Phase Locked Loop (PLL) based self-oscillating controller for LCC resonant converters

The paper describes a controller for the LCC resonant converter that employs a Phase-Locked Loop (PLL) to generate switch timing signals from measurements of current in the resonant circuit. A major advantage of the control methodology is that operation is automatically restricted to be above the resonant frequency thereby ensuring inductive switching. Furthermore, the ´phase-locked´ nature of the controller improves robustness by reducing the system´s sensitivity to parameter variations and permits more of the converter´s frequency characteristic to be utilised, offering the potential for higher power densities to be achieved.