سلام به همه ی دوستان عزیز
راستش من چند وقت پیش یه نقشه منبع تغذیه سوئیچینگ یافتم که طرف هم ایرانی بوده ولی برای خارجی ها گذاشته بوده..
و این هم توضیحاتی که همراه متن بود :
You must remeber all methods are based on Faraday's law and just rearranged so you can find the unknowns.
Faraday's law:
E= N*AE *(dt/dt) * E-8
E is the voltage across the transformer winding, N is the number of turns on the winding, Ae is area of core in cm^2, DB is flux change (gauss) and dt time for flux to change (seconds)
Now we rearrange the terms and plug in some definitions and we can get the following for finding number of primary turns.This is for halfbridge. For Forward or Fullbridge you double this number because they have to support the rectified mains not just half.
V(in) * E8 / (4 * Fs * Bmax *Ae) = NT(pri)
Now for the core volume to support the power we need:
Lets set up a design for 500watts:
The primary current will be equal to :
Ip= 3 *P(out) /V(in)
V(in) will be calculated based on 110VAC line at it highest value:
130 VAC therefore with a voltage doubler we can expect about:
2(130 * 1.4) = 370 VDC after rectifiers
therefore Ip = 1500 /370 = about 5 Amps from this we calculate the input power which is 1500/ .85 for 85% eff which is about 1750 watts.
core size = .68 * P(out) * current density / Fs * Bmax
Choose a industry standard of 500 c.m. /A for current density and we get:
AcAe = .68 * 1500 * 500E3 / 100E3(Fs) * 1200 (bmax) =4.25 cm^4
If we check the ETD49 specs we find that its AcAe is about 5.7 cm^4 which is a good choice for this design
Look what happens when we raise the Fs to 200KHz:
AcAe = .68 * 1500 *500e3 / 200e3(Fs) *1200(bmax) =2.125 cm^4
so you can see the higher the frequency the smaller the core within reason (copper loss, core temp and other things come into play)
In this case we used a Bmax of 1200 and could have used up to 1600, recalucate using 1600 and then we get 3. 18 cm^4 which means we might be able to use an ETD44 coreset now for the turns calculation:
If we use the highest voltage we expect on our transformer windings when the supply turnon:
N(pri) = 370(V(inmax)E8 / (4 * 100E3 * 2400(B(max) *2.11(Ae) =
18Turns for ETD49 and for ETD44 = 23 Turns
Now a good guess for the secondary is Ns = VS/VP I want an output of 35 volts , so that means after the rectifiers I need twice that and to help with transits and load changes I will increase that by 5% or so make it 80 volts , I expect at low line to have about 110 volts after the main rectifiers using a 110VAC input so now my secondary turns will be :
18*(80/110) = 13 turns make it 14, After you wind and test your transformer you might find you need to add or take off a winding or two. And at high line you wil need 11 turns make that 12.
So there is your transformer calculations regardless of how you do it the frequency along with the Amount of flux will determine the output power and the core size along with the size of the winding area and wire size.
All this is more or less what I have found in appnotes,books and other articles plus a little experience mixed in. It is up to the designer or DIY to verify this thru research and reading as this forum is full of material covering this subject and I will not get in a contest with which is right or wrong, however if you find an error or have a question I will try to help if I can and I will correct the errors you find ... just remeber a transformer is just that and the law and priciples for their design is basic and well documented its just when you lump them into a design at high frequency that a lot of care must be taken for them to provide proper results.
یه سایتی رو هم معرفی کرده برای دیدن مشخصات هسته ها :
http://coremaster.com/2000_core.htm
اگر ممکنه اساتید سوئیچینگ ( etgpsp - Ebi SMPS - Ghasede del - ahmadmn و... ) و دوستان گرامی دیگر ، نظر خودشون رو بیان کنند که ایا از نظر فنی مشکل داره و اگر مشکل داره برای رفعش یه اقدامی بکنیم که دوستان علاقه مند در این زمینه هم استفاده ای کرده باشند.
راستش من چند وقت پیش یه نقشه منبع تغذیه سوئیچینگ یافتم که طرف هم ایرانی بوده ولی برای خارجی ها گذاشته بوده..
و این هم توضیحاتی که همراه متن بود :
You must remeber all methods are based on Faraday's law and just rearranged so you can find the unknowns.
Faraday's law:
E= N*AE *(dt/dt) * E-8
E is the voltage across the transformer winding, N is the number of turns on the winding, Ae is area of core in cm^2, DB is flux change (gauss) and dt time for flux to change (seconds)
Now we rearrange the terms and plug in some definitions and we can get the following for finding number of primary turns.This is for halfbridge. For Forward or Fullbridge you double this number because they have to support the rectified mains not just half.
V(in) * E8 / (4 * Fs * Bmax *Ae) = NT(pri)
Now for the core volume to support the power we need:
Lets set up a design for 500watts:
The primary current will be equal to :
Ip= 3 *P(out) /V(in)
V(in) will be calculated based on 110VAC line at it highest value:
130 VAC therefore with a voltage doubler we can expect about:
2(130 * 1.4) = 370 VDC after rectifiers
therefore Ip = 1500 /370 = about 5 Amps from this we calculate the input power which is 1500/ .85 for 85% eff which is about 1750 watts.
core size = .68 * P(out) * current density / Fs * Bmax
Choose a industry standard of 500 c.m. /A for current density and we get:
AcAe = .68 * 1500 * 500E3 / 100E3(Fs) * 1200 (bmax) =4.25 cm^4
If we check the ETD49 specs we find that its AcAe is about 5.7 cm^4 which is a good choice for this design
Look what happens when we raise the Fs to 200KHz:
AcAe = .68 * 1500 *500e3 / 200e3(Fs) *1200(bmax) =2.125 cm^4
so you can see the higher the frequency the smaller the core within reason (copper loss, core temp and other things come into play)
In this case we used a Bmax of 1200 and could have used up to 1600, recalucate using 1600 and then we get 3. 18 cm^4 which means we might be able to use an ETD44 coreset now for the turns calculation:
If we use the highest voltage we expect on our transformer windings when the supply turnon:
N(pri) = 370(V(inmax)E8 / (4 * 100E3 * 2400(B(max) *2.11(Ae) =
18Turns for ETD49 and for ETD44 = 23 Turns
Now a good guess for the secondary is Ns = VS/VP I want an output of 35 volts , so that means after the rectifiers I need twice that and to help with transits and load changes I will increase that by 5% or so make it 80 volts , I expect at low line to have about 110 volts after the main rectifiers using a 110VAC input so now my secondary turns will be :
18*(80/110) = 13 turns make it 14, After you wind and test your transformer you might find you need to add or take off a winding or two. And at high line you wil need 11 turns make that 12.
So there is your transformer calculations regardless of how you do it the frequency along with the Amount of flux will determine the output power and the core size along with the size of the winding area and wire size.
All this is more or less what I have found in appnotes,books and other articles plus a little experience mixed in. It is up to the designer or DIY to verify this thru research and reading as this forum is full of material covering this subject and I will not get in a contest with which is right or wrong, however if you find an error or have a question I will try to help if I can and I will correct the errors you find ... just remeber a transformer is just that and the law and priciples for their design is basic and well documented its just when you lump them into a design at high frequency that a lot of care must be taken for them to provide proper results.
یه سایتی رو هم معرفی کرده برای دیدن مشخصات هسته ها :
http://coremaster.com/2000_core.htm
اگر ممکنه اساتید سوئیچینگ ( etgpsp - Ebi SMPS - Ghasede del - ahmadmn و... ) و دوستان گرامی دیگر ، نظر خودشون رو بیان کنند که ایا از نظر فنی مشکل داره و اگر مشکل داره برای رفعش یه اقدامی بکنیم که دوستان علاقه مند در این زمینه هم استفاده ای کرده باشند.
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