where to start to build an SMPS - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th July 2008, 08:48 PM   #11
diyAudio Member
 
Join Date: May 2008
Default THE FIRST STEP IN MAINTAINING SAFETY IN SMPS

Hi jegandren,

While designing and working on smps, provide a discharge path for the reservoir/filter capacitors. These capacitors can store a huge amount of energy and if touched can release that energy on you, which may be fatal.
The discharge path could be a high value resistor or a resistor in series with LED in both input and output section of your circuit. I personally prefer the later as after input supply is removed, the LEDs will indicate whether the Capacitors have discharged or not. Wait till the LEDs go off and after that you will have full freedom to put your hands anywhere in the circuit without any sort of risk of electric shock. Electric shock in smps can be fatal and please don't allow yourself to have that experience.


__________________________________________________ ___________________________
IDEAS ARE MONEY IF THEY CAN BE USED ON GROUND.
বাস্তবে ব্যবহৃত চিন্তাধারাই মানুষের প্রকৃত সম্পদ।
  Reply With Quote
Old 8th July 2008, 09:24 PM   #12
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
If you want to get your feet wet with switch mode supplies, may I suggest first starting with something relatively harmless - like a DC/DC upconverter. Something that starts with a (current limited) lab supply and goes to something that won't kill you if you touch something. Once you can reliably overcome the inevitable newbie hurdles, and the pile of vaporized HEXFETs you'll get along the way, then move on to something off-line.
  Reply With Quote
Old 10th July 2008, 07:39 PM   #13
diyAudio Member
 
CHACALPOWERS's Avatar
 
Join Date: Jul 2007
Default FULL BRIDGE x HALF BRIDGE: Whatś the best?

Hi dears

I built some half bridge smps but, now, I want build a full- bridge, 13,8V - 60 amp. smps. Is there advantage in FB ?
Thank you very much
  Reply With Quote
Old 11th July 2008, 08:04 PM   #14
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Quote:
Originally posted by Tolik
The best, & most accurate simulator for SMPS is prototype board only
I don't want to rain on anybody's parade, but SMPS design is not to be undertaken lightly.

Before you embark on such a project, you should have a clear idea of what your objective is. Then think whether you can achieve the same result with a conventional power supply. These are much better suited to home construction.

SMPS are often problematic in terms of emc. EMC.

EMC regulates the permitted emissions of equipment.

It is the designers responsibility under European law to ensure that devices do not emit excessively. This legislation is part of the criminal code, and successful prosecutions can result in jail sentences.

I am not suggesting that you run the risk of prosecution, but you should be aware of the potential antisocial consequences of your designs.

Fullscale EMC testing is impractical (uneconomic) for amateurs.

Unless you anticipate a career in SMPS design, it is a field better avoided.

w

OK, you may not be in Europe...
  Reply With Quote
Old 11th July 2008, 08:16 PM   #15
Tolik is offline Tolik  Israel
diyAudio Member
 
Tolik's Avatar
 
Join Date: Mar 2007
Send a message via Skype™ to Tolik
Quote:
This legislation is part of the criminal code, and successful prosecutions can result in jail sentences.
Did anybody here heard about a person, that was thrown in to the prison for unsuccessful SMPS design ?
__________________
Кто умеет делать - делает. Кто не умеет - учит. Х.Л. Менкен.
Those who can, do. Those who can't, teach. Those who can't teach, do research. H.L. Mencken
  Reply With Quote
Old 11th July 2008, 09:18 PM   #16
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Quote:
Originally posted by Tolik


Did anybody here heard about a person, that was thrown in to the prison for unsuccessful SMPS design ?
It's not a good idea to trivialise this subject.

Before EMC legislation background noise levels were rising globally to the point where, if unrestrained, the normal functioning of many devices we take for granted such as mobile phones might nowadays be difficult or impossible.

The legislation was successful in reversing this rise.

If you operate an untested SMPS you run the risk of minor or even severe interference to your neighbours and even, in rare instances, to safety critical services.

In my book, this constitutes antisocial behaviour, however minor.

Radio noise is environmental pollution.

Do you deny that this is the case?

w

Tolik, I'm not taking a dig at you. One of the things we most need prototypes for is EMC test.
  Reply With Quote
Old 11th July 2008, 11:39 PM   #17
Tolik is offline Tolik  Israel
diyAudio Member
 
Tolik's Avatar
 
Join Date: Mar 2007
Send a message via Skype™ to Tolik
Quote:
If you operate an untested SMPS you run the risk of minor or even severe interference to your neighbours and even, in rare instances, to safety critical services.
Quote:
Radio noise is environmental pollution.
I agree...


Generally we are talking about power supplies for audio equipment. Excessive EMI, will first interrupt functioning of whole audio system... So building of LOW noise PSU is main target here. Next, almost 80% SMPS discussed here, are low power - less than 300...500W, and almost neither of these projects not going to be produced in quantities more than 1-2 units. I don't really think, that several, even bad designed, low/ medium power supplies are containing a threat to ecology, or communications.

You better tell us how to measure or avoid EMI/RFE . It will be much more intresting here.
__________________
Кто умеет делать - делает. Кто не умеет - учит. Х.Л. Менкен.
Those who can, do. Those who can't, teach. Those who can't teach, do research. H.L. Mencken
  Reply With Quote
Old 12th July 2008, 12:00 AM   #18
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Typical EMI probes can be seen here

Uncalibrated probes can be fabricated quite readily from rigid co-ax, although the sheild must be perforated to permit correct connection in the case of the loops. You can find the connection details in e.g. the ARRL Antenna Book. The straight probes simply have a small stub of the inner conductor exposed.

It is unfortunately not possible to quantitatively test equipment in the absence of a quiet environment, which usually means a shielded room.

It is an unusual SMPS that passes EMC test on first submission, be it ever so small.

w

Most SMPS fail on conducted emissions. These can be detected by coupling to the supply cable. Oh, keep your current loops small. Watch your risetimes. IIRC CISPR B testing goes up to 2GHz. You ain't gonna hear that on no audio system...
  Reply With Quote
Old 12th July 2008, 12:33 AM   #19
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Simulation is great for control-loop modelling.
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 12th July 2008, 06:29 AM   #20
jahonen is offline jahonen  Finland
diyAudio Member
 
jahonen's Avatar
 
Join Date: Jan 2002
Location: Kuopio, Finland
I have seen hugely excessive EMI levels (20-30 dB over the B-requirement level 30/37 dBµV) even with very small non-isolated power supplies. I don't think that such excess will affect the audio system in any other way than FM/AM-reception. Most problematic frequencies are generally around 50-200 MHz.

Personally, for me, low EMI levels indicate carefully designed circuit/PCB and gives also other performance benefits. I feel that excessive EMI-levels are a clear indication that something is very wrong and must be fixed.

Most of the cases I have seen, it is rarely the PCB itself which radiates, but the cables attached to the PCB form an effective antenna for common-mode noise. Differential mode is seldom a problem, due to small loop areas. Common mode radiation is much harder to suppress.

A very good cheap test for EMI (requires reasonably wideband oscilloscope, though) is to short circuit a oscilloscope probe right at the tip to the ground collar. Throw that ground clip away though, it is pretty much useless for SMPS and digital measurements due to excessive loop area it creates, thus it picks all the magnetic noise.

Then connect this short circuited probe to the ground of the PCB. Now, do you see any high-frequency noise at mV levels? If you do, then don't bother to try EMC-testing until you have fixed what you see using this test. Remember, it only takes few µA of common mode RF-current to create high EMI levels. Higher the frequency you see, then more serious the issue is.

Regards,
Janne
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
SMPS Trouble, wont start - need some advice! Full schematic silversweden Power Supplies 5 3rd January 2009 01:21 AM
Simple 110 - 240 VAC to 2 x 30 VDC 50 - 100W SMPS .... where do I start?? Baldin Power Supplies 4 10th February 2007 12:12 PM
low V Start for SMPS cunningham Solid State 1 16th July 2004 07:58 AM
I want to build a GC, where to start? BAM Chip Amps 9 11th July 2004 04:32 PM


New To Site? Need Help?

All times are GMT. The time now is 07:23 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2