In control systems operating with AC voltage, AC UPS is the most suitable. The offline or standby topology structure is very simple and clear. These products are inexpensive, so they are the most common type of AC UPS. Under normal circumstances, offline UPS transfers the main power from the input terminal to the output terminal, without any other interaction except for charging the battery connected in parallel with the main power circuit. If the main power supply fails, the UPS will switch from the main power circuit to the battery circuit. The transition time from UPS losing main power to battery power cannot exceed 10ms. A 10ms switch usually does not affect downstream equipment, but can protect systems sensitive to voltage fluctuations.
通信UPS有两种类型：改进型（模拟）正弦波输出设备和纯正弦波输出设备。每种类型的通信输出都不同。
改进的正弦波装置从电池组获取电压，并以尽可能简单的形式产生类似于正弦波的波形输出。虽然这种类型的UPS成本相对较低，但也存在一些缺点。电压的大幅跃变可能会损坏下游设备的输入电路。这些巨大的跃变还可能导致UPS输出中出现大量开关瞬变。这可能导致小型PC和PLC电源模块过早失效。
纯正弦波 UPS 将产生与 120/230V 主电源馈送的波形相同的正弦波形输出。纯正弦波 UPS 是可编程逻辑控制器 (PLC)、分布式控制系统 (DCS) 和工业 PC (IPC) 等敏感控制设备的最佳选择。虽然需要更多电路，但由 UPS 供电的控制设备使用寿命更长，从而降低了总拥有成本。
Critical task applications require more advanced UPS, namely dual conversion or online UPS. This UPS will never be in standby mode. The battery circuit is actively connected to the system. If the main power supply is interrupted, there will be no interruption or voltage drop in the output, thus achieving seamless operation of the battery. The online system has built-in filtering and regulating devices. During normal operation, it converts the input power from AC to DC, and then converts it back to AC through an inverter.