JAJSG35B August 2018 – October 2024 UCC28950 , UCC28951
PRODUCTION DATA
The UCC2895x controllers combine all the functions necessary to control a phase-shifted, full-bridge, power stage in a 24-pin TSSOP package. The controller includes two synchronous-rectifier (SR), gate-drive outputs as well as the outputs needed to drive all 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 ADEL pin. This adjustment allows the user to optimize the dead time for their particular power circuit and to achieve ZVS over the entire operating range. In a similar manner, the dead times between the full-bridge switches and the secondary SRs may be optimized using the DELEF input. This dead time may also be dynamically adjusted according to the load, using the ADELEF input to the controller. A DCM (discontinuous conduction mode) option disables the SRs at a user settable light load to improve power circuit efficiency. The controller enters a light-load-burst mode if the feedback loop demands a conduction time less than a user settable level (TMIN).
At higher-power levels, two or more UCC2895x controllers may be easily synchronized in a leader/follower configuration. A SS/EN 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 configured for voltage mode or current mode control. Cycle-by-cycle current limiting is provided in voltage mode and peak current mode. Users can set the switching frequency over a wide range making this controller suited to both IGBT and MOSFET based designs.