PROTECTIVE CIRCUIT FOR UNINTERRUPTIBLE POWER SUPPLY SYSTEM

PURPOSE:To prevent the effect of an accident on a sound machine by inserting a diode polarity blocking currents in the direction of a common battery from a DC intermediate circuit. CONSTITUTION:When a smoothing capacitor 14 is short-circuited, short circuit currents are made to flow through a short-circuit point from a common battery 2, the short circuit currents are detected by a first current detector 18, and a battery breaker 17 is tripped. A first unintrruptible power equipment 30 is detached from a sound second uninterruptible power equipment 40 and the common battery 2. The voltage of the common battery 2 drops during a time when the short circuit currents are made to flow, but a reverse blocking diode 41 obstructs the flowing of currents through the short-circuit point from the second uninterruptible power equipment 40. Accordingly, the effect of an accident on the sound uninterruptible power equipment can be prevented.