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Simple 12V, 1A SMPS Circuit

Simple 12V, 1A SMPS Circuit

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The following content explains two simple 12V, 1 Amp switch mode power supply (SMPS) circuit using the very reliable VIPerXX IC from ST microelectronics.

Overview

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:

1) SMPS using VIPer22A

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 VIPer22A 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.

You may also want to read this: 24watt, 12V, 2 amp SMPS using a single IC Most recommended for you.

Circuit Diagram

simple 12V 1 amp SMPS circuit

PCB Layout

simple 12V 1 amp smps PCB layout

Transformer Winding Data

simple 12V 1 amp smps ferrite transformer winding data

2) Another 12V 1 amp simple SMPS using IC  TNY267

12V 1amp smps circuit using TNY

How it Works

The simple smps circuit shown above uses the popular tiny switch IC TNY267. It is a tiny mosfet based 120V to 220V switching oscillator IC which only requires configuring with a ferrite transformer and a stepped down Vdd operating voltage.

The design is so simple that a mere visualization of the schematic is enough to tell us the functioning details quickly.

The stepped down start voltage is acquired from stabilizing network using a 180V zener diodes and the fast recovery diode BA159 after rectifying the mains 220V through a 1N4007 diodes and the 10uF/400V filter capacitor.

As soon as this voltage is applied to the IC, it begins oscillating and its internal mosfet begins switching the ferrite transformer primary at the predetermined oscillating frequency.

Being a flyback design, the secondary also starts conducting during the OFF cycles of the primary through mutual induction and generates the required 12V voltage at the output side.

This voltage may not be stabilized, therefore an opto-coupler based feedback is used and the link is configured with the exclusive shut down pinout 4 of the IC.

This ensures that the output never exceeds, and remains fixed at 12V 1 amp proportion.

Transformer Winding Data

The transformer winding is actually quite straightforward, and may be done in the following manner. Keep in mind that the black dots indicate the start points of the winding which is very important, and must be strictly followed while winding the transformer.

The primary wound using 36 SWK super enameled copper wire upto 150 turns, while the secondary is wound using 26 SWG wire upto around 12 to 15 turns.

The core can be a standard E19 type ferrite core having a bobbin with central core cross section area of approximately 4.5mm by 4.5mm.

SHARING IS CARING!


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!



172 thoughts on “Simple 12V, 1A SMPS Circuit”

  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!

  2. Circuit is nice
    Can you share pcb file in whatever software you used so that we can use toner transfer method to prepare pcb.
    If you share 1:1 scaled pdf in black and white that is also fine

    Request to share it for all projects ehere uou have shown pcb layout.
    This will be highly appreciable.
    Thanks
    Ulhas rane

    • Thank you,

      The PCB is not designed by me, it was presented by ST microelectronics datasheet for “10 watt air-conditioner power supply”, so I do not have any further details except what is furnished in the above article.

  4. Hi Swagatam,
    Firstly, I must thank you for having this knowledge published in here.

    I need bit more knowledge in making the 2nd circuit.

    In there, I only see two black dots for the transformer. Could you please explain me why?
    Are you able to show a sample picture of a transformer?

    Secondly, by using 7805 regulator, can I get 5V up to 1A?

    Appreciate your advises on above.

    Thanks & regards
    Lakshan Fernando

    • Thank you Lakshan, the black dots indicate the starting point of the winding, and the pins where the respective diode circuits needs to be connected. But since only two ends are present on the two sides you can do the winding without taking this into account. However while testing if you don’t get the required output you can just swap the secondary pins with the diode/filter circuit for rectifying the problem.

      The transformer should like this: https://www.homemade-circuits.com/ee-core-trafo/

      7805 will give you a maximum 1 amp but you may have to mount it on a large ehatsink.

  6. Good day Sir, it is possible to get a 12vdc from a commercially-available SMPS 18-36vdc power supply?
    i thought of adding a 7812 IC, i just don’t know how and what other components needed! thanks!

    • Hi Amor, yes you can use a 7812 with 18V DC to get the required 12V from it. But don’t use with 36V because it will make the IC too hot! A single 7812 on heatsink would be just enough, and if possible add a 100uF/25V at the output

  10. 25 years back if you had asked me to repair any transistor radio, even the ones that came tied in a gunny sack with thousands of pieces – I WOULD HAVE GUARANTEED ITS REPAIR to its near original state. NOW i AM ONLY WATCHING my younger brethren making things work, and believe me I enjoy a lot because they modt certainly stir up whatever grey cells are left up in my brain. Recently a similar smps circuit repaired by some one on you tube employed 8022 (either AP 8022 or AD 8022, i cant say) and repaired a 12V 1A smps supply. I have seen the application circuit on the manufacturers’ site and wish someone could make and tell me in such details as the instant example. Is anybody watching?

  12. 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

    • 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

  16. 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.?

    • 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

  18. 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

    • Plaese refer to the datasheet of the IC for a detailed information about the design

      application-notes.digchip.com/005/5-10593.pdf

  20. 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?

    • 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…

  24. 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.

  26. What is chassis ground?
    How is it different from the normal ground? N how should I connect the chassis ground terminals in practical connection?

  28. 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?

  32. 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

  34. 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?

    • 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…

  40. 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.

  42. Gani, yes you can try it…if the winding comfortably accommodate in the trafo then surely you might succeed in making it work.

  44. Dear sir Swagatam. Using ferrite core of cfl is Ok, by removing out all copper wire and then change to the new one as the data showed here as freq nearly same and hole loc Ok.

  46. 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.

  52. 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.

    • 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.

  54. 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,

    • 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.

  56. 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

    • 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)

  58. 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.

    • 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.

    • 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.

    • Can you please tell me what are the expected voltages at few test points so that I can debug the circuit.

    • 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

    • 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.

    • 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.

    • 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.

    • 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.

    • 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

    • 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?

    • 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.

    • 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

    • 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.

  60. 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

  66. 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 !

    • 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.

  70. 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.

    • yes buddy that's right, if the diodes are faulty it might send AC instead of DC to the caps and blow them of

  72. 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.

    • 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

  74. 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?

    • 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

      • 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?

  76. 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

    • 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.

  78. Thanks for your reply.
    How can we achieve 80 to 300 Volt Range. What changes to be done in above circuit for desired Range

  80. 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.

  82. Hey Swagatam,
    Really good Job, I really appreciate it.
    I am an electronics designer and was looking for such design. I really liked it.
    But can you please suggest me which transformer you had used for this. Is it ferrite transformer. Can you please tell me where can I buy this transformer or at least its part number.

    Thanks in advance.

    • Thanks Krunal,

      The circuit is by STmicroelectronics and indeed it looks superb.

      the transformer is built over ferrite cores since it's an SMPS design, however the transformer cannot be procured readymade, you will have to build it as per the shown data.

      The wire, bobbin and the cores can be easily procured from your local electronic spare part retailer….or if you are in Mumbai you can get these from Lamington Road.

      • Hello Swagatam,

        Thanks for the reply.
        Actually I am from Nagpur and now working at Rajasthan in rural area, Here I could not get them.
        Still I have asked my friend from Mumbai & expect to get them soon.
        Once again Thanks for your help.
        Regards.

  84. Sir, can you please tell me how to design PCB for this circuit. I tried designing the same circuit using Proteus but can't find transformer package in it.

    • 2 amp cannot be achieved with this IC, because 1 amp is the maximum limit from this IC, still you try winding two strands of wire together in parallel for the secondary turns and check the response.

  92. hai,
    I am new, I designed this above circuit. I got some issues VDD Voltage is 4.1 v some viper is not switching,
    can any one guide me.
    thanx

  94. hi sir,
    i m facing problems in calculating primary , secondary and auxiliary winding's.please help me to calculation of exact winding's for 5 V,1 A smps.

    Kindly reply as soon as possible.

    thank you

    • Shaikh, you just have to vary R6 for getting any desired voltage in the range…the winding can be as suggested in the article.

  96. Hello Sir

    I got the current value by changing transformer winding's SWG, but one more problem has taken place, that SMPS is getting too hot, and after that it is restarting it self.

    What can be the problem?

    • Hello Bharat,

      I think the transformer is not wound correctly, please see the black dots those indicate the "start" of the winding….. did you follow those correctly?

      the IC will reset if it detects overload…. which could be either at the output in the form of an actual overload or a wrongly wound primary….

    • OK got it….alternatively you can attach a small aluminum heatsink over the IC…this will stop the circuit from resetting….

    • that's equal to 350 mA which is perfectly within the range of the design…it would be difficult for me to troubleshoot it from here…

      the winding has polarity (start/finish) and that can be crucial, please check it and also try rewinding the secondary by using two strands of wire in parallel instead of one.

  100. Hello Sir

    I have implemented same design on PCB. I'm facing some problem. Like 5 V are coming perfectly on controller board, but when I connect relay board with it, and switch any two relay even, power supply is getting restart. Why this is happening so, i did't got any reason, can you pl help us?

    Kindly reply as soon as possible.

    • Hello Bharat,

      check the current consumption of the relay coil, by connecting a DC ammeter in series with the relay coil.

      or may be you have not made the circuit correctly as per the given instructions.

  102. hi sir,
    i m facing problems in calculating primary , secondary and auxiliary winding's.please help me to calculation of exact winding's.

    Kindly reply as soon as possible.

    thank you

    • Hi Shaikh,

      all the details regarding the trafo winding are furnished at the bottom of the article, please click on the last diagram, you'll find all the required data and the related layout diagram.

  104. hello sir,
    i have design same circuit 12v,1 Amp SMPS. But the problem is when i connect the load and it will consume more then 100mA current then voltage get drop to 11 volt.so could i maintain constant voltage 12 volt along with the load. or if voltage drop does it effect on stability.

    • hello shaikh,

      that should not happen, if you have made it exactly as explained above then the smps should be able to withstand full 1 amp current… at 100mA the voltage should not drop…

      the wire gauge determines the amp capacity of the smps, are you sure you used the specified wire dimensions?

    • 1N4007 is not a fast switching diode, BA159 is a fast switching diode.

      But I have seen many SMPS use ordinary diodes such as 1N5408 etc at the output so you can try a 1N5408 which is same as a1N4007 but much higher in amps.

  114. is there any replacement of D8-STPS2H100? As it is not available in market.

    Kindly reply as soon as possible.

  122. Dear Mr. Arya, it's not so critical, you can make it by winding a reasonably thick magnet wire over any type of ferrite core. Through some trial and error make the number match the shown value approximately….I think about 50 turns using 25SWG wire on any ferrite core would be good enough

  124. Mr. Swagatam this thing is looking great for starter's scenario, can you give the detail about each components you have used in this circuit?

  126. sir i have an ic cd6283cs audio amplifier circuit. i give 12v to use this circuit it gets heated up if input is more. and in datasheet it is given that it can handle upto 171v and utput 1500watts. it will be like that? on 12v only it gets heated then how come it will survive on 171v?

    • Rushi, the datasheet which you have referred to is of a TAZ (transient absorption zener) not your amplifier IC…..

      the datasheet for your IC is probably not available on the net, so can't suggest much about it.

  136. Hello Pankaj,

    555 is an evergreen versatile IC and will be there for at least another 50 years…may be its not available in your area.

    Anyway, in your transistor circuit you can add a 100k pot in series with one of the transistor base resistors, this will give you an option for the required adjustments.

  140. Dear Sir,

    I am student of B.tech ECE.. I was trying to make SMPS of 150W (of voltage range 60 – 210 Volts DC & about 1 Amp. current). You are kindly requested to guide me for the same & oblige. My main problem is which transformer is to be used & the feedback circuit. I shall really appreciate if you could give me entire circuit.

    Thanks & Regards,
    Aseem Mittal (09417753155)
    aseem.mittal19@gmail.com

    • Dear Aseem,

      I don't have much idea about the transformer winding details, so I am sorry I won't be able to help with the project.

      By the way what is the output voltage of the design?

  142. Hi P Pandey,

    You can either connect three 1N5402 diodes in series with the battery and directly connect it with your phone, it will hopefully start charging it.
    Alternatively you can just include a 4 ohm, 2 watt resistor in series with the battery positive and connect it directly with the cell phone for initiating charging of the phone.

  144. yes you can achieve it by adding additional winding layers connected parallel to the existing secondary layer inside the transformer

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