The following content explains a simple 12V, 1 Amp switch mode power supply (SMPS) circuit using the very reliable VIPerXX IC from ST microelectronics.
Introduction
With the advent of modern ICs and circuits, the age old iron transformer type of power supply are surely becoming obsolete. Today power supplies are much compact, smaller and efficient with their functioning. Here we discuss one outstanding switch mode power supply circuit which can be easily built at home for deriving clean, ripple free 12 V DC.
Thanks to ST Microelectronics IC, the VIPer22A, which has made the construction of truly efficient and compact SMPS power supply unit possible that too by using a very few number of electronic parts.As can be seen in the picture, the circuit is indeed very small, compared to the power that is available from it. It's just 50 by 40 mm in its dimensions.The circuit diagram is very easy to understand, let's study it with the following points:
How the SMPS Circuit is Designed to Work
Looking at the figure we can easily see that the configuration does not involve too many stages or parts.
The input mains AC, as usual is first rectified using ordinary 1N4007 diodes which is fixed in the bridge network mode.
The rectified high voltage DC is filtered using the high voltage capacitor.
The next stage is the crucial one which incorporates the outstanding chip VIPer 22A manufactured by ST Microelectronics.
The IC alone functions as the oscillator and induces a frequency of around 100 KHz into the primary winding of the ferrite E core transformer.
The IC is absolutely rugged and is internally protected from sudden voltage in rush and other voltage related component hazards.
The IC also incorporates built in over heat protection which makes the IC virtually indestructible.
The voltage induced at the input is effectively stepped down at the output winding, due to low eddy current losses, about 1 amp current becomes available from a relatively tiny ferrite transformer.
With the coil specs shown the voltage is around 12 and the current is around 1amp.
A special feedback circuitry is also included in the circuit for maintaining high degree of protection and power saving features.
The feedback loop is implemented via an opto-coupler which becomes active during abnormal circuit conditions.
When the output voltage tends to rise beyond the set threshold the feed back loop becomes operative and feeds an error signal to the IC FB input.
The IC instantly comes into an corrective mode and switches off the input to the primary winding until the output returns to the normal range.
Circuit Diagram
PCB Layout
Transformer Data
Okeya Boboye says
Hello please I am trying to build a battery charger with this smps.
I want to obtain 12V, 3A for the output.
Input would be about 220V, 50Hz.
How can I manipulate your design and also select the right material, that will give this requirement?.
Thank you
Swag says
Hello,
sorry higher current than 1 amp may not be possible from this design unless voltage output is reduced below 12V, because the IC is rated to handle a maximum of 1 amp
Krishnam says
Is the specific transformer available in market? Or have i to design it myself?
Swag says
as far as I know it is not available in the market, you will have to build it according to the specified details
Adrees mohmand says
Hi sir.
This blog make my problem easy. but i have a question. if i increase the winding turn in parallel for achieving high current at output i-e (7A-10A), while keeping remaining circuit unchanged. Is this is possible.?
Swagatam says
Thanks Adrees, sorry that may not be possible because the mosfet inside the IC itself is not designed to deliver that much current, the maximum rating being just 1 amp
Faiq Ahmed says
can you please understands me the feedback with voltage refrance how it works to regulate the voltage? also tell this topology is DCM or CCM .one more thing how this ic can use tfor both modes interchangeabily
Swagatam says
Plaese refer to the datasheet of the IC for a detailed information about the design
http://application-notes.digchip.com/005/5-10593.pdf
Harish Kr Singh says
Hi, please tell me how to modify this circuit & transformer to make 24V DC/500mA output?
1. Will it work if I double the secondary winding and primary & auxiliary remain the same as in above circuit?
2. I'm planning to replace 7805 with 78L05 that will lower the output current to 5V/100mA, this will increase maximum current of 24V output. will this work?
2. Should I need to change value of L2, R3 or any other discrete component?
Swagatam says
Hi, yes that's possible, you can try increasing the secondary turns to around 30 turns and also tweak the R6/R7 values to get 24V…a 780L5 can be used for restricting current, but a better way would be to make sure that the load connected with 78L05 is itself not rated to consume more than 100mA…
FHATUWANE KINGSLEY Tshiovhe says
Hi. can I still use LNK623 instead of using viper22a??
Swagatam says
It cannot be used in the above design, LINK switches have their own specific circuit which you can follow
FHATUWANE KINGSLEY Tshiovhe says
Hi, can I buy that transformer at any electronics store or I have to build it myself???
Swagatam says
Hi, you will need to build it yourself or get it made-to-order, ….it's not available ready-made.
Faiq Ahmed says
Aoa how r u? Brother i have made it but problem is that it show 12 v on DMM but when i connect with led light it drop to 8 volts .where is problem?
Swagatam says
Hi Faiq, what is the voltage and current specs of the LED??
Please note that the transformer is the cubical element in this design and in fact that's true in all SMPS designs….so make sure you have built the transformer with utmost accuracy….if possible please get it build from a professional winder…
Swagatam says
sorry there's a typo in the above comment….I meant to say crucial and not cubical…
Anonymous says
Sir, whether supply should be 230v or what?
I mean i gave 230v supply and thermistor blowed off. What shoulf i do??
Swagatam says
yes it is designed to work with 220V mans, I think you might have done something wrong in the design…get a professional help from any nearby source
Unknown says
Sir. What does chassis ground mean and how is it different from ground symbol?
N how should i connect the chassis ground terminals in practice connection?
Nitishkumar Ar says
What is chassis ground?
How is it different from the normal ground? N how should I connect the chassis ground terminals in practical connection?
Swagatam says
chassis is supposed to be the metallic cabinet inside which the circuit is housed.
the negative line of the circuit is supposed to be connected with this metallic cabinet, and the metallic cabinet in turn is supposed to be connected to the mains earth pin via the mains cord.
Mark Anthony says
Ok.tnx for advice.ill try that one.
Swagatam says
Hi Mark, I am not sure exactly what you are intending to make, I guess the following circuit might be more suitable to your need
https://homemade-circuits.com/2011/12/simple-led-automatic-daynight-lamp.html
Mark Anthony says
I gave up on modifing the already made smps and returned it to my friend.instead ill copy your design.
https://homemade-circuits.com/2011/12/cheap-yet-useful-transformerless-power.html
with 12v(load)led in series and ldr in the middle. I have some question.
Do i need to adjust or raise the voltage so that the led would make its highest performance? My parts are
Ldr
Transistor npn
100k variable resistor
1k resistor
Is it ok to add regulator ic.lm7812.i got some spare.just for added protection.
Mark Anthony says
Good day to you sir..
Can you pls help me design an smps for 12volts for an led with label dw-5630-6led-2b3c. With an LDR switch.
Im a newbie on electronics and wanted to learn more.cheaper parts would be much appreciated.
Swagatam says
Good day Mark, please tell me the voltage and current specifications of the LEd, you can get it from the datasheet of the part, that will help me to understand your requirement in detail
Mark Anthony says
Quantity: 3; Emitter Type: 5630 SMD; Total Emitters: 6; Power: 3 W; Color BIN: White; Rate Voltage: 10 V
Mark Anthony says
The current is 1amp.i have many question and problems.hope you could help me learn more..
Swagatam says
dividing 3 by 10 gives 0.3 amps
multiplying it by 3nos gives around 1 amp.
It means you can use the SMPS circuit that's explained in the above article for your need…
R6 or R7 can be suitably adjusted for reducing the 12V to 10V
Mark Anthony says
Tnx for your help… can i ask what is the voltage needed for the ldr?
Swagatam says
you can connect the LDR in parallel with R6, during daytime this combination will hopefully keep the opto switched ON and the SMPS output switched OFF
Mark Anthony says
Tnx for your help sir.. your ideas are great.
Swagatam says
you are welcome!
Mark Anthony says
Good day to you sir swagatam..
A new problem came up.
When my ldr is lighted and decreases risistance the smps increases its voltage.thats the reason why my led wont go totally off.does putting a regulator would help(lm7810) solve the issue?
Hoping to learn more from you sir..
Tnx
Swagatam says
Mark, manually experiment by changing the R6 or R7 values and identify which adjustment causes the most effective disabling of the output…you can then put the LDR in parallel with that resistor for the required response
Mark Anthony says
Sorry to cause you so much trouble.but actually the smps i was refering to was an already made one.with some smd type of parts.
Is there a way i can modify it outside the already made smps??
Swagatam says
in that case you can use an external light activated switch such as this one:
https://homemade-circuits.com/2012/01/how-to-make-light-activated-day-night.html
Swagatam says
modifying the smps circuit could be difficult without studying the stages carefully
Jeran Toledo says
Sir how to make power supply 12v. With switch
kakipancingMUAR bandardiraja says
hello sir,
thank for the great sharing.
from the circuit i see the out is 12V and another voltage regulator at 5V.
what is the current for 5V?
i want to build a PSU, for 12v 1amp and 5v 2amp. if i can combine the circuit. it will be superb.
thank you in advance for guide.
Swagatam says
thank you kakipancingMUAR
the shown 5V would be also producing a max current of 1 amp.
5V 2 amp could probably be achieved by extracting a calculated tap from secondary and terminated out without a 7805.
ASPERO Research says
how to calculate Transformer parameter to increase current?
Sujit Chavada says
Hello Sir,
I am new in SMPS design. I am facing a problem in this SMPS. SMPS remain ON for 15 second, after that it going to OFF for 7 second, again ON for 15 second and again OFF for 7 second. Such cycle continue. In ON condition, it giving 13.8V and in OFF condition it giving 0.8V. I apply 12V/100mA DC motor as a load. Kindly help me in this problem.
Thank You,
Swagatam says
Hello Sujit, It would be difficult to understand the issue precisely, but normally this would happen if the IC is going in the shutdown mode due to overheating or over current.
This would most probably happen due to a wrongly configured transformer….check the inductance of the primary it should match the given specification.
also add a small heatsink with the IC.
pankaj pandey says
hello sir,
how are you sir…after a long time i am here again with my another quarry …dear sir I have a inverter and it is giving me some problems…the problem is regarding to its charging function…earlier it starts trickle charging to the battery..when voltage reaches to 14 volt..but now it does not cuts the power after full charging of the battery…when the battery fully charged …then inverter makes humming sound and burnt the ac fuse..
So kindly help me about the problem..
Thanks a lot
Pankaj pandey
Swagatam says
Hello Pankaj,
it would be difficult to judge without a practical diagnosing. most probably the relay associated with the full charge cut off circuit is responsible for this….it could be correctly tripping at the full charge level but in the process shorting something through its other pair or contacts.
check the response of the relay by supplying a varying voltage through a variable power supply across the battery points (without any batt connected)
Krunal bhongade says
Hi Swagatam,
Thanks for great tutorial.
I am trying this circuit and getting the result.
Now I am drawing 80mA of current at 12V through this circuit and it works perfectly. But when I increase the load to 150mA, the ST Viper22A gets too hot and cuts the supply for some time so the output voltage falls from 12V to 2V. After sometime it again starts supplying 12V.
The IC is getting overheated and it trips. Could you please suggest something.
Thanks in anticipation.
Swagatam says
Hi Krunal, this circuit is rated to handle upto 1 amp, so 150mA shoudn't be a problem at all, not sure what might be causing this, most probably if the transformer is not built correctly could cause the circuit to malfunction, so it could be your trafo that's not correctly wound, please check it again and if possible take the help of a professional winder.
the above design is by STmicroelectronics so it should be perfectly correct with its data, for more info you can visit the original website from the given link in the article.
Krunal bhongade says
Hello,
Thanks for the reply.
I had given this transformer winding data to a professional manufacturer from Delhi and he has built it using the same data. Moreover the transformer is not at all heating up but its only the IC to heat up. I checked the voltage at Vdd of IC which I found to be -2V which seems to be wrong(still the output vtg is 12V), also the output of the rectifier is just 5V. All the components are cool while the IC is heated up.
Any suggestions.
Krunal bhongade says
Can you please tell me what are the expected voltages at few test points so that I can debug the circuit.
Krunal bhongade says
Sorry for wrong readings. I was taking wrong reference ground.
The voltage at Vdd pin of Viper22A is 12 VDC and
voltage across rectifier capacitor (47uF/400V) = 318 VDC
Swagatam says
The transformer will not heat up, it is the fet inside the IC which will heat up if the winding are not correctly wound….especially theprimary winding is the one which will can make the IC hot if not wound correctly. According to the data the inductance of primary winding must be 3mH, please confirm this first…moreover all the winding has polarity which can also create an issue.
I am not sure about the voltages at different points, and is basically not required to be checked, because if the winding is correct and the IC is genuine then the circuit should work at the first go….considering the connections are all OK.
Krunal bhongade says
Hi, Thanks for all your suggestions.
Can I just reverse the primary winding and check? Will it cause any problem?
Also I do not have any LCR meter to check inductance.
I have ordered my components from element14 so IC should be genuine.
Also I am getting 12V at the output upto 80mA, so I think the connections are also OK.
Please suggest.
Swagatam says
Hi, I think it can be tried, you can reverse the primary ends with the circuit and see the effect…however checking the inductance is more important as that would quickly help to solve the issue.
Krunal bhongade says
Hello, Good Morning.
I checked by reversing the primary ends, but this time I was not getting any output voltage at the output.
I have asked my friend to measure the inductance of it, and will update here after I get result.
Also, I would like to know if the IC is only used for switching, can I replace it with another MOSFET or optocoupler and driving it with 60KHz using LM555.
Also, I am not able to understand how the auxiliary winding is able to supply 12V to this IC.
I would like to know your experienced suggestions.
Thanks in advance.
Swagatam says
Good morning, The above circuit cannot be modified in anyway and is not recommended, if you want to use discrete parts for the making the same design then you can try the following circuit:
https://homemade-circuits.com/2013/10/12v-24v-1-amp-mosfet-smps-circuit.html
the internal circuitry of the IC is initially switched ON through the drain connection, which internally applies a triggering voltage to the Vdd (@1mA), this action switches ON the mosfet which in turn causes the auxiliary winding to kick and apply a rising unregulated voltage to Vdd…when this voltage exceeds the internal limit, the internal regulator switches OFF, causing the mosfet and the IC to switch Off….the cycle now keeps repeating the sequence at around 60kHz
Krunal bhongade says
Hello, So I got the measured inductance and is only 0.046 mH.
I don't understand why my manufacturer did not paid attention to this.
What should I do now? Will it work just by adding an inductor in series?
Swagatam says
Hi, you should get it done afresh and this time from a qualified winder who knows how to measure and assign the inductance values to the coils, because it seems this trandfrmer could have many winding errors .
adding a series coil will not do.
If you are in Mumbai get it done from Lamington road.
or if you have the access to a hand winding machine you can try it yourself at home.
Krunal bhongade says
Ohh, I am overwhelmed with your detail description, Thanks.
Yes, I think I have to look for another winder.
I am working in very rural area of Rajasthan without any access to advanced things except internet (Thank GOD). Also I have never been to Mumbai before. Still I would try to do something.
I am doing this as for my hobby. It would be really nice if you can suggest some winder.
Thank You very much for all your help.
Regards,
Krunal
Swagatam says
You are welcome Krunal, I hope you get the issue resolved as soon as possible.
winders can be difficult to find online, alternatively you can try it winding by hand… with a lot of care and patience you could possibly succeed with it.
lokesh lokesh says
Hello sir plzz plzz do update same sort of post on FB.. Instead of here..
in Fb we can comment and have ur reply notification here really feeling hectic to find reply or comments back..
even for typing..
since this method is not much user friendly and transparent. it my suggestion
on behalf of everyone I am requesting u since some of my (electronic hobbyist) friends are having same opinion.. as most of us don't use Email and this website much compared to Fb and WhatsApp in there phone..
I respect ur knowledge and patience so I wish its being utilised to everyone in proper way..
i hope my msg convinced…
seeking for your valuable reply. .
Thank you regards your Fan Lokeshelectronic
Swagatam says
Hello Lokesh, I appreciate your emotions, however since this is my site so I will want visitors to come to my site, not to some external site like facebook.
moreover it's not at all difficult to comment and receive replies from my site…you just have to tick the "notify me" box and all my replies will reach straight to your email.
even anonymous readers can post questions here
Aqilah Zainuddin says
Hello Sir. Would you mind sharing your PCB in PDF file? Thank you Sir 🙂
Asket Bhullar says
Soooooory… its TRUE !
Asket Bhullar says
3 pin triac is not IC . Any chip with 4 or more pins is called IC, this is what I learned. No intention of insult pl. But I like Ur up-frontness, pl never hesitate for what ever comes to ur mind, Love U !
Swagatam says
sorry I am not sure to which comment you are addressing to?? but answering to your suggestion I must say that a 3-pin device can also be an IC….take for example 7805, 7812, TL431 these are all ICs.
Asket Bhullar says
I'll get back 2marow.What do u feel about the bleeder resist after the MOSFET !
Swagatam says
mosfet is inside the IC
Asket Bhullar says
Thanks Bud, let me check up. Other thing which came to my mind to check the bridge diodes indevudaly . I,ll get back on the outcome.
Swagatam says
yes buddy that's right, if the diodes are faulty it might send AC instead of DC to the caps and blow them of
Unknown says
I am Office Automation Techi, I have a problem with one power supply SMPS, there is a 470 mfd 400v capacitor after bridge rectification on A/C side getting blown even after changing the MOSFET along with it. Its blown thrice even after checking the rest of circut. It is further found that MOSFET is not burning.
Swagatam says
check the voltage across the capacitor points, if it's exceeding 400V then that might be causing the explosion….if voltage is not the issue then probably you can try a non-polar capacitor and see if it works…a bad quality capacitor can also be the culprit
Bharat Surani says
Hello Sir
currently we are using original ST L7805, the issue with it is, we converting 12v DC to 5v DC for consumption of up to 50mA. After putting it on testing we come to know that L7805 is heating too much, temp is not being measured yet, but it is enough to burn up your finger, will it make any kind of damage to further circuitry or L7805 will burn out within small life time?
Swagatam says
Hello Bharat, if it's getting hot at 50mA then either the IC is not original (faulty) or there's some mistake in the connections.
Please measure the current using an DC ammeter in series with the load.
78XX can never get burning hot since they all have an internal thermal protection facility which don't allow their case temp to go beyond 100 C
when hot the IC will simply cut of the supply to the load and shut down itself until the heat reaches within the tolerable limits
Bharat Surani says
Yes sir, I have both kind of 7805, the original one and fake identified by it's heat sink thickness. Both are getting warm up, where in the connection, I have 12V at pin1, Gnd at pin2 and 5V output at Pin3. I'm using 12v 1A ready made power adapter as source and converting it to 5V for controller. Is there any corrections needed?
Swagatam says
Bharat, please check the output current consumption, I am sure it cannot be just 50mA..please confirm this.
Bharat Surani says
Sir, I'm double sure about the consumption, I have also studied the datasheet of components used. It is not exceeding 50mA.
Swagatam says
at 50mA any 78XX will not become burning hot according to me. Not sure what could the fault in your case.
Bharat Surani says
Sir, is there any other connections needed? around 78xx.
Swagatam says
left pin is input, center is ground, and the right side pin is the output for the load, that's all is required for getting the results from this chip….no further connections are required.
Bharat Surani says
Ok thank you sir for reply. One last que. is there any specified life time of ST L7805?
Swagatam says
thanks bharat, if the IC is operated within its specified tolerable limits then it can go on almost forever.
Bharat Surani says
Thanks a lot for suggestions sir.
VISHAL says
Ok. If possible please suggest any other IC for range 80-300 Volt AC.
Also do you have any tutorials related to Photodiode Interfacing. I am facing a lot of fluctuations while designing Signal Conditioning Circuits for BPW34
Swagatam says
sorry, I do not know about any SMPS IC with that input range.
You can try LM567 IC for signal conditioning of the photo diode.
VISHAL says
Thanks for your reply.
How can we achieve 80 to 300 Volt Range. What changes to be done in above circuit for desired Range
Swagatam says
that might not be possible because the IC is rated for 85V to 285V operation, which cannot be changed.
Swagatam says
…actually it's 265V and not 285V, so it's even less than what I mentioned
VISHAL says
Hello
Can we use the above circuit with an Input AC Voltage range of 80 Volt AC to 300 Volt AC with Output Voltage Constant 12 Volt, 1 Ampere.
Swagatam says
the operating range is from 100V to 285V