need help new to smps power supply design

venki

Member
2005-05-07 7:13 pm
india
Hi,

I am trying to make an AMP a 3-way speaker system. Each speaker is driven by a 35W ampl. So the total power comes to about.210 watts. The voltage required is around +/-30 V. If i go for a comventional PSU it will cost me a lot.

By the way I am from india. ;)

I would like to build a SMPS. But the problem is I dont know anything about it. Any SMPS gurus please help me out with design.

The power supply requirement is

+/- 30V
20A.

I would like to get info about how to build a transformer for the same. The dimensions etc. How to calculate it. Also since I am from india, will the parts be availble in india? (core etc).

Thanx in advance,
venki.:D
 

venki

Member
2005-05-07 7:13 pm
india
Ok I think I am too ambitious :clown: I have brought down the current rating from 20A to 10A and voltage to +/- 25V (bcus i kicked our one IC from my design I am planning to go with passive crossovers instead of the active one.

Can anyone help me out now pleezzz... :bawling:

Thanx,
Venki.:D
 

ghemink

Member
2004-06-14 2:26 pm
Japan
venki said:
Ok I think I am too ambitious :clown: I have brought down the current rating from 20A to 10A and voltage to +/- 25V (bcus i kicked our one IC from my design I am planning to go with passive crossovers instead of the active one.

Can anyone help me out now pleezzz... :bawling:

Thanx,
Venki.:D


Don`t go for an SMPS, too much trouble and designing one from scratch is not easy, not cheap and dangerous (high voltages). Just get a normal conventional transformer, a diode bridge and a few caps.

Best regards

Gertjan
 
hi there...wev'e been through this before......a disclaimer is that advice isn't given to anyone who hasn't grasped the dangers of going into the 1st time off-line smps deepend. Off-line designs or H.V work require a good oscilloscope and understanding what one sees......Start by doing something simpler.....i.e go linear......

richj
 

venki

Member
2005-05-07 7:13 pm
india
Hello all,

thanx for the response. The problem with not going with the conventional design is that we dont get 10A transformers here. I will have to get it wound it will cost me a lot ( :mad: ). Eva I do know basics about SMPS I studied about this in my graduation. If any of you could give me some tips to modify the SMPS of PC it would be nice.

Thanx,

Venki:D
 

aman

Member
2004-03-15 5:20 am
delhi
smps

hi venki,
i m aman from india living in delhi and interested in building amplifiers. My advice to u is that since building smps is very difficult u may go for the conventional psu. If u cant get a 10ampere transfromer then u can u can use two transformers of 5amp each for two channels (each three way system) and these are easily available in india.
 

venki

Member
2005-05-07 7:13 pm
india
hi richwalters,

What i mean is that i just know the theory that is it but dont have any idea about the tranformers (mainly designing size other factors). Sorry about that I didnt mean to confuse you :angel:

aman about the 5 amps tranfomer i think it is a good alternative? i will have to check it out in our local store.

Thanx again to all..

venki:D
 
now correct me if i'm wrong but smps stands for
Switching Magnetic Power Supply, which boils down to a simple magnetic field power supply. however if your talking about a switch mode power supply then i'm essentially no help. my area of expertise is Pulse Width Modulated Magnetic reflow power supplies. for example i built this awesome supply right before i graduated that gave me roughly 10 amps peak 2 amps rms @ +\- 35 Vdc using only an inductor a irf-510 and a neon bulb to isolate the fet from the collapsing magnetic field, a few diodes and 2 250V caps removed from computer power supplies. this supply was just an experi to see what i could do so i didn't have any switching circuits on it i was just using the make break properties of a switch. if you want me to draw up some diagrams just let me know.

Adrian
 
I'll echo what other people have said, and try to persuade you to go for a conventional transformer solution. Off-line mains SMPSUs are not things to design until you really understand them.

A good on-line simulation resource is:

http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/smps_e.html

Surely you can buy toroidal transformers for a conventional supply from Europe or the US? I know they're heavy and freight charges may be high but it's a safer way to go.

If you want to learn about SM power supplies, why not make a tranformer/rectifier/capacitor supply, and have a go at building a switch-mode dc-dc regulator (buck regulator) to provide a nice stabilised output for your amp? Once you understand buck-regulators, you will be in a better state to move on to off-line switchers.
 
Building a SMPS is pretty simple nowadays...
Unitrode/TI data sheets and applications notes can get you 95% of the way...
Where people go wrong with SMPS is the LAYOUT!!!!
Make sure to use a grounded plane board and in most cases the app notes will have a layout for you in actual size... There are guidlines to layout you can find and read about...
Also use a LOW switching frequency such as 200KHz or such...
Probably the number one reason I see failed switchers, is the COMPENSATION.... This is basic control theory nothing difficult..
You will need to break out your BODE plots and design a error compensation control loop that has good gain and phase margin...
Before you do anything..RESEARCH and READ first....
You can start off with the book by Pressman..I don't agree with everything in that book but it is a good starting point...
One book that did impress me because it had lots of good info was Power Supply Cookbook 2nd edition by Brown.. I was impressed at his no nonsense approach...and I did agree with about 90% of the book..... These books are very simplistic and good for starting out.... Later more advanced reading should include the famous Caltech crew of Middlebrook,Vorperian,Cuk, Dean Venable...

Chris