The distribution system with the rectangular voltage waveform is useful for the electrical equipment with the dc voltage source because the high input power factor is obtained by using the diode rectifier circuits. This paper presents a single-phase type AC/DC converter using a novel power factor correction (PFC) technique to realize the unity effective power factor and stable output dc voltage for both the distribution systems with sinusoidal or rectangular voltage waveform. Also, this paper presents the estimation and judgment of the input voltage waveform and its stability and the design of the estimation gains. The new control strategy has a notable advantage that it is flexible for both sinusoidal and rectangular waveforms to realize the good characteristics. The effectiveness of the proposed control scheme has been verified by experiments.