Dual SmartRectifier and DirectFET® Chipset Overcomes Package Source Inductance Effects and Provides Accurate Sensing for Synchronous Rectification in DC-DC Resonant Converters

The off-line-power-supply market is increasingly demanding greater power efficiency and, even more often, multiple output voltages. While the general market trend and government regulations have been driving AC-DC-converter-efficiency requirements, the second trend is a function of applications´ power requirements as is the case in typical consumer-electronic equipment such as LCD TVs. This paper describes how an innovative chipset achieves output synchronous rectification in LLC-resonant converters---amongst the most common topologies. Multiple secondary windings can easily generate several output voltages, but this approach increases the circuit complexity for efficient synchronous-rectification control. The proposed approach consists of an SOIC-8-packaged dual SmartRectifier controller coupled with DirectFETO® transistors.