Uninterruptible power supply utilizing a synchronized chopper for power

Abstract

This invention relates to an uninterruptible power source equipment to rectify a commercial power supply to charge a capacitor through a chopper circuit to a constant voltage, thus to utilize it as a constant voltage power source and to charge a back-up capacitor, thus to deliver a power from the battery to the constant voltage power source when the commercial power source is interrupted. The output of the constant voltage power source may be converted to an a.c. output by the inverter unit. The chopper circuit includes a reactor and a switching element responding to a control signal to effect on-off operation. The control signal is formed as a sine wave signal in phase with the commercial power source. This control signal may be applied to the inverter unit. The UPS equipment allows a sine wave current having a power factor nearly equal to 1 to flow in when the commercial power source is in a normal condition, thereby making it possible to improve the power factor of the power source and to reduce power wave form distortion. In addition, when the commercial power source is in an abnormal condition, a current flowing out from the battery is allowed to become a flat direct current, thus making it possible to utilize the capacity of the battery to the maximum degree. Thus, an economical, small and light control apparatus for UPS can be realized.