The configurations of a parallel-connected UPS circuit are provided in the present invention. The proposed circuit includes a neutral, a battery having a positive and a negative terminals, and a plurality of PFC boost converters, each of which includes a PFC circuit including an inductor having a first terminal coupled to the positive terminal and a second terminal, a rectifying bridge coupled to the second terminal of the inductor, and having a first terminal and a second terminal coupled to the negative terminal, a switch bridge having a first terminal coupled to the first terminal of the rectifying bridge and a second terminal coupled to the second terminal of the rectifying bridge, and a control switch having a first terminal and a second terminal coupled to the neutral.