Presently, almost all inductive wireless charge (WLC) devices -- the so-called charge pads -- have a thin-plane structure. Available WLCs on the market now follow the same working principle as an electric transformer, however, there is a big and fundamental difference: unlike the transformers used everywhere else, these inductive WLCs do not have magnetic cores. Without a magnetic core the transmitter and receiver coils of a WLC have much weaker magnetic coupling than a transformer with one. The magnetic coupling is measured by the so-call coupling factor. For most of the transformers, the coupling factor is around 0.95, while for inductive WLC, it is in the range of 0.3 to 0.6. It is well understood that the power transfer efficiency of a WLC is directly proportional to its coupling factor, therefore a low coupling factor also means low efficiency.

This invention is about a complete new inductive WLC structure and working principle. The new charging structure makes it possible to use a magnetic core, which is going to play a central role in enhancing the magnetic coupling between the transmitter and receiver. To make the new structure usable in wireless charging electronic devices, the magnetic core needs to have an airgap so that the to be charged device can be inserted into the gap. This WLC structure design is based on a fundamental formula for the energy stored in a magnetic field, which predicts that vast majority of the energy is stored in the airgap of a magnetic device such as the transformers with gapped magnetic core. Thus, this new WLC structure allows a cell phone or other device to be charged, be placed very close to the energy source, which creates a preferable operating condition to conduct highly efficient wireless energy transfer. 

With a magnetic core to be integrated into the WLC structure, it will be much more like the traditional transformers than the existing charge pads, thus provides the potential of taking the technical advantages of modern-day transformers, such as enhanced magnetic flux, minimal energy loss and reduced size and weights, all of which are made possible by using magnetic cores. For WLC, the added magnetic core will particularly enhance the magnetic coupling between the transmitter and receiver and thus power transfer efficiency. 

With much improved magnetic coupling and higher power transfer efficiency, some major advantages are expected to follow naturally in terms of the WLC performance and manufacturing, such as more compact transmitter and receiver design and reduced material usage and BOM cost. For example, with better coupling factor, the magnetic coils of the transmitter and receiver will need a smaller number of turns. With a magnetic core exists, the magnetic flux path is well guided and takes smaller area. Thus, not only the number of turns but also the coil size can be reduced, and this certainly reduce the amount of copper needed for making the coils, and lead to size reduction for both the WLC charging device and the device to be charged.