What is the output of Regulated power supplies? whether Peak DC or Average DC V? - Page 1
Forum section: electronics / beginners

author: techguru
author_rank: Regular Contributor
timestamp: December 23, 2018, 02:34:15 pm
content: Hi every one,What is Peak DC voltage and Average DC voltage?What is the difference between both?What is the output of RPS? Peak DC or Average DC Voltage?Thank you all...

author: soldar
author_rank: Super Contributor
timestamp: December 23, 2018, 04:13:00 pm
content: Peak, average, RMS, etc are mathematical concepts applicable to many magnitudes in engineering.Have a look herehttps://www.electronics-tutorials.ws/accircuits/average-voltage.htmlIn any case, the output of a regulated power supply should be stable and so the peak, average, RMS should be pretty much the same ... or you really can't call it "regulated".E.T.A.: Looking at your pdf attachment I see those are unregulated power supplies.

author: ArthurDent
author_rank: Super Contributor
timestamp: December 23, 2018, 04:55:07 pm
content: Soldar is correct and here is an oscilloscope display showing the same information. However, depending on whether the rectifier is half or full wave affects the ripple frequency of the output.http://www.zen22142.zen.co.uk/Theory/images/sine_time.png

author: techguru
author_rank: Regular Contributor
timestamp: December 25, 2018, 06:48:05 am
content: For example: 24V transformer with bridge rectifier and capacitive filter produces,peak dc voltage : 1.414*24=34Vaverage voltage :.9* 24=21.6V and difference is nearly 12V. Hence what is the output of Regulated power supplies, Whether Peak voltage DC or average voltage DC?

author: soldar
author_rank: Super Contributor
timestamp: December 25, 2018, 11:13:51 am
content: techguru, you need to understand the concepts. Your question as asked makes no sense. If you do not understand the concepts any answer we give you is meaningless. "What is the output of regulated power supplies?" This is a meaningless question. What regulated power supply? It is like asking what is the speed of a car or what is the pressure of a pump.So, let's start with this, what regulated power supply are you trying to analyze?

author: GeoffreyF
author_rank: Regular Contributor
timestamp: December 25, 2018, 02:53:55 pm
content: There must be sufficient input over output for the regulator to regulate. Therefore whatever comes between the mains and the regulator (eg: Transformer, rectifier, filter capacitors) is chosen as sufficient for that. In the context of a power supply, peak to peak is more than a "mathematical concept". It is highly relevant. Average is not but Root Mean Square (RMS) current is, a reasonable prediction of the heating effects in relation to a DC current of the same amount. If the wave form is too harmonic, which it usually isn't in power supply design, then RMS or averaging are not sufficient for design. Such a wave form would be problematic for a transformer or other parts of the supply.

author: techguru
author_rank: Regular Contributor
timestamp: December 25, 2018, 03:48:37 pm
content: Quote from: soldar on December 25, 2018, 11:13:51 amDC regulated power supply: 0-24V @ 3A

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 25, 2018, 04:09:30 pm
content: Quote from: soldar on December 23, 2018, 04:13:00 pmif one think like albert einstein, its not so. if we imagine we are very small ant, we will see a nasty alternating voltage at mV or uV or nV or pV level, however good the power supply is. this is ripple spec of a PSU. what "regulated" means is if a voltage overshoot, it will be pulled down, if its undershoot it will be pushed up by giving extra current to it. so what a regulated voltage means? is a voltage that is being pulled and pushed so it should be equal as or as close as possible to the set point, how much ripple this mechanism cause is how much resolution in the control feedback system. better control will result in cleaner psu like uV level of ripple. some control engineering gurus may argue with this such as word "if feedback is stable, there will be no oscillation/ripple", i know and i agree. we dont see it oscillate just because we dont have enough resolution to make the observation, naturally everything vibrate. fwiw...

author: Zero999
author_rank: Super Contributor
timestamp: December 25, 2018, 04:13:05 pm
content: Quote from: techguru on December 25, 2018, 03:48:37 pmPlease post a schematic.The voltage on the rectifier depends on the current drawn, as well as the capacitance and input voltage. With no load, the averagerectifier voltage will be close to the peak value of the input voltage and at high currents it will be much lower than that.

author: soldar
author_rank: Super Contributor
timestamp: December 25, 2018, 04:29:43 pm
content: Quote from: techguru on December 25, 2018, 03:48:37 pmThe output voltage is whatever you set it to. If you set it to 10 volts then the peak, average and RMS voltage of the output will be 10 volts. Because that is what "regulated" means.

author: Brumby
author_rank: Unknown
timestamp: December 26, 2018, 12:19:34 pm
content: The OP seems to be trying to make sense of the input to the regulation circuitry - and does, indeed, appear to have a gap in basic understanding.To the OP: Talkingonlyabout voltage will make no sense here. The conversation needs to include the current involved as well.

author: xavier60
author_rank: Super Contributor
timestamp: December 26, 2018, 12:59:59 pm
content: The ".9" from techguru's post came from the Hammond guide for FULL WAVE BRIDGE Capacitor Input Load.The "V (Peak) D.C. = 1.41 X Sec. V A.C." makes sense for the unloaded voltage.I assume that "V (Avg) D.C. = 0.90 X Sec. V A.C." means the fully loaded DC output voltage. I would expect it to be a bit higher than this for a transformer sized by their guide. "I D.C. = 0.62 X Sec. I A.C."Has anyone taken measurements lately?I guess that the 0.9 comes from 0.9 x RMS = Average, ignoring diode drop which should't be ignored really.The loaded DC output does not have to strictly equal the Average.

author: AngraMelo
author_rank: Regular Contributor
timestamp: December 26, 2018, 11:43:08 pm
content: I think what he doesn't see is that there are PS where you can set a specific voltage and some that you cantIf you have a linear PS, using a regular transformer you will have around 1.4*voltage of the transformer's secondary on the Bridge rectifier. If you then decide to use a regulator you will now be able to choose from 2 types: fixed regulators or variable regulators. The fixed regs will do all it can to maintain a specific voltage say for example 12V, it will keep constant 12V on the output. There are also the variable regulators, those let you "dial" a specific voltage. Like those variable voltage power supplies. So the regulated voltage is what the PS is designed to produce on its output.Sent from my SM-G950F using Tapatalk

author: xavier60
author_rank: Super Contributor
timestamp: December 27, 2018, 01:00:19 am
content: In post #6, the op says "DC regulated power supply: 0-24V @ 3A".The information in the Hammond guide is confusing.For the FULLWAVE BRIDGE Capacitor Input Load, the statement "V (Avg) D.C. = 0.90 X Sec. V A.C." is irrelevant.

author: fsr
author_rank: Regular Contributor
timestamp: December 27, 2018, 02:12:02 am
content: Any signal has a peak, average, RMS voltage, etc. Here you will find a very good explanation of the concepts. All the education section in that site is very good, i recommend that you read it from the beginning DC section, it's very good:https://www.allaboutcircuits.com/textbook/alternating-current/chpt-1/measurements-ac-magnitude/Now, if you take the output of a transformer and pass it thru a full-wave rectifier, at the output you will have a wave similar to the sinewave, but the negative parts now are positive too:Also, as the current has to travel across two diodes, you lose about 1.4v of voltage at the output of the bridge.Now, if you add a big capacitor to the output of the diode bridge, the capacitor will charge to the peak value of the output voltage from the bridge, and almacenate chage, so that it will power your load during the "gaps" of the output wave from the bridge. And so, the output voltage will tend to be more like a DC value. But at any time that the capacitor is supplying current to the load, it's discharging, so your output voltage will get more and more ripple, and less like DC, at higher currents. Bigger capacitors discharge less under the same current.That kind of PSU is an UNregulated one. A regulated PSU could be one built by adding a linear regulator like the LM7805 at the output of the UNregulated supply. The LM7805 will will output a 5v voltage if you supply it with a higher voltage (higher than the dropout of the LM7805). The capacitor will dischage the same than before, but as long as it doesn't discharges below the minimum voltage requirements of the 7805, the IC will continue to provide a stabilized 5v output.As you can see, the output of the regulated PSU doesn't matches the peak or average values of the input voltage.