Dc-dc converter having synchronous rectification without cross conduction

Abstract

An apparatus () is provided for preventing cross conduction in a synchronous rectifier of a DC-DC converter (). The DC-DC converter has an input MOSFET switch () coupled to primary windings () of an isolation transformer (), an output MOSFET switch () coupled to secondary windings () of the isolation transformer, and a complementary output MOSFET switch () coupled to an output terminal (). A synchronous rectifier timing circuit () comprises a first timing output signal circuit () responsive to a pulse width modulated signal for providing first and second timing output signals () that switches low at time tand high at time tto control the input MOSFET switch and output MOSFET switch, respectively, and a second timing output signal circuit () responsive to the pulse width modulated signal for providing a third timing output signal () that switches high at time tand low at time tto control the complementary output MOSFET switch.