switchmode powersupply winding ratio
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 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
 13th April 2005, 02:34 PM #1 SkinnyBoy   Banned   Join Date: Nov 2002 Location: Adelaide, Australia switchmode powersupply winding ratio alright, I'm a little confused (thats normal though) BUT! with a switchmode powersupply.... if I have a centre tapped 5 + 5 winding on the primary (its low voltage input) does my secondary winding have to be a ratio of half the total primary? SO!!! if I have 10 volts in, and 5 + 5 on the primary, and want 12volts out, do I need a single 6 volt winding on the secondary... yes? yeah, thats right, isn't it.. ok.. thanx 5 + 5 on the primary it is.... is that ok? and then a 6 turn winding for 12volts, and a... damn... alright... basically, I want to make a computer powersupply that will run off a car battery.... even while the engine is cranking... so it would be good if it could keep the voltages up even with 10 volts in... any ideas for the winding ratios? expecially seeing as I need 3.3 volts too...
 13th April 2005, 11:26 PM #2 Sch3mat1c   diyAudio Member     Join Date: Jan 2003 Location: Milwaukee, WI Follow the peak voltage. You have 10-0-10V and 10T CT = 20V peak across the length of 10T. That's 2V/T. So yes for 12V you need 6T, call it 7T with losses (core, winding, rectification etc.). If 10V is the minimum voltage you expect, then that should do it right there, right? If you need more then just add another turn or two, and "cruise" at a lower duty cycle. Oh, and as for the other voltages - you could buck regulate each one (as done on the motherboard for the processor's 1.7 to 2.5V these days), or of course use other windings. You'll just need to control the turns fractionally speaking... build it but don't varnish the transformer. Add or remove turns until the ratio between the voltages is right (ratio since voltage depends on input and duty cycle, assuming you're using choke input rectification and filtering on this thing..). Tim __________________ Seven Transistor Labs, LLC Projects and Resources / Electronic Design and Consultation
 14th April 2005, 05:27 AM #3 SkinnyBoy   Banned   Join Date: Nov 2002 Location: Adelaide, Australia the question is HOW do I get the right winding rations for the other voltages.... if I have 12 windings for 12 volts (which is ALOT of windows for a switchmode powersupply, then I need 5 windings for the 5 volts, and CAN"T get 3.3 volts.... its either 3 volts.... or 4 volts..
 14th April 2005, 06:55 AM #4 Sch3mat1c   diyAudio Member     Join Date: Jan 2003 Location: Milwaukee, WI Nope, just bend the wire square away from the center of the core at whatever point to get the fractional turns. Like I said, move it around until you get it right, then (I forgot to mention before) cement it in place. FWIW, 3.3, 5 and 12 share few primes so your first integer combo would be 33, 50 and 120 turns, just slightly inconvienient. (Heck, you'd use fewer turns on a 60Hz iron core transformer!) Tim __________________ Seven Transistor Labs, LLC Projects and Resources / Electronic Design and Consultation
 14th April 2005, 03:01 PM #5 Eva   diyAudio Member     Join Date: Oct 2003 Location: Near the sea Fractional turns require a split core, it doesn't work otherwise. Anyway, remember that the output voltage in such an unregulated topology is proportional to the input voltage so regulation is mandatory Standard ATX power supplies have only 5V and 12V windings with 3:7 ratio that actually provide about 8..10V and 20..24V peak, then these voltages are rectified and feed to a coupled buck inductor with multiple windings. Both transformer and inductor turn ratios are critical and have to be adjusted to compensate for diode and copper voltage drops Regulation is achieved by adjusting continuously the duty cycle to compensate for input and load changes. The 3.3V output is derived from the 5V transformer winding and has its own regulation achieved by shortening the duty cycle by means of a saturable reactor core It would be easier to start from a working ATX PSU and redesign the primary side since it would have already a lot of things working in the secondary side

 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 Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         Dx Classic Amplifiers         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post TroelsM Power Supplies 9 10th April 2009 10:08 AM rtarbell Parts 0 17th March 2007 02:09 PM gev Power Supplies 0 21st May 2006 07:41 PM demons_wing Class D 2 17th June 2004 10:52 AM richwalters Pass Labs 0 26th September 2003 08:20 PM

 New To Site? Need Help?

All times are GMT. The time now is 04:17 PM.