Wireless power delivery in dynamic environments
An adaptive system for efficient and long-range wireless power delivery using magnetically coupled resonators responds to changes in a dynamic environment, and maintains high efficiency over a narrow or fixed frequency range. The system uses adaptive impedance matching to maintain high efficiency. The wireless power transfer system includes a drive inductor coupled to a high-Q transmitter coil, and a load inductor coupled to a high-Q receiver coil. The transmitter coil and receiver coil for a magnetically coupled resonator. A first matching network is (i) operably coupled to the drive inductor and configured to selectively adjust the impedance between the drive inductor and the transmitter coil, or (ii) is operably coupled to the load inductor and configured to selectively adjust the impedance between the load inductor and the receiver coil.
1. An adaptive impedance matching wireless power transfer system ( 100 ) comprising:
a drive inductor ( 103 ) configured to receive alternating current electric power from a power source at a fixed frequency;
a high quality factor, (high-Q), transmitter coil ( 104 ) inductively coupled to the drive inductor;
a high-Q receiver coil ( 106 ) configured to be inductively coupled to the transmitter coil; and
a first impedance matching network ( 101 ) that is operably coupled to the drive inductor and configured to selectively adjust the impedance between the drive inductor and the transmitter coil, wherein the first impedance matching network comprises a plurality of capacitors ( 150 ) interconnected to form at least one switchable bank of capacitors, and a microcontroller ( 154 ) operably connected to the at least one switchable bank of capacitors, wherein the microcontroller is configured and operable to receive a measured operating parameter of the adaptive impedance matching wireless power transfer system and to use the measured operating parameter to selectively adjust the impedance between the drive inductor and the transmitter coil,
wherein the first impedance matching network ( 101 ) comprises a first π-match network with variable capacitances comprising a switchable first bank of capacitors ( 150 ) that are connected to a switchable second bank of capacitors ( 152 ) with a π-match inductor, and further wherein the microcontroller ( 154 ) is operably connected to both the switchable first and second banks of capacitors to selectively adjust the capacitance of the first and second banks of capacitors, thereby adjusting the impedance between the drive inductor ( 103 ) and the transmitter coil ( 104 ), wherein each capacitor of the first and second switchable bank of capacitors is coupled to the microcontroller through a network of controllable micro-switches and a gate drive filter, wherein the gate drive filter (Q) comprises a first resistor that couples the gate drive filter to the microcontroller, a second resistor that couples the gate drive filter to a voltage source, a diode (D) that couples the gate driver and filter to the micro-switches and the second resistor, wherein a cathode of the diode is coupled to the gate drive filter, and an anode of the diode is coupled to the microswitches and to the second resistor.
2. The system of claim 1 , wherein the drive inductor ( 103 ) comprises the π-match inductor.
3. The system of claim 1 , wherein the microcontroller ( 154 ) is configured to control the first switchable bank of capacitors ( 150 ) to achieve a capacitance that maximizes the forward transmission gain to the transmitter coil ( 104 ).
4. The system of claim 1 , wherein the microcontroller ( 154 ) is configured to exhaustively engage each combination of the plurality of capacitors to select a configuration that produces a minimum reflected power.
5. The system of claim 1 , wherein the microcontroller ( 154 ) is configured to use the measured operating parameter with a lookup table to selectively engage one or more of the plurality of capacitors.
6. The system of claim 1 , wherein the microcontroller ( 154 ) is configured to monitor a measured performance parameter of the system ( 100 ) and selectively engages a sequence of combinations of the capacitors to optimize the performance parameter.
7. The system of claim 1 , wherein the microcontroller ( 154 ) is configured to monitor one or more monitored operating parameters of the system, to calculate an optimal capacitance based on the monitored operating parameters, and to selectively engage one or more of the capacitors to approximate the calculated optimal capacitance, or wherein the at least one switchable bank of capacitors ( 150 ) comprises at least five capacitors.