Power controls for an implantable device powered using ultrasonic waves
Method and system embodiments for controlling power provided to a device implantable in a subject are described. In some embodiments, a method is performed at the implantable device to receive, from an interrogator, powering ultrasonic waves having a wave power. Then, energy from the powering ultrasonic waves is converted into an electrical signal to power the implantable device. Information that indicates whether more power or less power should be transmitted to the implantable device is transmitted to the interrogator.
1. A method of controlling power provided to a device implantable in a subject, comprising, at the implantable device:
receiving powering ultrasonic waves from an interrogator, the powering ultrasonic waves having a wave power;
converting energy from the powering ultrasonic waves into an electrical signal to power the implantable device, wherein the electrical signal generates a first voltage at a first voltage node;
determining an available power at the implantable device and a power consumed by the implantable device, wherein the available power comprises a supply power provided by the electrical signal;
determining if the first voltage exceeds a predefined voltage level;
in response to determining that the first voltage exceeds the predefined voltage level, opening one or more switches configured to generate the electrical signal from the powering ultrasonic waves to reduce the supply power; and
transmitting to the interrogator information that indicates whether more power or less power should be transmitted to the implantable device, wherein the information is associated with the available power and the consumed power.
2. The method of claim 1 , wherein the information comprises a request for either more or less power from the interrogator.
3. The method of claim 2 , wherein the request is generated based on an available power at the implantable device and a power consumed by the implantable device.
4. The method of claim 1 , wherein transmitting the information comprises:
receiving communication ultrasonic waves from the interrogator; and
emitting an ultrasonic backscatter of the communication ultrasonic waves, wherein the ultrasonic backscatter encodes the information.
5. The method of claim 4 , wherein emitting the ultrasonic backscatter of the communication ultrasonic waves comprises:
generating an electrical signal based on the communication ultrasonic waves; and
modulating the generated electrical signal based on the information, wherein the modulated electrical signal encodes the information into the ultrasonic backscatter.
6. The method of claim 1 , comprising receiving second powering ultrasonic waves from the interrogator that is configured to generate the second powering ultrasonic waves to have a second wave power based on the information.
7. The method of claim 1 , wherein the powering ultrasonic waves comprise a pulse width modulated (PWM) signal.
8. The method of claim 7 , wherein the interrogator is configured to adjust an instantaneous intensity value or a pulse width of the PWM signal based on the information.
9. The method of claim 7 , wherein the interrogator is configured to adjust the instantaneous intensity value and the pulse width of the PWM signal based on the information.
10. The method of claim 1 , wherein the powering ultrasonic waves are received at an ultrasonic transducer of the implantable device, and wherein determining the available power comprises:
determining a maximum voltage of the ultrasonic transducer; and
determining the available power based on the maximum voltage.
11. The method of claim 1 , wherein determining the available power comprises:
charging an energy storage device based on the electrical signal; and
determining the available power based on energy stored at the energy storage device.
12. The method of claim 11 , wherein the available power is determined based on a rate of change of the energy stored at the energy storage device.
13. The method of claim 1 , wherein determining the available power comprises:
controlling one or more switches to control a plurality of capacitors configured to convert the first voltage into a second voltage to power the implantable device; and
determining the available power based on a switching frequency of at least one of the one or more switches.
14. The method of claim 1 , wherein determining the consumed power comprises:
determining the consumed power of the implantable device based on an operating mode of the implantable device.
15. The method of claim 1 , wherein the consumed power is consumed by a load circuit of the implantable device, and wherein determining the consumed power comprises:
detecting a current value of an electrical current driving the load circuit; and
determining the consumed power based on the detected current value.
16. The method of claim 1 , comprising determining if the supply power exceeds the consumed power.
17. The method of claim 16 , comprising, in response to determining that the supply power exceeds the consumed power, charging an energy storage device based on the first voltage node, wherein charging the energy storage device reduces the first voltage.
18. The method of claim 17 , comprising, in response to determining that the supply power is less than the consumed power, discharging the energy storage device through the first voltage node, wherein discharging the energy storage device increases the first voltage.
19. The method of claim 17 , comprising determining whether the energy storage device is fully charged.
20. The method of claim 19 , comprising, in response to determining that the supply power exceeds the consumed power and that the energy storage device is fully charged, transmitting to the interrogator the information comprising an indication that the implantable device is being over powered.
21. The method of claim 20 , wherein the information comprising the indication is configured to be receivable by the interrogator and causes the interrogator to generate second powering ultrasonic waves that have a second wave power that is less than the wave power of the powering ultrasonic waves.
22. The method of claim 16 , comprising, in response to determining that the supply power is less than the consumed power, transmitting to the interrogator the information comprising an indication that the implantable device is being under powered.
23. The method of claim 22 , wherein the information comprising the indication is configured to be receivable by the interrogator and causes the interrogator to generate second powering ultrasonic waves having a second wave power greater than the wave power of the powering ultrasonic waves.
24. An implantable device, comprising:
an ultrasonic transducer configured to receive powering ultrasonic waves from an interrogator and convert the powering ultrasonic waves into an electrical signal to power the implantable device, wherein the powering ultrasonic waves have a wave power;
a first voltage node, wherein the electrical signal generates a first voltage at the first voltage node;
one or more switches configured to generate the electrical signal from the powering ultrasonic waves;
a power monitoring circuit configured to determine an available power at the implantable device and a power consumed by the implantable device, wherein the available power comprises a supply power provided by the electrical signal; and
a controller circuit configured to:
determine if the first voltage exceeds a predefined voltage level,
in response to determining that the first voltage exceeds the predefined voltage level, open the one or more switches, and
generate information that indicates whether more power or less power should be transmitted to the implantable device, and
wherein the ultrasonic transducer is further configured to transmit the information to the interrogator.
25. An interrogator device, comprising:
an ultrasonic transducer configured to:
transmit first powering ultrasonic waves to an implantable device, the first powering ultrasonic waves having a first wave power;
receive communication ultrasonic waves from the implantable device, wherein the communication ultrasonic waves comprises information indicating whether more power or less power should be transmitted to the implantable device; and
transmit second powering ultrasonic waves to the implantable device, wherein the second powering ultrasonic waves have a second power based on the information, wherein the second powering ultrasonic waves comprise a pulse width modulated (PWM) signal.