# Ac-dc adapters in series (or parallel)

multiple 220V to 5v, 2A ac to dc adapters connected to the same 2-phase input terminals
input voltage is 220v domestic supply.
is it safe to i join output in series to obtain 10v /15v/25v etc. ?

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berkeman
Mentor
multiple 220V to 5v, 2A ac to dc adapters connected to the same 2-phase input terminals
input voltage is 220v domestic supply.
is it safe to i join output in series to obtain 10v /15v/25v etc. ?
Do you mean just stack the output DC voltages? Sure.

What is the application? Can you Upload a sketch of what you want to do?

What is the application?
get 10 v power supply

berkeman
Mentor
get 10 v power supply
Why can't you find the right power adapter to get you the right output voltage and power?

davenn
davenn
Gold Member
2019 Award
multiple 220V to 5v, 2A ac to dc adapters connected to the same 2-phase input terminals
input voltage is 220v domestic supply.
is it safe to i join output in series to obtain 10v /15v/25v etc. ?

get 10 v power supply

I really cant understand why people want to do things the hard way ??
get a 12V 2A plugpack and use either boost or buck converters to get the required voltages
The converters are dirt cheap on eBay a few  each

here's one ideal for your needs, for US\$1.52, cheaper than a bunch of plugpacks in series

http://www.ebay.com/itm/DC-DC-Boost...864741?hash=item258c7e1b65:g:K-IAAOSwkl5XdjBM

Dave

NascentOxygen
Staff Emeritus
multiple 220V to 5v, 2A ac to dc adapters connected to the same 2-phase input terminals
input voltage is 220v domestic supply.
is it safe to i join output in series to obtain 10v /15v/25v etc. ?
Most DC adapters incorporate filtering and deliver relatively smooth DC, but some do not have filtering—their output being rectified AC. It seems that you recognize there may be cases where you need to ensure the supply to all primaries is of identical phase, e.g., in the case of unfiltered output I mention.

It can be safe, but only up to a point. If you keep to under 25V total then it should be okay. There's real danger of exceeding the pack's insulation rating if you try to stack these to get e.g., hundreds of volts out.

cause ive a bunch of 5v , 2amp adapters lying around
could they be stacked in parallel to get 5v, 4amps out of identical (same product) (5v , 2amp max ) adapters?
and will it be safe if different product , same ratings (5v , 2amp max )plupacks are used in parallel?

NascentOxygen
Staff Emeritus
cause ive a bunch of 5v , 2amp adapters lying around
could they be stacked in parallel to get 5v, 4amps out of identical (same product) (5v , 2amp max ) adapters?
and will it be safe if different product , same ratings (5v , 2amp max )plupacks are used in parallel?
It is certainly not recommended. And I would not power any device of value, not until the arrangement has been well-tested.

I think you should first plot Vo vs. Io over the full load range for the individual adapters. Then only parallel those having almost identical characteristics. You have plenty of the same model, so you should be able to find a couple that are very similar.

Power the parallel pair briefly to start with, then for increasingly longer periods, monitoring the case temperature. If there is any more heat than expected, discontinue the experiment. Test over the full range of loads, before trusting it to power any device that you value.

I'm assuming these are adapters incorporating transformer isolation and that include smoothing so that they output essentially smooth DC.

https://www.physicsforums.com/attachments/110502.gif

are there any 5v adapters of higher amp rating(higher than 2amp)?

are there any 5v adapters of higher amp rating(higher than 2amp)?

Your question seems to be wandering all over the place. Are you falling into an xy problem? (Google it.) What is it you want to do?

Your question seems to be wandering all over the place. Are you falling into an xy problem? (Google it.) What is it you want to do?
got this 5v 4 amp ebay

jim mcnamara
Mentor
What the others are saying is: instead of proposing solutions, tell us what you need. For example, you could say 'I need to power an XX at 5v 3amps, I have 3 converters'

That is a so-called XY issue - confusing proposed solutions with the real problem.

berkeman
berkeman
Mentor
stacked in parallel
Paralleling voltage sources is generally problematical. If they are simple transformer+rectifier+linear regulator type of power supplies, you may have a better chance of combining them in parallel.

But if they are the smaller, lighter switching power supply type of regulators, then putting their outputs in parallel can cause regulator stability issues. The individual control loops for each switching regulator can cause interference problems with the other regulator, and you can get oscillations and even output over-voltages. That can let the smoke out of the device you are trying to power.

As others are suggesting, just get a power supply of the correct size for your project -- that will work much better, and hopefully let you keep the smoke inside of your device.

in series should I have a reverse diode across each supply output to prevent back-driving on overload ?
if the load fails (short circuit or over-current), one of the supplies gives up before the other, then
one supply back-drives the other as with cells in a battery, or cells in a PV-panel.

NascentOxygen
Staff Emeritus