The power supply principle of the uninterruptible power supply system is that when the mains power is normal, the machine will convert the AC power of the mains power into DC power, and then charge the battery for use in case of power interruption; What I want to emphasize here is that the uninterruptible power system does not only operate when there is a power outage. For example, when the voltage is too low or too high, or when there is a sudden surge that can affect the power quality of the equipment's normal operation, the uninterruptible power system will operate to provide stable and clean power to the equipment. When the mains power is supplied normally, after passing through the filtering circuit, it is divided into two circuits that operate simultaneously. One is to charge the battery pack through the charging circuit, and the other is to use the rectifier circuit as the input of the inverter, and then provide power to the load through the inverter's conversion; From this, it can be seen that the output of the online uninterruptible power system is completely supplied by the inverter, so regardless of the quality of the mains power, its output is stable and not affected in any way.