This application note contains the necessary informa- tion to build a 100W inverse SEPIC (also called Zeta converter) battery charger. The novelty consists in driv- ing this topology synchronously using Microchip com- ponents, essentially pushing the efficiency over 95% at 8A. The Zeta converter has many advantages, such as input to output DC insulation, buck-boost capability and continuous output current, but it is difficult to control.