This paper proposes, a two-stage variable bus voltage high-voltage capacitor charging power supply technical scheme which adds a one-stage totem-pole bridgeless power factor correction (PFC) circuit on the basis of the half-bridge LLC resonant circuit, and solves the problem of the decline in charging efficiency caused by the excessive operating frequency variation range of the traditional LLC resonant power supply when the output voltage is higher. Since the totem-pole circuit itself has the function of power factor correction, the power supply design also has the advantage of being able to draw power directly from the grid without affecting the power quality of the grid. This paper first introduces the circuit topology and working principle of the two parts of this power supply design, and analyzes the output characteristics of the power supply under capacitive load by the equivalent resistance method. For the pre-stage totem-pole circuit, a double-loop controller is designed to realize the control of bus voltage and power factors, and a constant current controller with proportional-integral (PI) plus low-pass filtering control is proposed for the post-stage LLC circuit to reduce the adverse effects of high-frequency noise. Finally, through model construction and simulation analysis, the charging characteristics of high-voltage capacitor charging power supply at 3000V/1 A are studied, and the feasibility of the technical scheme, design and control strategy of the power supply is verified.