New approaches for controlling a resonant half-bridge flyback converter with wide voltage operation range

Abstract

Currently, adaptors and chargers are evolving towards a universal DC power source. The introduction of the USB-PD and USB-PD EPR standards define the path for such universalization. This way, they open the door to extend the usage of such adaptors for most of the rechargeable battery-based devices, from mobile phones to e-bikes. A truly universal adaptor needs to support high output power, which normally results in bigger size and weight. Overcoming these disadvantages, in combination with the USB-PD requirements, is the major driving factor of the current developments in the field. The investigation targets of this work has been defined within such context. Current flyback based converters show limited efficiency and size to achieve such targets. Forward converters, such as LLC converter, has limited input to output voltage range and need additional power stages to achieve the required range. The proposed topology to be investigated, “asymmetrical half-bridge flyback converter”, is one of the most promising converter topologies to achieve the given goals, mainly due to the hybrid flyback-forward nature of the converter presented by first time within the context of this work. The boundary conditions to achieve the maximum power density are described. An analysis of the proposed converter topology to probe its suitability for high power density is presented. Innovative control methods are proposed, especially to address low power conditions and wide input and output voltage range operation. Finally, the advantages of wide band gap devices applied to the converter are analyzed. The investigation has been backup with simulation and several hardware prototypes that show outstanding results in terms of efficiency, power density and wide voltage range operation. This research work has been carried out in cooperation with Infineon Technologies AG, most of the practical investigations has been carried out in its facilities at its headquarters in Neubiberg, Germany.