Inductive power and data transfer using energy injection
A wireless power transfer secondary or pick-up has a resonant circuit and a switch connected to the resonant circuit operable to produce a phase shift in an oscillating voltage or current in the resonant circuit. A controller is configured to operate the switch to introduce one or more controlled phase shifts in the oscillating voltage or current in the resonant circuit which encode data for detection by a coupled circuit.
1 . A wireless power and data transfer system comprising:
a wireless power transfer primary apparatus comprising:
a primary power transfer apparatus having a primary resonant circuit;
a primary controller configured to transfer power in a first interval; and
a phase detector operable by the primary controller to decode data in a second interval, subsequent to the first interval, in which the primary resonant circuit is not transferring power; and
a wireless power transfer pick up comprising:
a pick-up resonant circuit comprising an inductor and a capacitor configured to receive power wirelessly from the primary resonant circuit;
an energy storage element configured to store energy received by the pick-up resonant circuit;
a driving circuit connected to the pick-up resonant circuit to drive a resonant current and voltage in the pick-up resonant circuit;
a switch connected to the resonant circuit; and
a phase modulator configured to activate and deactivate the switch to encode data through phase modulation of the resonant voltage or current for detection by the phase detector, the phase modulator being configured to activate the switch to either:
i) short circuit the inductor at maximum current in the inductor and zero voltage across the capacitor, or
ii) open circuit the capacitor at maximum voltage across the capacitor and zero current in the inductor,
for a first time period comprising a fraction of a resonant cycle of the resonant current and voltage to create a phase shift in the resonant current and voltage whereby the resonant current and voltage has a new phase, and the phase modulator being configured to deactivate the switch after the first time period has elapsed to maintain the resonant current and voltage at the new phase, and wait for a second period of time corresponding to a plurality of cycles of the resonant current and voltage to elapse before reactivating the switch;
a sensor operable to sense a resonant voltage of the pick-up resonant circuit; and
a pick-up controller configured to compare the resonant voltage with a threshold and disable the driving circuit and phase modulator if the resonant voltage is greater than the threshold and enable the driving circuit and phase modulator if the resonant voltage is less than the threshold.
2 . The wireless power and data transfer system as claimed in claim 1 , wherein the wireless power and data transfer system further comprises a further resonant circuit configured to receive power wirelessly.
3 . The wireless power and data transfer system as claimed in claim 1 , wherein the phase modulator activates and deactivates the switch to transmit data in a form of binary phase shift keying (BPSK), or quadrature phase shift keying (QPSK).
4 . An implantable device comprising the wireless power and data transfer system of claim 1 provided in a hermetic housing.
5 . The implantable device of claim 4 , further comprising a pressure sensor configured to measure pressure through the hermetic housing.
6 . The implantable device of claim 5 , wherein the pressure sensor is connected to the pick-up resonant circuit or the energy storage element to receive power from the pick-up resonant circuit.
7 . The implantable device of claim 4 , wherein the wireless power and data transfer system is configured to supply power transcutaneously.
8 . The implantable device of claim 4 , wherein the wireless power and data transfer system is configured to operate with a coupling factor of 0.01.
9 . The system of claim 1 , wherein the first time period comprises a fraction of a resonant cycle that is less than a full resonant cycle.
10 . A method of controlling a wireless power and data transfer system having a primary apparatus comprising a primary resonant circuit and a phase detector and a pick-up having a resonant circuit comprising an inductor and a capacitor to phase modulate a current and voltage of the resonant circuit to encode data, the method comprising:
operating the primary resonant circuit to transfer power to a pick-up resonant circuit in a first interval;
storing energy received by the pick-up resonant circuit in the first interval;
stopping power transfer from the primary resonant circuit at an end of the first interval;
in a second interval subsequent to the first interval, during which power is not being transmitted from the primary resonant circuit, controlling a driving circuit connected to the resonant circuit to supply energy from an energy storage element to the pick-up resonant circuit to drive a resonant current and voltage in the resonant circuit;
controlling a phase modulator configured to activate and deactivate a switch connected to the resonant circuit to encode data through phase modulation of the resonant voltage or current for detection by the primary apparatus, by controlling the phase modulator to activate the switch to either:
i) short circuit the inductor at maximum current in the inductor and zero voltage across the capacitor, or
ii) open circuit the capacitor at maximum voltage across the capacitor and zero current in the inductor;
for a first time period comprising a fraction of a resonant cycle of the resonant current and voltage to create a phase shift in the resonant current and voltage whereby the resonant current and voltage has a new phase, and controlling the phase modulator to deactivate the switch after the first time period has elapsed to maintain the resonant current and voltage at the new phase, and wait for a second period of time corresponding to a plurality of cycles of the resonant current and voltage to elapse before reactivating the switch; and
detecting the phase shift, by a phase detector of the primary apparatus.
11 . The method of claim 10 , wherein the first time period comprises a fraction of a resonant cycle that is less than a full resonant cycle.
12 . The method of claim 10 , further comprising controlling the phase modulator to activate and deactivate the switch to transmit data in a form of binary phase shift keying (BPSK), or quadrature phase shift keying (QPSK).
13 . The method of claim 10 , further comprising controlling the driving circuit to inject energy into the pick-up resonant circuit when a voltage of the pick-up resonant circuit falls below a threshold.