Wireless charging coil filtering
View Patent ↗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. 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, which inductively couples with a proximately located receiving coil in a radio frequency communication device. An induced alternating current is passed through a second radio frequency blocking filter in the communication device, which limits radio frequency noise that could otherwise be created by the rectifier and control circuits in the communication device.
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;
a first RF inductor 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;
a first capacitance in the filter, 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;
a second RF inductor 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 in the filter, 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.
2. 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.
3. The apparatus of claim 1 , 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.
4. 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;
a radio frequency communication circuit coupled to the radio frequency blocking filter, configured to receive said power with reduced radio frequency noise;
a first RF inductor 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;
a first capacitor in the filter, 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;
a second RF inductor 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 in the filter, 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.
5. The apparatus of claim 4 , 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 5 , 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. The apparatus of claim 4 , 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.
8. The apparatus of claim 4 , which further comprises:
said filter having characteristics of a low pass filter with a high attenuation at radio frequencies.
9. The apparatus of claim 4 , 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.
10. The apparatus of claim 9 , which further comprises:
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.
11. The apparatus of claim 4 , 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.
12. The apparatus of claim 11 , which further comprises:
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.
13. The apparatus of claim 4 , 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 there between.