UPS (Uninterruptible Power System), that is, uninterruptible power supply, is a system equipment that connects batteries (mostly lead-acid maintenance-free batteries) with the load, and provides continuous and stable power supply to the load through the UPS host. It is mainly used to provide stable and uninterrupted power supply to a single computer, computer network system or other power electronic equipment such as solenoid valves, pressure transmitters, etc. When the mains input is normal, the UPS will stabilize the mains and supply it to the load. At this time, the UPS is an AC voltage stabilizer, and it also charges the battery inside the machine; when the mains is interrupted (accidental power failure) When the UPS is switched on, the UPS will immediately supply the AC power to the load by switching the DC power of the battery to the load, so as to maintain the normal operation of the load and protect the software and hardware of the load from damage. UPS devices usually provide protection against overvoltage or undervoltage.