Implementation of an Adaptive Dead Time in Resonant Converters

Abstract:
Conventionally, a short dead time is necessary to prevent short circuits in the input bridge of resonant converters. In addition, this dead time contributs to achieve zero voltage switching (ZVS) for the input switches. In case of ZVS, switching losses are almost eliminated. Although implemented by several control ICs, a fixed dead time is not always sufficient at every operating point to fully charge/discharge the parasitic half - bridge capacitors given by the converter design. To overcome these drawbacks, an alternative and more promising approach is the usage of an adaptive dead time. Here, a special control logic is needed determining the individual turn - on and turn - off events of the input switches. However, depending on the measuring system (voltage sensor, current sensor) there are different implementation methods.