Switched-Capacitor Power Ramping for Soft Switching

• US 20180212463A1
• Filed: 01/25/2017
• Published: 07/26/2018
• Est. Priority Date: 01/25/2017
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: Qualcomm, Inc.
• Inventors: van Boheemen, Edward, Weidner, Felix
• Granted Patent: US 10,315,526 B2
• Time in Patent Office: Days
• CPC Class Codes: B60L 53/122 Circuits or methods for driving the primary coil, e.g. supplying electric power to the coil
• CPC Class Codes: B60L 53/126 Methods for pairing a vehicle and a charging station, e.g. establishing a one-to-one relation between a wireless power transmitter and a wireless power receiver
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: H02M 7/4818 with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

The present disclosure describes aspects of switched-capacitor power ramping for soft switching. In some aspects, a resonant circuit of a wireless power transmitter includes a portion of capacitance that is switchable. This portion of capacitance can be disconnected from the resonant circuit to detune the resonant circuit, which may affect voltage or current flow in the resonant circuit. For example, when ramping transmitted power up or down, detuning the resonant circuit may enable an inverter of the wireless power transmitter to continuously soft switch through the power ramping process. By so doing, hard switching of the inverter can be avoided and the inverter can be implemented with lower-power or less expensive components.

Claims

1. A circuit for continuous soft-switching in a wireless power transmitter, the circuit comprising:

a coil having a first terminal connected to a first-phase-output of an inverter and a second terminal connected to a second-phase-output of the inverter;

a first capacitor having a first terminal connected to the first terminal of the coil and a second terminal connected to the second terminal of the coil;

a second capacitor having a first terminal connected to the first terminal of the first capacitor; and

a switch having a first terminal connected to a second terminal of the second capacitor and a second terminal connected to the second terminal of the first capacitor.

2. The circuit as recited in claim 1, wherein a capacitance value of the second capacitor is approximately five percent to ten percent of a capacitance value of the first capacitor.

3. The circuit as recited in claim 1, wherein a capacitance value of the second capacitor is approximately three percent to twelve percent of a capacitance value of the first capacitor.

4. The circuit as recited in claim 1, wherein the switch is implemented using an isolated-gate bipolar transistor (IGBT) or a reverse-blocking IGBT (RB-IGBT).

5. The circuit as recited in claim 1, further comprising:

gate drive circuitry having an output connected to a gate of the IGBT or the RB-IGBT; and

isolation circuitry having an output connected to an input of the gate drive circuitry and an input connected to a controller of the wireless power transmitter.

6. The circuit as recited in claim 1, further comprising an inductor interposed between the first terminal of the coil and the first-phase-output of the inverter.

7. The circuit as recited in claim 1, wherein the coil, the first capacitor, and the second capacitor form a resonant circuit, and opening the switch to disconnect the second capacitor detunes the resonant circuit.

8. The circuit as recited in claim 7, wherein the inverter comprises power switching devices and detuning the resonant circuit is effective to enable continuous soft switching of the inverter'"'"'s power switching devices.

9. The circuit as recited in claim 8, wherein detuning the resonant circuit is effective to enable the continuous soft switching with the inverter operating at frequencies that range from 81.3 kHz to 90 kHz.

10. The circuit as recited in claim 1, wherein the switch is a first switch and the circuit further comprises:

a third capacitor having a first terminal connected to the first terminal of the first capacitor; and

a second switch having a first terminal connected to a second terminal of the third capacitor and a second terminal connected to the second terminal of the first capacitor.

11. A method for initiating transmission of power by a wireless power transmitter, the method comprising:

disconnecting one of at least two parallel capacitors of a resonant circuit of the wireless power transmitter;

setting a frequency of an inverter of the wireless power transmitter to a first frequency;

initiating, with the capacitor disconnected and inverter operating at the first frequency, the transmission of the power to a wireless power receiver;

increasing an amount of the power transmitted to the wireless power receiver until a phase angle of the power in the resonant circuit reaches a predefined threshold;

connecting, responsive to the phase angle reaching the predefined threshold, the one of at least two parallel capacitors of the resonant circuit of the wireless power transmitter; and

setting the frequency of the inverter to a second frequency at which the transmission of the power continues.

12. The method as recited in claim 11, further comprising:

setting the frequency of the inverter to the first frequency or a third frequency that is different from the second frequency;

disconnecting the one of at least two parallel capacitors of the resonant circuit of the wireless power transmitter; and

reducing the amount of power transmitted to the wireless receiver to terminate the transmission of the power to the wireless power receiver.

13. The method as recited in claim 11, wherein disconnecting the one of at least two parallel capacitors detunes the resonant circuit of the wireless power transmitter.

14. The method as recited in claim 11, wherein connecting the one of the at least two parallel capacitors tunes the resonant circuit of the wireless power transmitter for optimal power transfer.

15. The method as recited in claim 11, wherein:

the first frequency to which the inverter is set is a frequency for which the resonant circuit is not tuned; and

the second frequency to which the inverter is set is a frequency for which the resonant circuit of the wireless power transmitter is tuned.

16. The method as recited in claim 11, wherein the predefined threshold for the phase angle of the power is at least 90 degrees.

17. The method as recited in claim 11, wherein the predefined threshold for the phase angle of the power is at least 130 degrees.

18. The method as recited in claim 11, wherein initiating the transmission of power with the capacitor disconnected and inverter operating at the first frequency is effective to maintain soft-switching of the inverter while the amount of power transferred to the wireless power receiver is increased to a nominal level.

19. The method as recited in claim 11, wherein the first frequency or the second frequency is within a range of approximately 81.3 kHz to 90 kHz.

20. An apparatus for wireless power transmission, the apparatus comprising:

an inverter to provide power by operating at two or more frequencies;

a resonant circuit connected to the inverter, the resonant circuit comprising;

a coil to transmit power to a wireless power receiver;

a first capacitor connected in parallel with the coil;

a second capacitor connected in parallel with the coil;

a switch interposed between a terminal of the second capacitor and

a terminal of the coil; and

a power ramp controller configured to;

open the switch to disconnect the second capacitor from the coil;

set an operating frequency of the inverter to a first frequency;

initiate, with the second capacitor disconnected from the coil and the inverter operating at the first frequency, transmission of the power from the apparatus to a wireless power receiver;

increase an amount of the power transmitted until a phase angle of the power in the resonant circuit is greater than 90 degrees;

set the operating frequency of the inverter to a second frequency;

close the switch to connect the second capacitor in parallel with the coil; and

transmit, with the second capacitor connected in parallel with the coil and the inverter operating at the second frequency, additional power from the apparatus to the wireless power receiver.

21. The apparatus as recited in claim 20, wherein the resonant circuit further comprises an inductor interposed between the inverter and respective terminals of the coil, first capacitor, and second capacitor.

22. The apparatus as recited in claim 20, wherein the switch is implemented with isolated-gate bipolar transistors (IGBTs) or a reverse-blocking IGBT (RB-IGBTs).

23. The apparatus as recited in claim 20, wherein the power ramp controller controls the switch via a switch control signal and the apparatus further comprises:

isolation circuitry to isolate the switch control signal from the IGBTs or RB-IGBTs; and

gate drive circuitry to drive, via the switch control signal, respective gates of the IGBTs or RB-IGBTs with which the switch is implemented.

24. The apparatus as recited in claim 20, wherein a capacitance of the second capacitor is approximately three percent to twelve percent of a capacitance of the first capacitor.

25. The apparatus as recited in claim 20, wherein the first frequency or the second frequency is within a range of approximately 81.3 kHz to 90 kHz.

26. The apparatus as recited in claim 20, further comprising a power supply to convert alternating current (AC) power of an AC power source to direct current (DC) power as input power for the inverter.

27. The apparatus as recited in claim 20, wherein the apparatus is embodied as a charging pad or transmitter pad of a wireless electric vehicle charging (WEVC) system.

28. A circuit for continuous soft-switching in a wireless power transmitter, the circuit comprising:

a coil having a first terminal connected to a first-phase-output of an inverter and a second terminal connected to a second-phase-output of the inverter;

a first capacitor having a first terminal connected to the first terminal of the coil and a second terminal connected to the second terminal of the coil; and

switchable tuning means having a first terminal connected to the first terminal of the coil and a second terminal connected to the second terminal of the coil, the switchable tuning means having a capacitance that is approximately three percent to twelve percent of a capacitance of the first capacitor.

29. The circuit as recited in claim 28, further comprising an inductor interposed between the first-phase-output of the inverter and respective terminals of the coil, first capacitor, and switchable tuning means.

30. The circuit as recited in claim 28, wherein the switchable tuning means in implemented at least in part with isolated-gate bipolar transistors (IGBTs) or a reverse-blocking IGBT (RB-IGBTs).