Study of AC-DC Converters with Isolated Transformers Applied to High Frequency AC-DC Power Conversion

At high frequency, such as 50 kHz, the behaviors of isolated transformers and diodes in rectifiers are considerably different from ones at low frequency, such as 50 Hz. The analysis and the experiment in this paper show that it suffers from poor power factor and low power output if conventional AC-DC converters with isolated transformer are directly applied to high frequency AC-DC power conversion. Thus, three topologies of AC-DC converters applied to high frequency AC-DC power conversion are proposed, studied and evaluated, to convert 50kHz/36V AC voltage to DC voltage of 12 V. The analysis and experimental results show that the AC-DC converters with an isolated transformer, a resonant capacitor and a class-E rectifier and with an isolated transformer, a resonant capacitor and a full-bridge rectifier are suitable for 50 kHz AC-DC power conversion. Therefore, this study provides the valuable and reasonable solutions to high frequency AC-DC power conversion.