Flexible bridge amplifier for wireless power

• US 11,038,374 B2
• Filed: 04/18/2017
• Issued: 06/15/2021
• Est. Priority Date: 04/18/2017
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Inventors: Prabhala, Venkata Anand, Schaecher, Stephan
• Primary Examiner(s): Kessie, Daniel
• Application Number:
  US15/490,587
• Publication Number:
  US 20180301934A1
• Time in Patent Office: 1,519 Days
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• 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: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007192 in response to temperature
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current

Abstract

A wireless power transfer (WPT) system that efficiently transfers power to portable devices over a wide range of load conditions and power output demands. The WPT system of this disclosure includes a full bridge topology. Changing the number of devices or the position and orientation of a device on the transmitter charge area may change the impedance and/or the load on the power transmitting unit (PTU). The WPT system of this disclosure may detect load impedance and/or power requested from the PTU. When the load exceeds a threshold, the WPT system will activate a second half bridge to operate in full-bridge mode. Similarly, the WPT system may detect the power requested and received and when the power drops to a certain threshold of power transmitted the WPT may turn off the second leg and operate in half-bridge mode.

Claims

1. A method comprising:

detecting, by a sense and control unit, a load impedance reflected to a power transfer circuit, wherein the power transfer circuit comprises;

a full bridge circuit comprising;

a first half-bridge circuit comprising a first high side switch and a first low side switch; and

a second half bridge circuit comprising a second high side switch and a second low side switch;

a first inductor and first capacitor in series that connect the drain of the first low side switch to the source of the first low side switch;

a second inductor and second capacitor in series that connect the drain of the second low side switch to the source of the second low side switch, wherein the reflected load impedance is coupled in series with a capacitor and coupled between the drain of the first low side switch and the drain of the second low side switch;

determining, by the sense and control unit, an output power of the power transfer circuit;

determining, by the sense and control unit, whether the reflected load impedance is less than an impedance threshold, and in response to determining that the reflected load impedance is less than the impedance threshold, selecting, by the sense and control unit, a half-bridge mode of operation of the power transfer circuit, wherein an efficiency of the power transfer circuit in the half-bridge mode of operation is improved over a full-bridge mode of operation of the power transfer circuit during operation when the reflected load impedance less than the impedance threshold;

determining, by the sense and control network, whether the output power is less than the output power threshold and in response to determining that the output power is less than the output power threshold, selecting, by the sense and control unit, a half-bridge mode of operation of the power transfer circuit, wherein the efficiency of the power transfer circuit in the half-bridge mode of operation is improved over a full-bridge mode of operation of the power transfer circuit during operation when either;

the reflected load impedance less than the impedance threshold, or

the output power less than the output power threshold;

determining, by the sense and control network, whether the reflected load impedance has crossed the impedance threshold, and in response to determining, by the sense and control unit, that the reflected load impedance has crossed the impedance threshold and is greater than the impedance threshold, selecting, by the sense and control unit, a full-bridge mode of operation of the power transfer circuit, wherein the efficiency of the power transfer circuit in full-bridge mode of operation is improved over the half-bridge mode of operation during operation when the reflected load impedance is greater than the impedance threshold;

determining, by the sense and control network, whether the output power has crossed the output power threshold, and in response to determining, by the sense and control unit, that the output power is greater than the output power threshold, selecting, by the sense and control unit, a full-bridge mode of operation of the power transfer circuit, wherein the efficiency of the power transfer circuit in the full-bridge mode of operation is improved over a half-bridge mode of operation of the power transfer circuit during operation when either;

the reflected load impedance greater than the impedance threshold, or

the output power greater than the output power threshold.

2. The method of claim 1, wherein selecting the half-bridge mode of operation comprises disabling the first half-bridge of the power transfer circuit.

3. The method of claim 2, disabling the first half-bridge circuit comprises turning off the high side switch of first half-bridge circuit and turning on the low side switch of the first half-bridge circuit.

4. The method of claim 1, further comprising:

determining by the sense and control unit, a DC input voltage of the power transfer circuit;

in response to determining that the DC input voltage is greater than a DC input voltage threshold, selecting, by the sense and control circuit, a full-bridge mode of operation of the power transfer circuit; and

in response to determining that the DC input voltage is less than or equal to a DC input voltage threshold, selecting, by the sense and control unit, a half-bridge mode of operation of the power transfer circuit.

5. The method of claim 4,

wherein the power transfer circuit rated to operate at a maximum DC input voltage,

the method further comprising, adjusting the DC input voltage threshold to half of the maximum DC input voltage.

6. The method of claim 1,

wherein the power transfer circuit is rated to operate at a maximum rated power output,

the method further comprising, adjusting the output power threshold such that the output power threshold is half of the maximum rated power output.

7. The method of claim 1,

wherein the power transfer circuit comprises a transmit resonator,

wherein the power transfer circuit is rated to operate at a maximum impedance reflected to the power transfer circuit through the transmit resonator,

the method further comprising, adjusting the impedance threshold to half of the maximum rated impedance.

8. The method of claim 1, wherein the sense and control unit adjusts the output power threshold and the sense and control unit adjusts the impedance threshold based in part on operating conditions of the power transfer circuit, wherein the operating conditions comprise one or more of ambient temperature, resonator current and power supply voltage.

9. The method of claim 1, further comprising:

determining, by the sense and control unit, an output voltage of a power converter of a power receiving unit (PRU), wherein the power converter unit comprises a component of the PRU and wherein the power converter unit supplies power received from the power transfer circuit to the PRU;

determining, by the sense and control unit, a power level received by the PRU,

in response to determining that the output voltage is less than an output voltage setpoint or that the power level is less than a power level setpoint, increasing, by the sense and control unit, a direct current (DC) input voltage;

in response to determining that the output voltage is greater than the output voltage setpoint or that the power level is greater than the power level setpoint, decreasing, by the sense and control unit, the DC input voltage;

in response to determining that the output voltage equals the output voltage setpoint or the power level is equal to the power level setpoint, further determining, by the sense and control unit, whether the DC input voltage is less than a DC input voltage threshold;

in response to determining that the DC input voltage is less than the DC input voltage threshold, selecting, by the sense a control unit, the half-bridge mode of operation; and

in response to determining that the DC input voltage is greater than the input voltage threshold, selecting, by the sense a control unit, a full-bridge mode of operation.

10. A sense and control circuit, comprising:

sensing circuitry configured to;

detect an impedance reflected to a transmit resonator connected to a power amplifier circuit,

determine an output power of the power amplifier circuit; and

determine a DC input voltage of the power amplifier circuit,

wherein;

in response to determining that the impedance reflected to the transmit resonator connected to the power amplifier circuit is greater than an impedance threshold, the sense and control circuitry is configured to select a full-bridge mode of operation of the power amplifier circuit;

in response to determining that the output power is greater than an output power threshold, the sense and control circuitry is configured to select a full-bridge mode of operation of the power amplifier circuit;

in response to determining that the DC input voltage is greater than a DC input voltage threshold, the sense and control circuitry is configured to select a full-bridge mode of operation of the power amplifier circuit;

in response to determining that the impedance reflected to the power amplifier circuit is less than the impedance threshold, the sense and control circuit is configured to select a half-bridge mode of operation of the power amplifier circuit;

in response to determining that the output power is less than the output power threshold, the sense and control circuit is configured to select a half-bridge mode of operation of the power amplifier circuit; and

in response to determining that the DC input voltage is less than a DC input voltage threshold, the sense and control circuit is configured to select a half-bridge mode of operation of the power amplifier circuit, wherein the power amplifier circuit comprises;

a full bridge circuit comprising;

a first half-bridge circuit comprising a first high side switch and a first low side switch; and

a second half bridge circuit comprising a second high side switch and a second low side switch;

a first inductor and first capacitor in series that connect the drain of the first low side switch to the source of the first low side switch;

a second inductor and second capacitor in series that connect the drain of the second low side switch to the source of the second low side switch, wherein the reflected load impedance is coupled in series with a capacitor and coupled between the drain of the first low side switch and the drain of the second low side switch.

11. The sense and control circuit of claim 10, wherein to select the half-bridge mode of operation comprises disabling the first half-bridge of the power amplifier circuit.

12. The sense and control circuit of claim 11, wherein the sense and control circuit is configured to disable the first half-bridge circuit by turning off the first high side switch of the first half-bridge circuit and turning on the first low side switch of the first half-bridge circuit.

13. A device for wireless power transfer, the device comprising:

a transmit resonator;

a power amplifier circuit that includes;

a first half-bridge circuit comprising a first high side switch and a first low side switch; and

a second half-bridge circuit comprising a second high side switch and a second low side switch,

a first inductor and first capacitor in series that connect the drain of the first low side switch to the source of the first low side switch;

a second inductor and second capacitor in series that connect the drain of the second low side switch to the source of the second low side switch, wherein

the first half-bridge circuit and the second half-bridge circuit are arranged as a full-bridge circuit; and

a sense and control circuit that is configured to;

detect an impedance reflected to the power amplifier circuit via the transmit resonator;

determine an output power of the power amplifier circuit;

in response to determining that the impedance reflected to the power amplifier circuit is greater than an impedance threshold, select a full-bridge mode of operation of the power amplifier circuit, wherein the reflected impedance is coupled in series with a capacitor and coupled between the drain of the first low side switch and the drain of the second low side switch;

in response to determining that the output power is greater than an output power threshold, select a full-bridge mode of operation of the power amplifier circuit;

in response to determining that the impedance reflected to the power amplifier circuit is less than the impedance threshold, select a half-bridge mode of operation of the power amplifier circuit; and

in response to determining that the output power is less than the output power threshold, select a half-bridge mode of operation of the power amplifier circuit.

14. The device of claim 13, wherein the sense and control circuit is further configured to determine a DC input voltage of the power amplifier circuit;

in response to determining that the DC input voltage of the power amplifier circuit is greater than a DC input voltage threshold, select a full-bridge mode of operation of the power amplifier circuit; and

in response to determining that the DC input voltage of the power amplifier circuit is less than the DC input voltage threshold, select a half-bridge mode of operation of the power amplifier circuit.

15. The device of claim 14, wherein selecting the half-bridge mode of operation comprises disabling the first half-bridge circuit, including turning off the first high side switch of the first half-bridge circuit and turning on the first low side switch of the first half-bridge circuit.

16. The device of claim 13, wherein

the sense and control circuit is further configured to execute a continuous mode transition that avoids an abrupt change between the half-bridge mode of operation and the full-bridge mode of operation, and

the sense and control circuit is further configured to execute the continuous mode transition:

from an ending time of the half-bridge mode of operation to a starting time of the full-bridge mode of operation; and

from an ending time of the full-bridge mode of operation to a starting time of the half-bridge mode of operation.

17. The device of claim 13,

wherein the power amplifier circuit is rated to operate at a maximum rated power output, and

the sense and control circuit that is configured to adjust the output power threshold to half of the maximum rated power output.

18. The device of claim 13,

wherein the power transfer circuit is rated to operate at a maximum impedance reflected to the power transfer circuit through the transmit resonator, and

the sense and control circuit that is configured to adjust the impedance threshold to half of the maximum rated impedance.

19. The device of claim 13, wherein the sense and control circuit is configured to adjust the output power threshold and the impedance threshold based in part on operating conditions of the power transfer circuit, wherein the operating conditions comprise one or more of ambient temperature, resonator current and power supply voltage.