Digital Control and Light Load Efficiency Enhancement of LLC Resonant Converters

摘要

Controlling distributed power systems in a digital fashion is a clear trend of power electronic systemrnintegration. The LLC Resonant convertor topology is well known, with merits such as full range ZVSrnoperation for primary side switches, ZCS for secondary diodes along with integration of LLC topologyrninductors and transformers with a wide operating range. This paper presents a digital control implementationrnof LLC Resonant convertors, highlighting several advantages of digital control like duty cyclerncontrol, dead-band adjustment in real time, frequency control and adaptive thresholds for differentrnsafe operation regions. An active load circuit is used to tune the coefficients of the voltage compensator.rnProgrammable soft start/stop capability and slew rate control helps to avoid inrush current andrnaudible noise. Finally, hybrid burst mode control is presented which dramatically increases light loadrnand stand-by efficiency.