I think to make LED lamp circuit by using 1 watt LEDs (300mA and 3.6V). How to make circuit. But I can not use transformer.Because size and cost of transformer is high). Input single phase, 220V,50Hz AC supply. Please help me.


closed as too broad by Leon Heller, Daniel Grillo, Matt Young, Chetan Bhargava, Nick Alexeev Jul 25 '14 at 18:40

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ This question appears to be off-topic because it requires a circuit to be designed. \$\endgroup\$ – Leon Heller Jul 25 '14 at 13:55
  • \$\begingroup\$ You ought to consider marking your previous question as being answered correctly too (at some point). \$\endgroup\$ – Andy aka Jul 25 '14 at 13:59
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    \$\begingroup\$ Please answer all the questions. How many are you wanting to make? 1 - 10 - 1000s ? \$\endgroup\$ – Russell McMahon Jul 25 '14 at 15:27
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    \$\begingroup\$ See addition at end of Andy's answer. In your context this IS a $1 solution. Note that 5 cent x 1 Watt LEDs will be junk and have a very low lifetime. \$\endgroup\$ – Russell McMahon Jul 26 '14 at 14:16
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    \$\begingroup\$ Far be it from us to actually DESIGN anything here. Or discuss designs. Or to deal with anything like REAL electronics. Getting a $3 Chinese result from a $1 circuit when buit in a suitable environment (which is the case in this case). Horrors. People may actually learn something new!!! Wonder may be evoked! People may see that you can actually eschew the IC based well trodden path and perhaps (perhaps) get something that will fill the niche. That would never do. Disgraceful. .... Off with its head! (Exit Cheshire cat's smile stage right, Avant ...) \$\endgroup\$ – Russell McMahon Jul 26 '14 at 14:26

Here's a circuit that uses a high voltage buck type regulator: -

enter image description here


Its output voltage is 36V at 330mA but I reckon adjustment of the R8/R9 ratio should lower the voltage. Here is the digikey reference design page. You may not be able to get down to a low enough voltage to drive one 3.6V LED but a few in series would work.

Here's another idea: -

enter image description here

Here's the page it came from. And here's another circuit: -


enter image description here

This should give you a few ideas OR just go and buy one for $5



I'm tacking this on the end of Andy's answer as the question was open when I started this answer and had been closed by the time I finished answering it - ie it had been closed while I was in the process of answering.

If I was able I'd post this as a separate answer:

Here is a design that may meet your requirement.
It uses a high frequency transformer which you can have wound at local labour rates. With proper supervision this could be done by relatively unskilled people as long as they can follow instructions. Also, for your suggested order size you can probably get a local company to do this at an acceptable cost.

Full description here:

IGBT powers ultra low-cost offline wall adapter

This has output voltage feedback but it could be converted to LED string current feedback with ease.

Note use of IGBT as main switch.
The MBT3945 is a bipolar thyristor acting as a voltage triggered clamp on the gate. Read the circuit description to see how it works. The same function could be achieved with two low cost bipolar transistors.

The circuit is less complex than it may at first appear. 5 capacitors, 6 diodes, 6 resistors, 1 optocoupler, 1 zener, 1 ...

enter image description here Their circuit is 110 VAC powered. If you are in Kerala then you probably want 230 VAC operation.
It will work at 230 VAC with more care.

This IGBT STGPL6NC60D will probably be suitable. iT costs about $US0.50 from Digikey in the quantity you mention.
Data sheet here It is a fast device - liable to be very adequate for your task.

If this circuit is too complex for you then you are liable to have problems with any "good" circuit. What you are trying to do is a non trivial task and inherently dangerous. Taking too many shortcuts will kill your users.

  • \$\begingroup\$ Sorry .. It is too costly .. I want circuit less than $1. \$\endgroup\$ – Arshid KV Jul 25 '14 at 14:01
  • \$\begingroup\$ Remember this is a question and answer site and not a free design service - the ideas in my answer are for you to research other solutions more appropriate to your requirements. Cost of $1 wasn't mentioned so this fact has come rather late in the day. \$\endgroup\$ – Andy aka Jul 25 '14 at 14:11
  • \$\begingroup\$ @Andyaka He's unlikely to build them BUT at present he is headed towards killing himself with his high enthusiasm and low knowledge level, so a bit extra help seemed in order :-( :-). I do have a circuit which should work and may be < $1 with luck. I'll try to get to post it sometime. Somewhat ill at present. \$\endgroup\$ – Russell McMahon Jul 25 '14 at 15:49
  • \$\begingroup\$ @RussellMcMahon some antipodean flu or something LOL \$\endgroup\$ – Andy aka Jul 25 '14 at 15:57
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    \$\begingroup\$ @Andyaka - Sorry to add to your answer as above - but there was a putative Balrog* on the Bridge of Khazad-dûm and I had better things to do with my time than to fight it with a whole new cloned question and answer. Needs must twill happen, but why should it need? * It may have in fact just have been been a Boojum. \$\endgroup\$ – Russell McMahon Jul 26 '14 at 14:21

Buy an LED driver on eBay? They are quite cheap


  • \$\begingroup\$ You need a constant current output if it is just for lighting at constant intensity \$\endgroup\$ – user32885 Jul 25 '14 at 13:40
  • \$\begingroup\$ sorry .. I want circuit .. \$\endgroup\$ – Arshid KV Jul 25 '14 at 13:55
  • \$\begingroup\$ You will not be able to make anything that is cheaper than you can buy on eBay from China \$\endgroup\$ – user32885 Jul 25 '14 at 14:32
  • \$\begingroup\$ @DirkBruere I MAY be able to show him how to build something "cheaper than China" but I need more information first. [Rectify mains. One transistor! self oscillating converter. Special cct from long ago. Needs HF transformer but this can be small and cheap. \$\endgroup\$ – Russell McMahon Jul 25 '14 at 16:19
  • \$\begingroup\$ Quite often from a DIY perspective the box to put it in is the most expensive item! \$\endgroup\$ – user32885 Jul 28 '14 at 8:21

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