New driving scheme for high-efficiency synchronous rectification in wide-input-voltage-range DC/DC converter has output current always flowing through a low-resistance switch

A new scheme for driving the synchronous rectifiers in the output side of DC/DC converters has the output current always flowing through a low-resistance switch, even when the input-side switch(es) are not conducting. The gate-source voltage of the synchronous-rectifier switches is independent of (instead of proportional to) the dc input voltage, therefore this scheme is especially well suited to converters that must accommodate a wide range of input voltage, e.g., >2:1. The scheme is based on two auxiliary output-side windings and additional driving circuitry (inverter + driver). To validate the concept, we designed, built, and tested a half-bridge converter for 24 Vdc to 1.5 Vdc at 10 A. The dependence of circuit operation on circuit parameters is analyzed (driver parameters, transformer coupling), and simulation and experimental results are presented.