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Having trouble looking for a power adapter with 3.7v 2000mA dc output specs

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kevindd992002

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I'm using a zBoost YX-520I cellphone signal booster and suddenly its power supply is blinking and does not power the device. In my experience, blinking power adapters indicate a short. The power adapter has a solid green when NOT connected to the device but as soon as it is connected to the device, it blinks. This can only mean that it's either shorted or its output current rating is reached (overcurrent). I tried using a 4.5V power supply and it powered up the device but I know that that is not good practice (I did that just to test). That simply means that the power supply of the device is broken.

I'm having a hard time looking for a power adapter with output rating of 3.7V 2000mA. Can anyone help me on this? Oh and btw, how do I know if this adapter is linear or switching?

Thanks for the help.
 

You should see if you can measure the current draw when using the 4.5V power supply.
At the output of the 3.7V power supply, connect a load resistor to see if the power supply can take the load. Try with 2Ω resistor. That will mean a current draw of 1.85A. See if the power supply LED is on or it blinks. This way, you'll be certain if the power supply is ok or not.

One way of knowing if it's linear or switching will be by considering its weight. A linear power supply should be much heavier than the switching one as the linear one will have a heavy transformer and a linear regulator with heatsink. The switching one will be based on an SMPS circuit, which will use ferrite transformer and will have smaller heatsink(s) due to greater efficiency.

Hope this helps.
Tahmid.
 

Tahmid said:
You should see if you can measure the current draw when using the 4.5V power supply.
At the output of the 3.7V power supply, connect a load resistor to see if the power supply can take the load. Try with 2Ω resistor. That will mean a current draw of 1.85A. See if the power supply LED is on or it blinks. This way, you'll be certain if the power supply is ok or not.

One way of knowing if it's linear or switching will be by considering its weight. A linear power supply should be much heavier than the switching one as the linear one will have a heavy transformer and a linear regulator with heatsink. The switching one will be based on an SMPS circuit, which will use ferrite transformer and will have smaller heatsink(s) due to greater efficiency.

Hope this helps.
Tahmid.
Click to expand...

Today, I brought the 3.7V power supply to work and tested it with a DC Current Source as my load. I swept the current load from 0 to 2000mA with 10mA steps. With the first sweep, the output voltage of the power supply dropped to 0 at around 330mA and it started to blink (as I expected). With the second sweep, it passed 330mA and dropped out at around 750mA which seems to be an improvement of some kind. With the third sweep, the power supply was able to handle the full 0 to 2000mA range without any problems (no blinking - solid green light). This observation shocked me and led me wondering what made the power supply work. What do you think happened? Was there some kind of "jump start" that fixed the power supply?

Oh by the way, the power supply is as small as the old Nokia cellphone chargers and are very light. Am I sure that this is a switching power supply then?

Thanks.

EDIT: False positive! After writing my response here, I tried sweeping current load again from the power supply and it started to blink at 330mA again. Does this indicate a faulty power supply already?
 
Last edited:

You might have an intermittent short, in case insulation has broken internally (and invisibly). It is liable to happen between the coaxial wire and the ground, at a spot where there has been a lot of flexing.
 

Start with 1000-1500 mA and see what happens. One other possibility is that the current sensor in the power supply could be damaged, so the current readings are not proper and the power supply stops working at a current lower than it was rated for.

Oh by the way, the power supply is as small as the old Nokia cellphone chargers and are very light. Am I sure that this is a switching power supply then?
Click to expand...

Yes.


Hope this helps.
Tahmid.
 

Tahmid said:
Start with 1000-1500 mA and see what happens. One other possibility is that the current sensor in the power supply could be damaged, so the current readings are not proper and the power supply stops working at a current lower than it was rated for.
Click to expand...

Tried that already, as soon as I turn on the DC source at 1000mA, the psu doesn't work anymore. Is it possible to fix this or something?
 

It might be, but you may be better off buying a new power supply. Depends on you though.
 

Tahmid said:
It might be, but you may be better off buying a new power supply. Depends on you though.
Click to expand...

Yeah, I think it would be better to buy a new power supply but the thing is where?
 

If you can't find one, you may be able to build one for yourself. Or you can use a DC-DC converter circuit that will provide 3.7V output with more common input voltages such as 12V.
 

Tahmid said:
If you can't find one, you may be able to build one for yourself. Or you can use a DC-DC converter circuit that will provide 3.7V output with more common input voltages such as 12V.
Click to expand...

I'm not too confident building one myself. Are you suggesting I make a DC-DC converter or purchase one?
 


Tahmid said:
If you can not find a fixed voltage output device, you may use one with a variable voltage and you can adjust the output to 3.7V.

Here's one such device: **broken link removed**
Here's more: **broken link removed**
https://www.amazon.com/Tekpower-Variable-Supply-1-5-15-HY152A/dp/B000RO8J98
https://www.cybermarket.co.uk/shop/power-supplies/bench-top-power-supplies.html
https://www.circuitspecialists.com/bench-power-supply-csi1802x.html

Hope this helps.
Tahmid.
Click to expand...

Thanks but those are just too big. Those are like the variable power supplies we use at the lab at work. We use Kenwood PW18-2ATPYB.
 

If you have a 12V power supply, like I said before, you can use a DC-DC converter like this: **broken link removed**

You can use a 12V power supply, such as this one: **broken link removed**
 

Tahmid said:
If you have a 12V power supply, like I said before, you can use a DC-DC converter like this: **broken link removed**

You can use a 12V power supply, such as this one: **broken link removed**
Click to expand...

Great, thanks. And the output current capability of that DC-DC converter would be equal to the current capability of the 12V power supply?
 

No, the capability of the DC-DC converter is set by the converter itself and the limitation of the power supply. The converter specifies a maximum capability of 3A.

The capability of the 12v supply is 3A. So, maximum power output is 36W. When converted to 3.7V, that equates to a current of 9.73A (if efficiency = 100%). So, a DC-DC buck converter can draw up to nine point something ampere and still be within limit of the power supply capacity.

The converter is rated at a maximum of 3A and this is less than the 9A I calculated.

Hope this helps.
Tahmid.
 

Tahmid said:
No, the capability of the DC-DC converter is set by the converter itself and the limitation of the power supply. The converter specifies a maximum capability of 3A.

The capability of the 12v supply is 3A. So, maximum power output is 36W. When converted to 3.7V, that equates to a current of 9.73A (if efficiency = 100%). So, a DC-DC buck converter can draw up to nine point something ampere and still be within limit of the power supply capacity.

The converter is rated at a maximum of 3A and this is less than the 9A I calculated.

Hope this helps.
Tahmid.
Click to expand...

Great, thanks for the explanation.
 

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