Q-factor detection method

Patent metadata

Field	Value
Publication number	US-11437862-B2
Application number	US-202017010608-A
Country	US
Kind code	B2
Filing date	Sep 2, 2020
Priority date	Jul 1, 2020
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

A wireless transmitter with Q-factor measurement is presented. In some embodiments, a method of performing a measurement test in a wireless power transmitter includes adjusting an input voltage to a bridge circuit; setting up transistors in the wireless power transmitter to form an LC oscillating circuit that includes a transmit coil and a capacitor circuit; measuring a VDET sinusoidal voltage from the LC oscillating circuit; and determining a result from the VDET sinusoidal voltage. The result can be calculation of a Q-factor and/or determination of presence of a foreign object.

First claim

What is claimed is:

1. A wireless power transmitter, comprising:
a transmit coil coupled between a first node and a second node;
a first half-bridge circuit coupled between an input voltage and a ground, the first half-bridge circuit including a first transistor coupled between the input voltage and the first node and a second transistor coupled between the first node and the ground;
a second half-bridge circuit coupled between the input voltage and the ground, the second half-bridge including a third transistor coupled between the input voltage and the second node and a fourth transistor coupled between the second node and the ground;
a capacitor circuit having a plurality of capacitors coupled between the first node and the second node;
a measurement circuit coupled to the capacitance circuit and to the first node; and
a transmit driver coupled to provide a control signal to the measurement circuit, the first half-bridge circuit, and the second half-bridge circuit,
wherein during a measurement test, the transmit driver configures the first half bridge circuit to turn the first transistor and the second transistor off, configures the second half-bridge circuit to turn the third transistor off and turn the fourth transistor on, and enables the measurement circuit to form an LC oscillating circuit between the input voltage and the ground that includes the transmit coil and the plurality of capacitors in the capacitor circuit, monitors a sinusoidal voltage across the transmit coil in the LC oscillating circuit to determine a voltage amplitude across the transmit coil, and determines a result from the voltage amplitude across the transmit coil, and
wherein the capacitor circuit includes a capacitive divider formed in the LC oscillating circuit and the measurement circuit includes a bipolar junction transistor (BJT) coupled to the capacitive divider.

2. The transmitter of claim 1 , wherein the result is a Q-factor, wherein the Q-factor is calculated from the voltage amplitude at the first node and a current amplitude at the first node determined by the transmit driver.

3. The transmitter of claim 1 , wherein the result is indication of presence of a foreign object.

4. The transmitter of claim 1 , wherein the second half-bridge circuit is coupled to the second node through an inductor.

5. The transmitter of claim 1 , wherein the transmit coil is a configurable multi-coil system.

6. The transmitter of claim 1 , wherein the transmit coil is configured for high power operation.

7. The transmitter of claim 1 , wherein the transmit driver includes
a bridge driver having a first driver coupled to the first half-bridge and a second driver coupled to the second half bridge;
an analog-to-digital converter coupled to receive analog signals and provide digital signal; and
a processor, the processor coupled to the bridge driver and to the analog-to-digital converter, the processor executing instructions to
adjust the input voltage;
configure the first transistor and the second transistor of the first half-bridge circuit for the measurement test;
configure the third transistor and the fourth transistor of the second half-bridge circuit for the measurement test;
enable the measurement circuit;
receive the sinusoidal voltage during the measurement test; and
provide the voltage amplitude based on the sinusoidal voltage.

8. A wireless power transmitter, comprising:
a transmit coil coupled between a first node and a second node;
a first half-bridge circuit coupled between an input voltage and a ground, the first half-bridge circuit including a first transistor coupled between the input voltage and the first node and a second transistor coupled between the first node and the ground;
a second half-bridge circuit coupled between the input voltage and the ground, the second half-bridge including a third transistor coupled between the input voltage and the second node and a fourth transistor coupled between the second node and the ground;
a capacitor circuit having a plurality of capacitors coupled between the first node and the second node;
a measurement circuit coupled to the capacitance circuit and to the first node; and
a transmit driver coupled to provide a control signal to the measurement circuit, the first half-bridge circuit, and the second half-bridge circuit,
wherein during a measurement test, the transmit driver configures the first half bridge circuit to turn the first transistor and the second transistor off, configures the second half-bridge circuit to turn the third transistor off and turn the fourth transistor on, and enables the measurement circuit to form an LC oscillating circuit between the input voltage and the ground that includes the transmit coil and the plurality of capacitors in the capacitor circuit, monitors a sinusoidal voltage across the transmit coil in the LC oscillating circuit to determine a voltage amplitude across the transmit coil, and determines a result from the voltage amplitude across the transmit coil, and
wherein the capacitor circuit includes a capacitive divider formed in the LC oscillating circuit and the measurement circuit includes an amplifier coupled to the capacitive divider.

9. The transmitter of claim 8 , wherein the result is a Q-factor, wherein the Q-factor is calculated from the voltage amplitude at the first node and a current amplitude at the first node determined by the transmit driver.

10. The transmitter of claim 8 , wherein the result is indication of presence of a foreign object.

11. The transmitter of claim 8 , wherein the second half-bridge circuit is coupled to the second node through an inductor.

12. The transmitter of claim 8 , wherein the transmit coil is a configurable multi-coil system.

13. The transmitter of claim 8 , wherein the transmit coil is configured for high power operation.

14. The transmitter of claim 8 , wherein the transmit driver includes
a bridge driver having a first driver coupled to the first half-bridge and a second driver coupled to the second half bridge;
an analog-to-digital converter coupled to receive analog signals and provide digital signal; and
a processor, the processor coupled to the bridge driver and to the analog-to-digital converter, the processor executing instructions to
adjust the input voltage;
configure the first transistor and the second transistor of the first half-bridge circuit for the measurement test;
configure the third transistor and the fourth transistor of the second half-bridge circuit for the measurement test;
enable the measurement circuit;
receive the sinusoidal voltage during the measurement test; and
provide the voltage amplitude based on the sinusoidal voltage.

15. A method of performing a measurement test in a wireless power transmitter, comprising:
adjusting an input voltage to a bridge circuit, the bridge circuit includes a first half bridge with a first transistor coupled between the input voltage and a first node and a second transistor coupled between the first node and a ground and a second half bridge with a third transistor coupled between the input voltage and a second node and a fourth transistor coupled between the second node and the ground;
setting up the bridge circuit by turning the first transistor, the second transistor, and the third transistor off and turning the fourth transistor on to form an LC oscillating circuit that includes a transmit coil and a capacitor circuit coupled between the first node and the second node;
enabling a measurement circuit that is coupled to the transmit coil and the capacitor circuit;
measuring a VDET voltage amplitude acro

Assignees

• Renesas Electronic America Inc
• Renesas Electronics America Inc

Inventors

• Deng Chenggang

Classifications

• G01R27/2688

  Measuring quality factor or dielectric loss, e.g. loss angle, or power factor (power factor related to power measurements G01R21/006; testing capacitors G01R31/016) · CPC title

• H02J50/12 Primary

  of the resonant type · CPC title

• H02M3/33573

  Full-bridge at primary side of an isolation transformer · CPC title

• H02J50/60 Primary

  responsive to the presence of foreign objects, e.g. detection of living beings · CPC title

• H02M1/327

  against abnormal temperatures · CPC title