Data communication in a transcutaneous energy transfer system

1. A method of communicating data in a transcutaneous energy transmission device, comprising

transferring electrical power from an external primary to an implanted secondary by driving the external primary with a first time-varying electrical signal such that a second time-varying electrical signal is induced in the implanted secondary;

encoding the first time-varying signal with a data signal by modulating an attribute of the first time-varying electrical signal as electrical power is transferred from the external primary to the implanted secondary, wherein encoding the first time-varying signal with a data signal includes modulating the amplitude of the first time-varying electrical signal, wherein the amplitude of the first time-varying electrical signal is modulated using a transformer having a secondary side coupled in series between a power supply and a drain of a power transistor used to transfer power from the primary to the secondary; and

receiving the data signal at the implanted secondary by demodulating the secondary time-varying electrical signal as electrical power is transferred from the external primary to the implanted secondary.

2. The method of claim 1 , further comprising

sensing power consumption in the implanted secondary; and

alternating the electrical power transfer between a power supply mode and an idle mode responsive to the sensed power consumption in the implanted secondary;

wherein the operation of encoding the first time-varying signal with a data signal by modulating the amplitude of the first time-varying electrical signal occurs during the power supply mode.

3. The method of claim 1 , further comprising

alternating the electrical power transfer between a power supply mode and an idle mode responsive to power consumption in the implanted secondary;

wherein the operation of encoding the first time-varying signal with a data signal by modulating the amplitude of the first time-varying electrical signal occurs during the idle mode.

4. The method of claim 1 , wherein the data signal is a first data signal, the method further comprising

encoding the second time-varying signal with a second data signal by modulating an attribute of the second time-varying electrical signal as electrical power is transferred from the external primary to the implanted secondary; and

receiving the second data signal at the external primary by demodulating the first time-varying electrical signal as electrical power is transferred from the external primary to the implanted secondary.

5. The method of claim 4 , further comprising time multiplexing the first and second data signals.

6. The method of claim 4 , wherein

encoding the first time-varying signal with the first data signal includes modulating the amplitude of the first time-varying electrical signal at a first amplitude level;

encoding the second time-varying signal with the second data signal includes modulating the amplitude of the second time-varying electrical signal at a second amplitude level that is different from the first amplitude level; and

the first and second time varying signals are modulated at the same time.

7. The method of claim 4 , further comprising

sensing power consumption in the implanted secondary; and

alternating the electrical power transfer between a power supply mode and an idle mode responsive to the sensed power consumption in the implanted secondary;

wherein the operation of encoding the second time-varying signal with the second data signal by modulating an attribute of the second time-varying electrical signal occurs during the idle mode.

8. The method of claim 4 , wherein

the second time-varying electrical signal is modulated by a resistive loading of a circuit that includes a resonant tank associated with the secondary; and

the first time-varying electrical signal is demodulated in the primary by sensing changes that occur in a primary current due to the resistive loading in the secondary.

9. The method of claim 4 , wherein

the second time-varying electrical signal is modulated by a reactive loading of a circuit that includes a resonant tank associated with the secondary; and

the first time-varying electrical signal is demodulated in the primary by sensing changes that occur in the primary current due to the reactive loading in the secondary.