METHOD AND APPARATUS FOR PRE-ALIGNMENT OF AN AUTOMATICALLY ALIGNING MAGNETIC FIELD SYSTEM
A wireless power transfer system includes a wireless power transfer device configured to determine a magnetic field, from among a plurality of directionally different potential magnetic fields that the wireless power transfer device is configured to generate, that has, at a receiver coil of an electronic device, a direction aligned with the receiver coil.
1 . A wireless power transfer device, the wireless power transfer device being configured:
to generate a plurality of directionally different potential magnetic fields; and
to select, from among the plurality of directionally different potential magnetic fields, a set magnetic field based on preliminary information about at least one of:
a gravity orientation of the wireless power transfer device relative to a gravity vector,
a bodily orientation of the wireless power transfer device relative to a patient's body, or
a plurality of load comparisons, each between first and second loads in first and second LC resonant circuits of the wireless power transfer device and in response to the wireless power transfer device generating a corresponding one of the plurality of directionally different potential magnetic fields, the first and second LC resonant circuits respectively including first and second transmitting coils.
2 . The wireless power transfer device of claim 1 , comprising:
at least one transmitting coil;
a driver configured to drive the at least one transmitting coil;
a memory storing instructions; and
a controller, the controller configured:
to select the set magnetic field based on the preliminary information and in response to executing the instructions, and
after selecting the set magnetic field, to generate the set magnetic field by driving the at least one transmitting coil via the driver.
3 . The wireless power transfer device of claim 1 , wherein the selecting the set magnetic field comprises determining a first amplitude of a first current, a second amplitude of a second current, and a phase difference between the first and second currents, the wireless power transfer device being configured to generate the set magnetic field in response to driving the first and second transmitting coils with the first and second currents.
4 . The wireless power transfer device of claim 1 , wherein the preliminary information is at least about the gravity orientation of the wireless power transfer device, and
wherein the wireless power transfer device comprises an inertial measurement unit (IMU) configured to measure the gravity orientation of the wireless power transfer device.
5 . The wireless power transfer device of claim 4 , wherein the preliminary information is further about at least one of:
a gravity orientation of an implantable medical device (IMD) relative to a gravity vector;
a bodily orientation of the IMD relative to a patient's body; or
a prior magnetic field previously generated by the wireless power transfer device and a prior gravity orientation of the wireless power transfer device relative to a gravity vector while the wireless power transfer device generated the prior magnetic field.
6 . The wireless power transfer device of claim 1 , wherein the preliminary information is at least about the bodily orientation of the wireless power transfer device relative to a patient's body.
7 . The wireless power transfer device of claim 1 , wherein the preliminary information is at least about the plurality of load comparisons.
8 . The wireless power transfer device of claim 7 , wherein a load comparison of the plurality of load comparisons comprises a comparison between a corresponding voltage ratio to a corresponding amplitude ratio,
wherein the corresponding amplitude ratio is based on a ratio of first amplitude of a first current provided to the first transmitting coil by a driver and based on a first bus voltage and a second amplitude of a second current provided to the second transmitting coil by the driver and based on a second bus voltage, and
wherein the corresponding voltage ratio is based on a ratio of the first bus voltage and the second bus voltage.
9 . A wireless power transfer system, comprising:
the wireless power transfer device of claim 1 ; and
an implantable medical device comprising a receiver coil,
wherein the selecting the set magnetic field comprises determining a degree of alignment between the set magnetic field and the receiver coil, and the set magnetic field is selected based on the determined degree of alignment.
10 . A wireless power transfer device, comprising:
a first transmitting coil oriented along a first axis;
a second transmitting coil oriented along a second axis different from the first axis;
a driver configured to drive the first and second transmitting coils; and
a controller configured:
to simultaneously and differentially drive the first and second transmitting coils, via the driver, and
to determine a first amplitude of a first current, a second amplitude of a second current, and a phase difference between the first and second currents, the first and second transmitting coils being configured to generate a magnetic field aligned with a receiver coil of an electronic device in response to the first and second transmitting coils being driven with the first and second currents.
11 . The wireless power transfer device of claim 10 , comprising an inertial measurement unit (IMU) configured to determine a gravity orientation of the first and second transmitting coils relative to a gravity vector,
wherein the controller is configured to determine the first amplitude, the second amplitude, and the phase difference based on the gravity orientation of the first and second transmitting coils.
12 . The wireless power transfer device of claim 10 , where the wireless power transfer device is configured to couple to a patient's body such that the first and second transmitting coils have a set bodily orientation relative to the patient's body,
wherein the controller is configured to determine the first amplitude, the second amplitude, and the phase difference based on the bodily orientation of the first and second transmitting coils.
13 . The wireless power transfer device of claim 10 , comprising:
a first LC resonant circuit comprising the first transmitting coil; and
a second LC resonant circuit comprising a second transmitting coil,
wherein the controller is configured to differentially drive the first and second transmitting coils to generate a plurality of directionally different preliminary magnetic fields, and
wherein, the controller is configured to determine the first amplitude, the second amplitude, and the phase difference based on a plurality of pairs of first and second reflected loads in the first and second LC resonant circuits, each of the pairs being in response to a corresponding one of the plurality of directionally different preliminary magnetic fields being generated.
14 . A wireless power transfer system, comprising:
the wireless power transfer device of claim 10 ; and
the electronic device, the electronic device being an implantable medical device.
15 . A method for transferring power from a wireless power transfer device to an electronic device, the method comprising:
selecting, from among a plurality of directionally different potential magnetic fields, a set magnetic field based on preliminary information about at least one of:
a gravity orientation of the wireless power transfer device relative to a gravity vector,
a bodily orientation of the wireless power transfer device relative to a patient's body, or
a plurality of load comparisons, each between first and second loads in first and second LC resonant circuits of the wireless power transfer device and in response to the wireless power transfer device generating a corresponding one of the plurality of directionally different potential magnetic fields, the first and second LC resonant circuits including first and second transmitting coils; and
generating, by the wireless power transfer device, the set magnetic field after selecting the set magnetic field.
16 . The method of claim 15 , wherein the electronic device is an implantable medical device.
17 . The method of claim 15 , wherein the preliminary information is at least about the gravity orientation of the wireless power transfer device, and
wherein the method further comprises measuring the gravity orientation via an inertial measurement unit (IMU) of the wireless power transfer device.
18 . The method of claim 17 , wherein the preliminary information is further about at least one of:
a gravity orientation of the electronic device relative to a gravity vector;
a bodily orientation of the electronic device relative to the patient's body; or
a prior magnetic field previously generated by the wireless power transfer device and a prior gravity orientation of the wireless power transfer device relative to a gravity vector while the wireless power transfer device generated the prior magnetic field.
19 . The method of claim 15 , wherein the preliminary information is at least about the bodily orientation of the wireless power transfer device relative to a patient's body.
20 . The method of claim 15 , wherein the preliminary information is at least about the plurality of load comparisons.