Method for regulating TETS power transfer
In an implanted medical device system, an internal controller, external power transmitter and methods for regulation of TETS power for an implanted medical device system are disclosed. According to one aspect, a method in an external power transmitter of an implanted medical device system includes determining a current in an external coil of the external power transmitter, multiplying the determined current by a supply voltage to determine a power delivered to the external coil, and controlling the power delivered to the external coil by adjusting the current in the external coil.
1. An external power transmitter of an implanted medical device system, the external power transmitter comprising processing circuitry configured to:
determine a current in an external coil of the external power transmitter;
multiply the current by a supply voltage to determine a power delivered to the external coil;
control the power delivered to the external coil by adjusting the current in the external coil; and
adjust the power to account for resistive losses in the external coil.
2. The external power transmitter of claim 1 , wherein the processing circuitry is further configured to control the power by adjusting a duty cycle of a pulse-width-modulated bridge circuit.
3. The external power transmitter of claim 2 , wherein the processing circuitry is further configured to determine the current while the pulse-width-modulated bridge circuit is active.
4. The external power transmitter of claim 3 , wherein the processing circuitry is further configured to estimate the current in the external coil based at least in part on peak coil current, a pulse width of the pulse-width-modulated bridge circuit, and an approximation of the current as a sine wave.
5. The external power transmitter of claim 1 , wherein the processing circuitry is further configured to use the supply voltage to compensate a current proportional integral derivative (PID) controller to maintain a constant power over different supply voltages.
6. The external power transmitter of claim 1 , wherein processing circuitry is further configured to determine the current by by continuously measuring a current output of a bridge circuit.
7. The external power transmitter of claim 1 , wherein the processing circuitry is further configured to determine the current by measuring a peak current in the external coil.
8. A method in an external power transmitter of an implanted medical device system, the method comprising:
determining a current in an external coil of the external power transmitter;
multiplying the current by a supply voltage to determine a power delivered to the external coil;
controlling the power delivered to the external coil by adjusting the current in the external coil; and
adjusting the power to account for resistive losses in the external coil.
9. The method of claim 8 , wherein controlling the power comprises adjusting a duty cycle of a pulse-width-modulated bridge circuit.
10. The method of claim 9 , wherein determining the current is performed while the pulse-width-modulated bridge circuit is active.
11. The method of claim 10 , wherein determining the current in the external coil comprises estimating the current based at least in part on peak coil current, a pulse width of the pulse-width-modulated bridge circuit, and an approximation of the current as a sine wave.
12. The method of claim 8 , further comprising using the supply voltage to compensate a current proportional integral derivative (PID) controller to maintain a constant power over different supply voltages.
13. The method of claim 8 , wherein determining the current comprises continuously measuring a current output of a bridge circuit.
14. The method of claim 8 , wherein determining the current includes measuring a peak current in the external coil.
15. A current control loop in an external device of an implanted medical device system, the current control loop including:
an H-bridge circuit configured to output a current to an external coil of the external device;
processing circuitry configured to:
determine the current to the external coil based on a current output of the H bridge circuit;
multiplying the current by a supply voltage applied to the external coil to determine a power delivered to the external coil; and
controlling the power delivered to the external coil by adjusting the current in the external coil, the adjusting being by controlling a pulse width modulation (PWM) duty cycle of the H-bridge circuit in response to the determined current; and
a current proportional integral derivative (PID) controller configured to control the PWM duty cycle of the H-bridge circuit.
16. The current control loop of claim 15 , further comprising a current sensor configured to measure the current of the external coil, the processing circuitry being configured to compare the measured current to a current that is based on a difference between a voltage across an internal coil of the implanted medical device system and a target voltage.
17. The current control loop of claim 15 , wherein the current output of the H-bridge circuit is further based on a supply voltage provided by a power supply external to the external device.