In order to overcome the deficiencies of the traditional low ripple DC regulated power supply's main circuit topology, such as complex circuit structure and large size, a new type of adjustable DC regulated power supply topology based on Buck-Boost inverter circuit is proposed to replace the two links of high frequency inverter and transformer step-up in the traditional structure with the Buck-Boost inverter link, which can be significantly simplified in terms of the circuit structure compared with the traditional structure. Compared with the conventional structure, this structure can be simplified significantly in terms of circuit structure. In order to realize the requirement of low ripple and high stability DC voltage output from this new type of adjustable DC regulated power supply, a composite control method based on proportional-vector proportional-integral is proposed for the Buck-Boost inverter circuit, that is, the capacitor voltage and inductor current in the Buck-Boost inverter circuit are taken as the state variables, and the inductor current is taken as the inner loop of the control, and the capacitor voltage is the outer loop of the control, and the two closed loops are decoupled by adopting proportional-vector proportional-integral composite control method. The decoupling control of the two state variables is realized by adopting the proportional-integral-vector proportional-integral composite control method for the two closed loops, and finally the effect is verified by simulation and experiment, and at the same time compared and analyzed with the traditional low ripple DC regulated power supply. The results show that the new adjustable DC regulated power supply topology based on Buck-Boost inverter circuit proposed in the paper and the control method proposed for the topology not only have small output DC voltage ripple, high steady-state accuracy and good dynamic performance, but also have the features of simple circuit structure and arbitrary adjustable output DC voltage, which are of good application value.