A Phase Locked Loop System for Soft Switching Tracking of Resonant Power Converters in High Voltage, High Power RF Applications

This paper describes a phase locked loop algorithm which can be used to maintain soft switching of a resonant power converter over a wide range of operating conditions. Magnitude and Frequency based modulation enables all commutations of the power converter to be "soft" in nature, meaning that the converter can be operated at high switching frequencies without significant compromise on efficiency. This lends itself to applications requiring higher power density than that possible with 50Hz technology. This paper advances previous work which fails to soft switch in the presence of significant load variation. Such a method is applicable to any resonant topology in applications ranging from high frequency converter based long pulse and continuous wave modulators to capacitor charger circuits.