Wireless Power Transmission Using a Capacitive Sensor

Patent metadata

Field	Value
Publication number	US-2020212729-A1
Application number	US-201916368777-A
Country	US
Kind code	A1
Filing date	Mar 28, 2019
Priority date	Dec 28, 2018
Publication date	Jul 2, 2020
Grant date	—

Abstract

A capacitor sensor array (or grid) over a wireless power transmission coil can include a first set of lines; a second set of lines intersecting the first set of lines; a first multiplexer coupled to provide a charge (e.g. in the form of a DC voltage) from a voltage source to the first set of lines and provide first signals to detect voltages on each line; and a second multiplexer coupled to provide a charge from the voltage source to the second set of lines and provide second signals to detect voltages on each line, wherein an object positioned with respect to the first set of lines and the second set of lines is located. According to some embodiments, a wireless power receive coil and a rectifier circuit can be used in forming a capacitor sensor, to sense the capacitance between the receive and transmit coils for better alignment between the two coils. Other embodiments are also provided.

First claim

What is claimed is:

1 . A wireless power transmitter comprising:
one or more transmission coils; a capacitor sensor positioned over the one or more transmission coils and comprising: first lines; second lines intersecting the first lines; a multiplexer circuit coupled to the first and second lines, the multiplexer circuit configured to provide a charge from a charge source to lines selected by the multiplexer circuit; and a monitor circuit for monitoring a rate of discharge of each of the first and second lines, the rate of discharge of each line depending on a presence of an object proximate to the line and on a charge transfer between the line and the object; wherein the power transmitter is responsive to the monitor circuit in power transmission.

2 . The wireless power transmitter of claim 1 , wherein monitoring the rate of discharge of each line by the monitor circuit comprises determining whether the line's voltage has reached a threshold after a predetermined length of time.

3 . The wireless power transmitter of claim 1 , wherein monitoring the rate of discharge of each line by the monitor circuit comprises comparing the line's voltage with other lines' voltages after each line was discharging for a predetermined length of time.

4 . The wireless power transmitter of claim 1 , wherein monitoring the rate of discharge of each line by the monitor circuit comprises determining a length of time taken by the line's voltage to reach a predetermined value.

5 . The wireless power transmitter of claim 1 , wherein monitoring the rate of discharge of each line by the monitor circuit comprises comparing a length of time taken by the line's voltage to reach a predetermined value with lengths of time taken by other lines' voltages to reach the predetermined value.

6 . The wireless power transmitter of claim 1 , wherein the multiplexer circuit comprises:
a first multiplexer coupled to the first lines, to provide a charge from the charge source to the first lines selected by the first multiplexer and to couple selected first lines to the monitor circuit; and a second multiplexer coupled to the second lines, to provide a charge from the charge source to the second lines selected by the second multiplexer and to couple selected second lines to the monitor circuit.

7 . The wireless power transmitter of claim 1 , configured to ground the first lines during power transfer.

8 . The wireless power transmitter of claim 1 , comprising a plurality of the transmission coils, wherein the transmitter is configured to perform power transfer by operating a transmission coil over which an object to be charged has been detected by the capacitor sensor, but to keep inactive each transmission coil over which no object to be charged has been detected by the capacitor sensor.

9 . The wireless power transmitter of claim 1 , wherein the wireless power transmitter is configured to shut off a transmission coil upon detecting a foreign object over the transmission coil.

10 . A wireless power transmission method comprising:
charging each of a plurality of first lines and a plurality of second lines, the first and second lines overlying one or more transmission coils; monitoring a rate of discharge of each of the first and second lines, to determine the presence and location of an object proximate to one or more of the first and second lines; and operating the one or more transmission coils in response to the monitoring operation.

11 . The method of claim 10 , wherein monitoring the rate of discharge of each line comprises determining whether the line's voltage has reached a threshold after a predetermined length of time.

12 . The method of claim 10 , wherein monitoring the rate of discharge of each line comprises comparing the line's voltage with other lines' voltages after each line was discharging for a predetermined length of time.

13 . The method of claim 10 , wherein the one or more transmission coils are a plurality of the transmission coils, and the method comprises performing power transfer by operating a transmission coil over which an object to be charged has been detected using said monitoring, but keeping inactive each transmission coil over which no object to be charged has been detected using the monitoring.

14 . A wireless power transfer apparatus comprising:
a receive coil for receiving a wireless signal and generating a corresponding AC signal; circuitry coupling the receive coil to a terminal, for rectifying the AC signal and providing a rectified DC signal on the terminal; wherein the circuitry is operable to monitor a capacitance in the receive coil as a function of a position of the receive coil relative to another object.

15 . The apparatus of claim 14 wherein the apparatus is a wireless power receiver.

16 . The apparatus of claim 14 , wherein the other object is a transmit coil.

17 . The apparatus of claim 16 , wherein monitoring the capacitance comprises applying a voltage to the receive coil and monitoring the voltage in the receive coil.

18 . The apparatus of claim 17 wherein applying the voltage to the receive coil comprises applying a voltage to said terminal.

19 . The apparatus of claim 18 , wherein the circuitry comprises a rectifier comprising:
one or more transistors coupled between the receive coil and the terminal; and driver circuitry for driving the transistors; and
applying the voltage to the receive coil comprises driving the transistors by the driver circuitry to the couple the voltage at said terminal to the receive coil.

20 . The apparatus of claim 14 wherein the circuitry comprises a rectifier comprising:
one or more transistors coupled between the receive coil and the terminal; and
driver circuitry for driving the transistors; and

monitoring the capacitance comprises driving the transistors by the driver circuitry to apply a voltage to the receive coil, and monitoring the voltage in the receive coil.

Assignees

• Integrated Device Tech

Inventors

• Smith Nicholaus
• Liu Rui
• Qi Tao
• Bavisi Amit D
• Jeong Chan Young

Classifications

• H02J50/60

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

• H02J50/402

  the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas · CPC title

• H02J50/90 Primary

  involving detection or optimisation of position, e.g. alignment · CPC title

• H02J50/10 Primary

  using inductive coupling · CPC title

• G01R31/382

  Arrangements for monitoring battery or accumulator variables, e.g. SoC · CPC title