A very compact simple transformerless power supply circuit is explained here using the concept of capacitive reactance for stepping down the input AC mains voltage.
The Transformerless Power Supply Concept
A transformerless power supply works by using a high voltage capacitor to drop the mains AC current to the required lower level which may be suitable for the connected electronic circuit or load.
The voltage specification of this capacitor is selected such that it's RMS peak voltage rating is much higher than the peak of the AC mains voltage in order to ensure safe functioning of the capacitor. An example capacitor which is normally used transformerless power supply circuits is shown below:
This capacitor is applied in series with one of the mains inputs, preferably the phase line of the AC.
When the mains AC enters this capacitor, depending on the value of the capacitor, the reactance of the capacitor comes into action and restricts the mains AC current from exceeding the given level, as specified by the value of the capacitor.
However, although the current is restricted the voltage isn't, therefore if you measure the rectified output of a transformerless power supply you will find the voltage to be equal to the peak value of the mains AC, that's around 310V, and this could be alarming for any new hobbyist.
But since the current may be sufficiently dropped level by the capacitor, this high peak voltage could be easily tackled and stabilized by using a zener diode at the output of the bridge rectifier.
The zener diode wattage must be appropriately selected according to the permissible current level from the capacitor.
CAUTION:Please read the caution warning message at the end of the post
Advantages of using a Transformerless Power Supply Circuit
The idea is cheap yet very effective for applications that require low power for their operations.
Using a transformer in DC power supplies is probably quite common and we have heard a lot regarding it.
However one downside of using a transformer is that you cannot make the unit compact.
Even if the current requirement for your circuit application is low, you have to include a heavy and bulky transformer making things really cumbersome and messy.
The transformerless power supply circuit described here, very efficiently replaces a usual transformer for applications which require current below 100 mA.
Here a high voltage metalized capacitor is used at the input for the required stepping down of the mains power and the preceding circuit is nothing but just simple bridge configurations for converting the stepped down AC voltage to DC.
The circuit of a cheap transformerless power supply shown in the diagram above is a classic design of a transformer less power supply circuit and may be used as a 12 volts DC power supply source for most electronic circuits.
However having discussed the advantages of the above design, it will be worth focusing on a few serious drawback this concept may include.
Disadvantages of a Transformerless Power Supply Circuit
First, the circuit is unable to produce high current outputs, but that won’t make an issue for most of the applications.
Another drawback that certainly needs some consideration is that the concept does not isolate the circuit from dangerous AC mains potentials.
This drawback can have serious impacts for designs which have terminated outputs or metal cabinets, but won’t matter for units which have everything covered up in a non-conducting housing.
Therefore, new hobbyists must work with this circuit very carefully to avoid any electrical casualty. The last but not the least, the above circuit allows voltage surges to enter through it, which may cause serious damage to the powered circuit and to the supply circuitry itself.
However in the proposed simple transformerless power supply circuit design this drawback has been reasonably tackled by introducing a high voltage capacitor after the bridge.
This capacitor grounds instantaneous high voltage surges, thus efficiently safeguarding the associated electronics with it.
How the Transformerless Power Supply Circuit Works
The working of this transformless power supply can be understood with the following points:
- When mains AC mains input is switched ON, capacitor C1 blocks the entry of the mains current and restricts it to a lower level as determined by the reactance value of C1. Here it may be roughly assumed to be around 50mA.
- However, the voltage is not restricted, and therefore the full 220V or whatever may be at the input is allowed to reach the subsequent bridge rectifier stage.
- The bridge rectifier rectifies this 220V C to a higher 310V DC, due to the RMS to peak conversion of the AC waveform.
- This 310V DC is instantly reduced to a low level DC by the next zener diode stage, which shunts it to the zener value. If a 12V zener is used, this will become 12V and so on.
- C2 finally filters the 12V DC with ripples, into a relatively clean 12V DC.
PCB Layout for the above explained simple transformerless power supply is shown in the following image. Please note that I have included a space for an MOV also in the PCB, at the mains input side.
WARNING: THIS CIRCUIT IS NOT ISOLATED FROM MAINS AC, THEREFORE ALL ITS POINTS ARE EXTREMELY DANGEROUS TO TOUCH WHEN CONNECTED TO MAINS AC........
youngking says
good day sir, thanks for the good work u’re doing for man kind. pls can u sugest the kind of transformerless variable power supply circuit i can use to set your circuit i just came across which is twin/split change over circuit because i can’t afford transformer type. thanks i will be walting for ur response.
Swag says
Hi Young king, what is the current requirement of the power supply? if it’s over 200mA I won’t recommend a capacitive power supply
Godson says
Hello sir Swagatam,
I needed a transformerless power supply that can conveniently be used to power an IC and you referred me to this article. Thank you very much sir.
In my application, the circuit will be permanently connected to mains supply, so I need it to be very free from power surge so that the connected components will not damage during operation. What modifications do I need to make in order to achieve this?
Swag says
Hello Godson, you can use the recommended design as given in the above article, just make sure C1 is selected as per the circuit’s current rating, for example if the current consumption of the circuit is 20mA, you can use a 0.33uF for C1 and so on…
Kesava Raj says
Instead of using zener we can use voltage regulator like LM7805 & 7812…
Swagatam says
ICs can be prone to surge currents, and can get damaged, zener diode is more appropriate
Kesava Raj says
For example if i use more then 3uf to 5uf capacitor. Need to increase zener watts or 1 watts enough.
Thank u sir…
Swagatam says
yes, then you will have to calculate and upgrade the zener power accordingly…yo can calculate the input current from the capacitor through the formulas as explained in the following article
https://homemade-circuits.com/2015/01/calculating-capacitor-current-in.html
or this one
https://homemade-circuits.com/p/capacitor-reactance-calculator.html
Kesava Raj says
Hai sir…
Small confusion sir…
I try this circuit using 224 capacitor..and i not use zener and R2..
The output coming 39 to 40v…
My doubt is if i use 12v zener o/p will come 12v means.. remaining 28v what happen sir,,if zener will cause damage or nothing happen…
For eg if o/p coming 150v means if we use 6v zener what happen .o/p will 6v or zener will damage sir…
Is there any limitations voltage to use zener?…pls guide me sir..
Without using R2 we can connect zener or not…R2 is used for voltage drop sir..
Pls tell 224 capacitor current value..
Swagatam says
Hi Kesava,
the excess volts will get shunted through the zener diode to ground.
the zener voltage has no restrictions, you ca use any.
you can use it without R2…. but R2 is recommended, and it can be lower than 50 ohms…
however if the input capacitor value is above 1uF then higher than 1 watt zener might be required…
Indrawan says
Dear Mr. Swagatam,
i have a mosquito zapper with 4v lead-acid battery in it. the charger circuit is similar as above, with C1=474 (is it 470nF?), no R2,Z1,and C2.
how to limit the charging voltage to say 4.5-4.6v to keep the battery in float charge range?
thank you.
Swagatam says
Hi Indravan, you can do that by simply using a 4.6V zener diode for Z1, or alternatively replace Z1 with 8nos of 1N4007 diodes in series, with its cathode towards the ground line side.
Indrawan says
about the 8-series of 1N4007, does they put in paralel with the battery?
so the anode of 1st-diode connected to batt(+) and the cathode of the last-diode connected to batt(-)?
and does the capacitor C2 is needed for this case?
Swagatam says
yes that's correct, C2 is optional, but including C2 would allow more average current to the battery and therefore faster charging
Indrawan says
Dear Mr. Swagatam,
i have put 8-series of 1N4007 in paralel with the battery, and my multimeter reads steady 5.29v at the battery terminals.
would you please help me to understand about the calculation here? why it needs 8-series of diodes and why my multimeter reads 5.29v?
please be patient with me sir, as i am completely newbie in electronics and still have my basic learning curve for it.
Swagatam says
Hi Indravan, due to its internal characteristics a diode would block around 0.6 to 0.7V and short-circuit the rest of the voltage when its conducting or in the forward biased condition… , which implies that 8 diodes would block 0.6 x 8 = 4.8V…therefore the output would show 4.8V.
In your case it's showing 5.29V which looks quite high, to correct this you can try reducing a couple of diodes in the series and adjust the output to the preferred lower level.
Indrawan says
it got quite steady as i need with 6-series of diodes.
thank you very much for your kind explanation Sir. 🙂
Swagatam says
you are welcome!!
Rajib says
Dear brother I made this power supply for my LDR light circuit. I made a PCB for that circuit including this power supply and found around 12.5 VDC across the capacitor diode. But the problem is the 12V relay is vibrating and the glow of the light is very low. When the circuit is powered from a separate DC source across the zener diode the circuit works perfect; no vibration. Is there any modification is required to use this power supply? Please advise.
Swagatam says
Dear Rajib,
you will need to connect another capacitor parallel to C2 with a value around 1000uF/50V, this will solve the issue
Rajib says
Dear brother, now its working perfectly. Can I remove capacitor C2 as 1000uF/50V has been added?
Swagatam says
Hi Rajib, C2 will help to safeguard switch ON surges better, if you want to remove it then make sure to connect an NTC thermistor at the input mains side of the power supply to prevent switch on surge into the connected circuit.
kirams says
Swagatam, thank you for your kind responses since 2013 and probably earlier!! Hats off to your consistency. I read through all the responses written on this page.
I came here to find if I can charge Li-Ion battery (The one in dead cell phone) using this circuit and you said it is not possible. But didn't get why it should not work. cell phone battery rating is 3.7v-4.2v. if we configure the circuit to give 5 to 6 v, 50mA would be more than sufficient for charging current, only thing is about auto cut-off. You had suggested cell phone charger circuit for Li-Ion batteries but should I directly connect the Li-Ion battery across 5V SMPS output. This is where I've stuck.
Other interesting note I wanted to tell others is your circuit is used in most cheap chinese mosquito zapper bats. Since it is cheap, it does not have zener diode and instead of capacitor, they have connected battery to be charged. So, I was thinking if I could use Li-Ion battery instead of Lead acid battery that they have.
Sorry, I've asked many questions and comments but please direct me to appropriate threads. and thanks for your help
Swagatam says
Thank you Kirams, I greatly appreciate your involvement with my site!
Li-Ion cells are costly and highly efficient cells and that's why I don't recommend charging them with the above cheap transformerless type design, where even the mains is not isolated.
It is ofcourse possible to use these power supplies for charging a Li-ion cell but is not advisable.
Li-ion normally accept and work with high current, for quick charging, which the above design may be incapable of delivering therefore the overall feeling is that one should avoid using such crude and dangerous versions of power supplies rather use an SMPS or transformer based designs.
Still if you plan to try it make sure you include the zener diode, otherwise it can become even more dangerous for the cell.
lima toshi says
Thank you thank you Swagatam you are the greatest, I was like 50% sure about adding extra ppc but I guessed it right lol but its all because of you sir, I am learning a lot only after I found your great site, wish I had found it sooner but its never too late BTW I never thought I will learn so much in less time, and its all because of great and kind man like you who gives hope to new beginners like me, in what we just loves to spend time on whenever we get time. God bless you sir. Looking forward to learn as much as I can. Keep up the great work, appreciated.
Swagatam says
You are welcome Lima, keep posting your queries, your involvement will help others also to learn more… keep up the good work…
lima toshi says
OK, surely i will(: thank you so very much sir, i just love this site… keep up..
lima toshi says
Ok, so I just have to add extra ppc to get the amperage needed, anyways thanks to you sir, I am learning a lot.
Swagatam says
yes that's right!!
lima toshi says
OK what i have learned so far:lol…. if i connect two extra Z2 and Z3 in series and parallel, will i get 24Volt-@2amp. Thank you.
Swagatam says
you are partially correct, it will give you 24V, but not 2 amp current, because current level is determined by the input capacitor value…..you can read more on this here
https://homemade-circuits.com/2015/01/calculating-capacitor-current-in.html
Norman Kelley says
Thanks for the quick response! I will build the circuit as soon as the parts arrive. Have a nice day!
Swagatam says
OK thanks!
Norman Kelley says
Hi, Swagatam,
In the above simple transformerless power supply, the circuit shows a reduced DC voltage after the zener diode and a ground connection. What provides the ground. It is not connected to the neutral, so what do I ground the connection to? I'm using this with a 120vac supply and I am using a 6v zener diode. I have connected a 1n4007 across the cap and the resistor as you suggested, but I don't know how to ground the low voltage circuit. I am using the low voltage(6vdc) to power a white LED in a night light circuit. Help! Thanks!
Swagatam says
Hi Norman, you don't have to connect anything in the indicated area, the ground symbol emphasizes the negative line in all DC circuits….so here too the symbol just signifies the negative common line in the DC section…you can simply ignore this symbol if you wished to.
SUDIP BEPARY says
i have a query about out put from this circuit that if there is variation on input voltage like 220 volt to 180 volt or below, will this circuit change the out put voltage ?
Swagatam says
NO, unless and until the input AC drops below the zener voltage value
Davis Kakumba says
hi swagatam , i made the circuit and its working i used it to power my 12vdc 3w led bulb, now how can i modify it to be used on 240V AC instead of 220v AC
Swagatam says
Hi Davis, you can use the same circuit for 220V as well as 240V.
3 watt LED will not work with this circuit.
Waqasafridi says
Sir I want to make an rechargeable 12v emergency light with battery level indicator without transformer plz help me
Swagatam says
waqas, similar circuits are already present in this website please search it through the given search boxes…
Sonal Kumari says
Sir ,thanks for your previous reply. Can you please recommend me any of your circuits without transformer suit able for the incubator circuit.
Swagatam says
Sonal, Would you be able to build an SMPS circuit? I don't think so.
So it's better to buy a ready made 12V 1 amp SMPS adapter and use it for the purpose
Sonal Kumari says
Sir can I use this circuit to power your egg incubator thermostat circuit.
Swagatam says
no you can't, either an SMPS adapter or a transformer based power supply can be used and is recommended.
mr. ravinder goyal says
can i change the polarity of input(Line and N)?
Swagatam says
yes you can!
kamlesh_sexy says
Hi friend,
I see that in the above pic, you used 12v zener, so the output of this circuit is 12v.
I did not get 12v 1w zener so I made little changes,
Here is my alteration:
I removed zener and placed with 7812 and replaced c2 with 10uf 16v..
this is correct????
Swagatam says
Hi friend, yes that will do, but if due to surge current 7812 blows-of then it will be a bigger lose than a 12V zener….put an NTC at the input to solve this issue
beni says
thanks,
i adding a 1N4007 diode parallel with the zener, i use 12V 1 watt zener ,then i use 12V 5 watt zener
the power is OK.OK.
But while the no-load power(If any consumer is not connected to the circuit) Warm up zener diode.
Swagatam says
you can keep the circuit switched OFF when there's no load connected because anyway without a load it may not be a good idea to keep the circuit switched oN
Arun Kumar says
I want 12v/300ma transformer less power supply circuit diagram please send link sir
Swagatam says
https://homemade-circuits.com/2014/02/simple-1-watt-to-12-watt-smps-led.html
beni says
Thank you Swagatam.
i can not speak english fluently.
i need a transformerless in this conditions:12V,180mA
i use C1 = 2uF/400V , Z1=12V 5 watt zener
output voltage =12.3v
but,while the no-load power, Warm up zener diode.(why the zener diode Heated ! ?)
and too: make two zener diodes in parallel each rated at 1 watt. but zener diode Heated !!!why ?
plz help.thanks.
Swagatam says
beni, a 5 watt zener is not supposed to get warm, but if it is then you can try adding a 1N4007 diode parallel with the zener in the same polarity, and check the difference.
Tiago NET says
R2 is NTC for inrush current or power resistor?
Swagatam says
R2 is an ordinary resistor but you can definitely replace it with a suitable NTC
amor says
Hi Sir,
can i use a 10k NTC in place of R2?
and a 474 630vac mylar in place of 105 400vac capacitor?
im using it as a power supply for a 12v relay driver circuit to power a 12v dc motor, can i just also use the same power source for the 12v dc motor?
thanks,
amor
Swag says
Hi Amor, yes you can try the mentioned components, it should work. If it is a relay that you want to connect at the output, you can eliminate the 12V zener, or use a 24V zener instead. Because a relay is a relatively heavy load and will never burn from a 474 capacitor’s surge, therefore the zener diode can be eliminated or a some higher value can be used.
amor says
Thank you Sir,
how about the 12vdc motor can i just tap it with the same power source? i mean one source to power both relay driver stage and a 12vdc motor load
Swag says
Amor, If the motor current is within 100mA or 200mA then it might be possible otherwise I won’t recommend using a capacitive power supply
amor says
good day Sir,
Without the 12v zener the output after the rectification will be 310vdc (as mentioned above) if i eliminate the 12v zener i think it is not safe for the relay driver stage to connect in the output Sir.
another thing Sir a dc motor will be connected to the relay output which is also a 12vdc my question is can i just tap the common terminal of the relay in the above power supply?
Swag says
Amor, a transistor driver stage won’t be required here. You can connect the relay coil directly at the output of the transformerless power supply, that’s the zener diode would be necessary. If your motor is a low current motor then you can tap the power from the same source otherwise not.
Tiago NET says
i need a transformerless in this conditions: 6V at 120VAC and 12V at 220VAC! have you circuit for this ?
Swagatam says
just change the zener value accordingly in the above shown design…that's all is neeeded
Vicky Gowtham says
hai friend…how can i do my project of mobile charge sharging transfromerless+
Swagatam says
Hi Vicky, have you previously built an SMPS circuit? if yes then you can try the following design for your requirement:
https://homemade-circuits.com/2014/02/220v-smps-cell-phone-charger-circuit.html
M- Furqan says
please sir tell me , i want 220v ac to 60v dc transformerless circuit without transistor
Swagatam says
you can use the above shown circuit and replace the zener with a 60V zener
Harvest Palm says
Sir, I have made egg incubator timer that you have written on another article, and I want to ask that, can I use this transformerless to be power supply the egg incubator timer circuit that use two 4060 ics?
Swagatam says
Harvest, no it's not recommended and might not work….use a 12V ad to dc SMPS adapter or a transformer power supply
MALAY WANE says
Sir i replaced 3 diodes but the problem remains same…every time the diode blows off.
Can i attach any resistor or capacitor in series to diode,and hece collect 12v power.?
Swagatam says
the zener should be rated at 1 watt…connect a 1N4007 also in parallel to the zener to reduce the stress on the zener…the 1N4007 anode should be connected to the positive line
MALAY WANE says
I tried this too but it still not working sir.
I am not getting the output.
Instead of zener,can i use any other component?
Swagatam says
It means your capacitor is faulty…you can try 7812 IC
MALAY WANE says
Hello sir,
I had made this circuit and trying to get output
But whenever i connect zener diode as shown,i gain the output of 1.5v while removing the zener i get 28v so can u plzz tell me where i am getting wrong?
How could i get 12v 1a finally..?
Swagatam says
Hello Malay, It could be due to a faulty zener diode or may be you are connecting it with a wrong polarity…try replacing it with a new one.
12a/1A from this power supply could be impractical and not recommended.
Unknown says
hello sir
i am tring to make supply from 220v ac to 72 v dc with 2ampere
could u please help me in it
Swagatam says
sorry I do not have this circuit at the moment…
Abu-Hafss says
Hi
You can try to find a center-tapped transformer having 220V input and output 36-0-36V rated 2A or 3A. Leave the center-tap and use the remaining two terminals of the transformer with suitable diodes (bridge rectifier) and 1000µ (or more)/100V capacitor to get 72VDC.
binu says
Sir good work. But what is the use of r2 50ohm 1w resistor. Can I use 100ohm resistor instead of this. Plz replay me.
Swagatam says
Binu, it's for limiting current, you can use lower values than 50 ohms, higher values can cause increased heat for the resistor and lower current outputs
khant hnin says
Please help me.Can I use 2uF/400V for C1?
1uF/400V is not available near my area.
Swagatam says
2uF will cause more surge current to flow into the circuit….you may use it, but make sure to employ two zener diodes in parallel each rated at 1 watt
pakol27 says
Can I use this circuit to power 12v computer Fan?
Swagatam says
yes, but at a slower speed…
pakol27 says
What should i do to maximize the speed of the fan?
Swagatam says
add anther capacitor parallel with C1
pakol27 says
Thank you Swagatam.. Can you give the modified circuit? Just to make sure that I make this right.
Swagatam says
My pleasure pakol, make C1 = 2uF/400V that's all, and preferably use a 12V 2 watt zener.
Saqib Mehmood says
Plz just tell me how capacitor contribute in step down ac voltages and what value of capacitor we will choose for 220-6v and how???plzzzz
Swagatam says
capacitor steps down the current not the voltage…voltage is controlled by the zener diode
Sudhee Krishnan B says
can i use regulator ics instead of zenar dode?
what is the dc output after the rectifier, without using the zenar ( capacitor is not removed)
Swagatam says
yes regulator ICs can be used, without a zener it would be restricted to the capacitor's breakdown voltage rating…..but that would create a lot of stress of the capacitor
basit momin says
For wat purpose the circuit can be used for……….
Swagatam says
for powering any DC circuit below 50ma
Ritwik Ghosh says
can you please explain the function of R1 and C1 ?
i mean why they are in parallel ?
Swagatam says
R1 makes sure that C1 gets discharged immediately while someone unplugs the unit from the mains socket, thus cancelling any chance of an electric shock to the user from C1 discharge
Nirvikal Lal says
I want to convert 230 or 220 vac to 5 or 6v dc without transformer so pls help me it's urgent i need for a project
Swagatam says
you can try the circuit discussed in the above article….use a 5V zener at Z1, and 0.33uF/400V for C1
Kusal Wijesingha says
there isn`t 50 ohm/1w resisiton to find then what can i use to that?
Swagatam says
the value is not critical, you can try other values such 33, 47 68, ohm etc.
Abu-Hafss says
Hi Swagtam
Can this supply be used to power up the following project:
https://homemade-circuits.com/2014/06/energy-saver-solder-iron-station-circuit.html
I am bit concerned about the voltage surges.
Swagatam says
Hi Abu-Hafss,
although I too don't recommend capacitive power supplies for operating sophisticated electronic circuits, the above circuit could become relatively safer if C1 is reduced to 0.47uF/400V….the zener diode is crucial here and should not be removed from the circuit.
Raja Banerjee says
Surprisingly in cheap led bulbs available in the market, they use 474K /250V main cap and no filter cap.and they are doing good… Now how these bulbs servibe in the 240 V mains?? thanks
Swagatam says
Yes it's possible, I'll try to address it soon in my blog
Deepam Paul says
Hello Sir;
I want to try this circuit for Making LED series for Diwali. I try to test this circuit using Circuit design PCB software but in this software there is no 250v electrolytic capacitor so i use 200v electrolytic capacitor so it give me a voltage of approximately 13V but i am satisfy with output current . My Doubt is if i use 250v electrolytic capacitor then it will give the 12v output voltage or less than 12 . And how much watt is R1.
Please tell me some PCB design software which use AC power supply component and can run stimulation test.
Swagatam says
Hello Deepam,
200V capacitor will also do, this voltage is not relevant to the the output voltage of the circuit, the zener diode is responsible for it.
Don't use simulators, they are very unreliable and mostly give misleading results.
Swagatam says
R1 will be always 1/4 watt
BlogSerba says
Have u made it?
my friend said we can't put resistor facing 220 volt AC
Swagatam says
a resistor can be inserted anywhere in a circuit for suppressing surge, the position is never critical.
ravindra metri says
Sir. Plz give ac oprated mobile battery li – ion batt circuit
ravindra metri says
Above circuit can i use in your Li-ion Emergency Light Circuit with Over charge and Low Battery Cut off Features circut. Instead off cellphone charger circuit
Swagatam says
No, it won't charge Li-ion batt
Pete Skinner says
I did try a .47uf with no luck but will try with a .68.uf. Thx for quick response! Great name by the way Swag.
Swagatam says
sure Pete! thanks, my pleasure:)
Pete Skinner says
They also have model TM-619-1(120vac) and TM-6331(120/220vac). When I plug in the 619-2(220vac) to 120vac the timer portion will work but the power supply is suppose to convert to 24vdc to run a relay which it is not doing. I have 2 brand new and neither will switch relay running at 120vac.
Swagatam says
you ca try increasing the value of the 0.33uF cap by putting another 0.33uF parallel to it or by replacing it with a 0.68uF/250V cap.
Pete Skinner says
have two TM-619-2 timers that work on 220v.Would like to run a 120v. Uses transformerless cap power supply. Components are .33uf cap with 1M ohm resister in parallel as well as 180 ohm resistors in series on both sides of 220v input. Bridge rectifier follows. Can you help?
Swagatam says
you can use the same circuit with 120V also, the output result from transformerless supply would be the same as for 220V.
Jagdeep Singh says
Sir
I made this circuit but sum time after r2 is burn
Help me
Swagatam says
Jagdish, use 474/400V in place of 105/400V
jason bobis says
Hello Swagatam Majumdar.. How can I make the output of this power supply be 12V 1A?
Swagatam says
hello Jason, getting current above 100mA is not recommended for capacitive power supplies…because it could dangerous for the connected load under those specs.
Niel Kristopher Vargas says
Do you have a 12V 1A transformerless? Or 2A
Swagatam says
presently i don't have it.
Swagatam says
50mA
Niel Kristopher Vargas says
How much AMPERE is this 12V transformerless,?
Shriram S says
Sir i want to replace a 12-0-12 transformer in one of my projects with this transformerless power supply you have mentioned here. I want your help in implementing it, would you please guide me on how to do it, whether i can use the same circuit mentioned above or any changes are required.
Thanks in advance
Swagatam says
Hi Shriram, what is the current requirement of your circuit? If it's above 100mA then capacitive power supplies as described above should not be used
Anonymous says
I think the circuit you designed, has a dc voltage of about half of line voltage.then the risk of shock is permanent.
M.Asloni
josef says
Hii…
what will be the voltage across the output terminals for this circuit, given that the Zener diode is not used for regulation?
Also, does the AC capacitor(PPC) act as the series reactance as opposed to the Series resistance(Rs) in a standard Zener Voltage regulator circuit?
Swagatam says
The voltage will be always equal to the input mains peak, for 220V AC it would be 330V DC.
In presence of load, whether a zener or any other load, the reactance behaves like a resistance and restricts current as per the load.
Justin Adie says
yes. however that is not practical when the power supply and device are in their container and freely movable by the consumer from socket to socket.
it is not, of course, reasonable to require a user to have a phase tester and insert it into a socket to test (and in fact for security reasons it is not quite that simple either).
i guess by not answering the question about fusing you are indicating either that it is not safe to use this circuit when there is no visual way to determine phase or you do not have an opinion on whether it is good practice (and effective) to fuse both poles.
as always, thanks for your time.
David Barner says
Justin, since this circuit utilizes a full wave bridge rectifier (the 4 diodes in a circle) input polarity is not an issue. All Swagatam was saying is that if you wanted to add a fuse for additional protection, then polarity would be important.
Swagatam says
Thanks for your understanding David, yes a fuse is not essential for the above circuit since it has a DC output, but for other appliances a fuse must be added to the LIVE line so that in case it blows of no Phase current stays floating within the house electrical.
Justin Adie says
and therein lies the problem! In my country (France) there is _no_ way to determine visually which line is the phase and which the neutral. the plugs and sockets are not physically polarised.
so what is the recommendation? to fuse both lines?
Swagatam says
You can simply identify them by using a line tester device, the touching the tester to the relevant lines will provide an illuminated neon indication for the phase line and no illumination for the neutral.
Justin Adie says
so it doesn't matter that the filtering circuit is on the neutral (tied to ground) rather than the phase?
is that true even for electrical systems that do not tie neutral to ground?
and does that also mean that it makes sense to put fuses at both terminals of this kind of AC circuit?
Swagatam says
It doesn't matter to the circuit operation, but certainly matters to living beings in terms of getting or avoiding a lethal shock.
Therefore when it comes to adding a fuse, it must be always added to the phase line, never to the neutral.
Justin Adie says
Hello
is input polarity important in this design? e.g. in many european countries there is no wiring standard to dictate which wire/pole is the phase and which is the neutral. and even if there were, the plugs can just be reversed.
and if input polarity is not important could you give a brief explanation why?
many thanks
Justin Adie
Swagatam says
For mains AC inputs the polarity is never critical because of its alernating nature which oscillates from positive to negative at the specified frequency, in your area and India it's 50Hz (50 cycles per second), therefore the polarity is undefined and becomes immaterial.
kirams says
I don't quite agree completely with this comment. There may not be a difference in the operation of the circuit but if Ground is connected to LIVE/PHASE instead of NEUTRAL, inner circuit becomes vulnerable for electric shock and there is no way to prevent this 🙁
Swagatam says
The ground connection is a different issue, we are not considering ground here, we are only discussing how the phase/neutral may be used for a given AC load.
The polarity consideration is not critical when the output is DC, just as in the above explained transformerless power supply, but is definitely crucial if an AC appliance is used such as fridge, geyser etc, and also in plug sockets, where the phase must always come through the switch in the socket…
Anonymous says
Please I would like to know if the output curent is realy 500ma
Swagatam says
No, it isn't.
Abu-Hafss says
Hi Swagatam
Is it possible to have current in between 100mA and 200mA?
Swagatam says
Hi Abu-Hafss,
It is possible, provided the load voltage is rated at the input mains level, otherwise most of the current would drop producing no significant enhancement in current.
Anonymous says
Hello Sir
I need get 5v dc to run a circuit which it contain 555 IC and 5v relay. How to convert this circuit to get 5v .
And also can I Use .22uf 400v for C1 instead of 105/400v for above circuit.
I'm
Aruna
Swagatam says
you can use a 5.1V zener in place of the shown zener, 0.22uF will not work because it won't be able to support the relay.
Nasso says
Can I use 2 identical Electrolytic Capacitors and Connect them in series so the 2 negative sides will be the external final capacitor terminals (or Reverse)
By that way Even I will have half the Capacitance of them but will give high capacitance value than the X rated and hence will give hi current
Please let me know here and at my e-mail: nshahbo@yahoo.com as well
Nasser
Swagatam says
It can be done, but their voltage should be above 400V for better safety, try the ones which are used in ceiling fans.
Visura Pathirana says
ple help me to build a transformerless power supply with an input of 230V and 50Hz which can give a output 45V and 0.27A.
Swagatam says
you can try out the circuit that's been discussed in the above article….use 5nos 105/400V caps in parallel for C1…..and be sure to connect an NTC thermister at the input of the supply.
Anonymous says
I want to use this circuit to power a little uhf transmitter but im afraid that i will get some ac hum in the sound, can you help me with adding a notch filter?
Swagatam says
use 0.22/400V for C1, and make C2 = 1000uF/25V you won't get any Hum……….read warning message given in the article.
Anonymous says
im going to build this circuit out of smt components what type of capacitors do you recomend for c1 and c2, and will this circuit work for 110v 60hz
Swagatam says
Use SMD for C1 and C2 also, yes the circuit will work for 110V AC as well..
Anonymous says
Hi, Sir,
is there any online calculator for this or any software. If so please post
Swagatam says
if you Google a bit, you might find one…not sure though.
Bibin Edmond says
Hi,
can u please post me a circuit for charging 4v 750ma SLA battery..
like this Battery
i would prefer a transformerless circuit..! and what would be the charging voltage of this kind of battery.. ?
Swagatam says
Very simply you can use any cell phone charger to charge it, if you want to make a transformer charger, you may use a 0-6V transformer/500mA with a standard bridge capacitor network. Connect this output to the battery via a 5 Ohm 1 watt resistor.
Bibin Edmond says
oh… gr8 thanks yaar… !
Anonymous says
hi
please explain how to determine the value of capacitor and resistor for 220v. AS exact value and determination will help me a lot
regards
Swagatam says
Hi,
The value of the capacitor will depend on the current requirement of the connected load.
You may find it using the capacitance reactance formula, please Google it you'll find many good sites which will explain it you in details.
Regards.
Anonymous says
Swagatam,
Thanks for the clarification. I found this blog by way of investigating further after reading the older article so hopefully others do the same before building that version!
In the end, I've decided that the Supertex ICs suit my needs best. I almost used the SR087, but your post on the LR645 pointed me to a better option.
Thanks again,
Zunaid
Swagatam says
You are welcome Junaid!
Anonymous says
Hello Swagatam,
Back in 2010, you published this helpful post on transformerless power supplies: http://www.brighthubengineering.com/diy-electronics-devices/77929-make-a-transformerless-power-supply/#
In it, you described the basic capacitive power supply (as above), a spike-protected capacitive supply, and finally a spike protected and mains isolated capacitive supply. You outlined why the latter version was far superior because of the obvious isolation and protection.
Since this article was posted much later, I'm wondering why you chose to give details about the non-protected, non-isolated version here instead of what you referred to as the "ultimate transformerless power supply which is very cheap to build, satisfies most of the needs, is spike free and is safely isolated from AC mains"?
You mentioned that the third version in the other article was also more efficient so I simply want to determine if there is a reason to build the version here instead or should I continue with the isolated and protected version.
The articles you've posted have been very helpful so far.
Respectfully,
Zunaid
Swagatam says
Hello Zunaid,
Initially when I tested the circuit using two caps at the two inputs, the line tester showed no leakage mains within the internal circuitry and that convinced me that the inclusion of two caps seals of the entry of lethal mains in to the preceding electronic circuit.
However after many months I happened to recheck the circuit and this time I touched the circuit with my fingers and was literally "shocked" to feel the lethal mains present inside the circuit, this result hugely disappointed me as I realized there was no way of eliminating this problem in capacitive PS.
Since now I no longer write for BH I'm unable to correct the article.
So that's the fact, however I have published many upgraded versions of capacitive PS in this blog, you may check them out.
Thanks very much for the update.
Regards.
Bright Hub says
Hello Swagatam, we at Bright Hub were also contacted about the outdated information on the article. We are updating it with the information you include here as well as a couple links back to your blog. If you have time, please check it out and let us know if anything else should be changed. Thanks!
Swagatam says
Hello, Thanks very much for contacting me! I really appreciate it.
As stated in the above response I would like to remove the last section of the article.
The portion which starts from "The last circuit shown is perhaps the most efficient……." and ends with "satisfies most of the needs, is spike free and is safely isolated from AC mains."
The last diagram will also need to be removed along with the above paragraph.
Kindly let me know if there's anything more you would like me to do!
Thank you.
Anonymous says
Hey Swagatam
C1 and R1 are used to step down ac voltage. but the stepped down voltage is ac or dc?? actually i need to build a 5v ac supply..
please help.
Regards
Rishi
Swagatam says
Hey Rishi,
C1 is for dropping the current, R1 is for discharging C1 when it's unpinned from the socket, R2 is for suppressing surge current.
The voltage after the bridge will be DC.
I am afraid 5V AC cannot be derived from this circuit, because after C1 it's all low current 220V AC
Anonymous says
can you help me regarding this problem??
sagar kanth says
hai sir will you explain the applications of transformless power supply in general life and industrial oriented
Swagatam says
Hi sagar,
The power supply can be used for powering any circuit which requires less than 50 ma of current for operating.
Thomas Vibakar says
Dear Swagatam,
The transformerless power supply circuit is really good. Similarly will you suggest me a homemade transformerless 12V 1A lead acid battery charging circuit with automatic cut off at 13.8V at max charging.
Thomas
Swagatam says
Hi Thomas,
I have already published many battery charger circuits in this blog, you may use the given search box for finding the suitable one for you
Sudeep Chand says
hi mr.swagatam,
am looking for a 12v 4-5amps or(max possible)value of current at output, am using it for tec1 12708 module and need only one out put so i cant go for a full smps circuit help me plz!
thanks in advance
Swagatam says
Hi Sudeep,
You can easily buy it readymade from te market, a 12V/5amp smps can be easily procured.
jac says
C1 and R1 are used for stepping down the input AC mains voltage? To which level can they step down?
Thanks.
Anonymous says
but you never mentioned it….looking throught your post…i never saw anything pertaining to the rating to be used.
please help. i want 18V at the output of my bridge, am using a 2.2uF and it is not giving me 18V. i am stuck.
Swagatam says
within a coupe of days i would be publishing a variable transformerles power supply circuit in my blog…the design will enable any voltage between 0 to 24V to be set as per requirement.
jac says
I meant, the particular part number of the zener diode that you used..
wasim says
hi
how can i convert into 6v dc out put?
thankssss
jac says
what is the purpose of 1N4007?
jac says
Which Z1 did you use? Part number?
jac says
Appreciate if you could mention each component's part numbers, for my reference only.
Fazal Ellahi says
hi dear SWAGATAM
if i need only 5v from this circuit then can i use 5v zener diode in it
help me to produce 5v
Swagatam says
Hi Fazal, yes you can use a 5V zener to get a 5V output from this circuit.
Anonymous says
Hi Swagatam,
why is it when i'm using a 12v/1watt zener the voltage output goes high and then the diode will open or busted. but if i used 5v/1watt there is no problem. can you help me with this?
Thanks
Anonymous says
Hi,
I've notice to your article How to Calculate and Deduce Current, Voltage Parameters in Transformerless Power Supplies. the C2 is 100uF/25V but here the C2 is 100uF/250V. which is the right capacitor to use?
Thanks
Anonymous says
Hi,
can i use 225K/400V (2.2uF/400V) for capacitor C1?
the electrolytic capacitor is now 10uF/250V?
Anonymous says
The voltage rating of the capacitor wont affect the circuit bahaviour as long as the voltage is 12V. So its OK to use any of the two but i prefer the 25V though.
Anonymous says
Hi,
i made this circuit but i encounter a little problem. the 12V/1w zener diode always blown up. is there any way to step up the max current of this circuit? because i want to this in a android tablet.
can u help me please.
i used:
1uf/630V (400V is not available in my area)
100uf/200V (250V is not available in my area)
1N472A – 12V/1watt Zener Diode
1n4007
Anonymous says
Z1 blew maybe because it exceeded its 1watt power rating. Now, you need to put a resistor between Z1 and the rectifier(diodes) to limit the current flowing on Z1 however the value of this resistor will depend on the current rating of your android tablet (we need math here). But i suggest you purchase an adapter for your tablet, no more worries!
Anonymous says
It is better to use LM7812 instead of Zener diode.
This will help to reduce power consumption while on NO LOAD
Anonymous says
oh yea just put a 7812 on 120+ dc.. DO NOT DO THIS….
Swagatam says
Charging a cellphone through a capacitive power supply is dangerous and is never recommended…I accidentally failed to notice that you are intending to use it for charging a cellphone…
get an SMPS charger instead..
Swagatam says
7812 will work!! since it's rated at 1 amp while the input current from the 105/400V is just 50mA…so even if it's 120V or 220V it will be forced to drop down to 12V ultimately….
but again this may be applicable only for ordinary circuits never for charging cellphones…..
Quetzalcoatl says
Hi there, what do you mean for a 105/400V capacitor?
Swagatam says
Hi Rajesh,
You may use it, it's almost the same value as 105/400V
Fazal Ellahi says
oh thanks a lot dear
Arun Das says
sir can u help me to convert 230v ac to 110v ac …step down circuit
Swagatam says
Arun, you'll need an auto-transformer for that
you can wind 300 turns of magnet wire (25SWG) over an iron laminated core (transformer E core) and connect the ends to the 220V, the 110V may be collected from anywhere at the middle of the winding