A hybrid resonant converter, which is an integration of a resonant switched capacitor converter and a LLC resonant converter, is investigated for the bus converter applications in 48V data-center power systems. High step-down ratio and soft-switching of all the active switches can be achieved by inserting a high frequency transformer into the resonant switched capacitor cell. Operation principles and characteristics of the hybrid resonant converter are analyzed in detail. Novel integrated magnetic structure with PCB winding and matrix transformer is studied for the high frequency transformer. A 1MHz 500W hybrid bus converter with 10:1 high step-down ratio is demonstrated. The peak efficiency of the experimental prototype is 96.4% while the power density is 650W/in3.