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

Abstract

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