Time quantity one-cycle control method is proposed in this paper for u
nity power-factor ac-dc converters. Converters controlled by this meth
od operate at constant switching frequency, require no current sensing
, have a simple control circuit, and exhibit resistive input impedance
at the ac side. Feedback loop design method is provided to minimize t
he current distortion when the output voltage ripple is not negligible
. Experimental results confirmed the theoretical prediction.