Method and apparatus for high voltage protection

1. A method for protecting a host device from one or more power surges transmitted from a sink device that is connectable to the host device via a power transmission line and a data communication line; the method comprising:

upon detection of the sink device being connected to the host device:

providing a limited level of power to the sink device over the power transmission line;

starting an authentication test of the sink device;

if the sink device passes the authentication test, providing a normal level of power to the sink device over the power transmission line; and

if the sink device fails the authentication test, providing a level of power to the sink device over the power transmission line that is the same or less than the limited level of power;

the method further comprising:

protecting the host device from a plurality of subsequent connections of the sink device;

providing a counter to count the number of subsequent connections of the sink device; and

varying the limited level of power based on the current value of the counter.

2. The method as claimed in claim 1 , wherein:

the host device completes the authentication test within a maximum authentication time interval; and wherein

the authentication test is deemed to have failed if the maximum authentication time interval is exceeded before the authentication test has been completed.

3. The method as claimed in claim 2 , wherein the maximum authentication time interval is adjustable.

4. The method as claimed in claim 1 , wherein if the sink device fails the authentication test, the level of power provided to the sink device over the power transmission line is zero.

5. The method as claimed in claim 1 , wherein:

the sink device comprises a component adapted to build up a power reserve from the power provided over the power transmission line;

and wherein the limited level of power is dependent on the time required to build up the power reserve.

6. The method as claimed in claim 5 , wherein:

the component comprises an internal capacitor; and

wherein the internal capacitor discharges the stored power on the data communication line.

7. The method as claimed in claim 1 , wherein the limited level of power provided to the sink device over the power transmission line comprises a limited level of current.

8. The method as claimed in claim 1 , wherein the host device is connectable to the sink device via a USB connection.

9. The method as claimed in claim 1 , wherein the counter counts the number of connections within a counter time interval and to reset the count to zero each time the counter time interval is exceeded.

10. The method as claimed in claim 1 , wherein:

if the sink device fails the authentication test, the authentication test is reattempted up to a maximum attempts number.

11. The method as claimed in claim 10 , wherein the maximum attempts number is adjustable.

12. The method as claimed in claim 1 wherein

the host device is one of a phone, a tablet or a laptop;

and wherein the host device comprises a battery charger circuit and a boost converter; and

wherein the boost converter is reversible so as to provide power over the power transmission line when a sink device is connected to the host device.

13. An apparatus for protecting a host device from one or ore power surges transmitted from a sink device that is connectable to the host device via a power transmission line and a data communication line; wherein the apparatus comprises a processor device adapted to control the power transmitted via the power transmission line and to provide an authentication module, and wherein the processor device being configured to:

upon detection of the sink device being connected to the host device:

provide a limited level of power to the sink device over the power transmission line;

start an authentication test of the sink device using the authentication module;

if the sink device passes the authentication test, provide a normal level of power to the sink device over the power transmission line; and

if the sink device fails the authentication test, provide a level of power to the sink device over the power transmission line that is the same or less than the limited level of power;

and the processor device further being adapted to:

protect the host device from a plurality of subsequent connections of the sink device;

provide a counter, the counter being configured to count the number of subsequent connections of the sink device; and

vary the limited level of power provided to the sink device based on the current value of the counter.

14. The apparatus as claimed in claim 13 , wherein:

the processor device is further configured to complete the authentication test within a maximum authentication time interval; and

wherein the authentication test is deemed to have failed if the maximum authentication time interval is exceeded before the authentication test has been completed.

15. The apparatus as claimed in claim 13 wherein the processor device is adapted to provide a current limiting module and the limited level of power comprises a limited level of current.

16. The apparatus as claimed in claim 13 , wherein the processor device is further configured to:

if the sink device fails the authentication test, reattempt the authentication test up to a maximum attempts number.