Why does my ISP router hate my "homemade" power supply??

[double_DD]

Hi all,

It's gonna be a long intro, so please buckle in, as it's a problem that's been bugging me for several days now. Thanks in advance.

So, I have 2 modems/routers, whatever the proper nomenclature is, one from ISP and one mine. I want to power them via USB-C rather then their original mains adapters (for reasons, that are hard to explain to sane people). Both routers come with 12V/3A mains adapters.
For this purpose I acquired USB-C charger with 250W and 5 ports, 2 of which can supply max 20V/3A. Since 12V isn't a standard PD voltage option (and to future proof, as the charger cannot supply 5V, 12V and 20V in case I add more devices to it), I decided to create my own charger (x2) consisting of 20V PD trigger + 12V buck converter, so at the output I have 12V that both routers need. Charger provides 3A, buck converter has only 2A, but I've monitored the consumption of both routers and I haven't seen usage of more than 1A (per device), so power-wise everything should be OK. Each router receives 12V/2A and only uses around 0.6A, max 0.8A.

So what's the issue? My router works perfectly, the ISP one is giving me a headache. In any combination of USB-C port, cable, and charger, my router always powers up and runs normally. ISP typically goes into "bootloop", where it restarts constantly (half a minute after starting the first LED goes to green, then they all turn red and router restarts, constantly). Every once in a while, it will start up normally and work for a couple off days, when we have this weird dance all over again. When I connect it back to mains adapter, it will boot properly the very first time. Plug is normal, 2-pin barrel jack of 6.3mm diameter, on both routers.

So, does anyone have any idea why the ISP router hates my guts??? What am I doing wrong here?
Any comment will be appreciated.
Thank you!!

( I don't have a load tester or oscilloscope to check if there are some weird spikes in the output voltage or behaviour of my chargers under load, but my router works with any port, cable or charger connected, so they both probably work just fine)

[CapLeaker]

Maybe the PSU doesn’t have enough filtering, not enough oomph, SMPS design, whatever…
I powered modems and routers on a linear PSU before without any ill effect. Maybe show us your PSU, cables etc…

[double_DD]

Hi,

Good questions.

I don't know what's in the USB-C charger, but the rest are cheap AliExpress components on the attached pictures. Should I buy different buck converter, something with a few more capacitors?

This is data from AliExpress for buck converter:

Input Voltage: 5v~30v (Must Be Higher Than The Output Voltage) Preferably Below 28v.
Output Voltage: 12v.
Output Current: 3a (Max) Normal 1.8a Over Plus Heat Sinking
Conversion Efficiency: 96% (Maximum)
Output Ripple: 30mv
Output Accuracy: ±0.1v
No-Load Current: 1ma
Operating Temperature: -40℃~+85℃
Operating Humidity: 20%~90
Size: 17*12*4mm(L*W*H)

Annoying part is that it *sometimes* works, but usually not.

[stj]

high frequency noise is messing with the ADSL/VDSL signals
and open your routers for a check, they often have rubish electrolytics in them that fail after a few years

[double_DD]

high frequency noise is messing with the ADSL/VDSL signals
and open your routers for a check, they often have rubish electrolytics in them that fail after a few years

So, should I buy different buck converter, something with a few more capacitors? Would that help with the filtration? Or?
I don't really wanna open it, it's working just fine with original mains adapter. If it dies, it will be replaced by ISP.

[sam_sam_sam]

Or you might have to have more filtering capacitors to get a more efficient output supply plus I might even put a blocking device on each input but use a low voltage drop diode for this application

[double_DD]

Or you might have to have more filtering capacitors to get a more efficient output supply plus I might even put a blocking device on each input but use a low voltage drop diode for this application

Sorry, you went above my level 😀 If you have some schematic for me to build or a link to a product I can buy then i might be able to understand your point. i'm not this good at this hobby. 😀

[stj]

put some caps on the buck convertor output.
preferably polymer or low-impedence electrolytics.
maybe 470uf polymer or 1000uf electrolytic

[double_DD]

put some caps on the buck convertor output.
preferably polymer or low-impedence electrolytics.
maybe 470uf polymer or 1000uf electrolytic

Thanks! Will try that!

[CapLeaker]

Hi,

Good questions.

I don't know what's in the USB-C charger, but the rest are cheap AliExpress components on the attached pictures. Should I buy different buck converter, something with a few more capacitors?

This is data from AliExpress for buck converter:


Annoying part is that it *sometimes* works, but usually not.

That this isn’t working right… I believe that.
So you got a power supply, then a buck converter going into the modem, in which has more buck converters inside? That’s inefficient and more of a cause something not good.
Next problem is that not all USB-C chargers are equal. Some of these USB-C chargers produce noise, ground loop, etc. they aren’t that clean. Also under load they drop voltage. Cabling becomes an issue as well. But this buck converter from Ali, has no real output filtering to speak of.

[double_DD]

So you got a power supply, then a buck converter going into the modem, in which has more buck converters inside? That’s inefficient and more of a cause something not good.

I mean, I do understand your concern, but realistically I'm not really that worried, after all we're talking about output power of <10W. Even if we exaggerate all the conversion losses, input power is still <15W. I certainly wouldn't use something like this to power something of 2kW.
Butt yes, lesson learned- it's never a good idea to buy the cheapest crap. I might try buying another buck converter from Ali with a few caps more, to see it's behaviour.

[CapLeaker]

Look if you can fiddle with the PD charger to output 15V not 20v. Then you don’t need buck converters.

[double_DD]

Look if you can fiddle with the PD charger to output 15V not 20v. Then you don’t need buck converters.

You don't think that both routers will mind 15V instead of 12V? Interesting...I might try that.

(I can get 12V on USB-C charger no problem, but the problem comes if I want to add more devices to charger, as it can't output 5V, 12V and 20V at the same time. I have a feeling it'll be exactly the same case with 15V.)

[sam_sam_sam]

You would not be able to do two different voltage at the same time as far as I know but you could use this device for more than one device but on the same usb power supply

https://www.ebay.com/itm/154199751911?var=454319125178

[double_DD]

You would not be able to do two different voltage at the same time as far as I know

That was the reason why I went with this convoluted setup with using 20V PD.

but you could use this device for more than one device but on the same usb power supply
https://www.ebay.com/itm/154199751911?var=454319125178

I do generally also use this, but both routers use "non-standard" 6.3mm barrel jack which I hadn't found in this ready-made type. Thanks anyway!

[CapLeaker]

You don't think that both routers will mind 15V instead of 12V? Interesting...I might try that.

(I can get 12V on USB-C charger no problem, but the problem comes if I want to add more devices to charger, as it can't output 5V, 12V and 20V at the same time. I have a feeling it'll be exactly the same case with 15V.)

I've got an older router here apart that was 12VDC fed. I looked at the 2 buck converters fed from the main power rail and one is max 16vdc input and the other is max 18vdc.
Set the PD to 15V, add a larger like a 3A to 5 A standard rectifier diode in series to drop 15V to 14.3V like a BY550 or HER503 or similar (to be more in tolerance) and bob is your uncle.

To be sure you'd have to open up the router and modem and check the datasheet on the buck converter or regulator right at the DC input section.

[double_DD]

I've got an older router here apart that was 12VDC fed. I looked at the 2 buck converters fed from the main power rail and one is max 16vdc input and the other is max 18vdc.
Set the PD to 15V, add a larger like a 3A to 5 A standard rectifier diode in series to drop 15V to 14.3V like a BY550 or HER503 or similar (to be more in tolerance) and bob is your uncle.

To be sure you'd have to open up the router and modem and check the datasheet on the buck converter or regulator right at the DC input section.

Thanks for the advice, it's much appreciated although this is going to be my "last resort", if I cannot get it to work any other way with 20V PD.