Whether there is a power gap depends on the design of the UPS.
The design of the power supply mode of UPS, due to cost, market, volume, weight, and other reasons, there are many forms, each form has different characteristics. Some use power frequency, some use high frequency, some are online, and some are backup. These forms are combined with power size and delay length to become colorful. Among these UPS power sources, some have conversion gaps such as 5 ms, 10 ms. For some, there is no conversion gap, that is, the conversion gap is 0 milliseconds.
When purchasing a UPS, you should understand the performance characteristics of various models, and choose the UPS that suits you according to the needs of your application. Different design structures have different costs. Just solve the UPS of lighting, you can ignore the conversion gap, in the lighting occasions with low requirements, even wait for the power outage, and then turn on the power supply. The cost of this form is relatively low.
However, for some important places, the UPS power supply is not allowed to have a gap, so it is necessary to buy an online type. A brief description is: the DC power after the mains step-down and rectification is connected to the inverter at the same time as the battery, the rectified voltage is slightly higher than the battery voltage, and the battery is kept floating (13.8 volts for a single cell). It took over the rectified power supply without any gap, and almost no change was felt at the UPS output.
If you want the UPS power supply to convert 0 gaps, you must buy this form of UPS power supply.
Mylion Mini DC UPS link: https://mylion.tech/product/mini-dc-ups-mu68w-12v-lithium-ion-battery-backup/