Alternating capacitive and resistive modulation for wireless power transfer

1. An apparatus comprising:

a controller configured to:

communicate with a power device by a first modulation mode;

detect a failure condition between the controller and the power device; and

in response to the detection of the failure condition;

communicate with the power device by a second modulation mode;

determine a number of cycles to communicate with the power device by the second modulation mode; and

return to communicate with the power device by the first modulation mode after a lapse of the determined number of cycles,

wherein the first modulation mode comprises capacitive modulation, and the second modulation mode comprises resistive modulation.

2. The apparatus of claim 1 , wherein the power device is a wireless power transmitter and the controller is a part of a wireless power receiver.

3. The apparatus of claim 1 , wherein the second modulation mode further comprises capacitive modulation, and a ratio of the capacitive modulation to the resistive modulation is variable.

4. The apparatus of claim 1 , wherein the controller is configured to:

send a packet to the power device, and

detect the failure condition in response to an absence of a response from the power device.

5. The apparatus of claim 1 , wherein the failure condition is based on a change in at least one of:

an output current;

frequency shift;

deadtime;

rectifier voltage; and

rectifier power.

6. A device comprising:

a resonant circuit;

a rectifier circuit coupled to the resonant circuit;

a controller coupled to the resonant circuit and the rectifier circuit, the controller being configured to:

communicate with a power device by a first modulation mode;

detect a failure condition between the controller and the power device; and in response to the detection of the failure condition;

communicate with the power device by a second modulation mode;

determine a number of cycles to communicate with the power device by the second modulation mode; and

return to communicate with the power device by the first modulation mode after a lapse of the determined number of cycles,

wherein, the first modulation mode comprises capacitive modulation, and the second modulation mode comprises resistive modulation.

7. The device of claim 6 , wherein the power device is a wireless power transmitter and the device is a wireless power receiver configured to receive power from the wireless power transmitter.

8. The device of claim 7 , wherein:

the failure condition indicates a failure at the wireless power transmitter to demodulate the signals being outputted from the resonant circuit.

9. The device of claim 6 , wherein the second modulation mode further comprises capacitive modulation, and a ratio of the capacitive modulation to the resistive modulation is variable.

10. The device of claim 6 , wherein the controller further configured to:

send a packet to the power device, and

detect the failure condition in response to an absence of a response from the power device.

11. The device of claim 6 , wherein the failure condition based on at least one of:

an output current;

frequency shift; and

deadtime.

12. A method for operating an apparatus, the method comprising:

communicating, by a controller, with a power device by a first modulation mode;

detecting, by the controller, a failure condition between the controller and the power device; and

in response to the detection of the failure condition;

communicating with the power device by a second modulation mode;

determining a number of cycles to communicate with the power device by the second modulation mode; and

returning to communicate with the power device by the first modulation mode after a lapse of the determined number of cycles,

wherein the first modulation mode comprises capacitive modulation, and the second modulation mode comprises resistive modulation.

13. The method of claim 12 , wherein the power device is a wireless power transmitter and the apparatus is a wireless power receiver configured to receive a power from the wireless power transmitter.

14. The method of claim 13 , wherein:

detecting the failure condition comprises detecting a failure at the wireless power transmitter to demodulate the signals being outputted by the wireless power receiver.

15. The method of claim 12 , wherein the second modulation mode further comprises capacitive modulation, and a ratio of the capacitive modulation to the resistive modulation is variable.

16. The method of claim 12 , further comprising:

sending, by the controller, a packet to the power device, and

detecting, by the controller, the failure condition in response to an absence of a response from the power device.

17. The method of claim 12 , wherein the failure condition is based on at least one of:

an output current;

frequency shift; and

deadtime.

18. The apparatus of claim 1 , wherein communicate with the power device by the first modulation mode comprises using the first modulation mode to encode a message in an amplitude shift key (ASK) signal, wherein the message specifies power transfer information.

19. The apparatus of claim 18 , wherein the ASK signal is a first ASK signal, and communicate with the power device by the second modulation mode comprises at least one of:

using the second modulation mode to encode the message in a second ASK signal; and

using the second modulation mode to encode another message in a third ASK signal, wherein said another message specifies another power transfer information.

20. The apparatus of claim 18 , wherein the power transfer information comprises at least one of:

an amount of power to be transferred by the power device;

a command to adjust a power level of power being transferred by the power device;

a command to maintain the power level of power being transferred by the power device; and

a command to stop a power transfer by the power device.