Stringing two PSUs of different voltage in series?

[iamdarkyoshi]

First, I have worked with these cheap power supplies before, I know they are a piece of shit, I will take appropriate precautions.

 

So I need a 5A 60V PSU for driving my 5A 60V buck regulator. Size and price is a concern, so instead of putting 5 of these in series: http://www.ebay.com/itm/AC-100-240V-To-DC-12V-5A-5-Amp-Power-Supply-Adapter-for-LCD-Monitor-5-5-x-2-5mm-/181749548995?hash=item2a511e07c3:g:H00AAOSw14xWOFOf

 

 

I thought I would put one of those in series with one of these: http://www.ebay.com/itm/AC-110V-220V-to-DC-48V-5A-240W-Voltage-Transformer-Switch-Power-Supply-Converter-/121555738541?hash=item1c4d495fad:g:zSMAAOSwzrxUyJh3

 

And I know, I will need to isolate the input ground from the output ground if it is not already.

 

My question is if it is a remotely good idea putting a 12V 5A supply in series with a 48V 5A supply. I will include a diode in reverse bias across each supply in case one goes into protection mode and decides to get backfed by the other, but has anyone had experience with this kind of arrangement?

 

My dad's hybrid battery charger has three meanwell constant voltage supplies and a meanwell constant current supply all in series for a constant current/voltage PSU for charging the battery, that works fine...

 

In theory it should work, they will be actively cooled... Opinions?

[Tmt97]

Do it, I wanna watch the pretty fireworks!

[AMICLG]

The cheap PSUs probably vary so much that you might have extremely dirty power.

 

If you do it just make sure the the wire where all are connected together can handle the amps. If the wire is less than 10ft you can use 16 AWG for 5A.

[iamdarkyoshi]

9 minutes ago, AdamIsaacLang said:

The cheap PSUs probably vary so much that you might have extremely dirty power.

 

If you do it just make sure the the wire where all are connected together can handle the amps. If the wire is less than 10ft you can use 16 AWG for 5A.

Wire is not even going to be 10 inches

[AMICLG]

Just now, iamdarkyoshi said:

Wire is not even going to be 10 inches

Still use 16AWG as it's the minimum for 5A DC current.

 

I don't see why it wouldn't work. I just wouldn't put anything expensive at the end of it.

[iamdarkyoshi]

1 minute ago, AdamIsaacLang said:

Still use 16AWG as it's the minimum for 5A DC current.

 

I don't see why it wouldn't work. I just wouldn't put anything expensive at the end of it.

Like the 60v10A buck regulator? Because that is what is going on the end lol

 

 I will add a fuse........

[AMICLG]

1 minute ago, iamdarkyoshi said:

Like the 60v10A buck regulator? Because that is what is going on the end lol

 

 I will add a fuse........

I meant whatever the buck is powering but it's a moot point if you individually fuse the output on each PSU and one finally before the buck.

 

 

[Stefan1024]

As long as minimum one PSU is on a "foating potential" (implemented with a isolating transformer) you won't damage anything.

But you add two regulators to the loop and if you are unlucky one (or both) PSUs get unstable and stats to oscillate.

 

Are you sure there is no single PSU aviable with the specifications you need? What is it for?

[iamdarkyoshi]

Just now, Stefan1024 said:

As long as minimum one PSU is on a "foating potential" (implemented with a isolating transformer) you won't damage anything.

But you add two regulators to the loop and if you are unlucky one (or both) PSUs get unstable and stats to oscillate.

 

Are you sure there is no single PSU aviable with the specifications you need? What is it for?

This:

 

 

[Stefan1024]

Just now, iamdarkyoshi said:

This:

 

 

Yes I saw this one too. Do you need a 68 volt, 5A input for the bench PSU?

[iamdarkyoshi]

1 minute ago, Stefan1024 said:

Yes I saw this one too. Do you need a 68 volt, 5A input for the bench PSU?

The max output is 60V, and the max input is 62V. The PSUs generally have a trimpot for the voltage. The challenge would be finding cheap enough parts that are small enough to stuff into the case

[Stefan1024]

6 minutes ago, iamdarkyoshi said:

The max output is 60V, and the max input is 62V. The PSUs generally have a trimpot for the voltage. The challenge would be finding cheap enough parts that are small enough to stuff into the case

Do you need that much output voltage?

With the 48 volt PSU (you can add up to 10%) you will get an output voltage of your bench PSU of ~45 volts.

[iamdarkyoshi]

1 minute ago, Stefan1024 said:

Do you need that much output voltage?

With the 48 volt PSU (you can add up to 10%) you will get an output voltage of your bench PSU of ~45 volts.

I do admit I want the full 60

 

I have needed it several times

[Stefan1024]

3 minutes ago, iamdarkyoshi said:

I do admit I want the full 60

 

I have needed it several times

Have you already bougth the other PSU?

 

As there are other options:

http://www.ebay.com/itm/60V-5A-5AMP-605D-PRO-DIGITAL-DC-POWER-SUPPLY-PRECISION-VARIABLE-ADJUSTABLE-/161953821797?hash=item25b5333465:g:LtMAAOSwq7JT8CXN

[iamdarkyoshi]

1 minute ago, Stefan1024 said:

Have you already bougth the other PSU?

 

As there are other options:

http://www.ebay.com/itm/60V-5A-5AMP-605D-PRO-DIGITAL-DC-POWER-SUPPLY-PRECISION-VARIABLE-ADJUSTABLE-/161953821797?hash=item25b5333465:g:LtMAAOSwq7JT8CXN

Ya I have had it for years. It has tons of programmable functions.

[Stefan1024]

Just now, iamdarkyoshi said:

Ya I have had it for years. It has tons of programmable functions.

Well if you like it risky you can try it with the two cheap PSUs. If they start to oscillate I can propose you a circuit to stabilize them. But I do not give a guarantee.