LLC performance enhancements with frequency and phase shift modulation control

This paper presents an algorithm that uses a combination of frequency modulation (FM) and phase shift modulation (PSM) to enhance both the controllability and efficiency of an LLC dc-dc converter. It will be shown that, the proper “marriage” of FM and PSM will result in the ability to support a wider range of operating conditions without comprising efficiency or control monotonicity. These operating points include but are not limited to: monotonic start up, light load regulation, high input voltage, constant-current and constant-power.