect the portable device; and
exiting the handshake protocol if an associated time window has expired, wherein the charging circuit cycles between the handshake profiles until a handshake is successfully implemented, and wherein if no suitable handshake profile can be implemented, accepting a charging profile that provides less than optimum charging current.
10. The system of claim 9 , wherein the current sensing module includes at least one of a current amplifier, a current sensing resistor, or an analog to digital signal converter.
11. The system of claim 9 , wherein the comparator is a digital module.
12. The system of claim 9 , wherein the comparator is an analog circuit.
13. A method for detecting a charging current provided to an arbitrary downstream portable device, the method comprising:
attaching a portable device to a charging circuit;
applying a handshake profile within a predetermined time window to identify a charging circuit port type and to connect the portable device to the charging circuit;
determining whether a handshake profile has been completed within the predetermined time window; making one or more system level decisions regarding charging of the portable device if the handshake protocol has not been completed, wherein the one or more system level decisions comprise: resetting the portable device; offering another handshake profile; alerting the portable device; and continuing charging the portable device.
14. The method of claim 13 , wherein if no suitable handshake profile can be implemented, accepting a charging profile that provides less than optimum charging current.
15. The method of claim 13 further comprising after a handshake protocol has been completed, detecting the charging current drawn by the portable device from the charging circuit; comparing the detected charging current with a threshold current value and generating an alert if the charging current is lower than the threshold current value.
16. The method of claim 13 , wherein the applying step further comprising: applying a first handshake profile; connecting the portable device to the charging circuit if the first handshake profile is successfully implemented; and applying a second handshake profile in case the first handshake profile is not successfully implemented.
17. The method of claim 15 further comprising exiting a handshake profile if the detected charging current is lower than the threshold current value.
18. The method of claim 15 further comprising applying a second handshake profile if the detected charging current is lower than the threshold current value.
19. The system of claim 3 , wherein the charging circuit further comprising a threshold database for storing one or more threshold current values.
20. The battery charging system according to claim 9 , wherein after the handshake protocol has been completed and if the detected charging current is lower than the threshold current value, the system is configured to monitor the current with the current sensing module, and the comparator.