Analysis modeling and simulation of low-voltage MOSFETs in synchronous-rectifier buck-converter applications

Nowadays voltage regulator modules (VRMs) are high switching frequency applications devoted to supply low-voltage and high current with more and more increasing slew rates. Excellent performances can be provided by using a synchronous-rectifier buck converter, which allows overcoming the limitations in terms of efficiency shown by a standard buck topology with Schottky diode. A proper design of the synchronous-rectifier is fundamental to obtain the desired performance from the converter due to its considerable contribute to the total power losses. In this paper analysis modeling and simulation of low-voltage power MOSFETs in synchronous-rectifier buck-converter applications are reported. The MOSFET model has been derived by using an advanced process simulator, which represents the device as a two-dimensional (2-D) finite-element grid. Structure parameters have been derived from flow-chart data pertaining to the MOSFET fabrication, which have been optimised by comparing measured and simulated electrical characteristics. Static and dynamic behaviors relative to the studied device have been simulated through a 2-D mixed device and circuit simulator, and used to extract the structure parameters till to obtain a good match with the experimental results. A synchronous-rectifier buck-converter application has been experimentally analysed by arranging a suitable breadboard, in which the same device type has been used for both the high-side and low-side switch. Simulation runs, performed by implementing a behavioral model of the MOSFET device, have been reported too.