Recently, various types of power batteries, with advantages such as high energy density, long driving range, and recyclability, have been widely applied in the field of new energy vehicles. There are problems of output voltage range, smooth transition between modes, efficiency and so on, by applying various composite converters based on resonant circuit for battery charging. A four-switch Buck-Boost merged with capacitor-clamped LLC converter is proposed as a charging circuit. This circuit can operate in both the capacitive and inductive regions of the voltage gain curve. It exhibits constant current control characteristics in a wide frequency modulation range of the capacitive region, and constant voltage characteristics at the optimum resonant point in the inductive region. This is beneficial for achieving constant current and constant voltage control of batteries. Decoupling control of the frequency and duty cycle achieves a wider voltage gain range of the converter, and voltage gain of the converter is continuous under the continuous change of load impedance. This facilitates a stable and smooth transition for constant current and constant voltage charging batteries and implements the control schemes that are applicable to different battery charging. In addition, the wide control range at wide gain can reduce output ripple. The circuit has the features of phase-shifted soft-switching between the arms of the bridge, enhancing capability of soft-switching and reducing on-state current in the multiplex bridge arm, low magnetic flux transformer and ultimately moving to and working at the optimum resonant point. All these aspects facilitate achieving high-efficiency power transmission. It is verified by simulation and experiment that the charging circuit satisfies ZVS and ZCS in the whole process of constant current and constant voltage control, and smooth switching between charging modes.