I need to build an ultra clean 14v DC power supply. Are volts push or pull ? - Page 1
Forum section: electronics / projects

author: Hextejas
author_rank: Frequent Contributor
timestamp: July 25, 2018, 03:32:22 am
content: 1st the question of are volts push or pull.I recall on another site that the teaching was that volts are pushed. Well in my noobieness I didn't think to challenge it.So perhaps my simple example can clarify my confusion.Assume that we have a 14v source and the circuit wants 14v. All is well, yeah.Now assume that we have a 28v source and the circuit still only wants 14v. Isn't the circuit still happy even though there is lots of unused volts. I, previously, had thought that it was the demands of the circuit that dictated the source requirement. Wont the circuit "ask for" only what it needs ?Thanks

author: JS
author_rank: Frequent Contributor
timestamp: July 25, 2018, 03:38:58 am
content: If you have a voltage source with too much current capability for the load and the load doesn't wantnand can't manage the extra voltage it will burn (the load, flames and all is possible)Keepinkg with a voltage source, but with the correct voltage output for the load, it needs to be able to deliver more current than the load will take, and the extra current (amps) won't do any harm while working correctly.If the aource can deliver way too much current and you have a failure on the load the extra current can produce more damage, so it's good to have the current limited to a maximum limit, a bit above the needs of the load. For permanent fixtures a fuse is the usual way, for the lab a lab power supply where you can select a current limit to protect the load while testing.JS

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 25, 2018, 03:51:05 am
content: One of the many, many applications of Ohm's law. While it may be difficult to identify the "resistance" associated with your box the law will show you how to think about the effect of increasing voltage.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 25, 2018, 03:51:28 am
content: Quote from: Hextejas on July 25, 2018, 03:32:22 amAre you talking about a regulator?

author: Hextejas
author_rank: Frequent Contributor
timestamp: July 25, 2018, 12:31:16 pm
content: Quote from: sourcecharge link=topic=126803.msg1698365#msg1698365Source, I don't think so. I was trying to predict what would happen if i used a 16v supply (that I have) in a circuit that I will build. I will need to get rid of the extra 2 volts.So maybe I am talking about a voltage regulator and didn't know it. Hah !

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 25, 2018, 12:35:19 pm
content: What does "ultra clean" mean here?What exactly are you trying to do here?You seem to be asking about solutions to an unstated problem?If you can reveal the larger picture here, perhaps we can help you understand volts, amps, regulators, etc.

author: james_s
author_rank: Super Contributor
timestamp: July 27, 2018, 11:04:27 pm
content: Quote from: Hextejas on July 25, 2018, 12:31:16 pm"Getting rid of extra Volts" is precisely what a voltage regulator does.

author: Hextejas
author_rank: Frequent Contributor
timestamp: July 28, 2018, 03:33:20 am
content: Richard, in my ignorance, I don't really know how to state the problem. As I was reading about different amps and preamp, there was usually a statement to the effect that the power needed to be clean of any ripples , spikes, and whatever one might encounter from a wall wart or the mains. Hence my taking that to be summarized as "ultra clean".Since that time I have been introduced to mean Well converters that seem to be what I want.

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 28, 2018, 03:57:27 am
content: Quote from: Hextejas on July 28, 2018, 03:33:20 amYes, well, "clean" is a relative term.Do you have some particular preamp and/or amplifier circuit that you have a particular interest in? It may be more meaningful to discuss real-world solutions vs. abstract theory. It will give you some real-world examples of voltage regulators and current supply vs. current load, etc. etc. You may be over-analyzing the power issues before you are even in a position to know what you really need.QuoteMeanwell is one of the better known "brand names" of commodity power supplies from China. They are popular for digital circuits and for electro-mechanical loads like CNC machines or 3D printers, etc.However, since they are switch-mode power-supply ("SMPS"), they are not necessarily "quiet" in the way that you might want for an audio preamp, etc. However filtering would be a good remedy to apply to the problem of a noisy power supply.

author: JS
author_rank: Frequent Contributor
timestamp: July 29, 2018, 12:21:48 am
content: For a linear PS I've found no issues with the venerable 317 or it's family for negative (337) or higher currents (338) suplies. The 780X and 790X are good enough when noise isn't cryticall and you want a fast solution for a standard voltage and you can afford the error, not being able to trim them.Once you get out of those parameters the applications needs a closer look, if you can, improving the PSRR of the circuit is a good idea, if you have a sensitive circuit filtering from a cleanish source might take you a long way.JS