Patent ID: 8143743

Claim:
An uninterruptible power supply apparatus, comprising: a load; an AC input receiving an AC input voltage; and a single-phase AC/AC converter connected to the AC input and including an AC inductor, a bus capacitor having a bus voltage, a boost arm having a first switch and a second switch, a common arm having a third switch and a fourth switch and a buck arm having a fifth switch and a sixth switch, wherein the buck arm is connected to the bus capacitor, the boost arm and the common arm in parallel, wherein a bus voltage parameter K is set in a range of 0≦K≦1, so that the bus voltage approaches to a DC voltage when K approaches to 1 while the load is light-load, the bus voltage approaches to a full-wave rectifying voltage when K approaches to 0 while the load is heavy-load, the first switch and the second switch of the boost arm, the third switch and the fourth switch of the common arm and the fifth switch and the sixth switch of the buck arm are controlled so that the bus voltage has a waveform including a DC segment when |sin(wt)|≦K and a full-wave rectifying segment when |sin(wt)|>K, where w is an angular velocity and t is a passing time, to implement a regulation of the AC input voltage, and an average voltage value of the bus during the full-wave rectifying segment is larger than that during the DC segment.