High voltage, high power, high efficiency, digitally-controlled LLC converter for telecom applications

This paper describes the development of a high voltage, high power, and high efficiency LLC converter used in a delta 3-phase rectifier that meets the requirements imposed by today´s telecom market. Initially, a comparative analysis of different LLC topologies is performed to determine the best option for the targeted application. Then, an empirical method, based on the plant frequency response, is introduced as a practical technique to design the voltage and current loop compensators. Next, a novel strategy is utilized to control the synchronous rectifier by executing an additional algorithm in the system microcontroller. Finally, a special filter is added to the voltage loop to mitigate the output voltage noise while maintaining a good dynamic performance. The techniques and solutions discussed in this paper have been successfully proven and implemented in a soon-to-be commercialized 12kW telecomgrade rectifier.