Analog Devices LTC4125

Description

The use of batteries in everyday devices is getting more ubiquitous. In many of these products, a chargingconnector is difficult or impossible to use. For example, some products require sealed enclosures to protectsensitive electronics from harsh environments and to enable for convenient cleaning or sterilization. Otherproducts may simply be too small to include a connector, and in products where the battery-poweredapplication includes movement or rotation, forget about charging with wires. Wireless charging adds value,reliability and robustness in these and other applications.There are many ways to deliver power wirelessly. Across a short distance of less than a few inches, capacitiveor inductive coupling is commonly used. In this article, solutions using inductive coupling are discussed.In a typical inductively coupled wireless power system, an AC magnetic field is generated by a transmit coil,which then induces an AC current in a receive coil just like a typical transformer system. The main differencebetween a transformer system and a wireless power system is that an air gap or other non-magnetic materialgap separates the transmitter and receiver. Furthermore, the coupling between the transmit coil and thereceive coil is typically very low. Whereas a coupling of 0.95 to 1 is common in a transformer system, thecoupling coefficient in a wireless power system varies from 0.8 to as low as 0.05.