Radio frequency identification for multi-device wireless chargers
Systems, methods and apparatus for wireless charging are disclosed. A charging device has multiple transmitting coils, a driver circuit configured to provide a charging current to the resonant circuit, and a controller. The charging cells may provide a charging surface. The driver circuit may be configured to provide a charging current to the transmitting coils. The charging device includes a radio interface configured for transmitting and receiving radio frequency identification (RFID) signals. The controller may be configured to transmit an interrogation signal configured to stimulate RFID tags through the radio interface when a chargeable device is initially placed on or near a surface of the wireless charger, refrain from initiating wireless charging of a chargeable device when a response to the interrogation signal is received, and negotiate a charging configuration when a response to the interrogation signal is not received.
1. A method for wireless charging, comprising:
transmitting an interrogation signal configured to stimulate radio frequency identification (RFID) tags through a first radio interface that is provided in a wireless charger;
refraining from participating in wireless charging when a response to the interrogation signal is received; and
negotiating a charging configuration when no response to the interrogation signal is received, wherein the interrogation signal is transmitted when a chargeable device is initially placed on or near a surface of the wireless charger;
wherein the interrogation signal is transmitted through an antenna that is configured as a loop surrounding one or more coils of the wireless charger, and
wherein the one or more coils are configured to receive a charging current when the wireless charger is charging the chargeable device.
2. The method of claim 1 , further comprising:
transmitting the interrogation signal through the antenna comprising one or more coils of the wireless charger, wherein the one or more coils are configured to receive a charging current when the wireless charger is charging the chargeable device.
3. The method of claim 2 , further comprising:
selecting the one or more coils based on location of the chargeable device relative to the surface of the wireless charger.
4. The method of claim 2 , further comprising:
configuring the charging current in accordance with the charging configuration when a response signal to the interrogation signal is not received.
5. The method of claim 1 , wherein the first radio interface is one of a plurality of radio interfaces provided in the wireless charger, and wherein each radio interface in the plurality of radio interfaces is coupled to an associated antenna such that different portions of the surface of the wireless charger are surrounded by different antennas.
6. The method of claim 1 , further comprising:
selecting the one or more coils based on location of the chargeable device relative to the surface of the wireless charger.
7. The method of claim 1 , further comprising:
negotiating the charging configuration when the response to the interrogation signal is received from an RFID tag previously determined to be associated with a different device; and
selecting the one or more coils based on locations of the chargeable device and the different device relative to the surface of the wireless charger.
8. The method of claim 1 , wherein the first radio interface is provided in a chargeable device, wherein the interrogation signal is transmitted after a wireless ping is received from the wireless charger.
9. The method of claim 8 , further comprising:
refraining from responding to the wireless ping when the response to the interrogation signal is received.
10. The method of claim 8 , further comprising:
transmitting a message configured to terminate charging to the wireless charger in response to the wireless ping when the response to the interrogation signal is received.
11. The method of claim 8 , further comprising:
displaying a message on a display of the chargeable device, the message indicating presence of an RFID tag when the response to the interrogation signal is received.
12. A wireless charging device, comprising:
a plurality of transmitting coils;
a driver circuit configured to provide a charging current to the plurality of transmitting coils;
a radio interface configured for transmitting and receiving radio frequency identification (RFID) signals;
a controller configured to:
transmit an interrogation signal configured to stimulate RFID tags through the radio interface when a chargeable device is initially placed on or near a surface of the wireless charging device;
refrain from initiating wireless charging of a chargeable device when a response to the interrogation signal is received; and
negotiate a charging configuration when a response to the interrogation signal is not received; and
an antenna circuit comprising a loop surrounding one or more coils of the wireless charging device, wherein the one or more coils are configured to receive the charging current when the wireless charging device is charging the chargeable device, and
wherein the controller is further configured to:
select the one or more coils based on location of the chargeable device relative to a surface of the wireless charging device.
13. The wireless charging device of claim 12 , further comprising:
an antenna circuit comprising one or more coils in the plurality of transmitting coils, wherein the one or more coils are configured to receive the charging current when the wireless charging device is charging the chargeable device,
and wherein the controller is configured to:
configure the antenna circuit to include the one or more coils based on location of the chargeable device relative to the surface of the wireless charging device.