Home » Induction Heater » Simple Induction Heater Circuit – Hot Plate Cooker Circuit

Have a Question?

Please feel free to ask any circuit related question and get a quick solution from me.

Simple Induction Heater Circuit – Hot Plate Cooker Circuit

The proposed induction heater circuit exhibits the use of high frequency magnetic induction principles for generating substantial magnitude of heat over a small specified radius.

The discussed induction cooker circuit is truly simple and uses just a few active and passive ordinary components for the required actions.

Update:

Learn how to design your own customized induction heater cooktop:
Designing an Induction Heater Circuit – Tutorial


Induction Heater LC Resonance Frequency and Current

According to the involved principle when a change in magnetic field is forced around a metal, electrons inside the metals get agitated and begins flowing across the metal, this is termed as eddy current. This flow of current in the metal or the introduced conductor causes a heat to be generated in the metal making it warmer.
The generated heat is proportional to (current)^2 x resistance of the metal.

The above heat is also directly proportional to the induced frequency and that’s why ordinary iron stamped transformers are not used in high frequency switching applications, instead ferrite materials are used as cores.

However here the above drawback is exploited for acquiring heat from high frequency magnetic induction.

Referring to the proposed induction heater circuit below, we find the concept utilizing the ZVS or zero voltage switching technology for the required triggering of the mosfets. The technology ensures minimum heating of the devices making the operation very efficient and effective.
Further to add, the circuit being self resonant by nature automatically gets sets at the resonant frequency of the attached coil and capacitor quite identical to a tank circuit.

The circuit fundamentally makes use of a Royer oscillator which is marked by simplicity and self resonant operating principle. However the main downside of the design is that it employs a center tapped coil as the transformer, which makes the winding implementation a bit trickier. However the center tap allows an efficient push pull effect over the coil through just a couple of active devices such as mosfets.

As can be seen, there are fast recovery or high speed switching diodes connected across the gate/source of each mosfet. These diodes perform the important function of discharging the gate capacitance of the respective mosfets during their non-conducting states thereby making the switching operation snappy and quick.

You can use IRF540 as the mosfets which are rated at good 110V, 33amps. Heatsinks could be used for them, although the heat generated is not to any worrying level, yet still it’s better to reinforce them on heat absorbing metals.

The inductor L2 terminating from center of the main induction coil is a kind of choke for eliminating any possible entry of the high frequency content into the power supply and also for restricting the current to safe limits.

Relatively the value of L2 should be high enough, a 2mH will do the job well. However it must be built using high gauge wires for enabling high current usage through it safely.

C1 and L1 constitute the tank circuit here for the interned high resonant frequency latching. Again these too musts be rated to withstand high magnitudes of current and heat.

Here we can see the incorporation of a 330nF/400V metalized PP capacitors.

Now comes L1, which is the most crucial element of the whole circuit. It must be built using extremely thick copper wires so that it sustains the high temperatures during the induction operations.
The capacitor as discussed above must be ideally connected as close as possible to the L1 terminals. his is important for sustaining the resonant frequency at the specified 200kHz frequency.

For the induction heater coil L1, many 1mm copper wire may be wound in parallel or in bifilar manner in order to dissipate current more effectively causing lower heat generation in the coil. Even after this the coil could be subjected to extreme heats, and could get deformed due to it therefore an alternative method of winding it may be tried.

In this method we wind it in the form of two separate coils joined at the center for acquiring the required center tap.

In this method lesser turns may be tried for reducing the impedance of  the coil and in turn increase its current handling capability. The capacitance for this arrangement may be in contrast increased in order to pull down the resonant frequency proportionately.
In all 330nF x 6 could be used for acquiring a net 2uF capacitance approximately.

Parts list for the above induction heater circuit or induction hot plate circuit

R1, R2 = 330 ohms 1/2 watt
D1, D2 = FR107 or BA159
T1, T2 = IRF540
C1 = 10,000uF/25V
C2 = 2uF/400V made by attaching 6nos 330nF/400V caps in parallel
D3—-D6 = 25 amp diodes
IC1 = 7812

L1 = 2mm brass pipe wound as shown in the following pics, the diameter can be anywhere near 30mm (internal diameter of the coils)


L2 = 2mH choke made by winding 2mm magnet wire on any suitable ferrite rod 

TR1 = 0-15V/20amps

POWER SUPPLY: Use regulated 15V 20 amp DC power supply.

Using BC547 transistors in place of high speed diodes

In the above induction heater circuit diagram we can see the mosfets gates consisting of fast recovery diodes, which might be difficult to obtain in some parts of the country.

A simple alternative to this may be in the form of  BC547 transistors connected instead of the diodes as shown in the following diagarm.

The transistors would perform the same function as the diodes since the BC547 can operate well around 1Mhz frequencies.


185 Comments

    • You can use BC547 transistor in place of the diodes. Connect base and collector together with the gate of the mosfet, and emitter to the drain of the other mosfet.

  1. Not worked swgtm. the material not even heat up & both mosfets burnt out. it specified 200kHz frequency. So can i use Astable multivibrator to set frequency 200Khz to drive the coils.

  2. hello swagatam.
    Plz suggest a circuit to run cooling fan externally. i bought a amplifier unit the heat sense fan stops automatically after 1 minute. need a solid state cheap circuit to run fan directly from mains. (fan rated 12vdc 0.25amp 2.5w)

  3. Hello Swagatam,
    I have built my one successfully with DC power source of 18V connected to L2 while the other side keep 12V to drive MOSFET. I am also connecting ammerter in series to L2 to monitor the current. With some bolts and nuts or steel rod. They can turn red hot without problem. Current goes up from original L1 coil without anything inside to some level according to the object inside the coil. Somehow, I try this with 1/2" diameter steel pipe with 0.5mm thickness. Current goes up and increasing. After a while when pipe is in red hot, current suddenly increase very rapidly and FET burn-out. At this point, everything stop. I have to change FET as it was shorted Drain-Source. I used IRFP250N and diode BYV26E, pretty high rated voltage and current but still failed. Do you have any idea what I did wrong? Is this due to FET or Diode? Thanks.

  4. Is there any alternative power supply? Cause its too expensive to buy a 20 A transformer then make it DC supply. By the way, could I use a power supply with adjuster in order to control the temparature of the induction coil?

    • sorry there's no direct alternative for high current. You can reduce it proportionately by increasing the voltage, but that would also require modifications in the work coil, the turns will need to be increased while the gauge will need to reduced accordingly.

    • thanks for the quick reply, I really want to learn more about induction heating. Where I can find a choke coil required L2 because I can't find one of it in some electronics store here in my place, is it okay not to put L2? I want to share my idea to you, I have a circuit design that I found in the internet to control temperature, how can I share it to you?

  5. is it safe that my transformer that is rated 6A only is giving me up to 10A of current. Because i connected it to a bridge rectifier and a 4700uF caps to make a dc power supply, then i successfully make the circuit work but when I measured the current flowing to the transformer using a clamp meter, it gives me up to 10A depending on the metal to be heated. is it still safe for the transformer producing greater current than its rating?

    • if it's showing more than the specified amps of the transformer means the voltage is being dropped proportionately in the course….so ultimately the total power is never being exceeded.

      as far as the above circuit is concerned, the coil would handle current depending upon its thickness, if it's correctly dimensioned it would be safe.

  6. Hello Swatam
    what changes I should make in the circuit to operate at 220V , two phases, each 110 V and a power of 6kW.
    and I'm thinking to cool L1 and L2 with water that circulates inside
    this is possible.

    • Hello Paul,

      Sorry, I think that may not be recommended and could require more number of turns for L1/L2…I do not have the data for calculating those.

    • The configuration will remain as is. The resistors could be increased to 1K 10 watt (wirewound) each, everything will need to be done through trial and error, though.

      For the mosfets you can use IRF840, however since mains voltage is involved, the risks of an untoward could be on the cards, I am not recommending use of 220V for this project.

  7. i have built one successfully but my capacitors tanks become very hot….
    i am using parallel cap at single point and where the all cap meet(at single point) they get very hot.
    should i mount capacitors on pipes at some distance?

    • you can use a 1000 watt halogen lamp in series with the mains input to the transformer, this will ensure that the initial amp intake does not exceed to dangerous levels.

  8. Thanks Swagatam
    I made my induction heater successfully now i want to increase its power..
    Can i increase power of this induction heater using more mosfets in parallel?
    Please scheme a circuit for parallel combination.
    Thanks

  9. Dear Swagatam, thank you very much for the details of the construction of this circuit. I built the heater and works well. I have a question related to the possibility to change the frequency of the system. I need differents frequencies. And I am thinking of if possible to change Capacitor and L at the same time to get any frequency. This is possible? Like for example 200Khz , 300 Khz, 400 and soon.
    Also I would know how I can calculate the magnetic intensity of the system.
    Thank you very much.

    • Dear Kamaljeet, without seeing the coil it would be difficult to suggest anything, anyway a commercial induction coil will require a sophisticated circuitry, much complex than the above published design…

    • The inductance value is not crucial, you can make it as per the given instructions in the diagram, yes with little modifications it can be converted for the pan type implementation.

  10. Hey, great thread. I was wondering what changes would need to be made to the schematic and the induction coil to work using 3.7vdc max 30amp load. This would obviously be used in a micro induction coil to heat small objects such as a sewing needle. And suggestion on coil size, wrapping and component change on the schematic would be greatly appreciated.
    Thanks!
    Dan

    • thanks Dan, I think it may have to be done through some trial and error since I do not have a formula for calculating the coil.

      The only thing I know is that as the turns increase and the diameter decrease the operating frequency and the current consumption also decrease proportionately, so on this basis you could probably do some experimentation.

      L2 and the other components except the voltage may not require a change as per my knowledge

    • hi sir…we try the circuit using the power supply of the computer as the power supply to the circuit….in our first try….the metal that we put on the middle of the working coil gets hot….but the mosfets gets hot too…..so we decided to change the heatsink with bigger one……after changing we try it again…….and the metal dont get hot……why is it happen sir??thanks for the reply

    • Hi Christian, I guess this could be related to some frequency variations due to the introduction/removel of the metal plate.

      heating up of the msgfets might be hampering the generation of the resonance frequency which might be getting corrected with the addition of the larger hetasink and resulting in an automatic correction of the frequency.

      Not sure though, this could be the reason.

      by the way you are not supposed to put a metal inside the working coil, this might seriously affect the functioning of the circuit

    • oh… that was quite silly of me, I completely forgot that a metal (magnetic) needs to be inserted inside the work coil for implementing the design, make sure the heatsinks are perfectly aloof and are not touching anything in the circuit….

      any power supply will do as long as it's able to generate 15 to 20 amps for the circuit.

    • C1 value needs to be arranged by putting many MKT capacitors in parallel.

      If you are using a pure DC from an SMPS in that case C2 can be eliminated….

  11. am working on this circuit from last few weeks but its not working as i expect it too. am using a coil of 12 gauge 9 turns center taped mosfet irfz44n ,22uf 4 caps in parallel adn the voltage suply is 15 v 12 amps its from a transformer ( battery charger) as i turn on the circuit the the mosfets blows up within seconds seeps like shor circuted help pe am not using any choke .

  12. am working on this circuit from few weeks and am facing the same proble as soon as i turn on the supply the current increses upto 40-70 amps and the mosfets blows up . am using irfz44n and 17v 10 amps power supplt from a transformer( its basically a battery charger) am not using any choke please help me out, ? 🙁

    • the choke (L2) is specifically introduced to limit current and to optimize resonance frequency, if you remove it the circuit is bound to fry immediately.

  13. Hello,

    My application requires that the object being heated (will be very thin) can be inserted and removed through the side of the coil, as both ends of that object will be fixed and unable to be pulled through the center of the coil. Are you able to tell me if there is any way to construct this without a completely closed heating coil (i.e. with a C-like cross-section instead of an O-shaped cross-section) to allow for side entry of a thin (~2mm diameter) object?

  14. Hello! Very intersting article!! But i need some help! Can you give me specific models for the D3-D5 (rectifier diodes), C1 capacitor & IC1 on the 1st circuit ?? Ampseres/volts for the IC1 voltage regulator??

    • Hi thanks, D3—D6 can be any rectifier diode capable of handling 25amp current, you can inquire about it with your local component dealer, he will know better and will guide you with the correct number.

  15. Ok! Something else…the Maximum DC current for the L2 (1st circuit) it's critical?? Let's say that we have a choke with Max. DC current 15A…it will be ok?? Or we need a higher value?

    • if 15amp is the breakdown limit of the choke then it will not do, if it's the optimal rating then it won't be a problem.

      I think the choke wire should be at least 2mm thick or made by using 2 strands of 1mm wire to be able to withstand 15amps

  16. My requirement is heating water ,approx 170ml, upto 90○C. Would it be possible using above circuit?
    If not what changes are required? Also would it be possible to run the above circuit on battery power?

  17. Hi

    I have put a similar induction coil in a range cooker, instead of a circular cast iron hotplate, I have a circular plate glass sitting in the old hotplate recess with the induction coil underneath, will the all the cast iron in the cooker top affect the induction unit.
    It worked for a while but now I am receiving an E0 error on the control panel, but I am going to switch to manual control, Potenimeter I think? would this help Thanks.

    Regards Denis.

    • Hi,

      sorry, I could not understand your question, do you mean you used a glass instead of cast iron and you are wondering if that would affect the results, then probably the answer is yes, if the cooker is a non-magnetic thing it won't react with the coil's magnetic induction and won't heat up.

      where do you intend to use the potentiometer?

  18. I need your help to design a working induction heater model for my son studying in 8th standard

    would like to get some details on exact materials and design

    Please help

    ramakrishnan

    9821075029

    • bill of material is provided in the article

      if you follow everything exactly as suggested, you could make it work successfully without much effort.

      however this project can be quite difficult for a school student.. as it might involve many complex measurements, adjustments and other related procedures

  19. helo sir! my name is biniyam i'm from east africa, ethiopia,i'm universiity student
    i sincerly ask u to help me om my semister project which is to replace "enjera"(which is staple food in ethiopia) making stove with induction cooking system

  20. Hello sir i make this circuits but not succed.
    I use mosfet irfp250
    Capasitor csd mer 165j400v
    470ohm 2w resistor
    12v 1w zea diod
    Diod 4100e
    10k 1/4w resistor
    Induction coill old pc power suply
    I use 24vdc 14amp power suply
    I make heting coill 9 trun copartube 7mm.coill diametar 1.5"
    So what is tha miss take.pless helf me

    • hello Saiful, where did you use the zener diode, if you used it for the 7812 it might have got burnt and shorted, make sure you use a 7812 IC as shown in the first diagram and not a zener diode….
      if you use a 12V/15amp transformer you can get rid of the 7812.

  21. hii im onkar ,
    i have made circuit using irfz44n ,diodes=1n5819
    and used the power supply of 24v/10amp. with lm7812cv as vr,also i used 2x.47 uf capacitors
    but when i start the supply my rectifer and choke coil gets too hot.and circuit does not work at all..
    what would be the problem ??pls reply me sir…

    • Onkar, it will be difficult to troubleshoot because I do not know what mistake you might have made in it.

      L2 is around 2mH…did you verify this inductance value?

      initially use a 200 watt bulb in series with transformer primary, and check whether the coil produces heat or not….

      the work coil needs to be built exactly as shown in the above figure, and same is true for the capacitor bank

      you can check a few you tube videos on this subject and see how it's is implemented practically…

    • Dear Prasetyo, the above design is a self resonating kind of circuit so I am not sure whether a coil with a different dimension would automatically adjust with it…or what necessary modifications might be required.

      you can try though by changing the L2 specs also, through experimentation

  22. hi Swagatam, Thank you for The circuit. I have a question and a clue. I want to measure the magnetic field in the working coil. As the frequency is higth, i don't know how to measure. Could you help me ? How Many tesla or mili tesla. can produce. (B) it is possible to measure or calculated. Thank you in advance

  23. Hi, Have you ever done or thought to a circuit relevant an induction heater with a function generator as a controller?
    The sense of this request is that I wish to build an induction cooker circuit with the possibilities to verify the frequency value, through my function generator I’m able to achieve a few KHz to a few MHz; my problem is How can I feed the cooker coil without a sort of amplifier? The power after function generator isn't sufficient to feed the coil. In other terms I wish to implement this: Function Generator -> Electronic -> Cooker Coil. Have you got any idea?

  24. Hi sir,
    I m use 17volt 25 amp tranform, is that work? If yes,tell me what the perfect inner and outer dimension of L1? If not, plz tell me what i do?

    Sir,
    The ICE give me 20 dc to input cct, is that successful for run cct? If not, plz tell me what i do?

    Sir,
    In our stor is difficult to find L2, can u tell me the dimension of it(L2 mean), and what the value of current and voltage flow in L2?

    THANKS SIR

    • Hi, yes 17V, 25 amp will do.

      L2 will need to be built by winding 22 SWG enameled copper wire until you reach a 2mH value. the current could be around 10 to 20 amps through L2
      there are some good videos in Youtube which you can see for a clearer view of the procedures.

    • Initially you should try with a lower voltage may be around 12V, if everything goes well then you can increase it to higher levels for acquiring higher heating ranges.

  25. Hi sir
    Thank you for your support,,
    It working successfully.
    ,, sir,, how i cam calculate mathematical representations of current,voltage and frequency?

    Thank again sir.

    • Hi, I am glad you could succeed with the above project, but I am sorry I am not entirely sure about the mathematical details of this concept…

      If you wish you can send the working details of the project with pictures and get paid for the submission, I'll publish it in my website.

  26. Hi,
    for a school project i need to construct an AC induction cooktop and was wondering if you could help me put together a part list for a much weaker induction cooktop than yours, it only has to warm up a few ML's of water. is this something that is possible?

  27. Hi Swagatam, i love your projects and my son regularly builds them at school in science lessons.
    i lastly got him the parts to build a simple Royer style induction heater working from 12v DC but i wonder could your simple inverter circuit using the IR 2153 from 12v DC be changed to build a more exciting and challenging induction circuit ? would it be as simple as adding capacitors to the secondary with working coil?
    i thank you in anticipation.

    regards Kevin

    • Thanks Kevin, I am glad your son is liking my projects!

      my simple inverter circuit is quite similar to the above induction heater concept, so if we try to modify it will ultimately take the shape of the above design.

      However the 50 watt mosfet inverter circuit from this website can be definitely tried for making a versatile and a more flexible induction heater circuit:

      http://www.homemade-circuits.com/2012/09/mini-50-watt-mosfet-inverter-circuit.html

    • Yes Hi Swagatam, a very interesting self oscillating circuit i will build it one day.
      However my aim is to get Dan (my son ) to build something more controllable which is why i mentioned the IR 2153 controller, i would like him to achieve some shutdown / protection techniques either with current a transformer or other direct circuitry and from what i have seen of this IC it does most of this, so if there is any chance of further guidance in this direction i would very much appreciate it.
      It does not have to be very powerful but a nice little controllable safe circuit, as in over current and short circuit protection these are the techniques that i would like Dan to start learning.

      regards Kevin.

  28. Hi, Could you please explain in more detail how the the switching occurs? After the first Mosfet turns on, I don't follow what causes it to turn back off, and the other to turn on. Thank you

    • Hi, since both the fets cannot switch ON together due to the slight difference in their switching characteristics, let's assume T2 initiates first on power switch ON,
      as soon as this happens its gate potential is instantly grounded by its own drain/source terminals via D2 and L1….dropping its gate potential to a a level where it's forced to shut off.

      This enables T1 to initiate the process and it eventually ends up shutting off in the same manner…the cycle keeps regenerating and continues rapidly giving rise to the required phenomenon…

  29. Is the following true?: As the voltage builds on drain one, it causes more voltage to appear at gate 2? And then when Vd1(voltage on drain of T1) hits 15V when the inductive path resistance is a short, Gate 2 now has 15V on it, that drains the voltage on gate 1 to ground? Also, when is the cap being charged and discharged with respect to the rest of the timing of the circuit? Thank you

    • That;s OK. What I'm saying, is that after current has been flowing through L2 and the top half of L1 for a while. the voltage on the drain of T1 goes from zero to the supply voltage, which then allows the supply to be applied to the gate of T2, tuning it on. I think.. But since the work coil isn't wound on a core, I see very little, if any, voltage induced in the other half of the work coil. So, I can't figure out how the work cap ever gets charged.

    • No, the voltage at drain will be above zero only when the device is not conducting, and will be zero the moment it starts conducting.

      the work coil definitely needs to be mounted on a core otherwise the resonance will never happen and the devices could get damaged.

      the core here is the metal which is being heated, that is the iron bolt or rod whatever it may be.

      the capacitors, the coil and the iron core together forms a "tank" circuit which reaches the resonance level during the operations and causes the desired heating effect.

  30. Hello
    what is the maximum temperature which our metallic target reach inside the coil?
    and i wanna to know moreover current , what parameters effect on the final temperature (like frequency, voltage , coil diameter , etc) ?
    i assembled your designing circle , and the frequency has a tolerance between 70 to 120 kHz,can you give me an advise what's the matter?

    i really appreciate it in advance.

    • Hello, it will depend on the input current and the coil wire thickness, and also the voltage level, higher parameters will allow higher temperatures and vice versa…..

      it's a self-resonating type of circuit, and the frequency will adjust as per the inductor efficiency…..a better optimized coil will enable better resonance and proportionately more heat.

    • It my be possible if the mosfets are appropriately upgraded with higher current ratings and the supply is also proportionately increased with higher current capacity.

  31. Hi, thanks for the explanation. Really helpful stuff. I'm trying to make a heating circuit using Li-ion 3.7V battery. The end result is to heat a small piece of stainless steel. Don't know if I can use this technique as the battery power isn't that much. If I can please guide me how and if not , can you provide an alternative ? I'm looking at resistive heating

  32. hey swagatam im having isues with designing a mini induction heater can i use a set of irfz44n transistors for building a small zvs driver and if possible can you give me a half bridge schematic!

    Frank:

  33. Sir,
    I am feeling difficult in making L2 , can u explain how to make it, by describing about type ferrite rod to be used , length and diameter of copper wire and ferrite material (ferrite rod / ferrite ring ) or any alternative instead of L 2

    • Adithya, L2 will need to be made over a ferrite core preferably, and the inductance will need to be determined as mentioned in the article, and also make sure the wire is thick enough to handle the current, could be around 1mm thick.

Leave a comment

Your email address will not be published. Required fields are marked *

Archives