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High Current Transformerless Power Supply Circuit

High Current Transformerless Power Supply Circuit

Updated:

The simple configuration of a transformerless power supply circuit presented below is able to provide high current at any assigned fixed voltage level. The idea seems to have solved the problem of deriving high current from capacitive power supplies which earlier seemed a difficult proposition. I assume I am the first person to have invented this.



Introduction

I have discussed a few transformerless power supply circuits in this blog which are good only with low power applications, and tend to become less effective or useless with high current loads.

The above concept utilizes high voltage PP capacitors for dropping the mains voltage to the required level, however it is unable to raise current levels as per any desired particular application.

Although, since the current is directly proportional to the reactance of the capacitors, means the current can be lifted just by incorporating more capacitors in parallel. But this puts a risk of high initial surge currents which might destroy the involved electronic circuit instantly.

Adding Capacitors to Increase Current

Therefore adding capacitors might help to increase the current specs of such power supplies but the surge factor must be first taken care of for making the circuit feasible for practical usage.

The circuit of a high current transformerless power supply explained here hopefully, effectively handles the surge developing from power transients such that the output becomes free from the dangers, and provides the required current supply at the rated voltage levels.

Everything in the circuit is kept just as its old counterpart, barring the inclusion of the triac and zener network which actually is a crowbar network, used for grounding anything that goes above the rated voltage.

In this circuit the output would hopefully provide a stable voltage of around 12+ volts at around 500 mA of current without the dangers of any accidental voltage or current influx.

CAUTION: THE CIRCUIT IS NOT ISOLATED FROM MAINS AND THEREFORE INVOLVES HIGH RISK OF ELECTROCUTION, APPROPRIATE PRECAUTION NEEDS TO BE EXERCISED.

UPDATE: A better and a more advanced design can be learned in this zero crossing controlled surge free transformerless power supply circuit

Parts List

R1 = 1M, 1/4W

R2,R3 = 1K, 1/4 WATT

C1----C5 = 2uF/400V PPC, EACH

C6 = 100uF/25V

All DIODES = 1N4007

Z1 = 15V, 1 watt

TRIAC = BT136

A neatly drawn PCB for the above high current transformerless power supply may be seen below, it was designed by Mr. Patrick Bruyn, one of the avid followers of this blog.

Update

A deeper analysis of the circuit showed that the triac was dumping a significant amount of current while restricting the surge and controlling the current.

The approach taken in the above circuit for controlling voltage and the surge is negative in terms of efficiency.

In order to obtain the intended results as proposed in the above design and without shunting precious amps, a circuit with exactly opposite response needs to be implemented, as shown above

Interestingly, here the triac is not configured to dump power rather it's wired in a such a way that it switches OFF power as soon as the output reaches the specified safe voltage limit, which is detected by the BJT stage.

New Update:

In the above modified design the triac may not conduct properly due to its rather awkward positioning. The following diagram suggests a correctly configured version of the above, which can be expected to operate as per the expectations. In this design we have incorporated an SCR instead of a triac since the positioning of the device is after the bridge rectifier and therefore the input is in the form of a DC ripples and not AC.

Improving the above design:

In the above SCR based transformerless power supply circuit, the output is surge protected through the SCR, but the BC546 is not protected. In order to ensure a complete protection for the entire circuit along with the BC546 driver stage, a separate low power triggering stage needs to be added to the B546 stage. The amended design can be seen below:

SCR based transformerless power supply circuit

The above design can be further improved by modifying the position of the SCR as shown below:

So far we studied a few transformerless power supply designs with high current specs, and also have learned regarding their different modes of configurations.

Below we would go a little farther and learn how to make a variable version circuit using an SCR. The explained design not only provides the option of getting a continuously variable output but is also surge protected, and therefore become much reliable with its intended functions.

The circuit can be understood from the following description:

Circuit Operation

The left side section of the circuit is quite familiar to us, the input capacitor along with the four diodes and the filter capacitor forms the parts of a common, unreliable fixed voltage transformerless power supply circuit.

The output from this section will be unstable,  prone to surge currents, and relatively dangerous to operate sensitive electronic circuits.

The portion of the circuit on the right side of the fuse transforms it into a completely new, sophisticated design.

The Crowbar Network

It's in fact a crowbar network, introduced for some interesting functions.

The zener diode along with R1 and P1 forms a kind of voltage clamp which decides at what voltage level the SCR should fire.

P1 effectively varies the zener voltage from zero to its maximum rating, so here it an be assumed to be zero to 24V.

Depending upon this adjustment, the firing voltage of the SCR gets set.

Supposing P1 sets a 12V range for the SCR gate, as soon as mains power is switched ON, the rectified DC voltage starts developing across D1 and P1.

The moment it reaches the 12V mark, the SCR gets sufficient triggering voltage and instantly conducts, short circuiting the output terminals.

The short circuiting of the output tends to drop the voltage toward zero, however the moment the voltage drop goes below the set 12V mark, the SCR is inhibited from the required gate voltage and it reverts to it non conducting state.... the situation yet again allows the voltage to rise, and the SCR repeats the process making sure the voltage never goes above the set threshold.

The inclusion of the crowbar design also ensures a surge free output since the SCR never allows any surge to pass through to the output under all circumstances, and also allows relatively higher current operations.

Circuit Diagram

variable high current capacitive power supply circuit

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!



240 thoughts on “High Current Transformerless Power Supply Circuit”

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

  2. Hi Swagatam,

    I’m also an electronic entrepreneur with similar passion what you have. Thanks for all your efforts so far. I’ve been referring to your circuits for more than 8 years now. I have a question though.

    Is there a way to derive 5V, 150mA current to drive a 5V sugar cube relay from mains? And this time, it is not 220v-neutral, but i want to step down 2 phases – 440v (2 out of 3 phase AC mains input) to 5V.

    Also, the work is with 3 phase AC input without neutral. I tried all options before reaching out to internet.
    Any thoughts?

    • Thank you Vinay, Glad to have a dedicated reader like you!

      You can use the earthing line as the neutral and use any one of the 3 phase lines as the phase, this will solve the problem quickly, otherwise it can be a bit complex.

      You can use a spare mobile charger for this and use its output for driving the relay.

      Let me know if it is favorable to you, or if you prefer the other complex method.

  4. Hey There..!

    I was making an IoT project for which I needed a Lightweight, small sized power supply.
    So, I chose to use a Transformerless Power Supply but I am confused with its current ratings. I need 5V 3A max output from the supply. What components do I choose..?

    • Hi, I won’t recommend a capacitive power supply if the current is as high as 3 amps. Moreover the design won’t be isolated from the mains and therefore can be too risky. So, You must go for an SMPS according to me.

  6. Dear sir,
    I would like to assemble a air cooler using 12 peltier modules. Instead of feeding tec1 -12706 with 12v 72amps, I would like to connect them in series with an input of 144v dc 6amps. For this, I tried a halfwave rectifier and a smoothing capacitor of 400v 1000mfd.
    As per calculation, the dc output would be 240*0.5*1.414=169v. But I am getting about 340v with no load and 300v with a load of 2amps.
    Kindly suggest a solution as to how can I obtain 110-120v dc from the mains with current output of 6 amps

    • Dear Shivakumar, even with a single diode half wave rectification, the peak voltage will be 310V, and this will be stored and sent back to the load from the filter capacitor, and therefore you will always see a 310V at the output.
      if you remove the filter capacitor then the meter will show 120V, but still the peaks will be 300V, which can be dangerous for a 120V load.

      To solve this you may have to use more devices in series so that it works with 300V DC or use a transformer for stepping it down

  10. Dear Swag,
    This is regarding your second upgrade (the third diagram above)
    What is the purpose of 10K 1W resistor connected between the anode of BT 151 and the junction of the collector of BC 546 & the gate of BT 151?
    In fact, I tried this circuit. But the said resister is getting heated. What may be the reason?
    Thanks in advance

    • Hi Nirmal, it provides the gate triggering voltage to the SCR. You can try increasing its value to 22K and see if that still allows the SCR firing comfortably…

      • Dear Swag,
        I replaced 10K with 22 K 1W, but still it gets heated up and I also noticed failure of BC 546, three times.

        Actually I am new to transformer less power supply circuits. So, I would like to know in detail how the circuit BT 151, 10K (22K) 1W resister, BC 546, Zener and the two resisters at base of BC 546 controls surge and voltage.
        Thanks,

        • Dear Nirmal, the output is protected from surge because the output voltage is never allowed to increase above the selected zener value. The moment output level tries to go beyond the zener level, the SCR is switched OFF by the BC546 preventing the voltage to rise any further, conversely as soon as the SCR is switched OFF the output voltage is cut off which switches off the zener and BC546, switching ON the SCR and restoring power.

          But the BC546 may not be protected from high voltage so this will need a separate protection circuit, I’ll try to update it soon…

  18. hi sir for the similar kind of circuit in am getting 30 ma current output i am using the 105j(1uf) capacitor but i want to drive high load so i need more than 500ma is it better to add another 4 r 5 105j caps in parallel to each other

    • Hi Sanjeev, yes you can add more capacitors in parallel to get higher current, each 105 capacitor would give you at least 50mA.

      but make sure to add the triac controller as explained in the above article to control surge currents, and regulate voltage.

  22. Sir, how much power a transformer with the following specs can give ?

    230/14-0-14 5A

    Will it be 14×5=70 W or
    (14+14)×5= 140 W ??

  24. hello sir i want to switch 12v dc relay, using capacitive power supply but my zener diode is become over heat.
    so please solve my problem..

    • Hello Devkaran, for a relay you won’t require a zener, you can connect it directly with the DC from the capacitive output…the relay coil is much stronger than a zener and will be be able to regulate the capacitive output safely without any external support. you can use a 105/400V caapcitor for the capacitive power supply

      • thanks for immediate reply sir,
        but i am controlled the relay using pic12f675 micro controller. so micro controller have need pure dc and exactly 5v because i am using adc function and there is need to 5v .i am using 7805 voltage regulator for 5v.

        • OK, In that case you can use the 7805 for supplying the MCU, and connect the relay positive side directly with the capacitive bridge output.

          I hope you have understood the configuration….and also be cautioned regarding the dangers involved with a capacitive PS

    • with 10K resistor in series the BC546 shouldn’t have blown, anyway you can try connecting a 15V zener between the gate of the SCR and the emitter of BC546, this will hopefully solve the issue..

  32. Hi Swagatham
    I will use TL431 based voltage regulator with power transistor for high current handling.

    I have seen many rechargable tourches, Emergency lights, LED display circuits use capacitor based simple powersupply. Those work very effectively without any protection circuits such as SCR, TRIAC, Thermister, Zero-crossing circuit….etc. So, is it neccessorry a surge/spike protection circuit…..? If, yes, which circuit would be morethan 75% effective. Just provide link of that circuit.

    Probably, it should be Zerocrossing circuit.

    Thanks in advance.

    • Hi Anil, emergency light circuits use capacitor based power supply for charging battery at a very low current rate, therefore the protection stage is not included, still they do use a zener diode for regulation.

      you can use power transistor also, but a single SCR or triac handles everything perfectly and reliably, without depending on any special ICs or costly surge protection devices, and a SCr/triac suits better for high voltage circuits than power transistor.

      for zero crossing concepts you can refer to this page

      https://homemade-circuits.com/?s=zero+crossing+power

  34. Hi Swagatham,
    I have successfully assembled few capacitive powersupplies for illuminating one or two 20mA leds as nightlamps. I used 474pf, 630V, polyster capacitors. I always use a proper value zener diode at output for voltage regulation.

    My doubt, is it suitable, capacitors that use with seiling fan….(usually it’s value is 2.5mfd 400vac) for this type of powersupply….?

    • Hi Anil, yes it is OK to use fan capacitor also, it is the 400V rating that is important, but make sure that the zener wattage is proportionately upgraded as the microFarad is increased

  36. gud day sir am working on my circuit but i got some things i want you to clarify
    1 the orignal circuit had a 100uf/25v and yet this circuit am making has a ppc rated 1uf/400v at the output so i need some help there.
    2 what is the function of the 100k pot thanks alot

    • Hi Olupot, 1uF/400V is not necessary, you can replace it with a 100uF but make sure the voltage rating is twice of the intended output level.
      100k pot can used for raising the output voltage to higher limits than the zener value.

  38. good morning sir i apreciate the good work you do thanks alot. i have a question regarding the circuit is it possible for me to increase the output current to around 800mAand also can i use it to charge my small batt of 12v 7Ah.

    • Hi Oluput, that may be possible, but the triac can get immensely hot, you a replace the shown 1 amp with a 3 amp triac, then it would be fine.

      yes you can use it to charge a battery, however the above concept is not isolated from mains, therefore touching the wiring with hand can give a fatal shock…therefore it's not recommended for such applications which may not be covered.

  40. hello sir thanks for the great work. i take time to study each and every circuit you post that i find am in need of.so i have some question regarding this circuit
    1. can i get up to around 800 to 900mA from the circuit.
    2. is it possible to use this circuit to charge a small motorcycle batt of 12v/7Ah. i wil be greatful if i get it done for my small work bench thanks have ablessed day

    • Thanks Daniel,

      yes you can use it to charge a battery, however the above concept is not isolated from mains, therefore touching the wiring with hand can give a fatal shock…therefore it's not recommended for such applications which may not be covered.

    • The word "below" was mistakenly mentioned, it should have been "above"…I have corrected it and also posted a new modified and technically more correct version of the same. you can check it out at the end of the post.

      The opto coupler version is not updated because an opto could make the design unnecessarily complex and an overkill…

  44. Referring to your article

    "In order to obtain the intended results as proposed in the above design and without shunting precious amps, a circuit with exactly opposite response needs to be implemented, as shown below:""

    their is no circuit below these lines??

    someone in comments referred to circuit with optocoupler ,but in this post there is no cct involving optocoupler…..

    please point out the updated circuit resulting high current and stable voltage…….

    thanx in advance……carry on the good work.

  46. In order to obtain the intended results as proposed in the above design and without shunting precious amps, a circuit with exactly opposite response needs to be implemented, as shown below:

    where is the cct in article ?? there is only one cct under update heading???
    which cct is the right one ,and will not dump amperes…..??

    • obviously, the circuit design shown under the update is the one which is being discussed in that section.

      both are correct it depends which you feel is better.

  50. Hi Swagatam!
    Have you tested that last circuit with the BC546? because I took a look at it and thought: "the triac is iniatially not conducting, to conduct I need a pulse on it, and to have a pulse with some enough current to make it start conducting, I need that current flows through the diodes bridge, but how this could happen if the triac is not conducting? It seems that I need to give a "little push" at the gate's triac in order to it start conducting and after that have my BC546 in open state and therefore applying the collector voltage and consequently a current flowing through the triac's gate".
    The point is, there is no current flowing through the circuit at all until the triac starts conducting, but is depends on the circuit ahead it and the circuit ahead the triac depends that triac starts conducting… At programming we call that deadlock…
    thanks Swagatam!

    • Hi Thiago, the last circuit is just a suggestion, it has not been tested by me yet.

      yes, to initiate the BT136 some form of arrangement would be required, you can connect another 1uF/400V in parallel with the triacs MT1/MT2 or a 1K 1/4 watt resistor also could be tried.

    • Or two push buttons, one in parallel with MT1/MT2 in order to give that little push I commented and turn the power supply on, and another one in series with the gate in order to cut off the pulse on the triac and switch off the power supply. Maybe it could be a nice solution.
      I liked very much your design and I think of implementing it with what I said. I don't want to have a transformer on my project…
      Thanks again Swagatam!

    • thanks thiago, s push button with MT1/MT2 might not work because at the first zero crossing the triac will tend to switch OFF, shutting of the whole circuit.

      a capacitor or a 1K resistor as suggested by me earlier could be the only solution.

      anyway you can try both the solutions and see which one works more appropriately.

    • however the above issue could be corrected by adding a high value capacitor instead of the 1uF shown at the output side of the design….

    • Yes, maybe it could not work, I will simulate both approachs at proteus and I come back to you to let you know the results. Thanks again!

  52. hello
    i want to drive 12vRelay @ 30 ma with this method . Also want to add MOV .pl help which value of MOV i go with ? .

  56. To convert it into 5v power supply do we need to need to replace only the zener diode or some replacements are required too?

  58. Hi 🙂
    I want to make 12V 2A transformer less power supply. can u help me? please.
    because your given circuit doesn't provide much current.
    Thank you

  68. Hi Swagatam,

    Im just starting to find/search for a small low cost PS for driving ESP8266 boards, where the requirement is 5V or 3,3V with 350-500mA and found that your site have the most info about these transformerless PS, but I am confused after looking at all the differet diragrams on your site, so my questions is you have such a diagram on your site and can send post the link ? .. if not, which diagram will be best and what changes are needed ?
    thx in advance for your support.
    PS input would be 220Vac – 50hz

  70. Dear Swagatam Majumdar,

    Greetings !!!!

    I need 5v 1ahm output AC to DC transformer less circuit, if you can make this circuit in past, please send the details following email id :

    mu2003777@gmail.com

    09586516661, 09898586746

    i am waiting for your answer !!!!

  72. Dear Sir,

    If i change the zener diode to 15V, do you think the voltage will follow, how about the current? how much current it will give? the current will depend only to the zener or to the 5x capacitor in the input.? thanks

    odie

    • Dear Odie,

      yes the output voltage will change according to the zener value.
      current will depend on the input capacitor value.

  74. Sir is this your finalized circuit for the high current transformerless power supply

    3.bp.blogspot.com/-Y7aCY8rtB44/U_cx5MAANjI/AAAAAAAAIDE/Xj–z257fYU/s1600/efficient%2Btransformerless%2Bpower%2Bsupply%2Bcircuit.png

    i am getting no dc output from this circuit.. how can you trigger the traic with a DC control signal without using an optocoupler… and please tell me how to configure the circuit to get the output voltage

    • RT, a triac can be fired from any DC source, an opto coupler is used only when the triac stage needs to be isolated from the DC stage, otherwise it is not essential.

      please check your circuit carefully there could be some mistake in it.

    • you are welcome, you can also think about becoming a paid contributor to this site by submitting circuit related projects and concepts…..

  80. Oh, sorry sir, actually at first I could not find your answer….

    But sir,
    is not possible to make transformer less 15V, 3Amp DC power supply ?

    • Narottam, transformerless can be in the form of SMPS, capacitive type is not recommended for such high current…the best is transfomer type which is the most reliable.

  82. Sir,
    I want to make 15 volt, 3 amp DC power supply in this process for giving the power supply of the project of "wireless cellphone charger" please help me with your advice that which components or value of components will be the change fo making it ?

    And one more question, here the wattage of the resistor R1 is 1/4 watt, is it sufficient ?

  84. Sir,
    I want to make a DC power supply of 15 volt, 3 amp for the project of "Wireless Power Supply".
    So please help me with your advice that what components will be the change for making it and which circuit is the best for this ?

    And one more question, here the wattage of the resistance R1 is 1/4 watt is it sufficient ?

    • Narottam, you can make it by using an LM338 IC, you can easily find the circuit idea in the datasheet of the IC, or even in this website itself….you will need a 0-24V/5amp transformer for supplying the input to this IC regulator circuit

      R1 is only for discharging the capacitor when the circuit is being plugged out of the socket…higher wattage is not required…1/4 watt is enough, moreover the value is 1M that's too high for any possible damage.

  86. Hi Swagatam,
    Based on this article How much current it will produced? Is the circuit is been tested? and what type of capacitor you used for this paralled caps.
    Thanks & more power to your blog

    • Hi Odie, it can be used for generating up to 500mA without much heating of the triac…it's a tested design

      all the capacitors must be metalized polyester type..

  88. hi,
    can i used electrolyte capacitor in series, with inverse polarity each other to substitute non polar dropper capacitor in your circuit, let say i use two 2.2uf/400V elco , arrange in series with opposite polarity

  90. Dear sir,
    I want to makr a transformerless power supply to gain 12v 1-2A DC.
    Please help me sir how can i do it…
    Thank you..

    • Dear Malay, you must go for an SMPS based circuit instead of a capacitive one, which is never suitable for such high current applications.

    • Thank you sir.
      I have one query. There will not be any Neutral line. Input will be any 2 phases. i.e RY or YB or RB.
      So is it possible.?

    • yes any phase from the 3 phase can be used with the above design….neutral may not be required. but I am not exactly sure about it? you may have confirm it practically.

    • hai i made the above circuit its working fine but the problem is when i connect 110vac its not working can you tell me the reason .

    • Hi, that's cannot be possible, any AC input higher than the zener voltage should work.

      remove the triac connection and check again…

    • technically it may be possible, but strictly not recommended because the above design is not isolated from mains and is too crude and dangerous to be used as a cell phone charger

  100. dear Swagatam,
    it's good AC-DC converter. Can you explain more details transistor, triac stage?
    when circuit work normally, current through zener, 100k resistor and 100k variable resistor about 10mA, voltage at base of NPN transistor about 1V cause open transistor. Therefore, voltage at G gate of triac about 0V, triac off => it's not logic, am i wrong??
    hope your help!
    thank you.

    • dear unknown, actually there should be a 1K 2 watt resistor across the triac MT1/MT2….so when power is switched ON, the circuit will switch ON with a low current via the 1K, and switch ON the triac for a full conduction with the rated current of the capacitor….however as long as 30V is not reached the transistor will not conduct, but when this happens the transistor will conduct and cut off the triac…this sequence will go ON very rapidly at microsecond rate, making sure that the output voltage never exceeds the 30V mark or above the zener voltage mark.

  102. Dear Mr Majumdar,
    Your electronic skill is superior. Thanks for showing everything with diagram.etc. My question is:
    Do you have a schematic diagram of a transformerless power supply 220v AC in. and 3.3v 400mA DC out?
    Thanks in advance Christer

  114. Hello Sir can i use this circuit for microcontroller based project , i am in search for Mc based fan regulator transformerless supply , will u plz tell me how can i take output for zero crossing detector through it , plz reply soon, Thanks

  116. That was a pretty quick response, i wonder how you must be coping up with tons of queries you might be getting in various threads you've started 🙂
    Now, I agree with your response, and was of the same opinion to start with. Well my aim was to try and see if size and weight can be reduced, hence started exploring this alternative. SMPS uses a transformer as well, so i was thinking of going for regular mains transformer 12v 1Amp, with a LM1117 ahead to get the regulated 3.3v as desired. I do understand that SMPS is better, but seems to me to be a overkill for the application. Let me know if you think otherwise. Thanks a ton again !

    • thanks pushkar,
      SMPS concepts utilize a small ferrite transformer and the whole unit could be five times lighter than an identically rated iron transformer. Moreover these are cheaper and much long lasting than their transformer counterparts.

      You can buy a 12V 1amp adapter from the market if you find it difficult to build yourself.

      LM1117 may not be necessary, just use a 7805 IC to drop the 12V to 5V and then followed by three of 1N4007 diodes to further drop it to 3.3V approximately

  118. Kudos to your work Swagatam ! I'm looking for deriving 12v dc to operate a relay in a wireless switch rated around 150 ma. Also, want to further step down 12v dc to 3.3v dc (precise) for the sensitive wireless circuit to work. Current required is around 500ma here. Is it safe to use a regulator IC like LM1117 to buck 12v to 3.3v in this non-isolated power supply circuit, without blowing the IC off ? Point to be noted here is that, the load is not always present as its a switch, in contrast to the LED load discussions above which is always present. Total load current will vary from 50ma to 650ma peak, which should be managable as per discussions above. Your expert guidance awaited …..

  122. Dear Respected Sir,
    Can I use BC546 to run 25pcs 150mA LED and 2 pcs 39v Zenor Diode serially in the Second like circuit? What is the use of 1uf ceramic Cap at output? what is BJT stage?

    Could you tell me which Transformerless simple circuit is suitable to run 25 pcs of 150mA LED serially/paralleled initial switch on surge protected. I am unable to find suitable circuit in your oceanic blog. I have tried NTC 10D ( 10hom) before bridge rectifier but it is not feeling much warmth NTC after immediate disconnection, post Bridge rectifier serially seems to have not effect of NTC.I used a 225k(2.2uf) Cap and 10uf 250v cap as filter.

    • Dear Bubai,

      Don't use any of the above circuit, instead you can a simple design as shown here

      4.bp.blogspot.com/-Ao044-f_094/USJX2xXmq9I/AAAAAAAADLw/QXbrfjnDjHc/s1600/surge+protected+led+driver+circuit.png

      ….use the second circuit, connect all the 25 LEDs in series at the output of the circuit…and and use a coil in place of the NTC

      make this coil by winding about 300 turns of 30SWG enameled copper wire on any ferrite core, or you can use the coil from any old relay for the same but the relay coil resistance should not be more than 100 ohms for good brightness.

  124. Sir,
    According to Second schematic LED blown out First switch on 2 times tested.
    tested using single 225k(2.2uf) Cap and 36v and 12v zenor alternating result same used 50k pot instead 10k.
    LED not lighted completely just a flash and gone but not all 150mA LEDs used.

    Let me know how to overcome this problem?

    1st Circuit is tested okay really protecting from surge created by Capacitor by delay effect used 470uf Cap.

    • Bubai, you shouldn't have connected the LEd directly at the output, you should have first confirmed the voltage by adjusting the pot, and once it was adjusted to the LED level, only then the LEd included.

    • …in the second circuit please connect a 0.1/400V cap parallel to the triac MT1, MT2 otherwise the triac will fail to sustain its conduction.

  126. Dear Sir how can i convert 62volt .30mA ( this is telephone line dc supply ) to 12 volt & .750 mA current please give circuit s about this ,thanks

  128. so your saying there is no way to build a power supply like that, or should I just assume that they just connected all +24v and 24vgnd's together for the sake of the type of connection used?

    • yes you are right, just terminate the outputs separately through different wires, that's all….at the most you could use separate diodes for the positives in order to create some sort of isolation.

  130. Or could you just design a power supply than can produce (3) +24v leads and (3)+24vgnd with a transformer…. something that can push about 10 amps i already have a center top 120-12/12 at 5amps transformer

  136. sir how to increase current at output upto 5 amp? Is this ckt is very safe & easy as use transformer for drive LED? can we use "Universal High Watt LED Current Limiter Circuit – Constant Current Circuit for LEDs" circuit as in your blog on right side of this ckt for constant current generator for LED?

    • Ashok, capacitive power supplies are never safe or efficient for low voltage DC applications.

      You must use an SMPS for your requirement as explained by me in your other comment.

  138. Thanks for your quick reply.

    Actually I want to control brightness of LED by using a Potentiometer

    Please tell me where to incorporate a POT safely… in this circuit.

    Thanks for your quick reply.

  142. I have tried using 475uF 40v Cap in C6 Flickering lowered but a audible sound still there.

    Also Please check why Consuming 157miliAmp at 230v AC that is around 36 watt in a Good quality AC Ameter aw well as in mulitmeter selecting AC amp.

    I am trying to build a led Lamp for my Planted aquarium with 1 watt or 3 watt LED in RED, BLUE, WHITE Color because I cannot afford imported High lumen High power LED amp.

  144. I have successfully made some LED project from you blog Thanks very much for that. but, in this project though I have not made any mistake arranged according to the diagram checked several times but getting 95 volts DC at C6 terminal output, for a single 225k PF and 15v Zenor.

    I used 1pcs 225K capacitor 2 run 1 watt LED 4 pcs serially but flickering also producing audible flickering noise replaced 100 mfd by 475mfd 63v Polarized capacitor visual flickering diminished but faint audible noise still remain. Is BT136 producing sound or capacitor no heat at no components Triac, R2 R3 and 15v 1/2 watt Zenor diode after 8 hours running.

    But consuming 156-160 miliamp at 230v AC Adding more 225k 250v PF producing more flickering audible noise as well as current and intensity of led and current consummation.

    I have tested this project in Breadboard as well as Vero board found same result. can you explain How can be fixed?

    • Thanks Prosenjit,

      Change C6 to 10uF/400V and check, it's the capacitor that could be causing the flickering noise.

      I'll update a new circuit soon in the above article, you can try that if you are having problems with the above.

  146. The cost of PP capacitor is high here in Nepal so using 5 of them is way costly, can you propose another circuit with at least 500mA current?

    • A capacitive power supply will require many PP capacitors without it you can make a 500mA unit, the best thing would be to buy a cheap reliable SMPS circuit from the market costing just Rs.100/-

  148. Sir Arun again.
    All the problems of my circuit have been solved myself.
    Now i am in the middle of constructing a wireless audio system.
    My intention is stated below:
    A blower ( instead of fan ) is placed nearer to TV both sits in the hall of my house. So when i am turning on TV fot entertainment, it would be necessary to increase the volume of TV to overcome the sound from the blower. So i have decided to make a wireless audio control system which is intented to place at a comfortable distance from me and help me in hearing the exact sound as heared from the TV.
    It is supposed to take the audo from the audio output jack ( To VCR ) of the TV and let it be processed and transmitted to air by a homemade FM transmitter. Then a FM receiver kept at the other place captures the aired signals and reproduces the original sound signals. I want to include a jack for headset also so that i could enjoy TV at night without disturbing others……
    So could you plz help me in starting this project…. I am exopecting your help throughout this project

  150. Sir, i have to ask you one doubt. This is not related to the current problem. My question is : Any other means exist to step up a 120 V AC voltage to 230 V AC instead of a step up transformer ?? ( like a popup capacitor in a transformerless power supply )

    • Arun, yes you can do it using charge pump circuits, but the current will not be sufficient.

      en.wikipedia.org/wiki/Voltage_doubler

  152. That memory element shown in the diagram is intented to inform us the current status of the overhead tank.The red LED associated with that portion will be turned on once that tank is filled and retains that ON condition for a long time. It willn't be affected by any power failures. So we can get know whether the tank had been filled or not at any time..
    It was working perfectly at first weak. But after that, it is not getting turned on automatically when water overfowing detected by the Auto off trigger. But when a power failure occurs after the overflowing detected and current returns, it is getting turned on. I think sufficient voltage is not reaching the sensing node of the memory cell which may be causing this problem… So by the by what z ur opinion abt thz sir ??

  154. Sir, after a long time i came back again. This time seeking your valuable help in one of my previous project….. I have sent it to hitman2008….
    Plz check it and reply me soon sir

  156. Sir.
    You missunderstood my intention.
    I mean ;
    Eventhough the sensing voltage is to be taken for the opamp stage , it will get affected by the reference 12 V supply when the battery is under charging and a resulting voltage appears as the voltage for the opamp. Am i right sir?
    If yes why couldn't it be possible to feed this resulting voltage to the opamp for sensing ???
    In my design, i have chosen the maximum power saving mode for the battery.
    If i am feeding the battery voltage as the sensing one, the opamp stage will function always even during discharging period ( which is not recommended ) drawing a current of 9 mA from the battery.
    But in my design, i have selected the 12 V rail as the sensing voltage itself since a resulting voltage between this and the battery voltage appears during charging, and this resulting voltage is getting compared till certain cut off. Thereby by my design, no unnecessary current drawings are there from the battery during power failure.

    You didn't reply to ma last question.
    CAN I MAKE THE CUT OFF POINT BY CONSIDERING CURRENT FLOW TO THE BATTERY DURING CHARGING ( selecting a cut off voltage at the point when the current flown to the battery has been completely stopped ) ??????

  158. Good morning Sir.
    Is it possible to take current flowing to the battery as reference to make charging cut off at fully charged condition ???
    Means, considering the current flowing to to the battery from source during charging, and select a threshold voltage level at which the current bcomes zero ( no more current flows to the battery ) as the cut off point.

    But when i am noticing the charging of my two series connected 4.66 V batteries, i have found that, initially the charging current rises to a high level ( say 130 mA ) and slowly it is getting reduced . At last it bounces back and forth between some current level ( say 47.2 to 47.6 mA ) it is not becoming zero.

    • Hi Arun,

      the voltage that is been fixed is referred as the reference voltage and the sensing voltage needs to be taken from the battery.

      add a feedback resistor 100k from the output of the opamp to pin3 for restricting the fluctuations at the thresholds.
      I have covered all these comprehensively in all the 741 battery charger circuits in my blog.

  160. Sir would you mind checking your hitman2008 inbox again ?

    THEN AFTER THAT
    :-
    If i am getting that much current (160 mA ) from that config.,
    will it be possible to add several capacitors in parallel with each additional zener diode taken place in the circuit along with a MOV and safety resistance ( for surge protection ) deliver higher value currents ??????

    • Arun with 8V you eed to connect the parallel LEDs in strings of two and possibly add a 50 ohm resistor i series with each string.

      if you add a zener diode ,the current may not increase as per the requirements and calculations.

      with low voltage loads a capacitive powers supply will not work correctly ad efficiently.

  162. After checking my circuut i found the following current consumption

    For parallel config. Of batteries ( 4.5 V )
    1). Current taken from the source to battery for charging 39 mA
    2). Current drawn from the battery during discharging is 80 mA (little brightness)

    For series config. ( 8.8 V )
    1). 39 mA
    2). 160 mA ( more brightness )

    Since in both cases charging current is same, i chose the series config. because i need more brightness.
    Is my selection fruitfull Sir ?

    Also i could understand that a single power supply will not deliver sufficent current during charging phase ( 2* 30 mA of a relay + 39 mA for charging the battery + 7 mA for operating the circuit components = 106 mA whereas the 1.5 uF alone can only draw a maximum of 85 mA ).

    So could you please tell me whether it is possible to use any combination of two 12 V 1 W zener (parallel or series) could be used in association with two parallel 1.5 uF capacitors in a single power supply. Surge current to be avoided by a MOV and a Surge limiting resistance ???????????????

    • Arun,
      With a low voltage DC source such as a battery, series or parallel connection both will give same consumption and brightness for the LEDs if configured correctly, I dont understand how it is differing in your case…strange.

      I could not understand this question:

      Also i could understand that a single power supply will not deliver sufficent current during charging phase ( 2* 30 mA of a relay + 39 mA for charging the battery + 7 mA for operating the circuit components = 106 mA whereas the 1.5 uF alone can only draw a maximum of 85 mA ).

      If you use zener diodes which regulate voltage by sinking current with a capacitive power supply, it will cause it too become highly inefficient and will drop its current greatly

      I think you should use a cell phone charger as the input instead of a capacitive power supply.

  164. Since the power supply is not able to draw above 80mA from the 1.5 uf capacitor and higher value capacitors causing high surge current problems, i have
    designed the circuit in such a manner that No two relays activates simultaneously during charging time to avail sufficient charging current to the battery, after charging no current is required to battery so the availablr current is used to activate the two relays effectively. Similarly during discharging time, both relays are idle due to the absent of power supply therby saving the current from battery.
    THEREBY I HAVE AVOIDED THE LOW BATTERY CUT OFF BY OPAMP STAGE.

  170. Sir,
    Could u plz tell me what are the lower cut off voltagr and higher cut off voltage of a portable emergency battery showing 4.17 V

  172. Sir i didn't get what u were suggested last time. Could u pls help me in modifying the current circuit by varying DC output using TRAIC BT136 with 24 V zener used
    U have already posted based on SCR ( which is having varying 0-24 V DC ). But i need a one based on TRAIC.
    If we can modify thz like that, will we get high current ouputs( say upto 500 mA ) like in the current ckt ?

  174. Sir, could u plz suggest me
    4 Hrs ON 20 HRS Off timer ckt with caliberations which can be understood easily ( 4017 or 555 )

  176. Sir i have used BT136 instead of SCR. What 2 do now to make that ckt functional ?
    And what abt this ckt, regarding the high voltage (40 V ) prolblem ???

  180. In the intention of getting 12 V output, i have connected a 12V 1 W zener. But the problem is i am getting high voltages ( say 40 V ) even in single capacitor config. What 2 do ?
    On checking your High current transformerless surge currentlimitted power supply ckt similar to thz, i didn't get any output

  182. Sir,
    You warned me not to use capacitors in parallel in the power supply discussed b4 since it causes high surge currents. Can i use this schematic ?
    Or the one in the below link with one capacitor being replaced by parallel config

    2.bp.blogspot.com/-z8OiKZpXIvg/UY3rG8dkgMI/AAAAAAAAEHg/9YMwKeEFwPw/s1600/variable+transformerless+power+supply+circuit.png

    • yes it will work in such circuits but it's always good to use smps designs for getting the correct and efficient results

  184. Hey, I tried and made the same circuit mentioned above, but the problem is that the output its giving is above 250v and I need it almost 50v. How can I get upto 50v??
    Can I use 78xx series for the output?

  186. i want to made this circuit voltage output of 30 voltge for glow 10 LED in the series. please tell me i need to change here capacitor or other component.

  188. I am using this circuit for a 12v 20 watt led, but it is not glowing completely as compared to 12v battery.the output of the circuit is 12v and 0.54Amps.10 watt led is working properly
    what can i do for about 30 watt Led,can i use this circuit for 20 and 30 watt Led after increasing the amps upto 1amp?

    • I wouldn't recommend the above design for operating a 20 watt or higher LEds, it's better to go for an 12V/ 2amp SMPS readymade unit, which would provide a safe, reliable and permanent solution………. and also will be free from lethal mains shocks.

  192. what can i do for about 50v output..
    and how can i increse the amps about 1amp..plz explain in proper manner so i can understand it,i am new in electronics..

  194. sir it 105 and 1uf the same if yes then it can be use in this circuit Simple Pure Sine Wave Inverter Circuit – 500 Watt Pure Sine sir can 105/400vpp use instead of 2uf or two 1uf? thank you.

  196. sir please can i replace 105/400vpp in place of 2uf/400v can i also use this circuit to power my remote circuit which need 5v supply?

    • yes you can replace 1uF with 2uF, but this circuit is not recommended for delicate electronic circuits since it's not isolated from mains.

    • R2 is not crucial, it can be removed, the zener ensures that the triac conducts only after the desired zener voltage becomes available at the output, and thus keeps this voltage constant at the output.

  200. After running the 20W LED with 10uF for more than a month, it fuses suddenly. First LED fused, then C6 bursts (33uF/63V).

    The reason I am suspecting:
    I was driving another 12V/0.056A fan for cooling from same 36V O/P with resistance driver.
    1. First resistance (1W) driver fails, which fails the fan to run.
    2. LED get hot and burnt.
    3. Peak voltage increased across C6 and it burnt.
    Another possibility of damage: The power extraction may be too high and those Chinese LED will be certified someday for its voltage and current 🙂

    Next modification I am thinking:
    1. to use 30W LED to get 20W power. You will get 30% margin of protection.
    2. Stable circuit for fan. 36->12V may be problematic with traditional LDO regulator. How about capacitor divider before rectifier?

    BTW, my 3.3uF, 6W (6x1W) is running since last three months 24×7.

    -CM

    • Was your 20 watt LED rated at 36V? In that case the fan wouldn't have done anything wrong, however if your LED was rated for a lower voltage then definitely the application was incorrect.

      I think before connecting any LED it must be ensured first that the output voltage exactly matches with the LEd forward voltage.

  202. Sir,
    Are you test it…..

    Because R2 is getting very hot…….

    I am used in R2 1k 1 Watt……

    PLZ solve my problem if you have any solution.,……

    • please don't become restless….the site is all about learning through discussions, experimentation, calculation etc.

      Try using a higher value for R2, try a 10k, 1 watt resistor.

  204. hello Swagatam,
    can i use this circuit to run a 12V 0.2A dc cooling fan continuously ? if not why? what changes done with circuit, or what V/A rated fan i must use?

  208. Inteersting Info CM! I am sure the visitors would greatly benefit from this.

    Actually I am already committed to sharing my exclusive ideas with the readers, if you think you have a better plans for me where you could use my innovations for generating some sort of income for both of us, then who knows I may slowly wind up here and start concentrating on the new job;)

    Anyway, thanks a lot for showing your kind concerns! appreciate it.

  210. Thanks friend!

    It feels very satisfying when I see readers succeed with my projects!

    Yes, I'll be careful about somebody stealing my credentials, I appreciate your suggestion very much!

    Many thanks!

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