This router ups setup diagram, not an circuit diagram. It’s about a circuit that keeps your WiFi router or Broadband modem always on even in power cuts so that we can use the WiFI.
A 12 V UPS battery is used as backup power source. To charge that, as well as for powering the modem, an 12 Volts power adapter is used here, it should be rating of 1 Ampere to do this job perfectly.
In this router ups circuit, we see adapter is directly connected to battery. As battery is of 12V and gives some 12.5 volts always, we need to step it down to 10V for modem. Find the diagram below.
Working of this Router UPS for modem
Simply here IN4007 diodes are used for forward voltage drop. IN4007 diodes are easy to find and cheap too. It has maximum forward voltage as 1.1V in 25*C. As the modem in this project requires 10V@550ma, the forward voltage comes to 0.55×1.1=0.605Volts. Together 4 diodes reduces voltage by 2.42volts. So 12.5-2.42=10.08Volts is fed to modem which is within 1% tolerance level, so acceptable.
Many modems/routers have an even wider input voltage range, you can directly hookup the 12V battery without any worry to build this ups for router.
TP-Link MR3220 is such a router, it accepts input voltage from about 7v up to 15v happily.