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Surge Protected Cheap Transformerless Hi-Watt LED Driver Circuit

Surge Protected Cheap Transformerless Hi-Watt LED Driver Circuit

The increased number of complaints from the readers regarding burning LEDs associated with my earlier posted transformerless 1 watt LED driver circuit, compelled me to solve the issue once for all. The power supply section of the circuit discussed here remains exactly identical to the previous configuration, except the inclusion of the "switch ON delay feature" which has been exclusively designed by me and added in the circuit for rectifying the burning LED problem (hopefully).

Suppressing In-rush Surge in Capacitive Power Supplies

The complaints that I kept on receiving were undoubtedly because of the initial switch ON surge which kept destroying the 1 watt LEDs connected at the output of the circuit.

The above problem is pretty common with all capacitive type of power supply, and the problems has created  a lot of bad reputation to these types of power supplies.

Therefore normally many hobbyists and even engineers opt for lower values capacitors fearing the above consequence in case larger value capacitors are included.



However as far as I think, capacitive transformerless power supplies are superb cheap and compact AC to DC adapter circuits which requires little effort to build.

If the switch ON surge is tackled appropriately, these circuits would become spotless and could be used without the fear of any damage to the output load, especially an LED.

How Surge is Developed

During switch ONs, the capacitor quite acts like a short for a few microseconds until it gets charged and only  then it introduces the required reactance to the connected circuit so that the appropriate amount of current only reaches the circuit.

However the initial few micro second short condition across the capacitor inflicts huge surge to the connected vulnerable circuit and is sometimes enough for destroying the accompanied load.

The above situation can be effectively checked if the connected load is inhibited from responding to the initial switch-ON shock, or in other words we can eliminate the initial surge by keeping the load switched OFF until the safe period is reached.

Using a Delay Feature

This can be very easily achieved by adding a delay feature to the circuit. And that's exactly what I have  included in this proposed surge protected hi-watt LED driver circuit.

The figure shows as usual an input capacitor, followed by a bridge rectifier, until here everything's pretty common capacitive power supply.

The next stage which includes the two 10 K resistors, two capacitors, transistor and the zener diode form the parts of the important delay timer circuit.

When power is switched ON, the two resistors and the capacitors restricts the transistor from conducting until both the capacitors get fully charged and allows the biasing voltage to reach the transistor base, illuminating the connected LED after a delay of about 2 seconds.

The zener is also responsible for prolonging the delay for two seconds.

The 1N4007 diode across one of rhe 10K resistors and the100 K resistor across one of the 470uF capacitors  helps the capacitors discharge freely once the power is switched OFF so that the cycle can repeat enforcing the surge protection into action on each occasion.

More number of LEDs may be connected in series for increasing the power output, however the number may not exceed 25   nos.

Circuit Diagram

UPDATE:  A more advanced design is discussed in this zero crossing controlled surge free transformerless power supply circuit

The videos below show the LEDs illuminating after about a second on power  switch ON.

Complaints From the Readers (Resistors burn, transistor becomes hot)

The above concept looks great but is probably not working well with the proposed high voltage capacitor power supply.

The circuit has to be researched a lot before it becomes completely free from troubles.

The resistors in the above circuit are unable to withstand high current requirements, same is true for the transistor which also becomes quite hot in the process.

Finally we can say that that unless the above concept is thoroughly studied and made compatible with a capacitive transformerless power supply, the circuit cannot be put into practical use.

A Much Robust and Safe Idea

Even though the above concept failed to work it doesn't mean the high voltage capacitive power supplies are completely hopeless.

There's one novel way of tackling the surge issues and making the circuit failproof.

It's by using  many 1N4007 diodes in series at the output or in parallel to the connected LEds.

Let's have a look at the circuit:

 

 

The above circuit is yet to be tested for many months, so these are still early days, but I don't think the surge from the capacitor will be high enough to blow the 300V, 1 amp rated diodes.

If the diodes remain safe so will the LEDs.

More diodes may be put in series for accommodating more number of LEDs.

 Using a Power Mosfet

The first circuit attempt which seemed to be vulnerable itself to surge causalities can be effectively remedied by replacing the power BJT with an 1 amp mosfet as shown in the following diagram.
The mosfet being a voltage controlled device, here the gate current becomes immaterial and therefore a high value 1M resistor works perfectly, the high value makes sure that the resistor does not heat up or burn during the initial power switch ON. It also facilitates a relatively low value capacitor to be used for the required delay ON surge suppressing feature.

A little investigation revealed that the high voltage transistor in the first diagram is actually not needed, rather it can be replaced with a high current Darlington TIP122 transistor as shown in the following diagram.

The high voltage surge from the capacitor becomes ineffective against the high current specs of the transistor and the LEDs and no damage is caused to them, in fact it forces the high voltage to drop to the specified allowable safe limits of the LEDs and the transistor.

The TIP122 also allows the use of a high value base resistor thereby making it sure that it does not become hot or blow off in the course of time, it also allows the inclusion of a low value capacitor at the base of the transistor for implementing the required delayed switch ON effect.

Using a Power BJT

The above design further improves in terms of safety and surge suppression when used in a common collector mode, as given below:

 

 

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!



109 thoughts on “Surge Protected Cheap Transformerless Hi-Watt LED Driver Circuit”


  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. What is the maximum current it can handle?
    I believe it is only ~70mA.
    If so will adding 2 more 1uF/400 as parallel increase it to 210mA?
    Does this circuit not require filter capacitor?
    If required what will be the ideal value of the capacitor?

  3. Hello sir
    If i use .2W 25 LEDs instead of 1W LEDS what are the modifications suitable for that circuit?I talk about circuit which was made using Tip122 transistor.

    Thank you.

    • Hello Pushpike, you can use the last circuit which is shown in the above article without any modifications

      just change the 56 ohm resistor to 10 ohm resistor.

    • Thank you.
      another 2 questions,
      1.If i need to use 40 or 50 .2W LEDs in circuit. What is the best option for me?
      2.Do these circuits suppress lightning surges??

    • you can connect all 50 LEDs in series with the proposed circuit….iy will be fine, no changes are required

      no this circuit is not designed to suppress lighting bolts.

    • If i use MOV and PPTC devices series and parallel with this circuit.I can avoid both of these problems know.If it is ok,Please give me the proper ratings of this two devices which is suitable for my circuit.

      Thank you,

    • MOV will not last a lightning strike, in fact no device will control a lighting bolt except a well earthed rod.

      An MOV and a NTC can be used for controlling 220V switch ON surges only…any 330V MOV will do the job, and any 5 ohm type NTC will be great.

  4. Hello Swagtam,

    I am working on making 2 in 1 LED bulb where there will be 12w normal light will be there and 1w to 3w Night light will be there in the same bulb.

    But, I need your help to guide me how I can achieve this. When this light will be first switched on then it will glow as normal 12w LED Bulb, once it is switched off for 2 seconds and switched On this will glow as night lamp with 1w LED.

    I am thinking to use flip-flop electronic circuit to achieve the above. Please give me your suggestion.

    • Hello Nitrous, a flip flop could make the design unnecessarily complex, I think it can be implemented using an ordinary SPDT switch…the center pin goes to the (+) of the input supply… out of the two outer pins, one connects with the LED (+) through a calculated 12W resistor, while the other pin connects with the LED (+) through a calculated 1 watt resistor.

  5. Dear, Thanks for this fruitful article. I made this ckt. It's a good ckt but 1uf capacitor become very hot so I leave this ckt and searching better one. again thanks a lot.

  6. Dear Mr Swagatam Ji, One the simplest thing I fail to understand by seeing the circuit given by you for 1watt powersuplly(transformer less) with surge protection that you have used only 1microfrad 400v capacitor and as far as I calculate it can only give 106 ma of current with a input main of 230vac 50hzs so at the output stage how we can gat 350ma of current to light 1watt LED with required brightness. Since I am new member and we're just reading your posts very interestingly since last one month I wanted to get the knowledge from you first because I am really interested in making few led projects of my own.

    • That's correct, but that can be compensated by using three 1 watt LEDs in series, 3 would provide a light equivalent to a single 1 watt LED, although you may have to spend 2 extra LeDs, the circuit will be free from heatsinks, current controllers etc.

      please feel free to ask everything you may be interested in, in fact i may already have all the tutorials you may be looking for.

  7. Dear i have tried ur last circuit with One pcs of 105uf instead of 3.3uf capacitor with MJE13005 and zener 15v for five 1watt LED in series.But still MJE13005 and 56ohm resistance are getting so much hot.For over come this problem i used 200k instead of 100k but result is negative.Also brightness is decreased after use of 105uf capacitor than 3.3uf.What can i do now pls help me.

  8. Dear i have tried ur last circuit with 3.3uf capacitor, MJE13005 and zener 15v for five 1watt LED in series.But MJE13005 and 56ohm resistance are getting so much hot.I think it will burst out if i continue.Also other parts are remain in normal condition except MJE13005 and 56ohm resistance during running.So pls give me solution urgently.

  9. Dear how many capacitor i used 1 or 2 in series for optimum brightness of the LED?Also is this circuit is harmful for inverter(When main is absence)?

    • No, increasing capacitors will not help to increase brightness rather it will make the circuit more vulnerable to surge currents….if all 90 LEDs are used only in that case increasing capacitors in parallel can be safe for increasing brightness of the LEDs.

  10. Dear if i use 13005 transistor instead of Tip 122 then it will worked? also if i use 2.2/2.5/3.3uf capacitor instead of 1uf then what have to changed in this circuit? How many LED can be driven by using this 2.2/2.5/3.3uf capacitor for proper brightness?Actually i want to drive 4/6/8/10/12 sets of 1 watt LED in series by this circuit.Pls help me by ur useful comments

    • Dear Saeed, yes surely you can try MJE13005, and also try using higher value capacitors instead of 105/400V, but make sure the LEDs are connected across emitter/ground of the transistor and a zener connected across base ground of the transistor….you can go on and connect upto 90 LEDs in series

  11. Sir i made the last one circuit as you comment above i used 3 12v zener in series for 36volt but i used 10 LED in series it uses 3.6v but actually because of lack of current voltage get drop. so as you design last one circuit it is used for how much LED 1 watt in series? i used last one but i want ask what about 1st one circuit as in article you write some blogger is suffer resistor burning. is 1st one is suitable for my application as i want to use 20 no 1 watt LED in series.

    • Ashoke, you should use a 12V 1amp SMPS if you are intending to use 1 watt LEDs, for ultimate safety and long life….capacitive supplies will not provide optimal illumination and 100% protection

  12. what happen when supply of ac reverse because we cant chk neutral & negative every time at AC power plug? For safety what we can make provision? can we provide any diode?

  13. sir i made last one circuit but when i start the supply 100ohm/1/4watt resistor burn. So after that i remove that resistor and move the series of LED at position of 100ohm resistor as shown in 2nd last circuit but when apply supply LED get blew why happen this? please help me.

    • which LED did you use? only 1 watt should be used, remove 100 ohm use 22ohm instead, and replace the 1uF with a 100uF ….then check

  14. could you please introduce a LDR for any suitable circuit in the above to use as a automatic day night lamp.

  15. Hello Sir,
    I have built this circuit, but a few components are not available here in Paraguay at local shops. I used a 1uf 640V ceramic cap, and a 1uf 50V electrolitic Cap. I only hook one 1W LED up, but the first try, it blew… Do I need to have 3 hooked up? Also, do I need a resistor in series with the LEDs? For testing purposes, is there a resistor i can use as a dummie load for the LEDs / or a Diode? So that I can check outputs, and currents without shorting out the circuit or destroying lots of LEDs? (they are still about $1.25 each here)

    Thank you

    • Hello Joseph, I have answered your question in the previous comment (just above this comment)

      You can use a 100 ohm, 1 watt resistor in series with the LED, however it's strange your LEDs are blowing of, this could have happened if the above mentioned protections were not taken, yet still the chances would be 1 in 10

    • Thank you for your replies, I am sorry about the double post, from my phone (the first post) I couldn't tell that I completed the process all the way.

      I do not believe I had experienced an On delay (how long of a delay are we talking here?) so I will try the larger cap. regarding my last question, besides just adding a 100 ohm resistor, is there a direct replacement for the LED so that i can take measurements without loosing more LEDs? I have done some searching but have really not found any good answers… If i short the output, what is the maximum current this circuit can supply? (do i have to worry about destroying components if i just measure the amperage across the outupt)

      Thank you for your help, in the past I have been pretty good at building circuits correctly, but I do not have a breadboard to work with so its a little different for me.

    • The delay effect is introduced so that the LEDs can be safeguarded from the initial switch ON surge, it could be a 1 second delay at the most for implementing the above.

      The current is hardly 70mA for a 105/400V capacitor, and it's not responsible for the blowing up the LEDs, it's the initial switch ON surge that's doing so measuring with some other alternative won't help with a solution.

      However if your LEDs are blowing-of each time, the issue could be something else because even with the surge coming the LEDs would blow up may be one in 10 times, never always.

      please try the last circuit shown above, you may try it using 5mm LEds, and a 474/400V cap at the input, if it works alright, you may proceed with a 105/400V cap and 1 watt LEDs.

    • Hello again,
      Is it ok to have a 50V cap instead of a 25V cap? I have the last circuit built, but there still seems to be no delay, although I am using 22uf at 50V.
      Plugging it in, the LED did survive, but it was making an odd squealing sound, about the 5th time testing it i heard an arch sound (but did not see anything) and unplugged it immediately. Now the LED is very dim.

      Any suggestions?

      Thanks for your help

    • Hello Joseph,

      that's very strange. I have built dozens of these units all have worked perfectly, even the most ordinary one without any surge suppression stage worked for months before bursting.

      Are you sure about the capacitor that you are using? They must be rated at 400V and of very good quality

      a squealing sound is again very strange because we do not have any kind of oscillator or frequency generating stages involved.

      your input capacitor should be like these:

      i01.i.aliimg.com/wsphoto/v0/1140853215/Free-shipping-Metal-film-font-b-capacitor-b-font-font-b-105j-b-font-font-b.jpg

      please try replacing the TIP122 with MJE13055 and check the response using the last circuit.

  16. Hello sir,
    I have tried this circuit, but it blows the 1w led, do I need to use 3 leds in series like the schematic? Can I make this circuit run only a single 1w or 3 lw led? Also, for testing and not destroying leds (here they are quite expensive still) is the a recommended resistor I can use in place if the leds? Or should I use just a n4007 as the diode?

    I forgot to mention I am using the circuit with the tip122, and I have 220v here
    Thank you

    • Hello Joseph, are you getting the delay effect in your circuit, if not then there could be something wrong with the connections.

      or try increasing the value of the 1uF capacitor to 22uF or any other higher value for getting a delay effect.

      alternatively you can put the LEDs in the emitter arm of the TIP122 instead of the collector arm, this will make things extremely safe.

      LEd count is not crucial…

      You may also try the second circuit and use six diodes in series instead of the shown 12nos if you intend to use only one 1 watt LEd

  17. Hello Swagatam,
    at your last circuit, you use 12 V for zener to drive 3 units LED with transistor so should be no issue if I use 3.7 V to power up single 3 watt LED. CMIIW
    Rgds,
    Yofan

  18. Hi Swagatam – I have made and tested the circuit that has 6 diodes per LED and it is working fine for last 3 days.

    Regards
    Gopal

  19. but in this link it is of 5mm led know i am having 8mm .5 waat led . so in the earlier circuit why it is not possible

    • In the referred link,the circuit employs two high voltage capacitor and resistor network for suppressing surge, this would help prevent your leds from getting damaged from switch ON surge currents.

  20. sir in earlier circuit ,when i connected 25 led(8mm,.5 watt)in series and when i checked ampier it was about 20 mA and volt was about 70 V. and when i connected 25 of same led in parellel on the output on the other(25) led and when i measured ampier it was also about 20mA. but when i connected parellaly the wattage of led will become 1 watt and i should get 40mA know why i was able to get the same 20 mA.

  21. sir when i reduced the input capasitor from 105 j to 474j i saw the brightness of the led become reduced.so now i have done 25 nos in series of .5watt so how much i can do parallely.

  22. hai sir i have tried this circuit but my leds are going one by one i have put 1000uf and 470 uf capasitors and mje 13005a transistor why my leds are going can u tell me pls.

    • Hi Abraham, how many LEds have you used and what's the specification of the LEDs?
      Please mention these, accordingly I'll tell you the modifications for safeguarding the LEDs..

    • hai sir i had used 8mm .5 watt. 25nos in series .and 1 hour i had kept it on.after 1 hour 1by1 started blinking.in that circuit i had used 1000uf and other one 470uf and transistor mje 13005a .1st when i did that circuit 1st 10k resister was hotten then i changed 10k quater watt to 2 watt then there was no problem but the blinking of circuit is continuing and after 1-2 min the blinked led will go. can u pls tell me the reason.

  23. Hi Swagatam,
    can u build the same circuit with use of battery, so that whenever supply goes, the LED should not get turned off for about 1 hour or less…

    thank u in Advance

    • Hi Jignesh,

      You can make the following design:

      1.bp.blogspot.com/-I2zlapFq6RM/UML_NxUJy2I/AAAAAAAAB3w/27ZLDjK9C9g/s1600/simple+modem+UPS+circuit.png

      Replace the adapter with a capacitive power supply as above and connect LEDs across the shown output terminals

  24. Sir,,
    In your 3 rd circuit at this blog, the MOSFET MLP1N06CL which pin i connect where.
    pin 1 is Gate
    Pin 2 is Drain
    Pin 3 is Source

  25. Sir,

    So that my circuit output is 16v without load. is it any problem in my circuit.
    sir i am used
    1uf 400v ppc caps
    4nos of IN4007 for bridge and 12nos in series
    100uf 160v electrolytic caps
    5 nos of 8mm White leds

    PLZ help me out…

    • the voltage will be equal to the filter capacitor voltage rating, without any load connected.
      as soon as you connect the load, the voltage will adjust as per the load specs.
      5 leds would create a voltage drop of 3.3 x 5 = 16.5V
      that's exactly what you are getting, remove them ad it'll be 160V.

      if it's happening without load means there's something wrong with your component connections.

    • hi sir,

      as per your previous blog you said that

      Swagatam MajumdarAugust 6, 2013 at 9:58 AM

      Hi Aruna,

      The total LED forward voltage drop value should match the total diode fwd voltage drop. 12 diodes gives 12 x 0.6 = 7.2V, this much voltage will suffice just two LEDs….for more LEDs you must go increasing the number of diodes as explained

      so why now u say the output voltage without load is 160v and also i check it with your circuit diagram its same as it is..

    • Avik, The above statements are correct, i did not understand how you are relating them, please explain your question properly.

      the diodes themselves are the load in the second circuit

    • because when i made this circuit with and without load i getting 16v dc 60ma where i used 100uf 100v capacitor and also like aruna Wrote on her blog,
      but u said that

      Swagatam MajumdarJanuary 30, 2014 at 11:37 AM

      the voltage will be equal to the filter capacitor voltage rating, without any load connected.
      as soon as you connect the load, the voltage will adjust as per the load specs.
      5 leds would create a voltage drop of 3.3 x 5 = 16.5V
      that's exactly what you are getting, remove them ad it'll be 160V.

      if it's happening without load means there's something wrong with your component connections.
      So I am not undrstand what U say….

  26. Ok Sir, Thanks for feedback now i understand.
    so sir would you please tell me what is the output volt and current of that circuit you made and also what is total power consumption…
    Sir please tell me…….

  27. Dear Sir,
    I read your blog and also that link, in this calculation i got input capacitor's resistance but input capacitor give about 315v and 70mA but after filter capacitor and diode i got 16v 70ma so (315-16)V=299v is loss for filter capacitor and diode but i got 70ma current in output..

    so that scenario is not clear for me…
    So sir would you explain it…
    PLZ…

    • Dear Avik, you must use a 400V filter capacitor, for example you can use a 10uF/400V capacitor as the filter capacitor then you would get the suggested 310V DC output

  28. Hi,
    I made your 2nd circuit with 1uf 400 PPC cap.
    Output voltage 16.22volt
    carrent .06 mA
    so total .97 watt
    Now question is how to calculate voltage and current loss in that circuit…

    PLZ Suggest me……..

    Thank for the circuit….

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