Efficient design methodology for inductive energy transmission

摘要

Wirelessly transferred energy for mobile devices, systems and sensors provides a huge number of advantages, which find a direct application in all areas where the connecting cable represent a development bottleneck or a mechanical, electrical and biological challenge. In the domain of consumer electronics, the wireless energy transmission can be used in order to charge laptops, tablet PCs, smart-phones and any kind of daily used mobile device which must be regularly charged. In the area of the industrial production where electronic systems are brought on mobile and articulated parts of the robots, the wireless energy transmission technology is very useful to transfer the energy on badly reachable parts by avoiding the huge problems related to twisted cable structures or galvanic contacts. Another application domain for wireless energy transmission concerns the medical devices and implants. Medical electronic devices which are used in operation rooms must be absolutely aseptic. Indeed, supply cables and their physical plugging interfaces to the device constitute an ideal location for the housing of pathogenic agents like bacteria and virus. The wireless energy transmission technology presents the advantage to allow the fully hermetical encapsulation of these critical devices. In a same way, it can be used to supply implants and actuators inside the body where any cabling constitutes a open door for infections. In terms of this technology instead of traditional power supply systems, suitable transmitter and receiver modules have to be developed [1]. Nevertheless the design of such modules is significantly different from the approach used in classic power electronics. Only if the effects and benefits related to higher transmission frequencies are taken into account, a good system design can be achieved. In order to get a reliable transmission system, a robust design methodology is necessary. This is presented in this paper. For maximum efficiency, not only the quality of the components must be considered. Hence the impedance matching of the entire system plays an essential role. In this context, the effect on the magnetic energy stored in the surrounding space will also be considered and optimized. For a rapid development the design tools are equally important and a two-step approach is then recommended. In the first step, a fundamental circuit design is carried out with the help of a quick PEEC method. The procedure required for this purpose will be described below. A subsequent simulation by means of a full wave solver then allows a very accurate prediction of the systems behavior. Finally, the application of the described methods will be presented, by considering the example of a transmitting coil optimized for the highest possible lateral displacement tolerance. Using this approach, a wirelessly supplied monitor has been realized, transmitting 25W electrical power over a distance of 5 cm over a large area of 1200cm~2 and even more.