The phase shifted full bridge (PSFB) converter is used for DC-DC conversion in various applications, for
example, in telecom systems to convert a high voltage bus to an intermediate distribution voltage, typically
closer to 48 V. PSFB stage provides voltage translation as well as isolation from the line voltage, since
this topology includes a transformer.
This application report presents the implementation details of a digitally controlled PSFB system
implemented on the high voltage phase shifted full bridge (HVPSFB) kit from Texas Instruments. This kit
converts a 400 V DC input to a regulated 12 V DC output and is rated for operations up to 600W. Both
peak current mode control (PCMC) and voltage mode control (VMC) implementations are described.
These highly integrated microcontroller-based realizations feature adaptive zero voltage switching (ZVS)
and various synchronous rectification schemes, which are discussed here. Details for generating complex
gate drive waveforms, required by these control schemes, and intelligent timing control, to optimize
system performance under changing operating conditions, are provided. A step-by-step guide to run the
HVPSFB project is also included. A constant high system efficiency above 10% rated load, novel PCMC
waveform generation based on on-chip hardware mechanisms, and simple system implementation are the
highlights of this solution.