Control architecture for LLC resonant converter
PhD student Anuj Maheshwari with Advisor K. Haran
An LLC series resonant dc-dc converter is an attractive solution for the dc-dc conversion stage in many applications, including battery charging, solar energy harvesting, and LED driver, due to its high efficiency and power density, and low electromagnetic interference over a wide load range. The controller design for LLC resonant dc-dc converter is challenging due to the large number of poles whose locations vary with operating conditions. A controller’s ability to reject input disturbance is required to reduce the input filter size and increase power density. Also, the high bandwidth of the controller allows for a fast transient response. The control architecture, shown in Figure-1, utilizing the output diode current measurement essentially reduces the control-to-output transfer function for an LLC resonant converter to first order and provides a very high degree of input voltage disturbance rejection with a minimal increase in control-loop complexity. Analytical and simulated frequency response for control-to-output transfer function, shown in Figure-2, validate the first order behavior of the converter.