Hi all,
I found This kinda "big" transformer in an old apple psu. its an EE transformer, I would like to use it as a transformer for a car SMPS.
but I need to know if its good, and how to calculate the nuber of winding for primary and secondry's. and most important... how much power it can supply(watts). what i would like is to get about 56Vdc+/-.
can anyone help me with this thing?
Thanks,
Kinser
I found This kinda "big" transformer in an old apple psu. its an EE transformer, I would like to use it as a transformer for a car SMPS.
but I need to know if its good, and how to calculate the nuber of winding for primary and secondry's. and most important... how much power it can supply(watts). what i would like is to get about 56Vdc+/-.
can anyone help me with this thing?
Thanks,
Kinser
EE Core for Car SMPS
Kinser,
Seen your posts in some of the other Power Supply threads. Couple of questions: Is this a flyback or half-bridge topology?
You can usually tell if there are two hi-voltage transistors as opposed to only one. If flyback, then you might have a hard time with respect to the leakage inductance, as the core for the transformer has a small gap. 
If I'm looking at photo 1 OK, it looks like there is no gap, so you should be OK.
Check out some of my other poses in the Power Supply forum (I don't know how to re-direct you there with a hyperlink, sorry) for reference material and books to use. Geo. CHryssis' book, High Frequency Switching Power Supplies (c) 1989 breaks up SMPS design inti chapters by the sections of the supply.
Chapter 6 (I think- it's been a long time since I've looked at the book), is devoted entirely to the transformer (for forward topologies), and the transfermer-choke (for flyback topologies). It shows you how to calculate the number of turns based on frequency, material type, topology, and a whole host of other parameters.
If this book is available in Israel, I would recommend picking up a copy, or borrowing it from a library.
Best of luck, and let us SMPS gearheads know how this turns out.
Steve
Kinser,
Seen your posts in some of the other Power Supply threads. Couple of questions: Is this a flyback or half-bridge topology?
You can usually tell if there are two hi-voltage transistors as opposed to only one. If flyback, then you might have a hard time with respect to the leakage inductance, as the core for the transformer has a small gap. If I'm looking at photo 1 OK, it looks like there is no gap, so you should be OK.
Check out some of my other poses in the Power Supply forum (I don't know how to re-direct you there with a hyperlink, sorry) for reference material and books to use. Geo. CHryssis' book, High Frequency Switching Power Supplies (c) 1989 breaks up SMPS design inti chapters by the sections of the supply.
Chapter 6 (I think- it's been a long time since I've looked at the book), is devoted entirely to the transformer (for forward topologies), and the transfermer-choke (for flyback topologies). It shows you how to calculate the number of turns based on frequency, material type, topology, and a whole host of other parameters.
If this book is available in Israel, I would recommend picking up a copy, or borrowing it from a library.
Best of luck, and let us SMPS gearheads know how this turns out.
Steve
probably 150 - 200 watts.
before taking the transformer apart, figure out the winding ratios --
with an ohmeter determine which of the pins are connected to each other -- you can connect an audio oscillator at 10kHz to one of the sets of windings and measure the resulting voltages on the other pins to determine the turns ratio (just make sure that your oscillator doesn't get too loaded by the transformer). Be careful because there will be high voltage on one or more of the windings.
you might find that using the original primary as the new secondary is going to work fine in your application -- you will need to adjust the duty cycle of the switcher, take into consideration the voltage drops in the rectifiers and chokes etc.
before taking the transformer apart, figure out the winding ratios --
with an ohmeter determine which of the pins are connected to each other -- you can connect an audio oscillator at 10kHz to one of the sets of windings and measure the resulting voltages on the other pins to determine the turns ratio (just make sure that your oscillator doesn't get too loaded by the transformer). Be careful because there will be high voltage on one or more of the windings.
you might find that using the original primary as the new secondary is going to work fine in your application -- you will need to adjust the duty cycle of the switcher, take into consideration the voltage drops in the rectifiers and chokes etc.
Hi, I have done a stupid thing, earlly today I took off all of the windings, so I guss I might as well throw it away.
but what about the transformer on an AT power supply? I have two of them still on the AT board, cauld I use both of them to get more power?
BTW the transformer had one mosfet at the primary(I think, I had a quick look at it). Also I have one LT494 and one 7500(they are the same) Is there any SMPS circuit thats based on this chip? could you post It if you have one?
Thanks,
Kinser
but what about the transformer on an AT power supply? I have two of them still on the AT board, cauld I use both of them to get more power?
BTW the transformer had one mosfet at the primary(I think, I had a quick look at it). Also I have one LT494 and one 7500(they are the same) Is there any SMPS circuit thats based on this chip? could you post It if you have one?
Thanks,
Kinser
SMPS
Kinser-
jackinnj's QEX article is a realy good one. It's very thorough and several pages long. He sent it to me a couple of weeks ago, and I'm still digesting it.
BTW, don't throw that old core out- you can still use it, as it might not be as hard as you think to identify the core material and get specs on it. If it IS a flyback transformer-choke, there are some SMPS circuits you might be able to use it in, just not this one.
As for the two AT transformers you have, I wouldn't use them on the original AT board, but make your own pc boards (you're probably gonna do that, anuway).
There are alot of circuits for +12V center-tap push-pull topology using the TL494. You can even make separate separate power supply modules for each channel, using one core for each module, synchronizing the two '494s together to eliminate beat frequencies. This way, each channel can have its own dedicated power supply. It's actually really easy to do. Go to onsemi.com and look up TL494. Synchronizing is on the page 9 of the datasheet.
Kinser-
jackinnj's QEX article is a realy good one. It's very thorough and several pages long. He sent it to me a couple of weeks ago, and I'm still digesting it.
BTW, don't throw that old core out- you can still use it, as it might not be as hard as you think to identify the core material and get specs on it. If it IS a flyback transformer-choke, there are some SMPS circuits you might be able to use it in, just not this one.
As for the two AT transformers you have, I wouldn't use them on the original AT board, but make your own pc boards (you're probably gonna do that, anuway).
There are alot of circuits for +12V center-tap push-pull topology using the TL494. You can even make separate separate power supply modules for each channel, using one core for each module, synchronizing the two '494s together to eliminate beat frequencies. This way, each channel can have its own dedicated power supply. It's actually really easy to do. Go to onsemi.com and look up TL494. Synchronizing is on the page 9 of the datasheet.
well, you now have all the equations -- instead of 165V on the primary of the transformer you have a different number -- 12V
you can omit the "housekeeping" power winding on the transformer since it's possible to avail yourself of the 12V from the battery.
the circuit of figure 18A (the TL494 and the "base-drive-transformer") is the same, you have to change the turns ratio in the transformer -- which is T1 in figure 18B -- of course this changes the inductance etc. but you should be able to figure it out from the text.
you can omit the "housekeeping" power winding on the transformer since it's possible to avail yourself of the 12V from the battery.
the circuit of figure 18A (the TL494 and the "base-drive-transformer") is the same, you have to change the turns ratio in the transformer -- which is T1 in figure 18B -- of course this changes the inductance etc. but you should be able to figure it out from the text.
2SC2335 Transistors
Kins-
Those are the main switching transistors, and since they will see over 320V across them, they are most likely 400V, 8-15A rated NPNs.
Not a real good choice if you want alot of current on the primary. You could change them to some good N-Channel MOSFETs rated at 60V. Any N-Channel MOSFET over a 30A drain current ratinf will do- there are many choices.
As for your AT transformer cores, if they came out of a 200-250W AT box, then they are probably good for about 60-80W continuous power, with extended peaks of 200-250W. That is a dirty little secret behind all those impressive ATX power supply ratings. 500W (continuous) from an ATX box?
I don't think so. for a 500W rated unit, more like 120W continuous, even with forced-air cooling.
Anyway, I'm babbling again, I always do that. In all honesty, 80W CONTINUOUS power PER channel is more than plenty for your needs. And remember about using two PWM supplies in synchronicity. It will look cool, work great, impress your friends and get you all the girls!
Kins-
Those are the main switching transistors, and since they will see over 320V across them, they are most likely 400V, 8-15A rated NPNs.
Not a real good choice if you want alot of current on the primary. You could change them to some good N-Channel MOSFETs rated at 60V. Any N-Channel MOSFET over a 30A drain current ratinf will do- there are many choices.
As for your AT transformer cores, if they came out of a 200-250W AT box, then they are probably good for about 60-80W continuous power, with extended peaks of 200-250W. That is a dirty little secret behind all those impressive ATX power supply ratings. 500W (continuous) from an ATX box?
I don't think so. for a 500W rated unit, more like 120W continuous, even with forced-air cooling.Anyway, I'm babbling again, I always do that. In all honesty, 80W CONTINUOUS power PER channel is more than plenty for your needs. And remember about using two PWM supplies in synchronicity. It will look cool, work great, impress your friends and get you all the girls!
Re: 2SC2335 Transistors
go to www.onsemi.com and find some NPN's that will work in this application. if you pick up a textbook on smps design you'll see that the stress on the switching transistors is pretty severe. if you tool around the National Semi and OnSemi websites you'll find some interactive software which aids the design process and demonstrates the peak voltages and currents at criitcal nodes.
but an ATX supply will chug along and provide one heck of a lot of current -- what it won't do is remain stable if you demand relatively little current -- that's why the output inductors have to be oversized for ham radio operation (SSB and Class C) -- less so when you move down the food chain to audio and class AB operation.
a lot of ATX supplies are poorly designed -- the magnetics is one area where you have to be able to calculate with more than a four-function calculator. i think that Carly Fiorina personally designed the one I had with an HP computer -- another example of incompetence.
i just ripped apart a power supply for a Dell network server -- while the solder was really tough even with my big Weller gun I found two cold solder joints which probably caused premature device failure (or at best wonky behavior).
N-Channel said:Kins-
Those are the main switching transistors, and since they will see over 320V across them, they are most likely 400V, 8-15A rated NPNs.
Not a real good choice if you want alot of current on the primary. You could change them to some good N-Channel MOSFETs rated at 60V. Any N-Channel MOSFET over a 30A drain current ratinf will do- there are many choices.
As for your AT transformer cores, if they came out of a 200-250W AT box, then they are probably good for about 60-80W continuous power, with extended peaks of 200-250W. That is a dirty little secret behind all those impressive ATX power supply ratings. 500W (continuous) from an ATX box?
Anyway, I'm babbling again, I always do that. In all honesty, 80W CONTINUOUS power PER channel is more than plenty for your needs. And remember about using two PWM supplies in synchronicity. It will look cool, work great, impress your friends and get you all the girls!
go to www.onsemi.com and find some NPN's that will work in this application. if you pick up a textbook on smps design you'll see that the stress on the switching transistors is pretty severe. if you tool around the National Semi and OnSemi websites you'll find some interactive software which aids the design process and demonstrates the peak voltages and currents at criitcal nodes.
but an ATX supply will chug along and provide one heck of a lot of current -- what it won't do is remain stable if you demand relatively little current -- that's why the output inductors have to be oversized for ham radio operation (SSB and Class C) -- less so when you move down the food chain to audio and class AB operation.
a lot of ATX supplies are poorly designed -- the magnetics is one area where you have to be able to calculate with more than a four-function calculator. i think that Carly Fiorina personally designed the one I had with an HP computer -- another example of incompetence.
i just ripped apart a power supply for a Dell network server -- while the solder was really tough even with my big Weller gun I found two cold solder joints which probably caused premature device failure (or at best wonky behavior).
So,
I have a few Q's.
1. If I where to rewind the AT xformers for 12v center tap on primary and an output of about 40-0-40=56Vdc+/- on secondrys, could I use each one to power a moded P3A amp? because N-Channel said that they are 60-80 watts continues,200-250 watts extreme peak?
2. I downloaded some Power supply software from National Semi. its called "Switchers Made Simple", have any of you used it?
Thanks,
Kinser
I have a few Q's.
1. If I where to rewind the AT xformers for 12v center tap on primary and an output of about 40-0-40=56Vdc+/- on secondrys, could I use each one to power a moded P3A amp? because N-Channel said that they are 60-80 watts continues,200-250 watts extreme peak?
2. I downloaded some Power supply software from National Semi. its called "Switchers Made Simple", have any of you used it?
Thanks,
Kinser
if I recall, the "Simple Switcher" series relates to their (Nat Semi) line of buck and boost converters, but not to a push-pull or forward converter.
Before we go any further, tell me the component values on pins 4, 5 and 6 of the TL494 so we can get an idea of the switching frequency and dead time.
Before we go any further, tell me the component values on pins 4, 5 and 6 of the TL494 so we can get an idea of the switching frequency and dead time.
they all meet together and go to ground.
I have a web page with a car SMPS using TL494.
www.djquan.angelcities.com/smps.html
I have a web page with a car SMPS using TL494.
www.djquan.angelcities.com/smps.html
for the switching mosfets, you could use anything with >40A and between 50 to 100V rating. I used IRF1302 for the 200W (four in all) and IRF3205 for the 500W (six in all) which I think is overkill but I already had them so it wouldn't hurt.
for the 200W version, I have 6 turns per primary, and 16 turns per secondary. the primary is wound with 3 x 1mm wires, psecondary is 2x 1mm wires. I get +/-35V with that tranny.
for the 200W version, I have 6 turns per primary, and 16 turns per secondary. the primary is wound with 3 x 1mm wires, psecondary is 2x 1mm wires. I get +/-35V with that tranny.
TL494 Frequency
Kinser/Jack,
OK, using the following formula provided by Onsemi, TI and others:
f(clock) = (1.1)/R(t)C(t), where R(t)=18K, and C(t)=1000pF. Therefore, your clock freq should measure approx. 61.1 kHz on the scope, and your switching frequency will be half that, or ~ 30.5kHz.
With 10K on pin 4, I'm not sure of the max duty-cycle (Ton -v- Toff) will be, but if I had to take an educated guess, I would say the 10K resistor limits each output's duty cycle to about 45%. Again, this is just a guess.
As for the transformers, I'm not 100% sure about the max CONTINUOUS power they can handle, but 60-80W sounds right. In George Chryssis' book, the chapter on transformers gives good detail on finding out how much CONTINUOUS powe a core can handle, based on the cross-sectional area of your particular cores.
Kins-
go to this website,
http://www.onsemi.com/pub/Collateral/TL494-D.PDF
and see how simple it is to SYNCHRONIZE two TL494s together to eliminate beat frequencies. These can occur when two (or more) PWMs operate in close proximity to each other on the same (but not exact) frequency. So, one 494 can power channel one of the P3A Amp, and the other 494 can power the other channel.
As for the NatSemi SimpleSwitchers, they are great chips to work with (I've used them myself many times before- with great success), and there are so many different chips for many different applications. However, none of them are suitable for this high of power levels you're working with. -Stick with the '494.
If you're making, say, a +12V to +19V booster (we make/use them for powering our laptops in the field), the LM2587-ADJ is a great chip for this, but for a high power car amp, it's WAY too small.
Same story for the rest of the SimpleSwitchers.
I have used the Switchers-Made-Simple software, and it's pretty precise. The values for the components I calculated both using and not using the software were very close, and results from finished circuits using the software were very close to the calculated values.
Steve
Kinser/Jack,
OK, using the following formula provided by Onsemi, TI and others:
f(clock) = (1.1)/R(t)C(t), where R(t)=18K, and C(t)=1000pF. Therefore, your clock freq should measure approx. 61.1 kHz on the scope, and your switching frequency will be half that, or ~ 30.5kHz.
With 10K on pin 4, I'm not sure of the max duty-cycle (Ton -v- Toff) will be, but if I had to take an educated guess, I would say the 10K resistor limits each output's duty cycle to about 45%. Again, this is just a guess.
As for the transformers, I'm not 100% sure about the max CONTINUOUS power they can handle, but 60-80W sounds right. In George Chryssis' book, the chapter on transformers gives good detail on finding out how much CONTINUOUS powe a core can handle, based on the cross-sectional area of your particular cores.
Kins-
go to this website,
http://www.onsemi.com/pub/Collateral/TL494-D.PDF
and see how simple it is to SYNCHRONIZE two TL494s together to eliminate beat frequencies. These can occur when two (or more) PWMs operate in close proximity to each other on the same (but not exact) frequency. So, one 494 can power channel one of the P3A Amp, and the other 494 can power the other channel.
As for the NatSemi SimpleSwitchers, they are great chips to work with (I've used them myself many times before- with great success), and there are so many different chips for many different applications. However, none of them are suitable for this high of power levels you're working with. -Stick with the '494.
If you're making, say, a +12V to +19V booster (we make/use them for powering our laptops in the field), the LM2587-ADJ is a great chip for this, but for a high power car amp, it's WAY too small.
Same story for the rest of the SimpleSwitchers.I have used the Switchers-Made-Simple software, and it's pretty precise. The values for the components I calculated both using and not using the software were very close, and results from finished circuits using the software were very close to the calculated values.
Steve
The 1.41 rms multiplier is for sine waves, (40-0-40) 56v+/-, if you build a switcher out of a tl494 you'll use square waves which when rectified is roughly half pp, or if you have 70v pp square wave on your scope your dc rectified will be rouhgly 35v. Which is why you get +/- 24v for 1:2 ratio push pull smps trnsfor with 12v primary . Each half leg of the primary will see 24v pp (vdc2) and with a 1:2 ratio wind, each half leg of the secondary will have 48v pp for a total of 96v pp making a recitifed 24v+/- or 48v total.
kinser said:
you'll be hard pressed to get 500W out of the existing transformer -- this is because (among other things, the transformer probably can't handle the physics) --> there just isn't enough space to put the windings -- there is a balancing act between the required inductance of the primary winding, the peak and average current demand, the operating temperature of the transformer and the size of the window available for winding.
i have a torn up ATX supply -- the windings are #22 which will handle 2 amps -- this is fine on the primary of an offline, 200 watt switcher which will see 165 VDC on the primary. figure that your auto battery power supply at 500 watts would see 40 amps --
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