spilt rail supply with only one isolated supply? - Page 1
Forum section: electronics / projects

author: Gibson486
author_rank: Frequent Contributor
timestamp: February 15, 2023, 10:36:03 pm
content: When I make a split rail, do I need make both supplies are isolated, or can you just use one isolated supply and flip the polarity on it?

author: Marco
author_rank: Super Contributor
timestamp: February 15, 2023, 10:44:24 pm
content: You can use a switched capacitor inverter for the negative rail (or inverting buckboost or whatever). It's not necessarily simpler though.

author: Benta
author_rank: Super Contributor
timestamp: February 15, 2023, 10:45:41 pm
content: No idea. Mains, DC, low voltage, high voltage, power/current...?

author: TimFox
author_rank: Super Contributor
timestamp: February 15, 2023, 11:20:59 pm
content: So long as the original supply is isolated (not wired to "ground" or "common"), you can use an analog "rail splitter" (q.v.) to derive a common node.This is a useful technique for analog supply lines to circuits that have nearly the same current draw from the positive and negative rails.A simple example is an op-amp voltage follower driven from a resistive voltage divider across the original supply to the non-inverting input, where the output is the "common" node and has a limited current capability for the imbalance between the two rail currents.With equal resistors, the two rails will be + and - (Vsupply/2) .

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 16, 2023, 12:22:26 am
content: Here is what chatGPT says:If you are making a split rail power supply, it is important to use two isolated supplies rather than flipping the polarity on one supply. Using a single supply with reversed polarity will not provide a true split rail supply, as it will still have a common ground.A true split rail power supply requires two separate power supplies, with each supply providing a positive or negative voltage with respect to ground. By isolating each supply, there is no common ground between them, and the output can be used to power circuits that require a positive and negative supply.Using a single supply with flipped polarity will still have a common ground, which can cause problems when powering certain circuits. In addition, it may not provide the voltage levels required for a split rail supply.Therefore, it is recommended to use two isolated supplies to create a true split rail power supply.

author: Benta
author_rank: Super Contributor
timestamp: February 16, 2023, 12:28:10 am
content: Are we discussing with ChatGPT now? That's the dumbest I've ever read in my life, the robot talk seems to remove any remaining intelligence in this world.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 16, 2023, 12:44:54 am
content: I would love to leave it to Gibson486 to decide which of the 4 post answered his question the best.

author: Gibson486
author_rank: Frequent Contributor
timestamp: February 16, 2023, 02:28:19 am
content: Hahaha...not really what I was expecting in terms of the comments. I always thought you could do it as long as 1 was just isolated. However, I have a 50V non isolated switcher paired with a reversed polarity 50V isolated dc to dc supply to power an op amp. The opamp was not happy. So, either my opamp circuit is fubared, or I can't just use 1 isolated supply.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: February 16, 2023, 02:52:35 am
content: Cool. I assume you were to ask "DC/DC converter" and/or "switching regulator". The word "supplies" confused all of us, including chatGPT....