METHOD AND SYSTEM FOR RATIONING CHARGE OR ENERGY PROVIDED TO A PORTABLE DEVICE

• US 20120313571A1
• Filed: 06/09/2011
• Published: 12/13/2012
• Est. Priority Date: 06/09/2011
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Standard Microsystems Corporation (Microchip Technology Incorporated)
• Inventors: Knowlton, Timothy J.
• Granted Patent: US 8,994,321 B2
• Time in Patent Office: Days
• US Class Current: 320/107
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage
• CPC Class Codes: H02J 7/00718 in response to charge current gradient

Abstract

A charging method and system for rationing charge or energy supplied by a host to a portable device. The system includes a power switch, and a current sensing module connected to the power switch. The current sensing module detects instantaneous current drawn by the portable device. The system further includes a current register connected to the current sensing module for storing the instantaneous current value. A timing module generates timing information. The system also includes a charge register storing a cumulative charge drawn by the portable device. The cumulative charge is obtained by multiplying the instantaneous current value with the timing information. A threshold database stores a threshold value, and a rationing module connected to the host and the charge register continuously compares the cumulative charge value with the threshold charge value. When the cumulative charge value exceeds the threshold charge value, a control signal is generated.

Claims

1. A charging system for rationing a cumulative charge or a cumulative energy supplied from a host to a portable device, the charging system comprising:

a power switch;

a current sensing module, connected to the power switch, for detecting an instantaneous current drawn by the portable device;

a converter, at the output of the current sensing module, for converting the instantaneous current into a digital current value;

a current register connected to the current sensing module for storing the digital current value;

a timing module generating elapsed time information;

a charge register storing a cumulative charge value, the cumulative charge value obtained by multiplying the digital current value with the elapsed time information;

a threshold database storing a threshold value;

a rationing module configured for;

continuously comparing a cumulative value with the threshold value; and

generating a control signal when the cumulative value exceeds the threshold value.

2. The charging system of claim 1 further comprising a first multiplier, connected to the output of the current register for multiplying the digital current value with the elapsed time information.

3. The charging system of claim 2, wherein the current sensing module includes a current sensing resistor converting the instantaneous current into a corresponding voltage signal.

4. The charging system of claim 3 further comprising:

a voltage multiplexer, connected to the output of the power switch and the current sensing module, for multiplexing the corresponding voltage signal and an instantaneous voltage;

a voltage register for storing a digital voltage value; and

an energy register for storing a cumulative energy value obtained by multiplying the cumulative charge value with the digital voltage value.

5. The charging system of claim 4 further comprising a second multiplier connected to the output of the first multiplier and the voltage register, for generating the cumulative energy value.

6. The charging system of claim 4 further comprising a switch connected to the input of the current register and the voltage register.

7. The charging system of claim 4, wherein the cumulative value is at least one of the cumulative charge value or the cumulative energy value.

8. The charging system of claim 1, wherein the threshold value is one of a charge value or an energy value.

9. The charging system of claim 1, wherein the threshold database obtains the threshold value from the host via a data communication bus.

10. The charging system of claim 1, wherein the control signal is at least one of a disable signal or an alert signal.

11. The charging system of claim 1, wherein the current sensing module and the rationing module are implemented in discrete circuitry.

12. The charging system of claim 1, wherein the current sensing module and the rationing module are components on a single semiconductor fiber chip.

13. A method for rationing a cumulative charge or energy supplied from a host to a portable device over a universal serial bus (USB) port, the method comprising:

sensing an instantaneous current drawn by the portable device;

converting the instantaneous current into a digital current value;

storing the digital current value;

determining an elapsed time from beginning of charging to current time

multiplying the digital current value with the elapsed time to obtain a cumulative charge value;

storing the cumulative charge value;

storing a threshold value;

comparing a cumulative value with the threshold value; and

generating a control signal if the cumulative value exceeds the threshold value.

14. The method of claim 13 further comprising updating the cumulative charge value at predetermined intervals.

15. The method of claim 13 further comprising:

converting the instantaneous current into a corresponding voltage signal; and

converting the corresponding voltage signal into the digital current value.

16. The method of claim 15 further comprising:

detecting an instantaneous voltage supplied to the portable device;

converting the instantaneous voltage into a digital voltage value

storing the digital voltage value;

multiplying the digital voltage value with the cumulative charge value, in real time, to determine a cumulative energy value; and

continuously updating the cumulative energy value.

17. The method of claim 16 wherein comparing the cumulative value with the threshold value comprises comparing at least one of the cumulative energy value or the cumulative charge value with the threshold value.

18. The method of claim 17 further comprising multiplexing the corresponding voltage signal and the instantaneous voltage.

19. The method of claim 13 further comprising at least one of

disabling a power switch supplying current to the portable device;

disabling the power switch supplying current to the portable device and alerting the host;

or

alerting the host.

20. The method of claim 13 further comprising receiving the threshold value from the host.