This paper proposes a hybrid forward-flyback resonant converter with input series-output parallel connection for applications with wide input ranges. The upper part integrates a resonant forward converter and a flyback converter. By adjusting the duty cycle ratio of the resonant and flyback units appropriately, power conversion ratio and voltage gain can be controlled. The lower part is a high-efficiency resonant forward circuit operating with a fixed duty cycle, and the overall resonant state of the circuit can be adjusted by changing the phase difference between the upper and lower circuits, further broadening the voltage regulation range. The system reduces the design difficulty of magnetic components through fixed-frequency control and weakens the influence of excitation inductance on voltage gain. The converter achieves a high power density through the sharing of two resonant units. Additionally, the combination of phase shift and duty cycle maintenance ensures the soft-switching characteristics of switches and diodes on the primary and secondary sides, contributing to improved conversion efficiency. This paper details the working principles and key waveforms, theoretically analyzes its soft-switching characteristics, parameter design, and loss conditions, and constructs a prototype with 63–83 V input and 24 V/4.5 A output for experimental verification.