Wireless power transmitters with wide input voltage range and methods of their operation
View Patent ↗The embodiments described herein provide a power transmitter for wireless charging of an electronic device and methods of its operation. The power transmitter uses an inverter configured to generate a square wave from a potentially wide ranging DC input voltage. The inverter is configured to generate the square wave with a duty cycle that results in a desired equivalent voltage output, effectively independent of the DC input voltage that is provided. Thus, by generating a square wave with a selectable duty cycle the inverter provides the ability to facilitate wireless power transfer with a wide range of DC input voltages. Furthermore, in some embodiments the power transmitter may provide improved power transfer efficiency using a quasi-resonant phase shift control strategy with adjustable dead time and a matching network that is dynamically selectable to more effectively couple with the transmitter coil combination being used to transmit power to the electronic device.
1. A power transmitter for wirelessly charging an electronic device, the power transmitter comprising:
an input configured to receive a DC input voltage;
an inverter coupled to the input to receive the DC input voltage, the inverter configured to generate an AC square-wave signal having a duty cycle selected to provide a predetermined equivalent voltage;
a matching network coupled to the inverter to receive the AC square-wave signal, the matching network configured to generate a charging signal from the AC square-wave signal, the matching network including a plurality of switched capacitors;
a plurality of primary coils coupled to the matching network to receive the charging signal, the plurality of primary coils configured to be selectable in multiple different coil combinations, each of the multiple different coil combinations including a number of the plurality of primary coils, with at least one of the multiple different coil combinations including more than one of the plurality of primary coils to facilitate transmission with different numbers of primary coils, the plurality of primary coils configured to selectively transmit a power transfer signal to a receiver coil on the electronic device; and
wherein the plurality of switched capacitors are selectively switched based on the number of the plurality of primary coils in a selected coil combination used to transmit the power transfer signal such that the matching network resonates with the selected coil combination at a resonant frequency that closely matches a fundamental frequency of the charging signal.
2. The power transmitter of claim 1 wherein the inverter comprises a single-stage H-bridge topology.
3. The power transmitter of claim 1 wherein the inverter is configured to generate the AC square-wave signal with the duty cycle selected using a phase shifted topology.
4. The power transmitter of claim 1 wherein the inverter includes power transistor pairs, and wherein the inverter is configured to adjust dead times of the transistors based on a magnitude the DC input voltage.
5. The power transmitter of claim 1 wherein the inverter is configured to generate the AC square-wave signal at a plurality of different frequencies, and wherein the power transmitter is further configured to determine which of the plurality of different frequencies results in efficient power transfer to the electronic device.
6. The power transmitter of claim 5 wherein the power transmitter is configured to determine which of the plurality of different frequencies results in efficient power transfer to the electronic device based on feedback received from the electronic device.
7. The power transmitter of claim 1 wherein the matching network further includes an inductor.
8. The power transmitter of claim 1 wherein the selected coil combination is determined by selectively activing each of the plurality of primary coils to determine a coil combination that most effectively couples with the receiver coil on the electronic device.
9. The power transmitter of claim 8 wherein the coil combination is determined based on a feedback signal received from the electronic device.
10. The power transmitter of claim 1 further comprising an input voltage detector configured to determine a magnitude of the DC input voltage.
11. The power transmitter of claim 10 wherein the inverter is configured to select the duty cycle by utilizing a phase shifted technique to provide the predetermined equivalent voltage based on the determined magnitude of the DC input voltage.
12. The power transmitter of claim 1 further comprising a sensing circuit coupled to the plurality of primary coils, and wherein the sensing circuit is configured to sense a signal received on at least one of the plurality of primary coils to facilitate communication from the electronic device and control a power transfer amount to the electronic device.
13. The power transmitter of claim 1 further comprising a microcontroller, the microcontroller configured to control operation of the inverter, the matching network and the plurality of primary coils.
14. A power transmitter for wirelessly charging an electronic device, the power transmitter comprising:
an input configured to receive a DC input voltage that can vary in a range from about 5 to about 20 volts;
an input voltage detector coupled to the input and configured to determine a magnitude of the DC input voltage;
a single-stage bridge inverter coupled to the input to receive the DC input voltage and to generate an AC square-wave signal;
a matching network comprising a plurality of switched capacitors and a matching inductor, the matching network coupled to the inverter to receive the AC square-wave signal and configured to generate a sinusoidal-type charging signal from the AC square-wave signal, where the sinusoidal-type charging signal has a fundamental frequency;
a plurality of selectable primary coils coupled to the matching network to receive the sinusoidal-type charging signal and configured to selectively transmit a power transfer signal to a receiver coil of the electronic device; and
a microcontroller coupled to the input voltage detector, the inverter, the matching network, and the plurality of selectable primary coils, the microcontroller configured to:
control the inverter to generate the AC square-wave signal with a duty cycle selected based on the determined magnitude of the DC input voltage such that the AC square-wave signal provides a predetermined equivalent voltage;
control the plurality of selectable primary coils to selectively activate a coil combination that most effectively couples with the receiver coil of the electronic device, where the coil combination can include more than one of the plurality of selectable primary coils to facilitate transmission with different numbers of the selectable primary coils; and
selectively couple the plurality of switched capacitors in the matching network based on a number of the plurality of selectable primary coils in the activated coil combination such that the matching network resonates with the activated coil combination at a resonant frequency that closely matches the fundamental frequency of the sinusoidal-type charging signal.
15. A method of wirelessly charging an electronic device, the method comprising:
receiving a DC input voltage;
controllably inverting the DC input voltage to generate an AC square-wave signal having a duty cycle selected to provide a predetermined equivalent voltage;
generating a charging signal from the AC square-wave signal;
selecting a coil combination from multiple different coil combinations, each of the multiple different coil combinations including a number of a plurality of primary coils with at least one of the multiple different coil combinations including more than one of the plurality of primary coils to facilitate transmission with different numbers of primary coils;
selectively switching capacitors in a plurality of switched capacitors based on the number of the plurality of primary coils in the selected coil combination to resonate the selected coil combination at a resonant frequency that closely matches a fundamental frequency of the charging signal; and
driving the selected coil combination using the charging signal to transmit a power transfer signal to a receiver coil of the electronic device.
16. The method of claim 15 wherein the controllably inverting the DC input voltage to generate the AC square-wave signal comprises using a shifted phase topology.
17. The method of claim 15 wherein the controllably inverting the DC input voltage to generate the AC square-wave signal comprises adjusting dead times of a plurality of transistor pairs based on a magnitude of the DC input voltage.
18. The method of claim 15 further comprising generating the AC square-wave signal at a plurality of different frequencies, and determining which of the plurality of different frequencies results in efficient power transfer to the electronic device.
19. The method of claim 18 wherein the determining which of the plurality of different frequencies results in efficient power transfer to the electronic device is based on feedback received from the electronic device.
20. The method of claim 15 further comprising determining a magnitude of the DC input voltage and wherein the duty cycle is further selected based on the magnitude of the DC input voltage.