nikhil arora Posted June 21, 2006 Report Share Posted June 21, 2006 i have little idea that this can be done by two methods1> Tansformerless design2> Switching power supply designnow i want to have very small transformer or no transformer at all Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 21, 2006 Report Share Posted June 21, 2006 A transformer provides isolation for safety.A switching power supply can operate at a high frequency so the transformer's size can be very small.I bought some 5V/2A switching power supplies as surplus (2 years old, name brand) for a very low price. They are very small and are a very low weight.Chargers for cell phones are small switching power supplies. Quote Link to comment Share on other sites More sharing options...
zak4000 Posted June 21, 2006 Report Share Posted June 21, 2006 Whats a switching power supply?? ??? Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 22, 2006 Author Report Share Posted June 22, 2006 Guru Can you provide me some guidance for designing such a supply even some good links can help me...........Smallest possibe............zak4000 can know what are these fromhttp://en.wikipedia.org/wiki/Switching_power_supply Quote Link to comment Share on other sites More sharing options...
audioguru Posted June 22, 2006 Report Share Posted June 22, 2006 I bought my surplus 5V/2A tiny name-brand switching power supplies at a very good price. Their label says that the voltage is adjustable over a wide range but they are sealed so I will cut one open to try it.I don't know where to buy a high frequency core for the transformer, then it would be a nuisance to wind many turns of wire on the core. Of course, first I would need to refresh my long ago study of transformer theory. I have never made a transformer for a switching power supply. Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 23, 2006 Author Report Share Posted June 23, 2006 how can i buy such modulescan you send me some pics or similart things so i can get a ideai am also going to open one charger of my mobile phone so i can get more ideas Quote Link to comment Share on other sites More sharing options...
Sukhbinder Posted June 23, 2006 Report Share Posted June 23, 2006 if u r going to open up a mobile phone charger i suggest u use it for the power supply u need. most cell phone chargers can provide u with a voltage of 6-7V @500mA, which will be quite enough for ur demands. u could use normal rectifier diodes to drop the excess voltage by connecting them in series (u'll get a drop of 0.6v from each diode) since mobile phone chargers are quite cheap and are optimised for thir ussage, i suggest u use them, it more easy than building ur own. i have an ac-dc adaptor of a chinese make, it has a voltage o/p of 1.5,3,4.5,6,7.5,9 & 12V @1200mA. it uses different feed back resistors to set the voltage. ;) Quote Link to comment Share on other sites More sharing options...
nikhil arora Posted June 30, 2006 Author Report Share Posted June 30, 2006 i have open one of the charger i found no ic in it but just a small transformer and 1 or 2 transistor. and other components. thats it.i donot know how much ripple is there in the ouput of charger as i don't own cro. Quote Link to comment Share on other sites More sharing options...
indulis Posted June 30, 2006 Report Share Posted June 30, 2006 The transformer design isn't that bad... 25 turns primary and 5 turns secondary.For a SMPS, I think you could get away with a Feroxcube ER14.5 core with 3F3 material (inductance factor of 1400nH +/-25%) running at 400KHz on a single ended forward converter. It would have an ~ duty cycle of 46% (so reset wouldn't be a problem). Also the flux swing is limited to 2000 gauss (3F3 saturates around 3500 gauss @ 100C).Oh... this is all base on a 110VAC half wave rectified RMS voltage of~78V feeding the DC-DC. Quote Link to comment Share on other sites More sharing options...
indulis Posted June 30, 2006 Report Share Posted June 30, 2006 Here's probably more than you want to know about it... it shows a split primary winding of 13-13. This is because the program can't do half turns.TRANSFORMER PERFORMANCE SUMMARYDesign Name: Designer:Date/Time: 06/30/06 09:45:45 Project: UntitledNotes:TRANSFORMER DESCRIPTIONCore Family: ER Ferrite Core Weight (Grams): 1.800Geometry: ER14.5/3/7 Total Gap (in): 311.7uMaterial Name: 3F3/200K400K_100C Spacer Thickness (in): 155.8uManufacturer: PHILIPS Window Fill (%): 62.67CORE DESCRIPTIONEff. Core Area (m^2): 17.60u Min. Core Area (m^2): 17.60uWinding Length (in): 0.1024 Winding Height (in): 0.1398Avail. Window (m^2): 9.230u Area Product (m^4): 162.4pMin. Core Gap (in): 103.5u Volume (in^3): 20.38mInside Diameter (m): 4.700m Surface Area (m^2): 580.0uMean Length Turn (in): 1.020 Winding Shape: RoundMax. Permeability: 2.400k Max. B, linear u (Gauss): 2.400kSat. Flux Density (Gauss): 3.100k Res. Flux Density (Gauss): 1.100kMean Mag. Path Len. (m): 19.00mTRANSFORMER PERFORMANCE DATAFlux Swing Type: half wave Input Waveform: pulseDuty Ratio (Pct.): 0.5000% Current Rise/Fall (Pct.): 0%Output Power (Watts): 0.6885 Magnetizing Ind. (Henry): 237.2uPk. Flux Density (Gauss): 2.509k Core Loss (Watts): 0.2346AC Flux Density (Gauss): 977.9 Copper Loss (Watts): 259.6uAmbient Temp. (deg C): 55.00 Core AwAc (m^4): 162.4pTemp. Rise (deg C): 28.75 Frequency (Hertz): 400.0kVolts/Turn: 2.754USER DEFINED PERFORMANCE DATATrise 28.75 Winding fill % 62.67Tlevel 0 Total Weight (Pounds): 4.670mCopper Loss 259.6u Core Loss 0.2346Bac(max) 100.0k Bac 977.9Output Power 0.6885 Calculator 4.000Gap 791.7u Lmag 237.2uMax Strands 2.000 Min. Turns 1.000drive winding 1.000 Core weight 1.800Efficiency 65.89 Round Coef. 0.9900Winding pitch 1.000 Primary Turns 14.90Idens(max) 100.0k Bp(max) 100.0kVdrop2 4.725m Ploss 47.25uVterminal 35.80 Jn 20.13CuWt 0.2066WINDING DESCRIPTION, RATINGS, AND CHARACTERISTICSWinding Number: 1 2 3Primary or Secondary: pri sec priVolts Specified (Volts): 35.80 12.43 35.80Volts Average (Volts): 35.80 13.77 35.80AC Current (Amps): 10.00m 50.00m 10.00mDC Current (Amps): 0 0 0AC Resistance (Ohms): 0.2925 73.25m 0.4725DC Resistance (Ohms): 0.1060 62.59m 0.1492Power Loss, Copper (Watts): 29.25u 183.1u 47.25uCurrent Density (Amp/in^2): 129.9 828.0 129.9Wire Type: HF HF HFWire Size (AWG): 39 40 39Wire Height (in): 4.331m 3.898m 4.331mWire Width (in): 4.331m 3.898m 4.331mWire Strands: 8 8 8Turns: 13 5 13Number of Layers: 6.500 2.500 6.500Turns per Layer: 2.000 2.000 2.000Start ID: 1 3 1000Finish ID: 1000 4 2Pitch: 1 1 1Layer Insulation (in): 0 0 0Wrapper Insulation (in): 3.000m 3.000m 3.000mEnd Margins (in): 0 0 0Leakage Ind. Next (Henry): 1.296u 223.9n 0Leakage(L->Sector) (Henry): 0 0 0Leakage(Sector<-L) (Henry): 0 0 0Winding Capacitance (Farad): 5.628p 9.147p 11.08pCapacitance to Next (Farad): 9.078p 9.979p 0IR Drop 2.925m 3.663m 4.725mCopper Loss 29.25u 183.1u 47.25uLoaded Voltage 35.80 13.76 35.80Current Density2 20.13 128.3 20.13Winding Weight 98.78m 36.43m 0.1428DESIGN CONSTRAINTSMax Window Fill (%): 100.0 Max Temp. Rise (deg C): 50.00Max Pk. Flux Dens. (Gauss): 100.0k Max AC Flux Dens. (Gauss): 100.0kMax Cur. Dens.(Amp/in^2): 645.2k Waveform: squareAuto Margin for Lead Exit: no Pitch (dia/turn): 1K Conduction: 3.990 K Convection: 710.0K Insulation: 2.000m K Dielectric: 3.000Thermal Model Level: 0 Rac Method B&LSPICE MODEL AND SYMBOL NAMESSpice Model Name: not savedSpice Symbol Name: not saved Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.