This paper presents a voltage frequency conversion system with Digital Signal Processor (DSP). The digital control is used to achieve the variable frequency control. The topology of the proposed system is two-stage converter, where the first stage is a power factor correction (PFC) circuit and the second stage is a single-phase full-bridge inverter circuit. The PFC can control input AC voltage, which can achieve high input power factor. Otherwise, it also can supply a regulated DC bus voltage for the full-bridge inverter. The variable output voltage frequency can be controlled in the full-bridge inverter by using the DSP. Finally, a prototype system operates frequency varied from 50 to 400Hz is designed and implemented. The experimental results validate the advantages of the proposed variable frequency control.