A novel implementation of digital control for isolated DC/DC converters with transmission of digital duty cycle command

In this paper, a novel digital control solution for isolated DC/DC converters is presented, which induces little additional delay time to the control loop and is easy to implement synchronous rectification (SR) on the secondary side as well. In this digital solution, the compensator (PI regulator) set on the secondary side facilitates the SR implementation, and the digital duty cycle command is transmitted to the primary side serially at high speed in order to reduce the delay time. The whole digital control system is built in two FPGAs, one on the primary side and the other on the secondary side. A small transformer is used to fulfill isolation between primary and secondary side in the control loop. The experiment is carried out on a half-bridge converter with SR (220V AC input and 12V DC output).