On the Benefit of Synchronous Rectification to Boost up the Efficiency in Mobile Adapters

Mobile AC/DC power supplies as being used e.g. for notebooks face challenging conditions: they should be compact, lightweight, not get too hot without any forced cooling, shock proof etc. Due to global usage wide input voltage range is a must. With increasing power demand of the processor and additional features of the notebook, output power increases, thermal management becomes hence an increasingly difficult task. The article analyses the losses of its active components and proposes solutions for the optimization of the system. Due to large output currents secondary side rectification with active switches is mandatory. This task is facilitated by half bridge topologies, which eliminate the need for a control IC for the secondary side rectification. A further reduction of losses can be achieved if power factor correction and main stage use resonant power architectures.