Combining Power Adapters

Thread Starter

piBoss314

Joined Nov 24, 2021
5
Combining Power Adapters
To Obtain greater current
My desire is to obtain a greater current source. My question is: Can I parallel, say a 5v 1A with another 5v 2.1 amp to obtain a final supply of 5v 3.1A?
I'll try combining negatives and positives then solder the connector on the end.

Am I correct that the voltage must match, then the component will draw only what current it's capable of using? And thus, for example if i combined adapters that create an available 10A, I can still use this to charge my cell phone as long as the voltage is 5v, is this correct?

Hey, thanks for reading and any feedback provided!
Cheers - piBoss








 

Ya’akov

Joined Jan 27, 2019
6,580
Combining Power Adapters
To Obtain greater current
My desire is to obtain a greater current source. My question is: Can I parallel, say a 5v 1A with another 5v 2.1 amp to obtain a final supply of 5v 3.1A?
I'll try combining negatives and positives then solder the connector on the end.

Am I correct that the voltage must match, then the component will draw only what current it's capable of using? And thus, for example if i combined adapters that create an available 10A, I can still use this to charge my cell phone as long as the voltage is 5v, is this correct?

Hey, thanks for reading and any feedback provided!
Cheers - piBoss
Welcome to AAC.

While I appreciate your desire to format your messages so they look prettier, it comes at a price.

I am sure it looks good on your monitor, but many of us your choice of small, bold text makes reading your post difficult at best. Please, in the future, don't make your body text bold. Also, selecting a font size should be done with great care since the way it renders for you is not necessarily how it ends up looking for others.

Attributes like bold, italic, underscore, and strikethrough are useful to enhance the semantic content of your post, but they do not work well as decoration.

FYI below is a screenshot of how your message looks to me compared with the default font size. Once again, welcome to AAC and I hope you have many more messages to format here!

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Papabravo

Joined Feb 24, 2006
19,309
If you are going to do this, you need a strategy to inhibit "current hogging". In general, you are better off designing or buying a supply that meets your needs.
 

Irving

Joined Jan 30, 2016
3,132
A simple approach is to use two schottky diodes to prevent the higher voltage supply feeding back into the lower voltage supply (no two 5v supplies are ever identical, its generally 5v +/- 0.25v).

At low currents the higher voltage supply will provide most if not all the current but as this increases its voltage will drop until the lower voltage supply starts to take over. Depending on the exact approach to current limiting for each supply there will be a point where both supplies are offering their maximum current at the same voltage - however it won't necessarily be the full sum of currents or the best voltage..

The downsides of this approach are two-fold:
1. There is a voltage drop Vf in the diode of about 0.2- 0.5v depending on the specific diode and the current through it, so your 5v might be nearer 4.5v in the end;
2. There is a power loss of Vf x I in each diode, about 0.6 - 1.5W again diode & current dependent, which generates heat.

It can work for some situations, or as a stop-gap, but is generally not recommended.

1665582251549.png
 

Thread Starter

piBoss314

Joined Nov 24, 2021
5
A simple approach is to use two schottky diodes to prevent the higher voltage supply feeding back into the lower voltage supply (no two 5v supplies are ever identical, its generally 5v +/- 0.25v).

At low currents the higher voltage supply will provide most if not all the current but as this increases its voltage will drop until the lower voltage supply starts to take over. Depending on the exact approach to current limiting for each supply there will be a point where both supplies are offering their maximum current at the same voltage - however it won't necessarily be the full sum of currents or the best voltage..

The downsides of this approach are two-fold:
1. There is a voltage drop Vf in the diode of about 0.2- 0.5v depending on the specific diode and the current through it, so your 5v might be nearer 4.5v in the end;
2. There is a power loss of Vf x I in each diode, about 0.6 - 1.5W again diode & current dependent, which generates heat.

It can work for some situations, or as a stop-gap, but is generally not recommended.

View attachment 278231
A simple approach is to use two schottky diodes to prevent the higher voltage supply feeding back into the lower voltage supply (no two 5v supplies are ever identical, its generally 5v +/- 0.25v).

At low currents the higher voltage supply will provide most if not all the current but as this increases its voltage will drop until the lower voltage supply starts to take over. Depending on the exact approach to current limiting for each supply there will be a point where both supplies are offering their maximum current at the same voltage - however it won't necessarily be the full sum of currents or the best voltage..

The downsides of this approach are two-fold:
1. There is a voltage drop Vf in the diode of about 0.2- 0.5v depending on the specific diode and the current through it, so your 5v might be nearer 4.5v in the end;
2. There is a power loss of Vf x I in each diode, about 0.6 - 1.5W again diode & current dependent, which generates heat.

It can work for some situations, or as a stop-gap, but is generally not recommended.

View attachment 278231
Thank you very much Irving your detained response, it was helpful and I appreciate it! Cheers!
 

Thread Starter

piBoss314

Joined Nov 24, 2021
5
I thank all of you for your help. See I have about 10 12v 2A power supplies and wanted to try using them to power a device requiring 12v 8A instead of purchasing a new single power supply. Per all of your statements, I conclude I could potentially do it, kind of, but getting a single supply designed for such output is by far the best thing to do. For I don't want the voltage drop, using diodes nor the power loss with resistors.

Thanks again to all of you!
 

Jon Chandler

Joined Jun 12, 2008
390
Look for an XBox 360 power supply at thrift stores or PC recyclers. For a few bucks, these guys supply 12 volts at 12 – 16 amps depending on the model.

It also supplies 5 volts at a decent current. The 12 volt supply is turned on by connecting a control line to the +5v line.

SmartSelect_20221108_185642_Edge.jpg
 

Janis59

Joined Aug 21, 2017
1,482
Such supplies, even in ideally case being one factory one serie product will not pass ideally. And if one exerts 5.01 V and another 5.02 A then they shall compete from all their power to overkill one each, the mentioned case making, if output impedance be say 1 miliohm, then (5.02-5.01)/0.001=10 Amps or full short-circuit.
 
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