40 watt Electronic Ballast Circuit

Simple electronic fluorescent ballast circuits are difficult to find and build. A simple homemade electronic 40 watt ballast circuit is neatly explained in this article. The PCB layout of the proposed electronic fluorescent ballast is also provided along with the torroid and the buffer choke winding details.

Even the promising and the most talked about LED technology is perhaps unable to produce lights equal to the modern electronic fluorescent ballasts lights. The circuit of one such electronic tube light is discussed here, with efficiency better than LED lights.

Homemade Electronic Fluorescent Ballast

Just a decade ago electronic ballasts were relatively new and due to frequent failures and high costs were not generally preferred by everyone. But with passing time the device went through some serious improvements and the results were encouraging as they started becoming more reliable and long lasting. The modern electronic ballasts are more efficient and fail proof.

So what’s the exact advantage of using electronic flourescent ballast compared to the age old electrical ballast? To understand the differences correctly it is important to know how ordinary electrical ballasts work.

Electrical ballast is nothing but a simple high current, mains voltage inductor made by winding number of turns of copper wire over laminated iron core. Basically, as we all know a fluorescent tube requires a high initial current thrust to ignite and make the electrons flow connect in between its end filaments. Once this conduction is connected the current consumption to sustain this conduction and the illumination becomes minimal. Electrical ballasts are used just to “kick” this initial current and then control the supply of the current by offering increased impedance once the ignition is completed.

A starter makes it sure that the initial “kicks” are applied through intermittent contacts, during which the copper winding’s stored energy is used to produce the required high currents. The starter stops functioning once the tube gets ignited and now since the ballast is routed via the tube, starts getting a continuous flow of AC through it and due to its natural attributes offers high impedance, controlling the current and helping sustain optimal glow.

However, due to variation in voltages and lack of an ideal calculation, electrical ballasts can become quite inefficient, dissipating and wasting a lot of energy through heat. If you actually measure you will find that a 40 watt electrical choke fixture may consume as high as 70 watts of power, almost double the required amount. Also, the initial flickers involved cannot be appreciated.

Electronic ballasts on the other hand are just the opposite as far as efficiency is concerned. The one which I built consumed just 0.13 Amps of current @ 230volts and produced light intensity that looked much brighter than normal. The have been using this circuit since last 3 years without no problems whatsoever (though I had to replace the tube once as it blackened at the ends and started producing lesser light.)

The current reading itself proves how efficient the circuit is, the power consumption being just around 30 watts and an output light equivalent to 50 watts.

Its working principle of the proposed electronic flourescent ballast is rather straightforward. The AC signal is first rectified and filtered using a bridge/capacitor configuration. The next comprises a simple two transistor cross-coupled oscillator stage. The rectified DC is applied to this stage which immediately starts oscillating at the required high frequency. The oscillations are typically square wave which is appropriately buffered via an inductor before it is finally used to ignite and illuminate the connected tube. The diagram shows a 110 V version which can be easily modified into 230 volt model through simple alterations.

The following illustrations clearly explains how to build a homemade electronic 40 watt electronic fluorescent ballast circuit at home using ordinary parts.

PCB Component Layout
40 watt Electronic Ballast Component Layout


PCB Track Layout
40 watt Electronic Ballast PCB track side
Torroid Inductor
40 watt Electronic Ballast torroid inductor wiring
Choke Inductor
40 watt Electronic Ballast EMI choke
Parts List
MFR 1%
Ohm, CFR 5%
Ohms, 2watts
Heatsink is required for T1 and T2.

148 Replies to “40 watt Electronic Ballast Circuit”

    1. Hi,

      The choke inductor is not critical, neither is the torroid, however the torroid wire type and turns are critical. The torroid core is T13 or similar and the wire is single core insulated type, the core should be very thin can't say about the exact gauge.
      The choke utilizes E-cores, any small type will do, with as many turn as possible using enameled copper wire, gauge can be 25 to 30 SWG.

    2. Hi…
      i did everything as you stated. only thing am stuck with is..with the choke & torroid coil. can you please specify much more details or mention some equivalent parts avail in the market.


    3. Hi…bro…
      if you can send me any clear pic of PCB diagram or layout diagram….i can post the clear schematic diagram for you & everyone else..this will also helps me too…
      waiting for your esteemed reply….

    4. Bro, everything is shown quite clearly in the article above, if you are having difficulty understanding, you can specify those… I'll clarify them immediately.

      If possible I'll try to produce a clearer PCB diagram.

    5. Dear brother I have connected an electronic choke with ac like this way as it phase is connected directly to the input supply and it's neutral is connected via switch. But after some days of its working it choke blown away. My question is that is this due to the wrong input connection of ac supply to the choke. Please reply and thanks in advance jayanta

    6. Jayanta, the phase neutral connections are not critical for any AC device….you can freely connect the phase/neutral anyway you like across the ballast it won't harm anything in the circuit.

      Your ballast burned because of voltage fluctuations….you could try employing an NTC at the input along with an MOV for preventing such mishaps.

  1. Bundle of thanks for reply
    one other thing if upload the clear schematic of the design it will be easy as it is power circuit so it is risky without it.There are some areas which is not very clear.

    1. Hi,

      You are welcome!

      Actually I don't have the schematic, I modified the above circuit from a ready-made 110V version, and drawing a fresh schematic now will be difficult for me. The PCB layout is clearly given so if you can make the PCB, everything else becomes absolutely easy.

      I have used this design and it has proved very reliable to me so far.


  2. can we use this type of circuit to drive white LEDs?
    I've made mains LED driver with 0.22uF/400V capaciotr, but using it with a general(lower quality square wave) inverter duirng power cuts causing decreased light in LEDs and a more load to the inverter than required!
    So, how can we use an electronic choke/CFL ballast circuit which can easily drive many white LEDs powering from a general inverter?

    1. OK, it may light up but it is not recommended because the voltage from the inverter will be very high and might damage the LED lamp, try using a 100 Ohm 3 watt resistor in series first, then gradually modify the value of the resistor for best results.

  3. Dear Swagatham, first of all thanks ! I was looking for this circuit for quite some time . Now to the question I need this to drive a 56wPLL what tweaks would I have to make ?
    Thanks in advance,

    1. Dear Jithin,

      I don't think a 56w tube would work here, because even with a 40 watt tube the transistors become considerably hot, so a 56watt might not fit here.


    1. Hello Ajay,

      The torroid is the most important part of the ballast and cannot be modified in any way….the one shown in the diagram is the only option you can go for.

  4. Hello Swagatam !!

    In description value of R8 is mentioned as 2.2 ohm and in you comment for VAC you have mention R8 = 22 ohm !! which is correct value ? 22 ohm or 2.2 ohm ??

  5. Hi swagatam,, im searching over the net but i saw your blog.. i know this is not your topic here but will you mind teach me how to wire in series the (4)10watts flourescent bulb and using only (1) 40watts ballast?? Thanks in advance…

    1. No,, Swagatam.. is it posible on ordinary 40w electrical ballast on 4 10watts flouscent tubes?
      i already tried with parallel connection on the pin of tubes but the problem is only 1 tubes will light.. i hope you can give me some ideas my needs,, also im soory for my noob questions.. 😉

    2. Putting their pins in parallel is fine, however since their firing levels may be different therefore the one with the lowest value is igniting first.

      Try adding a 50 Ohms resistor in series with each tube light and see what happens.

  6. hi…. Swagatam.. This is rahul here, First I like to tell u thanks… can i use any alternate to torroid inductor because it is not available in my city.. i tried above ckt using inductor coil but it is not glowing…

    1. Hi,

      I have provided the PCB and the component layout, i think it's enough for building the circuit, because PCB would be anyway required for this project.

      making the circuit diagram would be difficult for me due to lack of time.

  7. Thanks Swagatam….. Sorry for the late reply. I'm from the physics background so i asked u about the circuit diagram.I'm not having any idea in PCB layout. Thats y……Any way thanks for your reply….

  8. I have a unusual question. What changes to this circuit would be needed to a drive a single 96 inch 100Watt UVA/UVB fluorescent tube? I've noticed that this circuit is very similar to the SunQuest Electronic Ballast in a lot of tanning beds we have today.

  9. hai myself githin

    Iam interested to know details about ur design, i got the concept but i want to know the design parameters.

    could u please tell me.
    1) which freg the oscillator works
    2) need of chock and the value
    3) need of Torrid Inductor
    4) how can i calculating the watts
    ( u discussed earlier changing the capacitor value need calculation method)

    i hope u will guide me my mail address vgithin@gmail.com contact no 09345772248.
    need ur contact details

    1. Hi Githin,

      I copied this from a ready made sample, so I don't know much about the calculations.

      The choke can be any type of coil wound over any type of ferrite core…use maximum possible number of turns, example you can try with 200 turns of 30 swg wire.

      I have explained the torroid detail in the article.

    1. Initially please connect a 60 watt bulb in series to confirm the results first…. if the tube illuminates would confirm your circuit and then we can proceed with further improvements like adding thermister, MOV etc.

      please also note that D2 cathode is connected to the track which is passing just under it

  10. Bro how can i drive 40w fused(1 end/ 2 end)Tube light by electronic ballast like as electrical ballast? Although i have tried it by shorting the fused end of the light but it do blink when power on then it run.Sometime in the mid of running of light it start blinking then get stable.In this way i reuse that fused light some day but my ballast burst out.So what is the safe solution of it?

  11. bro today im again try to reuse fuse tube lite also CFL as per ur instruction(shorting lite ends) but when i give power then lite start blinking with some time then it run.Is this normal condition or i continue this way will my ballast or CFL burst?

    1. bro connecting or shorting the two pins of the tube is not required.

      simply take out single wires from the corresponding sides of the ballast and connect them to any one pin on either side of the tube

  12. Bro make i clear it first.U said i have to take only 2 cables from each pairs of cable from out put section of the ballast.then i have to connect that 2 cables individually with any one pin on either side of the tube.is This configuration is allowed for 2 end fused tube or 1 end fused tube?if possible pls make it clear with diagram.

    1. at the bottom center edge of the PCB, you will find three pads closely placed.
      the rightmost pad needs to be linked with the track passing just below it.

    2. sir,
      i dont get you..
      i asked you that, there is a track which does not touches any pad.I asked you to which pad that track should be linked.?
      thank you

    1. mosfet will not work properly in place of a BJT in a ballast circuit…because the components are specifically selected for a BJT operation and not for a mosfet.

  13. To all the people asking for values and such, you should try LTSpice or another analog electronics simulator. It even has power analysis if you're trying to figure out how much wattage is going to be dissipated by the transistors, for example. Sadly, it does require some knowledge of how to make a schematic and figure out their 'unique' interface. Luckily, tons of good tutorials with pictures, though!

    I haven't seen if they simulate a fluorescent bulb, but you can add devices with custom behaviors/curves. Even without that, these programs are wonderful for learning electronics and well worth the effort to learn!

  14. can i do it on pcb ie pro-ject board GLno.12 i am a wireman and most of my client call me to replace electronic ballast tube light. but by reading you 40watt electronic ballast i feel i should try to repair all broken ballast it will hwlp my clent in some way. other they have to bring new one from the market.

  15. hi sir i want to make a robot that can implement the Swach Bharat Abhiyan for school science exhibition .
    for this i had planned to make three robo cars – first will work like a vaccum cleaner which took light weight things like paper and leaves to clean ,second will clean the splits on road or anywhere ,third will took off heavy things .but sir i have one problem with third robot.if anything comes in front of it ,it will took off that object but suppose there is a valuable object like a money purse than it will also took it .sir what can i do so that my robot took off only the waste things not any valuable things.

    1. Hi Ritish,

      that's not feasible, you cannot make a vacuum cleaner understand the difference between a valuable material from a scrap material….but this can be handled by a human being at the other end who could segregate the materials appropriately…,…but I don't think you will get too many valuable things on road…. 99% will be scrap and garbage.

  16. hello sir , i have one more problem regarding to my project swatch bharat abhiyan robot that described before , sir i thought that i will use solar pannel as a source of energy but how to run three dc motor and a c.p.u fan using a solar pannel . if i use batteries then the heavy weight will create problem .if i use ac current then the wire and the plug point will create problem .sir please advice me what to do .

  17. sir, i have made a robot that implement swatch bharat abhiyan . in project i have a problem that is "what source of energy i should use 1)solar energy but it cannot run 3 dc motors and 1 c.p.u fan 2)batteries but the weight will create problem 3)a.c. current but the plug point and the wires will create problem .so sir please kindly advice me .
    thank you for your kind advice

    1. you will need a relay timer circuit for that but adjusting the turning angle will be complicated…or you can make it through a remote control design that will be more sensible and manageable

  18. Hello Mr. Swagatam Majumdar,
    Thank you very much for all the information you posted on your website. It's very interesting and informative.
    I am sorry if this question is sort of off topic but you know alot about electronics and I can't seem to find the answer.
    I have been making portable insect traps that I use with a 12 volt Gel cell battery and a 40 watt fluorescent UV light bulb (u shaped type bulb).
    I have been buying simple DC ballasts from China that are rated to be used for fluorescent bulbs that are 10-40 watts. The ballasts work, however, they don't seem to reach their full brightness. When I measure the current, it only measure 1.2 amps with a 40 watt bulb. This seems much too low and I assume it should be 3.3 amps. So I'm assuming that this ballast is really only a 20 watt DC ballast and I am using the wrong ballast.
    I have ordered some other 40 watt DC ballasts to test them.
    My question is:
    1. If a DC ballast is rated at 40 watts and you use a 40 watt lamp, should the current be 3.3 amps? If it is lower, does that mean you are not getting the full wattage of the lamp?
    2. I have read that it's ok to use a 20 watt bulb on a 40 watt ballast. It may shorten the life of the bulb somewhat but it will run ok. If you use a 20 watt bulb on a 40 watt ballast, will the current drop to 1.7 amps or will it remain at 3.3 amps because the ballast is 40 watts?
    I am sorry if these questions or off topic. Unfortunately, i do not have the skills to build my own ballast and must purchase them but it is often difficult to find quality DC ballasts.
    Thank you

    1. Thank you Consumer Watchdog,

      if the operating voltage is 12V then yes it should 40/12 = 3.33 amps
      if it's lower then simply multiply it with 12 to get the effective wattage output from the ballast.
      technically a 20 watt load can be operated with a 40 watt source if the voltage is compatible with the load, because if the voltage is as per the load spec then current will not matter or affect the load in any manner.
      the current consumed by the 20 watt load will be 1.7amp

      1. Thank you so much for your helpful response. I'm sorry but I have one other question regarding the 20 watt lamp with the 40 watt ballast.
        If I connect the 20 watt bulb to the 40 watt ballast and the current measured is high, say for example 2.5 amps, does that mean the bulb is being overdriven? i talked to a company that sells dc ballasts and he told me that there cheaper dc ballasts will over drive the 20 watt bulb connected to a 40 watt ballast and it will shorten the life of the lamp. However, they have more expensive dc ballasts that will adjust the current to match the bulb and they will not overdrive the 20 watt bulb and it will instead be only 1.7 amps as it should be.
        Does this sound correct to you?
        Thank you again.

        1. Technically the current cannot become high, however since we are dealing with high frequency circuits, compatibility could be a critical factor and things could get unpredictable so if you see more current being consumed than the specified range then definitely the load is being overdriven and could get adversely affected in the long run.

  19. Hi Swagatam,
    I'm looking for a 12V inverter circuit to power 2 T8 fluorescent lamps of 36W each. The circuit mas include a battery charger to work with a 12V SLA battery. Do you have anything like this?

    Best Regards.

  20. Dear sir, Please help me .In my home 2 tube light Electronic choke had burned after I have checked it i realized transister 13005ED and Cap 682J was burned but it is very rare to find kindly provide equivalent TRANSISTOR and cap


    1. Dear Raj, the transistor MJE13005 is very popular and should be available in almost parts of the world…moreover there's no easier alternative to this part.

      the cap 682J can e replaced with 0.0068uF/250V

    1. Hi, please click on the on the diagram under the PCB Component Layout, you will be able to see the enlarged view of it…D2 could be clearly seen with its cathode downwards.

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