Rectifier is a device that converts alternating current into direct current, which can be used for power supply devices and detecting radio signals. Rectifier can be vacuum tube, ignition tube, solid silicon semiconductor diode, mercury arc, etc. On the contrary, a set of devices that convert direct current into alternating current is called "inverter".
In the standby UPS, only the battery needs to be charged, and there is no need to supply power to the load, so there is only a charger. In double-frequency UPS, this device not only supplies power to the inverter, but also charges the battery, so it is called rectifier/charger.
Rectifier is a rectifying device, which is simply a device that converts alternating current (AC) into direct current (DC). It has two main functions: one is to change alternating current (AC) into direct current (DC), which is filtered and supplied to the load or inverter; Second, provide charging voltage for the battery. Therefore, it can also act as a charger.