UPS (Uninterruptible Power System) is an uninterruptible power supply that contains energy storage devices and an inverter as the main component of the constant voltage and constant frequency. It is mainly used to provide uninterrupted power supply to computers, computer network systems or other power electronics. When the utility input is normal, the UPS will be the utility voltage regulator to supply the load, the UPS is an AC utility regulator, it also charges the battery; when the utility power interruption (accidental power failure), the UPS will immediately battery power, through the inverter conversion method to continue to supply AC power to the load, so that the load to maintain normal work and protect the load software and hardware from damage. With the computer application system requirements for power supply UPS is increasingly important, and gradually developed into a voltage stabilization, frequency stabilization, filtering, anti-electromagnetic and radio frequency interference, anti-voltage surfing and other functions of the power protection system. Especially in the power grid lines and power supply quality is not too high, anti-interference technology is backward, while the computer system requirements for the power supply is relatively high, the role of UPS is more obvious, UPS equipment usually provides protection against excessive voltage and voltage is too low.