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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.