Help With Dual Rail Power Supply

[eclorian]

I need a dual rail power supply for a project. Ideally I need ±22V. I have two Mean Well LRS-350-24 power supplies. Can I connect these in series and use the connection between the two as the ground? (The use of these two supplies is overkill for what I need with the wattage, but as a cost saving measure, I already have them sitting in a box and not being used.)​

Am I simplifying this too much, or is my understanding of dual rail too simplified? This is for a project that will be powering a series of op amps, and I need the voltages to remain fairly stable and accurate.

Any ideas/help would be greatly appreciated.

 

[rjenkinsgb]

Yes, that should work OK.

According to the data sheet the output to frame ground isolation rating is 500V AC, so the outputs are definitely floating by default.

It's a good idea to connect the 0V of the +/- supply to ground at some point, to avoid voltage on it due to capacitive leakage through the supply.

They will also adjust down to 22V according to the data.

 

[eclorian]

Forgive my inexperience, are you referring to "center tap" that would be the ground connection and connecting it to the earth ground?

 

[danadak]

Yes, that should work OK.

According to the data sheet the output to frame ground isolation rating is 500V AC, so the outputs are definitely floating by default.

It's a good idea to connect the 0V of the +/- supply to ground at some point, to avoid voltage on it due to capacitive leakage through the supply.

They will also adjust down to 22V according to the data.

Not an expert here, but how does one supply know what the other is doing if any load is
grounded to the virtual ground ?

Power supplies in series, can you ground the middle leg?

Let's assume I have two 15V DC power supplies. These power supplies are allowed to be connected in series (per the user's manual). I have a device that requires a signal from +15V to -15V (motor d...

electronics.stackexchange.com

Regards, Dana.

 

[rjenkinsgb]

Forgive my inexperience, are you referring to "center tap" that would be the ground connection and connecting it to the earth ground?

Yep, that's the idea.

Not an expert here, but how does one supply know what the other is doing if any load is
grounded to the virtual ground ?

They do not have to, they just each supply one leg (positive or negative) at the set voltage, to the common output "zero", the 0V of the +22V ... 0V ... -22V setup.

Grounding that 0V point helps prevent capacitive noise passthrough, or possible static buildup.

 

[crutschow]

Should be no problem connecting them as you want, but note that those are switching supplies so output high frequency noise could be a concern if your circuits need low noise operation.

 

[eclorian]

Should be no problem connecting them as you want, but note that those are switching supplies so output high frequency noise could be a concern if your circuits need low noise operation.

The main concern is a stable voltage source as this will be powering a series of op amps and I need the output voltage to be fairly accurate. The circuit is not practical by any means, but more of an experiment/project so I can complete my 2 year degree.

Grounding that 0V point helps prevent capacitive noise passthrough, or possible static buildup.

I am curious about connecting the virtual ground to earth ground. I have noticed that in many of the forums that talk about this, it is often required that the DC negative terminal not be connected to earth ground if two supplies are to be connected in series. Is this related to the design of such a power supply?

 

[rjenkinsgb]

I am curious about connecting the virtual ground to earth ground. I have noticed that in many of the forums that talk about this, it is often required that the DC negative terminal not be connected to earth ground if two supplies are to be connected in series. Is this related to the design of such a power supply?

Some PSUs have the negative connected to case / ground; that type either cannot be series connected or you need extra precautions.

The first thing I checked for the PSU type you mentioned was that the output was totally floating; it is.
(The 500V AC to frame ground rating).

As it is floating, you can connect them as you wish and add the 0V ground connection at the appropriate point without any problem.

 

[crutschow]

I need the output voltage to be fairly accurate.

Output of what?