Lateral GaN-based transistors (AlGaN/GaN HEMTs) use a two-dimensional electron gas (2DEG) as transistor channel. They enable efficient power converters with particularly high power density. Very high converter switching frequencies can be realized because of the low area-specific on-state resistance (for a given off-state voltage) and the very low gate charge which is required for switching. This allows for very compact power converters. The lateral device design opens the path for straight-forward monolithic integrationn of the needed powerelectronic functionalities on one chip.