7.1 Overview

The UCC3895 device combines all the functions necessary to control a phase-shifted full bridge power stage in a 20-pin package. It includes all the outputs needed to drive the four switches in the full-bridge circuit. The dead times between the upper and lower switches in the full bridge may be set using the DELAB and DELCD inputs. Further, this dead time may be dynamically adjusted according to the load level using the ADS pin allowing the user to optimize the dead time for their particular power circuit and to achieve ZVS over the entire operating range. At light loads a no-load comparator forces cycle skipping to maintain output voltage regulation. At higher-power levels, two or more UCC3895 devices may be easily synchronized for parallel operation. The SS/DISB input may be used to set the length of the soft-start process and to turn the controller on and off. The controller may be used in Voltage mode or Current mode control and cycle-by-cycle current limiting is provided in both modes. The switching frequency may be set over a wide range making this device suited to both IGBT and MOSFET based designs.