Highly efficient power electronics is needed for low volume and low weight future power conversion systems. The proposed project aims for the exploitation of novel gallium nitride (GaN) transistors for advanced switched power supplies. High voltage normally-off GaN power devices on Si substrates in vertical device architecture will be developed and its technology transferred to an European industrial environment. The devices are planned to reliably operate at elevated junction temperatures up to 225°C. The project covers the full value added chain from substrate technology and epitaxy to complete power electronic system prototypes. It brings together experienced partners in automotive technology, power electronic system and circuit design, power semiconductor technology, high temperature packaging technologies, GaN power device technology including GaN on Si epitaxy as well as sophisticated device characterization and reliability evaluation techniques. Therefore very good prospects for a successful realization of the project targets and for a competitive implementation of the new devices in an industrial environment are seen.