ELECTRONIC CONTROL METHOD FOR A PLANAR INDUCTIVE BATTERY CHARGING APPARATUS

• US 20090121675A1
• Filed: 11/09/2007
• Published: 05/14/2009
• Est. Priority Date: 11/09/2007
• Status: Active Grant

• Current Assignee: City University of Hong Kong
• Original Assignee: City University of Hong Kong
• Inventors: HUI, Ron Shu Yuen, HO, Wing Choi, CHUNG, Shu Hung, LEE, Chi Kwan
• Granted Patent: US 8,228,025 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence

Abstract

This invention provides an electronic control method for a planar inductive battery charging apparatus on which one or more electronic loads such as mobile phones, MP3 players etc can be placed and charged simultaneously. The power control circuit of the charging pad consists of two power conversion stages. Depending on the nature of the input power supply, the first power stage is an AC-DC power converter with variable output voltage control and a second stage is a DC-AC power inverter with constant current control. The combination of the two stages provides power control of the charging pad and generates AC magnetic flux of ideally constant magnitude over the charging areas within a group of primary windings that are excited.

Claims

1. A planar battery charging system comprising;

a primary power transmission side formed of an array of primary windings adapted to generate magnetic flux substantially perpendicular to a charging surface; and

a secondary power receiving side comprising a secondary winding associated with a battery to be charged and being adapted to receive said magnetic flux when a said secondary winding is placed on said charging surface;

wherein a said primary winding is energized by a control circuit comprising a first-stage power converter and a second-stage power inverter, wherein the first-stage power converter provides a variable DC-link voltage, and wherein the second-stage power inverter generates a fixed-frequency constant AC current to said primary winding.

2. A planar battery charging system as claimed in claim 1, wherein the first-stage power converter is current controlled.

3. A planar battery charging system as claimed in claim 1, wherein the first-stage power converter is voltage-controlled.

4. A planar battery charging system as claimed in claim 1, wherein the current fed to said primary winding is monitored to provide a feedback control of said variable DC-link voltage.

5. A planar battery charging system as claimed in claim 1, wherein a step-down transformer is provided between the output of said second-stage power inverter and the primary winding.

6. A planar battery charging system as claimed in claim 1, wherein said second-stage power inverter comprises a resonant tank that sets the frequency of said AC current supplied to said winding.

7. A planar battery charging system as claimed in claim 6, wherein said second-stage power inverter is switched at a constant frequency that is equal to the frequency of the resonant tank.

8. A planar battery charging system as claimed in claim 1, wherein the secondary side is adapted to receive power at an excitation frequency of the primary winding.

9. A planar battery charging system as claimed in claim 1, wherein the first-stage power converter comprises one of a boost converter, a buck converter, a flyback converter, a Cuk converter, and a Sepic converter.

10. A planar battery charging system as claimed in claim 1, wherein the second-stage power inverter comprises one of a full-bridge type, a half-bridge type, a Class D type, and a Z-source type inverter.

11. A planar battery charging system as claimed in claim 1, wherein each primary winding has the same excitation frequency and generates the same AC magnetic flux.

12. A planar battery charging system as claimed in claim 1, wherein the AC current supplied to the primary winding is sinusoidal.