WIRELESS CHARGING COIL FILTERING

• US 20110009057A1
• Filed: 07/07/2009
• Published: 01/13/2011
• Est. Priority Date: 07/07/2009
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Saunamaki, Esa Ilmari
• Granted Patent: US 8,655,272 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• 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: H04B 5/0037 for power transfer
• CPC Class Codes: H04B 5/0093 with one coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

Example embodiments are disclosed for limiting radio frequency noise created during wireless charging of rechargeable batteries in radio frequency communication devices. In an example embodiment, a power source circuit in a wireless charging device produces a source alternating current in a frequency range between 50 kHz and 20 MHz. The source alternating current is passed through a radio frequency blocking filter to limit radio frequency noise. The filtered source alternating current is then driven through a transmitting coil in the charging device. The alternating magnetic field produced by the transmitting coil inductively couples with a proximately located receiving coil in a radio frequency communication device, using contact-less electromagnetic induction. The radio frequency communication device may be a mobile communications device, FM radio, two-way radio, PDA, cell phone, laptop or palmtop computer, or the like. The alternating magnetic field produces a corresponding induced alternating current in a frequency range between 50 kHz and 20 MHz in the corresponding receiving coil in the radio frequency communication device. The induced alternating current is passed through a second radio frequency blocking filter that limits radio frequency noise that could otherwise be created by the rectifier and control circuits on communication device. The filtered induced alternating current is rectified to an appropriate DC charging voltage for the rechargeable battery. In this manner, radio frequency noise is limited during wireless charging of rechargeable batteries in radio frequency communication devices, to reduce the effects of such noise on the communication circuits and the RF antenna of the communication device. Moreover, RF performance is improved by limiting spurious emissions, RF noise, and harmonics generated in rectifier and control circuits. Antenna performance is improved by floating the charger coils in the RF frequencies of the communication device.

Claims

1. An apparatus, comprising:

a power source circuit in a wireless charging device configured to produce a source alternating current in a frequency range less than radio frequency;

a radio frequency blocking filter coupled to the power source, configured to limit radio frequency noise;

a transmitting coil coupled to the blocking filter, configured to inductively couple with a proximately located receiving coil in a radio frequency communication device, using contact-less electromagnetic induction, to wirelessly provide power with reduced radio frequency noise.

2. The apparatus of claim 1, which further comprises:

a first RF inductance in the filter, coupled between said power source and a first terminal of said transmitting coil, having a high impedance to frequencies in a carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise.

3. The apparatus of claim 2, which further comprises:

a first capacitance coupled between said power source and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

4. The apparatus of claim 3, which further comprises:

a second RF inductance in the filter, coupled between said power source and a second terminal of said transmitting coil, having a high impedance to frequencies in the carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise; and

a second capacitance coupled between said power source and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

5. The apparatus of claim 1, which further comprises:

said filter configured to limit radio frequency noise in a carrier frequency range of the radio frequency communication device.

6. The apparatus of claim 2, which further comprises:

said carrier frequency range being selected from the group consisting of a cell phone'"'"'s carrier frequency range and an FM-radio'"'"'s carrier frequency range.

7. An apparatus, comprising:

a receiving coil in a radio frequency communication device, configured to inductively couple with an alternating magnetic field produced by a proximately located transmitting coil of a wireless charger, using contact-less electromagnetic induction to produce a corresponding induced alternating current in the receiving coil, to wirelessly receive power from the charging device;

a radio frequency blocking filter coupled to the receiving coil, configured to pass said power as induced alternating current and limit radio frequency noise; and

a radio frequency communication circuit coupled to the radio frequency blocking filter, configured to receive said power with reduced radio frequency noise.

8. The apparatus of claim 7, which further comprises:

a first RF inductance in the filter, coupled between a first terminal of said receiving coil and said radio frequency communication circuit, having a high impedance to frequencies in a carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise.

9. The apparatus of claim 8, which further comprises:

a first capacitor coupled between said first terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

10. The apparatus of claim 8, which further comprises:

a second RF inductance in the filter, coupled between a second terminal of said receiving coil and said radio frequency communication circuit, having a high impedance to frequencies in the carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise; and

a second capacitor coupled between said second terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

11. The apparatus of claim 7, which further comprises:

said filter configured to limit radio frequency noise in a carrier frequency range of the radio frequency communication device.

12. The apparatus of claim 11, which further comprises:

said carrier frequency range being selected from the group consisting of a cell phone'"'"'s carrier frequency range and an FM-radio'"'"'s carrier frequency range.

13. The apparatus of claim 7, which further comprises:

said radio frequency communication device selected from the group consisting of a mobile communications device, FM radio, two-way radio, PDA, cell phone, laptop computer and palmtop computer.

14. The apparatus of claim 7, which further comprises:

said filter having characteristics of a low pass filter with a high attenuation at radio frequencies.

15. The apparatus of claim 8, which further comprises:

a first pair of parallel capacitors coupled between said first terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

16. The apparatus of claim 8, which further comprises:

a second RF inductance in the filter, coupled between a second terminal of said receiving coil and said radio frequency communication circuit, having a high impedance to frequencies in the carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise; and

a second pair of parallel capacitors coupled between said second terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

18. The apparatus of claim 8, which further comprises:

a first group of three parallel capacitors coupled between said first terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

19. The apparatus of claim 8, which further comprises:

a second RF inductance in the filter, coupled between a second terminal of said receiving coil and said radio frequency communication circuit, having a high impedance to frequencies in the carrier frequency range of the radio frequency communication device, to limit transferring the radio frequency noise; and

a second group of three parallel capacitors coupled between said second terminal of said receiving coil and ground potential, configured as an RF bypass for the carrier frequency range of the communication device, to bypass to ground the radio frequency noise.

20. The apparatus of claim 7, which further comprises:

said receiving coil and said transmitting coil being printed wiring coils configured to be positioned in a coplanar, juxtaposed relationship in close proximity to one another to enhance contact-less electromagnetic induction therebetween.