Capcitively coupled bi-directional data and power transmission system

DETAILED DESCRIPTION Accordingly, a power and data transfer system is provided which includes a portable device with a first contact circuit formed from a pair of contact pads having an outer surface covered with a dielectric material.
The portable device has a processing unit on it coupled to the first contact circuit.
The portable device interfaces with a host unit which has a second contact circuit on it.
The second contact circuit includes a second pair of contact pads which are also covered with a dielectric material.
A host processing unit is coupled to the second contact circuit.
The first and second contact circuits are adapted to form a capacitive interface when the portable device is positioned proximate the host unit.
The capacitive interface transmits power signals from the host unit to the portable device.
The same contacts are used to transmit bi-directional data signals between the portable device and the host unit.
In one embodiment of the invention, a matching capacitor is provided to increase the capacitive coupling between the host and the portable device.
In another embodiment, the host unit includes a portable device detector which senses when the portable device has been coupled to the host unit.
If no portable device is present, the host unit is prevented from transmitting any signals over the interface, thereby avoiding the wasteful emission of unused electromagnetic or radio-frequency signals.
Embodiments of the present invention are capable of supplying relatively large amounts of power to small portable devices, thereby permitting the inclusion of increased memory or processing capability on the portable device.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing description taken in conjunction with the accompanying drawings.