How to create schematic of a electronic power supply?

[supernovagirl]

so we have this project to create a power supply.
our instructor said that his requirements about the said power supply
must be followed. the specification of the power supply:

Vin = 230 v and it should have 3 outputs -> +5v, +/-15v and a 1.2v to 20v variable voltage regulator..
and all output current should have 3 amperes.also the transformer should have 3A max..

can anyone please help me to create the schematic or u can also help me provide one..
please..

thank u soo much in advance!!.. =)

 

[HOOfan 1]

Linear or switching mode?

 

[Brutus04]

slacker...

 

[frostedflakes]

Pretty sure this isn't the homework help forum.

 

[pcgeek11]

PLease do my homework for me. Please, pretty please?

Lazy ass do it yourself.

 

[tomoyo]

You know what's sadder is this is the poster's first post. You'd think they'd at least try a forum where people actually know them.

 

[BoomerD]

It's gonna cost ya pics...

I don't know if that's a rule here in Power Supplies, but it sure is over in Off Topic...

A poster with a name such as "supernovagirl" HAS to post pics to prove "she's" a girl...

 

[supernovagirl]

Linear or switching mode?

its a switching mode.

 

[HOOfan 1]

Well here is a schematic of a standard computer PSU for reference

http://www.hardwaresecrets.com/fullimage.php?image=5573

 

[Jeff7]

Well here is a schematic of a standard computer PSU for reference

http://www.hardwaresecrets.com/fullimage.php?image=5573

Geez...what process do you go through to even design something like that? Just go to college for electrical engineering and that information is learned as a result, or what? And how do you figure out the difference between when to use earth ground vs circuit common, or are they the same thing? So much cool stuff to learn...

 

[Twinpeaksr]

Geez...what process do you go through to even design something like that? Just go to college for electrical engineering and that information is learned as a result, or what? And how do you figure out the difference between when to use earth ground vs circuit common, or are they the same thing? So much cool stuff to learn...

you nailed it, EE degree or two and a good amount of experience. Looking at that it is amazing how much jumps out at my as knowing what they do and why they are there. I am sure I can also find ways to improve given enough time to study it. Of course designing this stuff for a living gives me an advantage!

Got to love engineering!

 

[Blain]

Why not just pay someone to do your work for you?

On second thought, why bother going to school at all...
Just buy a degree online!

 

[Modelworks]

google
bridge rectifier
lm317
pass transistor

for a switching supply google
555
mosfet
inverter

combine both and you should be able to create the schematic
hint : AC to DC to AC to DC = desired supply output

 

[Jeff7]

you nailed it, EE degree or two and a good amount of experience. Looking at that it is amazing how much jumps out at my as knowing what they do and why they are there. I am sure I can also find ways to improve given enough time to study it. Of course designing this stuff for a living gives me an advantage!

Got to love engineering!

Yeah; and I suppose that a fair amount of the stuff might come from a datasheet or app note. I can put together a circuit that looks all impressive, but all I did was follow the datasheets of a simple switcher regulator, a microcontroller, and an RS-232 converter chip - then connected a few dots.
It's probably in stages too, I'd guess. Develop the macro-level design and theory of operation, and then start putting in the pieces that get you there. The result looks all crazy and impressive, but the process of getting there was just a bunch of little steps.

If I ever go back to college, it'll probably be for electrical engineering. (I've got a B.S. in Mechanical Engineering Technology right now; my job has me doing some light electronics stuff too.) I don't know a whole lot about the process needed to put together a bunch of discrete components and have it do anything useful. It's much easier to program a PIC chip and have it do some of the grunt work instead.
It amazes me to look at old electronics, before any sort of ICs existed, and see the crazy stuff they were able to accomplish using only passives and simple semiconductors.

 

[Twinpeaksr]

Yeah; and I suppose that a fair amount of the stuff might come from a datasheet or app note. I can put together a circuit that looks all impressive, but all I did was follow the datasheets of a simple switcher regulator, a microcontroller, and an RS-232 converter chip - then connected a few dots.
It's probably in stages too, I'd guess. Develop the macro-level design and theory of operation, and then start putting in the pieces that get you there. The result looks all crazy and impressive, but the process of getting there was just a bunch of little steps.

If I ever go back to college, it'll probably be for electrical engineering. (I've got a B.S. in Mechanical Engineering Technology right now; my job has me doing some light electronics stuff too.) I don't know a whole lot about the process needed to put together a bunch of discrete components and have it do anything useful. It's much easier to program a PIC chip and have it do some of the grunt work instead.
It amazes me to look at old electronics, before any sort of ICs existed, and see the crazy stuff they were able to accomplish using only passives and simple semiconductors.

True, until you realize how many data sheets are wrong and have sample circuits that don't work. I wish it was that simple at times, but 90% of the time nothing works like it should. Doesn't help when trying to design for off highway where the environment is a major challenge.

 

[Modelworks]

It amazes me to look at old electronics, before any sort of ICs existed, and see the crazy stuff they were able to accomplish using only passives and simple semiconductors.

I grew up learning electronics in that era. In a way it is sad how many engineers just now coming into the field overlook basic components for task. Some immediately jump to looking for an ic to fill the need and when it doesn't exist start redesigning the entire circuit when a few basic parts could do the job. It also can be cheaper.

For example you can flash a led two ways easily.

IC -designed to flash LED - about $3 with led for each one
capacitor + resistor+transistor - $1 with LED for two


The circuit the OP wants is nothing more than converting AC to DC on the input with a bridge rectifier+ cap. The DC is then connected to a transistor that turns on and off really fast forming an AC current in the transformer that outputs the desired AC voltage on the other side based on the switching speed. That AC is then rectified back to DC and you have your power. I was building them in 1988 during high school as a hobby.


Here is a couple free pdf that have hundreds of simple circuits you can build with just transistors , resistors, capacitors
http://www.talkingelectronics.com/projects/200TrCcts/1-100TransistorCircuits.pdf
http://www.talkingelectronics.com/projects/200TrCcts/101-200TransistorCircuits.pdf

There are more at :
http://www.talkingelectronics.com/te_interactive_index.html

 

[bryanl]

See applications notes from:

National.com
Linear.com
Fairchildsemi.com

If efficiency won't affect your grade, choose linear over switching, and use 3-pin regulator chips, like the LM350.

 

[Mark R]

Well here is a schematic of a standard computer PSU for reference

http://www.hardwaresecrets.com/fullimage.php?image=5573

It's quite nice to see it drawn out like that. It's not actually a particularly complicated circuit.

Still, compared to modern PSUs it's pretty horrid. The push-pull driver, yucky magamp regulator and passive rectifiers are simple and cheap but don't give great performance or efficiency.

 

[Rubycon]

For example you can flash a led two ways easily.

IC -designed to flash LED - about $3 with led for each one
capacitor + resistor+transistor - $1 with LED for two

A little OT but...

I like the LM3909. Just an 8 pin DIP package, capacitor, LED and 1.5V provided by a single AA alkaline cell gives a powerful flash lasting for months nonstop! :awe:

 

[Twinpeaksr]

A little OT but...

I like the LM3909. Just an 8 pin DIP package, capacitor, LED and 1.5V provided by a single AA alkaline cell gives a powerful flash lasting for months nonstop! :awe:

I prefer a Spartan6 to flash my LED, then I can do it over Ethernet . If it's worth doing its worth overdoing!!

 

[Modelworks]

A little OT but...

I like the LM3909. Just an 8 pin DIP package, capacitor, LED and 1.5V provided by a single AA alkaline cell gives a powerful flash lasting for months nonstop! :awe:

Easiest way of all though is just to buy the flashing LED type and add the resistor

 

[Rubycon]

Easiest way of all though is just to buy the flashing LED type and add the resistor

Flashing LEDs can be driven directly off a DC supply - the internal circuit includes the dropping resistor.

The flash is also weaker and not as sharp. Additionally they need more power (6V) and consume milliamps whereas the 3909 has consumption in the microamp range!

 

[Jeff7]

Loads of info on power supplies.
Read here too - there's an Errata section on several mistakes in one of the PDFs.

 

[LiuKangBakinPie]

psurepair.freeforums.org

Ask mr Shovenose. Very friendly very helpfull chap