Boost converter is widely used as active power factor correction (PFC) pre-regulator. Its input voltage range is universal (90-265V), and its output voltage is regulated at about 380V. At low line (90V) the switch's rms current is high, so the conduction loss of power switch MOSFET is large and the efficiency of whole converter is very low. This paper proposes a new control method that the output voltage varies with the input voltage change. Under this control the MOSFET's on-time is shortened, and the switch's rms current decreases, which reduces the conduction loss and increases the Boost converter efficiency. The distribution of power loss is analyzed by computing software (mathcad 2000) and the realization of this special control method is given. A 1200W Boost power factor corrector with average current control is built up. In order to improve the diode's turn-off loss the performance of a 600V, 12A silicon carbide (SiC) Schottky diode is also experimentally evaluated. Measurements of overall efficiency and reverse recovery behavior are compared between SiC diode and fast recovery diode.