CONDUCTIVE LAYER OF A LARGE SURFACE FOR DISTRIBUTION OF POWER USING CAPACITIVE POWER TRANSFER

• US 20140197695A1
• Filed: 08/09/2012
• Published: 07/17/2014
• Est. Priority Date: 08/16/2011
• Status: Active Grant

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Waffenschmidt, Eberhard, Sempel, Adrianus, Van Goor, Dave Willem, Van Der Zanden, Henricus Theodorus
• Granted Patent: US 9,741,487 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/05 using capacitive coupling
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

An apparatus (300) for supplying power to a load in a capacitive power transfer system comprises a power generator (350) operating at a first frequency; a transmitter comprising a plurality of first electrodes (310) connected to a first terminal of the power generator (350) and a plurality of second electrodes (320) connected to a second terminal of the power generator (350) of a transmitter portion of the apparatus (300); and a plurality of inductors (340), wherein each inductor of the plurality of inductors is connected between a pair of a first electrode and a second electrode of the plurality of first and second electrodes, wherein each inductor comprises, together with a parasitic capacitor (330) formed between each pair of the first electrode and the second electrode, a resonant circuit at the first frequency in order to compensate for current loss due to parasitic capacitances.

Claims

1. An apparatus for supplying power to a load in a capacitive power transfer systems configured wirelessly distribute power over a large surface, comprising:

a power generator operating at a first frequency;

a transmitter comprising a plurality of first electrodes connected to a first terminal of the power generator and a plurality of second electrodes connected to a second terminal of the power generator of a transmitter portion of the capacitive power transfer system, wherein the plurality of first electrodes and the plurality of first electrodes and the plurality of second electrodes are mounted on the large surface; and

a plurality of inductors, wherein each inductor of the plurality of inductors is connected in parallel between a pair of a first electrode and a second electrode of the plurality of first and second electrodes, wherein each inductor comprises, together with a parasitic capacitor formed between each pair of the first electrode and the second electrode, a resonant circuit at the first frequency in order to compensate for current loss due to parasitic capacitances.

2. The apparatus of claim 1, wherein each inductor of the plurality of inductors is a variable inductor.

3. A method for reducing idle currents in a transmitter for supplying a power to a load connected in a capacitive power transfer system configured to distribute power over large surface, comprising:

operating a power generator at a first frequency having a first terminal and a second terminal;

connecting a first electrode, of a transmitter portion of the capacitive power transfer system to the first terminal of the power generator;

connecting a second electrode of the transmitter portion of the capacitive power transfer system to the second terminal of the power generator; and

connecting an inductor in parallel between the first electrode and the second electrode, the inductor having an inductance to create a resonant circuit with a parasitic capacitor formed between the first electrode and the second electrode, such that the resonant circuit resonates at the first frequency.

4. The method of claim 3, wherein the inductor is a variable inductor.

5. The method of claim 4, further comprising:

adjusting variable inductance of the variable inductor to cause the resonant circuit to resonate at the first frequency.

7. The circuit of claim 5, wherein the first periodic voltage signal consists of a first period of time and a second period of time, wherein during the first period of time a voltage level of the first periodic voltage signal is substantially positive, and during the second time period a voltage level of the first periodic voltage signal is substantially negative;

wherein the second periodic voltage signal consists of a first period of time and a second period of time, wherein during the first period of time a voltage level of the second periodic voltage signal is substantially negative, and during the second time period the voltage level of the second periodic voltage signal is substantially positive.

8. The circuit of claim 7, wherein each of the first and second time periods of the first periodic voltage signal substantially matches each of the first and second time periods of the second periodic voltage signal respectively.

9. The circuit of claim 8, wherein parasitic capacitances in a vicinity of the first and second transmitter electrodes are different, wherein the vicinity of the first transfer electrode and the second transmitter electrode includes at least a surface to which the first transmitter electrode and second transmitter electrode are mechanically connected.

6. A circuit for reducing common mode (CM) currents in a capacitive power transfer system configured to wirelessly distribute power over a large surface, comprising:

a first terminal connected to a first transmitter electrode of the capacitive power transfer system, wherein the first transmitter electrode forms a first parasitic capacitor to a protected earth connected to an earth ground; and

a second terminal connected to a second transmitter electrode of the capacitive power transfer system, wherein the second transmitter electrode forms a second parasitic capacitor to the protected earth;

wherein the circuit generates a first periodic voltage signal between the first terminal and the earth ground, the circuit further generates a second periodic voltage signal between the second terminal and the earth ground, wherein at least an amplitude of each of the first periodic voltage signal and the second periodic voltage signal is controlled to essentially offset the common mode (CM) current flowing through the first parasitic capacitor and the second parasitic capacitor.

10. The circuit of claim 6, wherein the circuit is further configured to change a width of each of the first periodic voltage signal and the second periodic voltage signal until the CM current flowing through the first parasitic capacitor and the second parasitic capacitor is essentially offset.

11. The circuit of claim 10, further comprising:

a switching bridge including a first pair of switches and a second pair of switches;

wherein the first pair of switches includes two switches, a switch is connected to the first transmitter electrode and a first terminal of a power supply generator and a second switch is connected to the second transmitter electrode and a second terminal of the power supply generator;

wherein the second pair of switches includes two switches, a switch is connected to the first transmitter electrode and the second terminal of the power supply generator and a switch is connected to the second transmitter electrode and to the second terminal of the power supply generator, the second terminal of the power supply generator is connected to the protected earth for connection to the earth ground; and

wherein switching of each of the first pair of switches and the second pair of switches is controlled to essentially offset the CM current flowing through the first parasitic capacitor and the second parasitic capacitor.

12. The circuit of claim 11, wherein the CM current is a sum of the currents flowing through the first parasitic capacitor and the second parasitic capacitor.

13. The circuit of claim 11, wherein the switching of each of the first pair of switches and the second pair of switches is controlled to change amplitudes of currents flowing through the first parasitic capacitor and the second parasitic capacitor until the amplitudes of the currents essentially cancel each other.

14. The circuit of claim 11, wherein the switching of the first pair of switches is controlled to change a width of a voltage pulse between the second transmitter electrode and the earth ground, wherein the switching of the second pair of switches is controlled to change a width of a voltage pulse between the first transmitter electrode and the earth ground.

15. The circuit of claim 11, wherein the first pair of switches and the second pair of switches are controlled in an asymmetric operation, wherein the asymmetric operation comprises a different duty cycle for control of the switches of the first pair of switches and control of the switches of the second pair of switches.