1. Field of the Invention
The present invention relates to a power charging system, and more particularly, to a non-contact power charging system and a control method thereof, in which power transmission can be interrupted when foreign materials are deposited on a charge plate of the non-contact power charging system, a charging operation can be continuously maintained at a stable voltage even if a non-contact power receiving apparatus moves by touching or displacement on the charge plate of the non-contact power charging system in the charging operation, and thus charging efficiency can be improved.
2. Description of the Related Art
Portable electronic devices, such as cellular phones, personal digital assistants (PDAs), portable media players (PMPs), digital multimedia broadcasting terminal (DMB terminals), MPEG audio layer 3 (MP3) players or notebook computers, cannot be plugged into a regular power source at home or office since they are generally used while the users are moving. Accordingly, the portable electronic devices are equipped with batteries or rechargeable batteries.
A charging system has been used to charge electric power, supplied from the regular power source, to the batteries or a battery pack of the portable devices via power supply lines or power supply connectors. However, when the charger and the batteries are connected or disconnected to replenish the electric power of the batteries with this connector supply system, an instant discharge may happen because of the potential differences between the charger connector and the battery connector. Hence the foreign substances will be gradually gathered on both connectors and finally there may be a fire disaster. Further, the collected humidity thereon will cause the discharge of the battery and other problems will be involved like the declining battery life, the low battery quality, and so on.
To solve the above-mentioned problems of the connector supply system, non-contacting charging systems have been developed. In this non-contacting charging system in accordance with the prior art, the device having the battery to be charged is placed over the primary coil of the non-contacting charging system and the battery will be charged by a secondary coil of the battery. The battery is charged with the induced electricity from the induced electromotive force of the secondary coil by the generated magnetic field from the primary coil.
The existing non-contacting charging systems with the prior art can only be used to supply the electricity to the portable devices. There are limited practical uses because they cannot be used in various alternatives.
Besides, if a metal is placed inside the effective radius of the generated magnetic field of the primary coil, there would be a lot loss of the electricity in the primary coil due to the changes of the magnetic field, so that non-contacting charging system may be damaged.