How to make a Rectifier with voltage regulator

[twist2b]

I know what I want, but I can't find any parts. Maybe you guys can help:

I need to take power from a wall unit and make it DC, now the problem is that I can't have waving. SO I need a voltage regulator!
I can't find a good place that sells a rectifier OR a voltage regulator.

But once I have those, I can just use 2 step down transformers in parallel to get a 12 V line and a 30 V line.

Any help?

 

[Torben]

I know what I want, but I can't find any parts. Maybe you guys can help:

I need to take power from a wall unit and make it DC, now the problem is that I can't have waving. SO I need a voltage regulator!
I can't find a good place that sells a rectifier OR a voltage regulator.

But once I have those, I can just use 2 step down transformers in parallel to get a 12 V line and a 30 V line.

Any help?

Hi there,

What you're describing is called a linear power supply. It sounds like you already know what voltage output you want, but what about current capability? You'll need to define that before you can start selecting parts.

What exactly do you mean when you say "wall unit"? Do you mean "wall wart"? If so then what do you already have?

You can make your own rectifier using 4 power diodes, but again, you'll need to determine what kind of current capability you need before you can decide what to use.

For the record, "waving" is actually called "ripple", and while the voltage regulator will allow you to minimize it, you will need to put one or more filter capacitors between the rectifier and the regulator in order to keep the regulator happy. However, if you're using a DC-output wall wart as the original power source then rectification and probably filtering will already be taken care of for you.

So:

1) What do you mean by "wall unit"?
2) What kind of current capability do you need?
3) How much money/time do you have to spend on this?
4) Which, if any, parts do you already have?


Torben

 

[twist2b]

Your a sexy man, Torben!
Yeah, I am just not amazing with technical names (sorry)
linear power supply's are expensive and connecting to a wall wart using a rectifier and a voltage regulator should not be to hard.
THis is NOT my project but this is kinda what I want mine to look like:
(ONLY the top part
https://stevehv.4hv.org/FBD/FBschematic.JPG
As you can see, it has 2 separate lines.
I do need a 12 volt and a 30 volt... though I am not 100% sure about the AMP's though Its supposed to be LOW amp.

Here is what I am building (and I want it to be plugged into a wall wart (again sorry for saying wall UNIT )
https://scopeboy.com/tesla/tl494-fullbridge.gif


Since your super awesome I need to ask something:
I want 12V on the second one (leave that part the same) but I need 30V to go through the other one (NOT 25.2) so what should I set the capacitors to?

I like using rectifiers instead of 4 diodes just because its less space and cleaner

as for the questions:
1) What do you mean by "wall unit"?
2) What kind of current capability do you need?
3) How much money/time do you have to spend on this?
4) Which, if any, parts do you already have?

1) I mean wall wart sorry.
2) In the first link the 2 A is fine I believe (the less amps the BETTER)
3) As much time as it takes, and I am not super worried about money. It's my senior project
4) ALL the parts in the second link schimatic... I just need to make it to plug into a wall wart


I am sorry that I am not amazingly good at explaining things... but trust me I understand this stuff (even though AC to DC regulating is kinda new) and I am ready to pull this off.... Thanks for any help!

 

[Menticol]

2 wall warts in parallel? I see the smoke comming... better if you get a more powerful wall wart (your desired DC volts, and more amps as you can, is better). As Torben said, they already took care of rectifing

 

[twist2b]

What are you talking about? Did you look at link one? Its ONE supply (this diagram LOOKS like 2, but its not, its just showing that its running 2 lines for the transformer)
And then its 2 parallel rectifiers from the transformer.

Nothing wrong here..

Also, for link 2 (the schematic I am making) It says 2 of the diodes need a heatsink... I don't need a large one do I? Would this work:
Farnell Export
Or should I get a larger heat sink?

Also, again your wrong with the amps, LESS amps in a flyback driver is better. HIGH voltage, LOW amps.... it works better that way.

edit - reviewing, this post MAY have come across as rude... I am sorry if thats true. I was just trying to explain and was NOT trying to be rude...

 

[Menticol]

Relaaax man! Take a deep breath... now insert the pin back... yes... now put the grenade down... eeeaaasyy .... that's great!

Low amp can mean anything from 0000000.1 uA to 100 mA... you need a number

Feeding the circuit with an external power supply, measure how much current does the circuit draw to get your desired results. Then you can now know big the heatsink must be and what regulator to use.

 

[twist2b]

Haha, AHH.

Ok, so the Amps will be 2A tops (as seen in link one of my second post on this thread)

I am kinda confusing myself for this night... I am giong to go to bed and just think it all over.

Thanks for all the help so far.. Please keep in touch

 

[Torben]

Hehe. Yeah, that's a nice picture, no?

1) I mean wall wart sorry.
2) In the first link the 2 A is fine I believe (the less amps the BETTER)
3) As much time as it takes, and I am not super worried about money. It's my senior project
4) ALL the parts in the second link schimatic... I just need to make it to plug into a wall wart

OK, why is lower current capacity better for you? Just to keep things simple? At any rate, 2A is more than an LM7812 is going to give you, even with a huge heat sink. With a maxed out heat sink even an LM317 only guarantees up to 1.5A. You'll probably end up using pass transistors to give the current capacity you need. And finding a wall wart which can provide enough juice to successfully provide both 12VDC and 30VDC outputs at 2A (I assume you want 2A each?) could be tricky.

One thing which is often said on this forum is that it's better to describe what you're trying to achieve, instead of how. Apparently you want to power a flyback circuit but you haven't said why. Are you trying to build a TV? A Jacob's Ladder? Spark generator? etc. Knowing that information might help someone here suggest a simpler way to get to where you're trying to go.


Torben

 

[Torben]

Also, again your wrong with the amps, LESS amps in a flyback driver is better. HIGH voltage, LOW amps.... it works better that way.

I think there may be some confusion here about current capability. As far as power supplies go, you generally want the power supply to have the highest reasonable ability to supply current, as long as it's at or above what the circuit being supplied will draw. Voltage is different. Think of it this way: from the power supply's point of view, voltage is pushed into the load, but current is pulled from the power supply by the load--and the load will not pull more current than it needs. So if you had a circuit which needed 12V but only 100mA, then it would be just fine to use a regulated 12V supply capable of 100mA, 1A, 100A, or whatever--the load will only draw the 100mA that it needs.

In short, for a well-regulated supply, the voltage must match the load's voltage, and the current capability must match *or exceed* the load's current draw.



Torben

 

[Mikebits]

Your a sexy man, Torben!

Lol, Hey Torben, here is your new theme song.

https://www.maximumdonline.com/themes/2sexy2.wav

 

[Torben]

Lol, Hey Torben, here is your new theme song.

https://www.maximumdonline.com/themes/2sexy2.wav

ARGH!

Made me laugh though.


Torben

 

[twist2b]

I am soooo sorry Torbon, yea I was saying that I can get a MAX of 2A (due to the transformer) At least, that was what the schematic was saying.

Now, I NEED the voltage regulator because I am making this:
http://scopeboy.com/tesla/tl494-fullbridge.gif
and I can't have those bumps (the microcontroller chips will not be very happy, AKA not work)



As for what I am making?
Flyback Rectifier:
(best pick I could find)
http://stevehv.4hv.org/FBD/arc1.JPG
And the schematic is the link above.
BUUUUTTTTTT I will be adding an audio source (hence, the audio modulator comes in handy [ TL494 ])
Ok, so to put them together:
http://scopeboy.com/tesla/tl494-fullbridge.gif
with the audio:
http://scopeboy.com/tesla/tl494-audio-fullbridge.gif

So as you can see its pretty awesome. YES, it does have good sound quality (watched a couple of youtube vids)

NOW, I can make that schematic no problem, BUT I want to plug it into a wall-wart and to do THAT, I need a voltage regulator.
Though it looks as though I do not need the regulator on the 30V only the 12.......
SO what you guys think?
I made a schematic to show you what I am doing:
**broken link removed**
(me being lazy in mspaint)
also, exuse the empty line next to C8, really just consider that whole line of 30V to be a replica of the 12V one with some changed parts/capacitors.

At the bottom right (the flyback driver) the other side is where the arc will be.
Thank you.




Excuse the fact that I am terrible at explaining things :'(

 

[Willbe]

2 wall warts in parallel? I see the smoke comming...

Nah, just measure or assume internal impedances, figure your load amps and if this arrangement will ever be open-circuited, get it to work on paper first maybe with current sharing resistors, and you're done.

 

[twist2b]

Nah, just measure or assume internal impedances, figure your load amps and if this arrangement will ever be open-circuited, get it to work on paper first maybe with current sharing resistors, and you're done.

Like I said above, its not in parallel, just looks it. It was displayed that way to show 2 lines to the transformer.

 

[Torben]

Hi again,

Aha! You're making a plasma tweeter. You'll want some subs with that as plasma tweeters have no bass response.

I'm a little confused as to where you intend to hook up the wall wart? The (top part of the) circuit you show is a linear power supply already--although it sure could use a fuse.

(I'm going to throw in my standard disclaimer at this point since I'm about to start tossing numbers about: I'm not an EE; I'm a hobbyist. I'm going to explain this as I understand it and as usual if I get something wrong I hope to be corrected by one of our resident gurus. I take no responsibility for anything: if you take my advice blindly and kill yourself, well, then you shouldn't'a oughta done that.)

As for the transformer, you don't want to use anything larger than the 25.2 VAC shown. The voltage rating of a transformer is usually given in RMS unless it's specifically stated that it's given peak-to-peak, and after rectification and filtering you get a DC voltage of 1.414 times the rated transformer secondary voltage. So with 25.2 VAC RMS from the transformer, you will have around 34V on the 30V line and around 16.4 V feeding the LM7812. I suspect that the 34V will be fine as it's unregulated and will sag somewhat when the load draws current from it. The LM7812 will be getting more input voltage than it really needs, so depending on the current draw it may or may not need a heat sink. Given what it's driving in this case I suspect that it won't need one (I'm not doing the math just now as it's just about dinnertime), but check out how warm it gets when the circuit is actually in use.

So my questions now:

1) I think the 25.2 VAC transformer was chosen for a reason and is fine; and
2) Where do you intend to attach your wall warts? Can you draw that on your schematic and post it?
3) Why do you think C8 needs to change?

Cheers,

Torben

 

[Menticol]

Why you don't try this speaker? **broken link removed**
Seems to be simpler, and is known to work

(ok, ok, calm down... I'm leaving...eaaasy maaan! hahahaha)

 

[twist2b]

Menticol - Haha, well actually I have the resources and I want something tougher.... that one that you showed me is NOT what I am looking for Sorry, but its just not a GREAT schematic and poor use on the mosfet (IMO) and slightly unstable. Though it DOES work well.......
Oh, and he originally got the idea from the one I am doing currently.

NOW SCRAM, HAHA

Torben -

1) I think the 25.2 VAC transformer was chosen for a reason and is fine; and
2) Where do you intend to attach your wall warts? Can you draw that on your schematic and post it?
3) Why do you think C8 needs to change?

1) But the second schematic I showed you needs 30V

2 + 3)

SO I did mucho grande research, and it turns out:
Power Supplies
I should use a 5500uF (I will be using a 5600uF due to price)
in parallel with a MC33167 (switch regulator, VERY efficient and reliable)
(oh and these puppies are capable of stepping up voltage!)

I will post a schematic of everything I will be doing soon.... I would really dig you guys reviewing it and grabbing the concept, seeing if what I am doing is not wrong (I am a senior that is going into EE, I have already taken MANY electrical classes at a community college though)


Now, you said that I can't use a transformer to produce 30V?
I have found several transformers that are:
In: 100-130
Out(2):0-30, 0-30

Remember that I am using the 30V schematic... I really need those 30V

Also, you guys think I should change the LM7812 to a switching regulator? WAY more efficient and not such terrible watt loss...


SO....... questions/comments???? PLEASE
I am having a lot of fun discussing this.

edit - reading Torbans post a second time (sorry it seemed all jumbled together... no "paragraphs".)
It turns out that it will end up having 34? And thats ok on the 30V line? HMMMMMMM... I obviously need to study transformers MORE.

edit2 - Haha, read it a third time (I am sooo A.D.D. sometimes at night/tired ) and you said the top part will be 100% fine for the main flyback driver? Even though the second part does not have a regulator?

 

[Torben]

Torben -

1) I think the 25.2 VAC transformer was chosen for a reason and is fine; and
2) Where do you intend to attach your wall warts? Can you draw that on your schematic and post it?
3) Why do you think C8 needs to change?

1) But the second schematic I showed you needs 30V

2 + 3)

SO I did mucho grande research, and it turns out:
Power Supplies
I should use a 5500uF (I will be using a 5600uF due to price)

That will give you a 10% ripple at 2A load on the 30V line. If you're positive that 10% is acceptable then go for it. Otherwise I'd go for the higher value cap. Make sure the cap is rated for at least 50V though.

With filter caps bigger is generally better, although you don't want to go too crazy because the greater inrush current needed to charge them can stress the diodes in the rectifier when power is first applied. Plus, past a certain point it doesn't really help to keep making them bigger.

in parallel with a MC33167 (switch regulator, VERY efficient and reliable)
(oh and these puppies are capable of stepping up voltage!)

On paper it would be a better choice, if not outright overkill. The LM7812 would be simpler. According to the datasheet for the MC33167, it is pretty sensitive to layout and has some tight tolerances. With the LM7812 you toss a couple of caps and maybe a heatsink on it and you're done.

General rule: don't make things harder than they have to be. Use the LM7812 for now, and get the rest of the circuit running. Once it works and the troubleshooting is done, then go back and rebuild the power supply if you want. If you make the power supply a separate unit (or even just a separate board) this will be easier because you won't need to touch anything else to rebuild it.

I will post a schematic of everything I will be doing soon.... I would really dig you guys reviewing it and grabbing the concept, seeing if what I am doing is not wrong (I am a senior that is going into EE, I have already taken MANY electrical classes at a community college though)

Posting a schematic of what you intend to build would sure make it a lot easier to help you, yes.

Now, you said that I can't use a transformer to produce 30V?

What? Where did I say that? If I said that I need to be slapped, but I'm pretty sure I didn't say that because saying that would be insane.

edit - reading Torbans post a second time (sorry it seemed all jumbled together... no "paragraphs".)

Huh. I could have almost sworn that those groups of sentences held together by common topics were paragraphs. Maybe I've just gone mad, though. Unless you are using some new definition of the word 'paragraph' of which I was not previously aware, I'd say that the problem is not jumbled writing but jumbled reading.

It turns out that it will end up having 34? And thats ok on the 30V line? HMMMMMMM... I obviously need to study transformers MORE.

This has nothing to do with transformers. If you take a sine wave and rectify and filter it, you will wind up with a DC voltage 1.414 times the RMS value of the sine wave, minus any diode drops from the rectifier. In this case, you have two diode drops in the rectifier, so you wind up with (25.2 * 1.414) - 1.4 = 34.2VDC.

The 34VDC might be OK for the flyback. Then again, that extra 4V might be the straw that broke the camel's back. I doubt it but I was speaking of the original flyback. If you are in doubt, then use the pass transistor and control pot from the original power supply circuit (which you should probably use anyway) and ramp things up slowly. If it blows up when you hit full power, you know that 34V is too much.

edit2 - Haha, read it a third time (I am sooo A.D.D. sometimes at night/tired ) and you said the top part will be 100% fine for the main flyback driver? Even though the second part does not have a regulator?

No, go back and read it again. Slow down and think about what you're reading; I try to think about what I'm writing so that I don't have to go back and explain myself--like I'm having to do right now.

I said I *suspect* it will be fine. It is fine for the circuit it was designed for. As long as your diodes, MOSFETs, and flyback can deal with it, then I think it's worth a shot. Like I said before (if that paragraph wasn't too long for you) I am not guaranteeing anything. The best way to know for sure is to read the datasheets and do the math yourself.

You still haven't answered the question about how the wall wart comes into the problem.


Regards,

Torben

 

[audioguru]

The power transformer will be too big and too heavy to be a wall-wart.

 

[twist2b]

Haha, you sounded a little anoyed this time around.... sorry for all that. I had been studying ALL day yesterday figuring this out.

Now, let me first explain the mis-understandings:

Huh. I could have almost sworn that those groups of sentences held together by common topics were paragraphs. Maybe I've just gone mad, though. Unless you are using some new definition of the word 'paragraph' of which I was not previously aware, I'd say that the problem is not jumbled writing but jumbled reading.

Haha, thats no what I was saying. I was talking about a spacific paragraph that looks gumbled to ME. Reading on a forum and reading a book are 2 seperate things, and personally I find a 1280×720 at night when I am tired is just a pain....

Now, you said that I can't use a transformer to produce 30V?

When I said this, I was refering to your argument that due to the RMS, the transformer is probably going to end up with 34V (which is why I should not use a 30V transformer but keep the 25.2)

No, go back and read it again. Slow down and think about what you're reading; I try to think about what I'm writing so that I don't have to go back and explain myself--like I'm having to do right now.

I am fully capable of reading your disclaimer and I know you have the possibility of being wrong. I did not know I actually had to refer the word "suspect" to ask a question about your thoughts. Apologies.



Now, I will not change ANYTHING in the 12V section, however, in the 34V section I can NOT use the LM7812. due to the fact that 90% of linear regulators can not handle anything over 24V (including this one) Not to mention I have to deal with 50W loss on a 30V line...

This has nothing to do with transformers. If you take a sine wave and rectify and filter it, you will wind up with a DC voltage 1.414 times the RMS value of the sine wave, minus any diode drops from the rectifier. In this case, you have two diode drops in the rectifier, so you wind up with (25.2 * 1.414) - 1.4 = 34.2VDC.

The 34VDC might be OK for the flyback. Then again, that extra 4V might be the straw that broke the camel's back. I doubt it but I was speaking of the original flyback. If you are in doubt, then use the pass transistor and control pot from the original power supply circuit (which you should probably use anyway) and ramp things up slowly. If it blows up when you hit full power, you know that 34V is too much.

That makes total sense, and yeah, I should just stick with that then. I knew those rules, I just realy could not concentrate by the end of the night.

Thanks for all that help, but as for the wall-wart I don't need the transformer to be ON the main plug (excuse the fact that I am not good with terms) I just need a normal plug with 2 leads.... I have seen PLENTY at my community college I attend. Then I can just go from there.