Powered 9/12-volt SOHO routers from a USB source

A home-made adapter-converter for powering common SOHO routers requiring 9/12 V voltage from any 5-volt source of sufficient power with a USB connector.


A few years ago, I had a pair of Sapido RB-1842 USB / WiFi routers . I carried one with me on trips, in order to make it easier to distribute hotel / apartment / mobile Internet, and the second I set stationary in a rural house, where only mobile Internet is available. Pretty soon it became clear that both needed autonomous power: they sometimes had to take it with them to the balcony to relay WiFi from a hotel lounge or a nearby cafe, and in the village they regularly turn off the lights for 10-20-40 minutes - laptops and gadgets work, the base station too, but there is no internet.

I was glad that the model was five-volt, I cut the cables from the power supplies of the routers, put the USB connectors “mom / dad” in the gap and, if necessary, powered them from ordinary banks. At the same time, one of the nameless banks bought from the Chinese turned out to be capable of simultaneously charging the battery and giving energy at the output voltage, and if it disappeared, it could switch to the battery. That is, it turned out a wonderful five-volt UPS, which was enough for about an hour and a half (in that bank there are two 18650 batteries) and for which no supervision was required.

The clouds are gathering

And recently I bought a Huawei E3272-153 modem (MegaFon M100-4) in the village , and it turned out that it does not work with these routers - the local script sends old AT commands that the modem firmware does not support. Altering the firmware of the router would require too much time, so I had to buy another one - TP-Link TL-MR3220 v2 . By the way, OpenWRT miraculously gets up on it, including its ROOter assembly .

This model is already 9-volt, like most stationary routers (they say that they are sometimes equipped with 12 V power supplies). Actually, the board itself has enough of five volts (modern processors are all low-voltage), but power is not supplied directly to the USB connector, as in five-voltage routers, but through a converter, on which a little less than a volt drops. In general, both the router and the modem somehow work from five volts, but the modem periodically loses connection.

Light at the end of the tunnel

Since I did not want to lose the convenient and miniature UPS in the form of a bank, and the router (the same or similar) was supposed to be taken with me on trips, these modules of boosting DC-DC converters were purchased in China :

View from above

View from below. For those who do not know English, the direction of conversion is shown.

The module is made on the XL6009 chip, equipped with built-in protection against both overload and overheating.

Check module features

At first I tested a little on a purely active load (a piece of a nichrome spiral).

12 V input, 12 Ohm load:


This is the maximum voltage that the converter gives out at such a load in a cold state - that is, the output current is about 1.4 A. The noise at the maximum is quite noticeable (when the voltage decreases, it quickly decreases). The microcircuit, the diode and the inductor warm up pretty quickly to about 70 degrees, the voltage drops, along with it the noise drops a bit:


5 V input, 12 Ohm load:


Here, the maximum voltage is about 9.5 V at a current of about 0.8 A. When heated, the voltage drops to 8.7 V.


5 V input, 8 Ohm load:



It is no longer possible to get long-term voltages higher than 6 V at a current of 0.75 A.

The results obtained, of course, are not very good, and they are very far from the declared 4 A, but the power is in the region of 5-6 W (9 V at 0.7 A or 12 A at 0.5 A) the converter gives out quietly, while heating moderately.

Build Features

It remains to solder a wire with a USB-A connector to the input, and any wire with a tubular plug of suitable thickness to the output. A smooth (with an internal contact in the form of a tube, not a plug) plug is quite suitable, since the current through it is less than an ampere. Most PSUs for routers have a smooth plug. The vast majority of routers use standard polarity (plus inside), but it is worth checking just in case.

It makes no sense to especially chase the thickness of the wires on both sides - a drop of a few tenths of a volt of weather will not do: at the input - because the converter automatically maintains the output voltage, and at the output - due to low currents and a large margin of voltage ( seven routers are sufficient for most routers).

By setting the desired output voltage with the trimmer screw (enough accuracy within a volt), you can connect the router. Since the converter is purely boosting, it will not work to remove the voltage below the input one. But this does not interfere with powering the five-volt routers through it, so the adapter turned out to be completely universal.


First of all, I tested the adapter in the village with TP-Link TL-MR3220 v2 and the Huawei E3272 modem (though in 3G / DC-HSPA mode, since 4G / LTE is not there yet), connecting a USB meter between the bank and the adapter. The whole structure consumes only about 0.7 A (the bank gives up to 1.5 A), the converter is slightly warm.

Later, I connected through it the urban 12-volt GePON-router Eltex NTE-RG-1402G with the declared power consumption of 10 VA, which is noticeably heated during operation. The converter pulled it too, although it warmed up to 60 degrees, while the router worked perfectly.

The last to connect was TP-Link TL-WR740N, which of this trinity is the most low-power - with it, the converter consumed only 0.35 A from five volts during loading, and 0.2 - during operation, without heating at all.


The task was solved successfully and in its entirety - now I can power any of my routers both from my own power supply unit and from any USB connector of sufficient power. Including from the bank, putting them on the balcony (and in the absence of it - hanging them in a bag outside the window), which is very useful when you have to live in a hotel and apartment for some time without normal stationary access to the Internet.

Of course, instead of all this, you could buy routers with built-in batteries, but this would greatly narrow the range of suitable models, especially in terms of compatibility with modems, and would make it difficult to replace with other models. And so we have a completely universal adapter, through which you can power almost any router from almost any source with a USB connector. At least directly from the desktop or laptop - unless, of course, the load-carrying capacity of USB ports allows (all my laptops gave out 1-1.5 A without problems).

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