Patent ID: 7148586

Claim:
An uninterruptible power supply system (UPS, comprising: arectifier for rectifying commercial alternating currant (AC) power from an input terminal and converting the AC power into direct current (DC) power; a charger for charging a battery with the DC power; the battery for providing the DC power; a DC-DC converter for boosting and/or dropping the DC power inputted from the battery by a predetermined level of the AC power; a D-class amplifier for receiving the DC power from the DC-DC converter and outputting a sine waveform power signal in response to a waveform control signal; a sine waveform controlling a sine waveform generation operation of the D-class amplifier; and a switching unit for switching the commercial AC power from the input terminal to a load in a normal mode, and switching the sine waveform power signal from the D-class amplifier to the load when an error of the commercial AC power is detected; wherein the D-class amplifier comprises a bridge circuit for power conversion, the bridge circuit comprising; a first inductance device (L 1 ) for high-frequency pass arranged on a path (A-L 2 ) between a second inductance device (L 2 ), arranged on a path for connecting a first node (A) and a second node (B), and the first node (A); a third inductance device (L 3 ) for high-frequency pass arranged on a path (L 2 -B) between the second inductance device (L 2 ) and the second node (B); a first capacitance device (C 1 ) including one end thereof connected to a third node (C) arranged on a path (L 1 -L 2 ) between the first inductance device (L 1 ) and the second inductance device (L 2 ), and the other end thereof connected to a ground side; a second capacitance device (C 2 ) including one end thereof connected to a fourth node (D) arranged on a path (L 2 -L 3 ) between the second inductance device (L 2 ) and the third inductance device (L 3 ) and the other end thereof connected to the ground side; and two load output terminals (X and Y) connected to the first and second node (A and B) respectively, wherein the sine waveform controller performs a control operation so that a difference between a turn-on time of one pair of switching devices (SW 1 and SW 4 ) provided in the D-class amplifier and a turn-on time of the other pair of the switching devices (SW 2 and SW 3 ) provided in the D-class amplifier can be generated and an output terminal (X or Y) can output voltage of the turn-on time difference every time a predetermined switching period is shorter than a commercial AC power period, and wherein the sine waveform controller adjusts the turn-on time difference in each switching period, and performs a control operation so that the voltage outputted through the output terminal (X or Y) corresponds to sine waveform power equal to the commercial AC power.