designing a SMPS 220V to 5,7,9V

Thread Starter

Moataz123

Joined Jan 23, 2020
8
Hello,
I'm trying to design a Power Supply SMPS 220v AC to 3 output ( 12v- 9v -5v) each 3Amp
I google it many time but I didn't find a circuit that can give me these ratings and I don't have experience in that
so can someone help me ?
should I use a flyback transformer or what ?

thanks in advance
 

MrAl

Joined Jun 17, 2014
6,949
Hi,

There are reference designs around for single outputs i would think you could start from that and work it into three outputs.
The designs all hinge on using a specially designed high frequency transformer though i am not sure if you want to do that or not.
So look for a single output circuit and see what you think. If you cant find one i'll try to find one myself. I've seen several online before.
The main switching part is usually a self contained IC chip that does everything pretty much. You just supply resistors, diodes, capacitors and that transformer, and an opto coupler.
This is the type of circuit used in many of the modern regulated wall warts that are used to charge cells phones and other things. They no longer use a bulky 50 or 60Hz power line transformer with diodes they use a switching circuit.
If you want to go with a power line type transformer though it gets simpler but that's the old way of doing it.
 

Thread Starter

Moataz123

Joined Jan 23, 2020
8
Hi,

There are reference designs around for single outputs i would think you could start from that and work it into three outputs.
The designs all hinge on using a specially designed high frequency transformer though i am not sure if you want to do that or not.
So look for a single output circuit and see what you think. If you cant find one i'll try to find one myself. I've seen several online before.
The main switching part is usually a self contained IC chip that does everything pretty much. You just supply resistors, diodes, capacitors and that transformer, and an opto coupler.
This is the type of circuit used in many of the modern regulated wall warts that are used to charge cells phones and other things. They no longer use a bulky 50 or 60Hz power line transformer with diodes they use a switching circuit.
If you want to go with a power line type transformer though it gets simpler but that's the old way of doing it.
thank you for replying
I have to design 2 power supplies
the output of the first one 5v, 9v, 12v
the output of the second 5v, 7v, 12v
each output 3A

I found this circuit on the internet, so I'm trying to modify it, does it will work and will be stable or not ?
https://www.homemade-circuits.com/make-this-33v-5v-9v-smps-circuit/

I searched for another flyback transformer and I found this one
https://docs.rs-online.com/86a1/0900766b80107118.pdf

so if I used TOP226Y instead of TNY267P, it will give me the required ratings ?

and how can I choose the suitable values of resistance and capacitances?
 

ronsimpson

Joined Oct 7, 2019
400
There is/was very good software for the TOPxxx power supplies. See if you can find it.

See if you can find a TOP226 design for about the same wattage. Then use the secondary side design for the TNY267.

There are two things that set the output voltage.
1) Turn ratio of the transformer.
2 turns= (3.3V + 0.7V), 3T turns=(5V+0.7V), (5T=9V=0.7) I did not look what type of diode so it the diode loss might be different.
2) The resistor divider in front of the TL431. In the example the 5V and 3.3V are regulated and the 9V is not watched by the TL431. Now the output is set so the average of 5V and 3.3V is what is regulated.
The math can be simple if you think of two (or 3) dividers. Think of 6.34k & 20k in parallel with 20k & 20K. Then the two 20Ks become a single 10k.
1579874633070.png
 

Thread Starter

Moataz123

Joined Jan 23, 2020
8
See if you can find a TOP226 design for about the same wattage. Then use the secondary side design for the TNY267.
So TNY267 will be replace by TOP226 in the primary side of the transformer
but I didn't understand where TNY267 will be putted

and for the required output voltage (5v-7v-12v) &(5v-9v-12v) can I obtain them with this transformer ?
https://docs.rs-online.com/86a1/0900766b80107118.pdf
 

MrAl

Joined Jun 17, 2014
6,949
thank you for replying
I have to design 2 power supplies
the output of the first one 5v, 9v, 12v
the output of the second 5v, 7v, 12v
each output 3A

I found this circuit on the internet, so I'm trying to modify it, does it will work and will be stable or not ?
https://www.homemade-circuits.com/make-this-33v-5v-9v-smps-circuit/

I searched for another flyback transformer and I found this one
https://docs.rs-online.com/86a1/0900766b80107118.pdf

so if I used TOP226Y instead of TNY267P, it will give me the required ratings ?

and how can I choose the suitable values of resistance and capacitances?
Hi,

I was actually thinking of the TOP family of converter chips.
The TOP227 does 150 watts.

I only fear that you dont have much experience with these kinds of converters and there are some dangers that you have to be careful about.

Check out www.powerint.com for design info.
 

Thread Starter

Moataz123

Joined Jan 23, 2020
8
Hi,

I was actually thinking of the TOP family of converter chips.
The TOP227 does 150 watts.

I only fear that you dont have much experience with these kinds of converters and there are some dangers that you have to be careful about.

Check out www.powerint.com for design info.
yes, Unfortunately, I don't have experience in that but I have to do these power supplies
so can you help me ?
 

MrAl

Joined Jun 17, 2014
6,949
yes, Unfortunately, I don't have experience in that but I have to do these power supplies
so can you help me ?
Hi,

I can get you going in the right direction but i am not sure if i want to do the entire design. I'll have to read up on these devices again and see what i can find out. But i do fear that you seem to have just a little experience in power converters and that may mean that you cant get it working riht. I hope you can, but you should realize that power converters are special devices that have some nuances that only people that work with those kind of converters would know. This means sometimes you have to find someone that designed one already of that kind.

The converters i designed were not of that type, although the designs i see on the web seem simple. But i also wonder do you have the experience to wind a transformer of this type?
Maybe you can describe briefly what kind of electronic stuff you have worked on in the past that would help me understand your standpoint a lot better. In the mean time, i'll try to read up on these particular type of converters.
Oh yeah also, what kind of test equipment do you own or can get a hold of? Testing the design is a very important aspect of a new design.
 

dendad

Joined Feb 20, 2016
3,253
You have asked the same question in multiple threads. I think you should stick with this homework thread only.

The only mains switchmode supply I designed was based around a TOPswitch part.
Be very careful as they involve dangerous power levels. And be prepared for smoke ;)

Are you actually going to build a supply or is this just a design exercise?
 
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Thread Starter

Moataz123

Joined Jan 23, 2020
8
Hi,

I can get you going in the right direction but i am not sure if i want to do the entire design. I'll have to read up on these devices again and see what i can find out. But i do fear that you seem to have just a little experience in power converters and that may mean that you cant get it working riht. I hope you can, but you should realize that power converters are special devices that have some nuances that only people that work with those kind of converters would know. This means sometimes you have to find someone that designed one already of that kind.

The converters i designed were not of that type, although the designs i see on the web seem simple. But i also wonder do you have the experience to wind a transformer of this type?
Maybe you can describe briefly what kind of electronic stuff you have worked on in the past that would help me understand your standpoint a lot better. In the mean time, i'll try to read up on these particular type of converters.
Oh yeah also, what kind of test equipment do you own or can get a hold of? Testing the design is a very important aspect of a new design.
You have asked the same question in multiple threads. I think you should stick with this homework thread only.

The only mains switchmode supply I designed was based around a TOPswitch part.
Be very careful as they involve dangerous power levels. And be prepared for smoke ;)

Are you actually going to build a supply or is this just a design exercise?
I design before a small power supply using the traditional transformer, 220v to 5vdc using 7805 (linear voltage regulator),
also I have made a transformerless power supply
+ many electronics project but my problem is the lake of experience in Power electronics

concerning the required SMPS, my task is to design the schematic and doing a simulation so I will try it on a simulation software
 

ronsimpson

Joined Oct 7, 2019
400
do you remember its name ?
"PI Expert Online" I have not used the online version I use the on my computer version.
I would try the software to make it simple try a 9V 50 watt supply and see what happens. Give me the schematic and transformer the software give you then we can add the 3.3V and 5V.
----edited----
I just went through a design and I get 3.3V, 6.7V, 9.6V. Because the number of turns are small the options are limited. In this example 1Turns=3.3V so 2T=6.6V and 3T=9.9. I could change the transformer for 1.65V/turn and get 2T=3.3, 3T=4.95, (5t=8.3 or 6t=9.96). Or maybe try 1.1V/turn 3T=3.3V, (4t=4.4V or 5T=5.5V), 8T=8.8v.
 
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