ELECTRIC POWER TRANSMISSION APPARATUS AND NONCONTACT ELECTRIC POWER TRANSMISSION SYSTEM

• US 20110266884A1
• Filed: 08/09/2010
• Published: 11/03/2011
• Est. Priority Date: 01/08/2009
• Status: Abandoned Application

• Current Assignee: NEC Tokin Corporation (Yageo Corporation)
• Original Assignee: NEC Tokin Corporation (Yageo Corporation)
• Inventors: Oka, Toshiaki, Wako, Naoki
• Application Number:
  US13/143,901
• Publication Number:
  US 20110266884A1
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A system for transmitting electric power from an electric power transmission apparatus (10) to an electric power reception apparatus (50) by using electromagnetic induction between a power receiving coil (60) and a power transmitting coil (40). The electric power transmission apparatus (10) comprises an electric power switching circuit (14), a first capacitor (20) and an electric power derivation circuit (30). The electric power switching circuit (14) includes a switching element (16) and an output point (P) and switches the switching element (16) at a predetermined switching frequency (f), thereby causing the electrical potential at the output point (P) to exhibit a predetermined variation, wherein the predetermined variation is an electrical potential variation obtainable by the half-wave rectification of a sinusoidal wave variation which has a predetermined amplitude. The first capacitor (20) is coupled between the output point (P) and a first constant electrical potential (ground). The electric power derivation circuit (30) includes the power transmission coil (40) and is formed to cause an AC variation of the foregoing predetermined variation to occur between the both ends of the power transmission coil (40). The electric power derivation circuit (30) is coupled between the output point (P) and a second constant electrical potential (ground).

Claims

1. An electric power transmission apparatus including a power transmission coil, the electric power transmission apparatus being configured to, upon arrangement of a power reception coil of an electric power reception apparatus at a predetermined position in the vicinity of the power transmission coil, transmit electric power to the electric power reception apparatus by using electromagnetic induction between the power reception coil and the power transmission coil, the electric power transmission apparatus comprising:

an electric power switching circuit including a switching element and an output point, switching of the switching element at a predetermined switching frequency causing predetermined variation of an electrical potential at the output point, the predetermined variation being an electrical potential variation obtainable by carrying out half-wave rectification for a sinusoidal wave variation having a predetermined amplitude;

a first capacitor coupled between the output point and a first constant electrical potential; and

an electric power derivation circuit including the power transmission coil, the electric power derivation circuit being coupled between the output point and a second constant electrical potential to cause, between opposite ends of the power transmission coil, an alternating current variation which is included in the predetermined variation.

2. The electric power transmission apparatus as recited in claim 1, wherein:

the switching element is coupled between a third constant electrical potential and the output point;

the electric power switching circuit further comprises an electrical potential variation inductor coupled between a fourth constant electrical potential and the output point; and

the predetermined variation is determined by the predetermined switching frequency f and inductance of the electrical potential variation inductor.

3. The electric power transmission apparatus as recited in claim 2, wherein the third constant electrical potential is a ground.

4. The electric power transmission apparatus as recited in claim 2, wherein:

the electric power derivation circuit comprises the power transmission coil and a second capacitor directly coupled to the power transmission coil; and

a second resonant frequency f₂ is lower than the predetermined switching frequency f, wherein the second resonant frequency f₂ is a resonant frequency in a case where a serial resonant circuit is formed by the power transmission coil and the second capacitor, and the second resonant frequency f₂ is calculated by using inductance of the power transmission coil in a case where the power transmission coil is viewed from the output point when the power reception coil is arranged at the predetermined area.

5. The electric power transmission apparatus as recited in claim 4, wherein the second resonant frequency f₂ meets the following condition for the predetermined switching frequency f:

0.5f<

f₂<

f.

6. The electric power transmission apparatus as recited in claim 4, wherein a first resonant frequency f₁ is higher than the predetermined switching frequency f, the first resonant frequency f₁ is a resonant frequency in a case where a serial resonant circuit is formed by the power transmission coil and the first capacitor and the second capacitor, and the first resonant frequency f₁ is calculated by using inductance of the power transmission coil in a case where the power transmission coil is viewed from the output point when the power reception coil is arranged at the predetermined area.

7. The electric power transmission apparatus as recited in claim 6, wherein the first resonant frequency f₁ meets the following condition for the predetermined switching frequency f:

f<

f₁<

2f.

8. The electric power transmission apparatus as recited in claim 2, wherein the predetermined switching frequency is designed to be 1 MHz or more.

9. The electric power transmission apparatus as recited in claim 1, wherein each of the first constant electrical potential and the second constant electrical potential is a ground.

10. A noncontact electric power transmission system comprising:

the electric power transmission apparatus as recited in claim 1; and

the electric power reception apparatus including the power reception coil.

11. The noncontact electric power transmission system as recited in claim 10, wherein:

each of the power transmission coil and the power reception coil is formed by disposing a planar coil on a substrate;

the substrate is made of magnetic material which has permeability of 1000 or less; and

the number of turns of the planar coil is 1 to 10 turns.

12. The noncontact electric power transmission system as recited in claim 11, wherein the planar coil is formed by winding wires with a spacing of 0.1 mm or more left between the wound wires.