METHOD AND APPARATUS FOR DETECTING OBJECTS IN CHARGING AREA OF WIRELESS CHARGING TRANSMITTER

• US 20180375385A1
• Filed: 09/12/2017
• Published: 12/27/2018
• Est. Priority Date: 06/22/2017
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Inventors: LI, GANG, Zhao, Ping, Chen, Fei
• Granted Patent: US 11,522,391 B2
• Time in Patent Office: Days
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• 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 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H03K 5/156 Arrangements in which a continuous pulse train is transformed into a train having a desired pattern

Abstract

A method for detecting objects in a charging area of a wireless charging transmitter includes providing a bridge circuit that generates a ping signal, and providing the ping signal to a transmitter terminal. The method further includes monitoring at least one of a current of a power supply connected to the bridge circuit, and a current at the transmitter terminal to determine if an eligible object is in the charging area. The ping signal has parameters including frequency, duty cycle, and phase shift angle, where at least one of these parameters varies with time.

Claims

1. A method for detecting an object in a charging area of a wireless charging transmitter, the method comprising:

supplying a bridge circuit with power from a power supply;

generating a ping signal by the bridge circuit;

providing the ping signal to a transmitter terminal, wherein the ping signal has a plurality of parameters including at least one of frequency, duty cycle, and phase shift angle, and at least one of the plurality of parameters varies with time; and

monitoring at least one of a current of the power supply and a current at the transmitter terminal to determine if an eligible object is in the charging area.

2. The method of claim 1, wherein the monitoring step further comprises:

determining if the at least one of the power supply current and the current at the transmitter terminal exceeds a predetermined value; and

determining an existence of an object in the charging area if the at least one of the power supply current and the current at the transmitter terminal exceeds the predetermined value.

3. The method of claim 2, wherein the ping signal has a limited number of pulses.

4. The method of claim 3, wherein the number of pulses is 4 or 5.

5. The method of claim 2, wherein the frequency of the ping signal decreases over time.

6. The method of claim 5, wherein an initial frequency of the ping signal is about 200 kHz, and the frequency of the ping signal decreases by about 5 kHz per pulse.

7. The method of claim 2, wherein the duty cycle of the ping signal increases over time.

8. The method of claim 7, wherein an initial duty cycle of the ping signal is 20%, and the duty cycle increases by 10% each pulse.

9. The method of claim 2, wherein the phase shift angle of the ping signal increases over time.

10. The method of claim 1, wherein the monitoring step further comprises:

determining if the at least one of the power supply current and the current at the transmitter terminal exceeds a corresponding threshold; and

stopping the generation of the ping signal if the at least one of the power supply current and the current at the transmitter terminal exceeds its corresponding threshold.

11. The method of claim 10, wherein the frequency of the ping signal increases over time.

12. The method of claim 10, wherein the duty cycle of the ping signal increases over time.

13. The method of claim 10, wherein the phase shift angle of the ping signal increases over time.

14. The method of claim 10, wherein the at least one of the plurality of parameters of the ping signal is held for a predetermined time before the ping signal changes.

15. The method of claim 14, wherein the predetermined time is 3 ms.

16. The method of claim 10, wherein the at least one of the plurality of parameters of the ping signal varies within 2 ms.

17. An apparatus for detecting objects in a charging area of a wireless charging transmitter, the apparatus comprising:

a bridge circuit coupled to a power supply for receiving a supply voltage, wherein the bridge circuit generates a ping signal, wherein the ping signal has a plurality of parameters including at least frequency, duty cycle, and phase shift angle, and wherein the bridge circuit generates the ping signal such that at least one of the plurality of parameters of varies over time;

a transmitter terminal coupled to the bridge circuit for receiving the ping signal;

a detection circuit that detects at least one of a current of the power supply and a current at the transmitter terminal; and

a determination circuit, connected to the detection circuit, that determines, in response to the at least one of the currents detected by the detection circuit, if an eligible object is in the charging area.

18. The apparatus of claim 17, wherein:

the bridge circuit is configured to generate the ping signal to have a limited number of pulses, and

the ping signal is characterized with at least one of (i) a decreasing frequency over time;

(ii) an increasing duty cycle over time; and

(iii) an increasing phase shift angle when the bridge circuit is a full-bridge circuit.

19. The apparatus of claim 17, wherein:

the bridge circuit stops generating the ping signal if the at least one of the power supply current and the current at the transmitter terminal exceeds a predetermined threshold, and

the bridge circuit generates the ping signal with at least one of (i) an increasing frequency over time;

(ii) an increasing duty cycle over time; and

(iii) an increasing phase shift angle over time.

20. The apparatus of claim 17, wherein the bridge circuit comprises:

a first transistor (Q1) having a source a first terminal connected to the power supply and a gate terminal that receives a first input signal (SQ1);

a second transistor (Q2) having a first terminal connected to a second terminal of the first transistor, a second terminal connected to ground, and a gate terminal that receives a complement of the first input signal;

a third transistor (Q3) having a first terminal connected to the power supply and a gate terminal that receives a second input signal (SQ3);

a fourth transistor (Q4) having a first terminal connected to a second terminal of the third transistor, a second terminal connected to ground, and a gate terminal that receives a complement of the second input signal;

a capacitor having a first terminal connected to a node between the third and fourth transistors; and

an inductor having a first terminal connected to a second terminal of the capacitor, and a second terminal connected to a node between the first and second transistors.