In this post I have explained 2 easy to build induction heater circuits which work with high frequency magnetic induction principles for generating substantial magnitude of heat over a small specified radius.
The discussed induction cooker circuits are truly simple and uses just a few active and passive ordinary components for the required actions.
Update: You may also want to learn how to design your own customized induction heater cooktop:
Designing an Induction Heater Circuit - Tutorial
Induction Heater Working Principle
An induction heater is a device that uses a high frequency magnetic field to heat up an iron load or any ferromagnetic metal through eddy current.
During this process electrons inside iron are unable to move as fast as the frequency, and this gives rise to a reverse current in the metal termed as eddy current. This development of high eddy current ultimately causes the iron to heat up.
The generated heat is proportional to current2 x resistance of the metal. Since the load metal is supposed to be made up of iron, we consider the resistance R for the metal iron.
Heat = I2 x R (Iron)
Resistivity of Iron is: 97 nΩ·m
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 circuits 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.
Using Royer Oscillator
The circuit fundamentally makes use of a Royer oscillator which is marked by simplicity and self-resonant operating principle.
The functioning of the circuit could be understood with the following points:
- When power is switched ON, positive current begins flowing from the two halves of the work coil towards the drains of the mosfets.
- At the same the supply voltage also reaches the gates of the mosfets turning them ON.
- However due to the fact that no two mosfets or any electronic devices can have exactly similar conducting specifications, both mosfets do not turn on together, rather one of them turns ON first.
- Let's imagine T1 turns ON first. When this happens, due to heavy current flowing through T1, its drain voltage tends to drop to zero, which in turn sucks out the gate voltage of the other mosfet T2 via the attached schottky diode.
- Here, it may seem that T1 might continue to conduct and destroy itself.
- However, this is the moment when the L1C1 tank circuit comes into action and plays a crucial part. The sudden conduction of T1 causes a sine pulse to spike and collapse at the drain of T2. When the sine pulse collapses, it dries down the gate voltage of T1, and shuts it down. This results in a rise in voltage at the drain of T1, which allows a gate voltage to restore for T2. Now, its the turn of T2 to conduct, T2 now conducts, triggering a similar kind of repetition that occurred for T1.
- This cycle now continues rapidly causing the circuit to oscillate at the resonant frequency of the LC tank circuit. The resonance automatically adjusts to an optimal point depending on how well the LC values are matched.
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.
How ZVS Works
As I have explained earlier, this induction heater circuit works using the ZVS technology.
ZVS stands for zero voltage switching, meaning, the mosfets in the circuit switch ON when they have minimum or amount of current or zero current at their drains, we have already learned this from the above explanation.
This actually helps the mosfets to switch ON safely and thus this feature becomes very advantageous for the devices.
This feature could be compared with the zero crossing conduction for triacs in AC mains circuits.
Due to this property the mosfets in ZVS self resonant circuits such as this require much smaller heatsinks and can work even with massive loads upto 1 kva.
Being resonant by nature, the frequency of the circuit is directly dependent on the inductance of the work coil L1 and the capacitor C1.
The Frequency could be calculated using the following formula:
f = 1 / ( 2π * √[L * C] )
Where f is the frequency, calculated in Hertz
L is the inductance of the Main Heating Coil L1, presented in Henries
and C is the capacitance of the capacitor C1 in Farads
The MOSFETs
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. However any other appropriately rated N channel MOSFETs can be used, there are no specific restrictions for this.
The inductor or inductors associated with the main heater coil (work coil) is a kind of choke that helps eliminating any possible entry of the high frequency content into the power supply and also for restricting the current to safe limits.
The value of this inductor should be much higher compared to the work coil. A 2mH is generally quite enough for the purpose. However it must be built using high gauge wires for facilitating a high current range through it safely.
The Tank Circuit
C1 and L1 constitute the tank circuit here for the intended 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.
1) Powerful Induction Heater using a Mazzilli Driver Concept
The first design I have explained below is a highly efficient ZVS induction concept based on the popular Mazilli driver theory.
It uses a single work coil and a two current limiter coils. The configuration avoids the need of a center tap from the main work coil thus making the system extremely effective and rapid heating of load with formidable dimensions. The heating coil heats the load through a full bridge push pull action
The module is actually available online and can be easily bought at a very reasonable cost.
The circuit diagram for this design can be seen below:
The original diagram can be witnessed in the following image:
The working principle is the same ZVS technology, using two high power MOSFETs. The supply input can be anything between 5V and 12V, and current from 5 amps to 20 amps depending on the load used.
Power Output
The power output from the above design can be as high as 1200 watts, when the input voltage is raised up to 48V, and current up to 25 amps.
At this level the heat generated from the work coil can be high enough to melt a 1 cm thick bolt within a minute.
Work Coil Dimensions
Video Demo
2) Induction Heater using a Center Tap Work Coil
This second concept is also a ZVS induction heater, but uses a center bifurcation for the work coil, which may be slightly less efficient compared to the previous design. The 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.
Primary Work Coil Specifications
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.
Tank Capacitors:
In all 330nF x 6 could be used for acquiring a net 2uF capacitance approximately.
How to Attach Capacitor to the Induction Work Coil
The following image shows the precise method of attaching the capacitors in parallel with the end termianals of the copper coil, preferably through a well dimensioned PCB.
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 the below shown 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.
Another Simple DIY Design
The following schematic shows another simple design, similar to the above, which can be constructed quickly at home for implementing a personal induction heating system.
Parts List
- R1, R4 = 1K 1/4 watt MFR 1%
- R2, R3 = 10K 1/4 watt MFR 1%
- D1, D2 = BA159 or FR107
- Z1, Z2 = 12V, 1/2 watt zener diodes
- Q1, Q2 = IRFZ44n mosfet on heatsink
- C1 = 0.33uF/400V or 3 nos 0.1uF/400V in parallel
- L1, L2, as shown in the following images:
- L2 is salvaged from any old ATX computer power supply.
How L2 is Built
Modifying into a Hot Plate Cookware
The above sections helped us to learn a simple induction heater circuit using a spring like coil, however this coil cannot be used for cooking food, and needs some serious modifications.
The following section of the article explains, how the above idea can be modified and used like a simple small induction cookware heater circuit or an induction kadai circuit.
The design is a low tech, low power design, and may not be on par with the conventional units. The circuit was requested by Mr. Dipesh Gupta
Technical Specifications
Sir,
I have read ur article Simple Induction Heater Circuit - Hot Plate Cooker Circuit And was very happy to find that there are people ready to help youngsters like us to do something ....
Sir I am trying to understand the working and trying to develop an induction kadai for myself ... Sir please help me understanding the designing as I m nt so good in electronics
I want to develop an induction to heat up a kadai of dia 20 inch with 10khz frequency at a very low cost !!!
I saw your diagrams and article but was a bit confused about
- 1. Transformer used
- 2. How to make L2
- 3. And any other changes in the circuit for 10 to 20 kHz frequency with 25ams current
Please help me sir as soon as possible ..It will be help full if u could provide with the exact components detail needed .. PlzzAnd lastly u had mentioned to use POWER SUPPLY: Use regulated 15V 20 amp DC power supply. Where is it used ....
Thanks
Dipesh gupta
The Design
The proposed induction kadai circuit design presented here is just for experimental purpose and may not serve like the conventional units. It may be used for making a cup of tea or cooking an omelet quickly and nothing more should be expected.
The referred circuit was originally designed for heating iron rod like objects such as a bolt head. a screwdriver metal etc, however with some modification the same circuit can be applied for heating metal pans or vessels with convex base like a "kadai".
For implementing the above, the original circuit wouldn't need any modification, except the main working coil which will need to be tweaked a bit to form a flat spiral instead of the spring like arrangement.
As an example, in order to convert the design into an induction cookware so that it supports vessels having a convex bottom such as a kadai, the coil must be fabricated into a spherical-helical shape as given in the figure below :
The schematic would be the same as explained in my above sevction, which is basically a Royer based design, as shown here:
Designing the Helical Work Coil
L1 is made by using 5 to 6 turns of 8mm copper tube into a spherical-helical shape as shown above in order to accommodate a small steel bowl in the middle.
The coil may be also compressed flat into a spiral form if a small steel pan is intended to be used as the cookware as shown below:
Designing the Current Limiter Coil
L2 may be built by winding a 3mm thick super enameled copper wire over a thick ferrite rod, the number of turns must be experimented until a 2mH value is achieved across its terminals.
TR1 could be a 20V 30amp transformer or an SMPS power supply.
The actual induction heater circuit is quite basic with its design and does not need much of an explanation, the few things that needs to be taken care of are as follows:
The resonance capacitor must be relatively closer to the main working coil L1 and should be made by connecting around 10nos of 0.22uF/400V in parallel. The capacitors must be strictly non-polar and metalized polyester type.
Although the design may look quite straightforward, finding the center tap within the spirally wound design could pose some headache because a spiral coil would have an unsymmetrical layout making it difficult to locate the exact center tap for the circuit.
It could be done by some trial and error or by using an LC meter.
A wrongly located center tap could force the circuit to function abnormally or producing unequal heating of the mosfets, or the entire circuit may just fail to oscillate under a worst situation.
Reference: Wikipedia
If we combine at least 4 boards from the second photo without the capacitors, with a total of 15 capacitors SIEMENS MKP B32650 CAPACITORS 0.22uF 1000V with a coil of copper 6 mm pipe by running water through the coil, you also need fans for the verites and 5 watt resistors. You can melt copper silver in a ceramic pot. You need a 45 volt 50 amp power supply.
Thank you very much for sharing your valuable feedback.
You can set the operating frequency to 10MHz.
hii sir i want to make a 10kw induction heater can you tell me a how to calculate a L,R,C in resonant tank and how to calculate a transformer turn at resonant side please you give a calculation with any example
Hi Harshit,
I do not have tested calculations for induction LC tank circuit. However you can do it with some trial and error method.
You can buy a ready made 1000 watt induction heater unit and then through some experimentation upgrade it to 10kva. I can help with this experimentation.
hi dear sir i want to find out prenciple in zvs please
Hi Sedigh, The ZVS principle is explained in the above article, please read it again, and let me know if you have any further questions.
sir, I want to design a induction heater so how to calculate a L, C, R and transform ratio
I am interested in heating up an aluminum rod to approx. 400-450 °F inside of a metal tube. This is inorder to extrude through a due. My question is, can this be done by placing the widings of the heater around a metal, (steel, or stainless) that would have an extrusion die on one end and a ram/piston on the other side?
Yes, that may be possible if the metal tube is perfectly magnetic.
So a carbin steel pipe will work, does it matter how many turns of wire are made? Would 12 guage copper wire work with a variable power supply?
If the carbon steel is magnetic then it might work. 12 Guage should be fine, however the number of turns must be exactly as indicated in the circuit diagram. You may also have to upgrade the MOSFET specification for getting the required amount of power output from the induction heater.
Can you provide a brief explanation of the number of turns? I am think the AL rod would be about 1 cm dia. and the carbon steel pipe would have an ID of about 1.1 cm with a die screwed onto the end. A ram rod would be used to push the softened AL rod through the die. I am thinking the heating area would be about 0.3 m or so with a total of 1 m carbon pipe, maybe the middle 1/3 as the heating section. Thoughs?
The number of turns is fixed and cannot be changed. It has to be exactly as specified in the diagram or in the readymade unit. In the readymade unit which I tested had 10 turns, and it could make a 4mm screwdriver rod red hot within 20 seconds.
Hello sir, am currently doing a research on portable solar pv induction cooker and I want to power my model with a 10 W solar panel. Could you please provide me with a circuit diagram of the system and what you deemed correct to be included in the system.
Hello Ambrose, induction heaters require high power supply for operating, 10 watt is too low, and cannot be used to power an induction heater circuit. You will need at least a 100 watt solar panel to get a reasonable output from the induction heater.
Thank you for your kind of sharing this circuit.
можно схемы для индукционного котла
Sorry, I do not have induction heater circuit for boilers.
многоуважаемый Сватагам болшое спасибо вам за ваш веб сайт
You are most welcome Begenc.
Please on the first experiment (Powerful Induction Heater using a Mazzilli Driver Concept) can I replace the L1 to heating element
Thanks
L1 is supposed to be an inductor coil, it cannot be replaced with a heating element.
The resonant circuit consisting of a 1.1 micro Henry coil and a 2 micro Farad capacitor resonates at approximately 100 KHz. Isn’t the oscillation frequency too high? Thanks!
Thank you Sir
this project Subject useful me
but Small doubt to me
uses of Capacitor in induction heater .
Thanks Moban,
The capacitors are for creating resonance effect in the LC circuit
Hello Swagatam
I have purchased ZVS driver (5-12V 120watt) from amazon.
What can be the inductance value of the coil in uH?
If I want 240watt can I supply 24V DC ?
thanks
Hi JK,
The inductance will need to be measured with a inductance meter for getting the correct value.
If it is rated to work with 12V, then I don’t think 24v can be used as the supply.
Hello Swagatam
Congratulations for this very good presentation you have done !
what modifications can be done to increase the power of 5-12V ZVS module?
thanks
Thank you JK,
I am glad you liked the explanation.
I think to increase the power the mosfet and the coil rating can be increased and along with this the input current can be also increased. Once these upgrades are done, a higher wattage load would be automatically allowed to heat up with appropriate high wattage.
Dear Swantam,
Thank you for your nice work.
I would like to have a microcontroller to control the temperature. How can it be added to this circuit?
Perhaps an arduino or pyboard (Micropython) can work well.
Thank you Patrick,
Sorry, my Arduino knowledge is not good, so it can be difficult for me to help you with this concept.
Hi Swagatam;
The environment volume is about 1,2 cubic meter. Desired maximum heat would be below 40 degrees C. I also have got chrome nickel wires in diameters of 0.2 mm and/or 0.4 mm. I may also use thick copper tube. Voltage is AC 220. Please advise if I may make my own low watt (about 20 or 40 Watt) heater resistor? Thanks and regards.
Hi Suat,
It can be difficult to calculate and create a resistor that would give 40 degrees C heat at 220V inside 1.2 cubic meter space. It is better to use a ready-made resistor instead of making one. You can get any desired amount of heat by experimenting with several wire wound resistors rated at 10K, or 20K 15 watt, connected in parallel across a 220V source.
Hi, your work is an excellent job. I have designed the ZVS and it works perfectly. Can you please help me with a circuit diagram of 5kw to 10kw using right and with and input supply of 220vac
Thank you, and glad you found the article useful. However, presently I do not have a 5 kW to 10 kW design with me, I will look for it, if I find it I will update the same in the above article soon
Please can I used 555timer to drive the MOSFET
I don’t think 555 can be used to build an induction heater circuit
a 555 could be used but a tl494 would be better. start your circuit with lowish voltage to your output devices. use 10 to 12v for your 555 and “mosfet driver”. vary your pwm for best waveform, then vary your frequency for resonance. use a shunt and one channel on you scope to monitor current. use the other channel to look at the voltage waveforms across your switching devices. parasitics are an issue at high current levels. flat wide copper strip or foil works well for conductors. for higher power. .as you push up your power level you might use litz wire-round copper tubing-rectangular tubing to improve efficiency. water cooled capacitors are used at very high power levels. phase locked loops will keep your circuit automatically tuned within a given range of frequencies. you will need heatsinks for your igbt, gan-fets or other switching devices. make yourself a sand box to work over so you dont start a fire. if you are melting steel put a cup shaped depression under your crucible in case it cracks or melts(my first crucible for steel wasnt up to the job – i speak from experience) i was glad i had the sandbox the tl494 prevents shoot-through, and has good waveform symmetry good luck
Thank you for your valuable feedback. Much appreciated.
The circuit with two current limiter coils is more interesting. I don’t understand that how is switching is done. Because both L2 and L3 coil is connected to 12v and mosfet. Current will take shortest path and don’t bother go through the working coil L1. But i understand well the circuit with 1 current limiting coil. Could you please explain. Thank You
Yes indeed the working of ZVS circuit is confusing and not easy to simulate. I think have explained it in the article. It’s the mosfets that do the actual switching of the work coil.
Hello,
Can i use the second circuit to melt silver?
Yes you can use it!
Understood…
Thank you so much
You are welcome!
Thanks Swagatam
In induction noobheater,
1.What is purpose of connecting diodes D3 and D4?
2. How rating of 2 choke coils is seleacted. Please clarify these doubts.
Hi Omkar, what is noob heater? Are you referring to the diodes D1, D2 in the first diagram? Ratings of the two coils L2, L3 in the first concept is determined by their inductance value and the wire thickness.
Yes D1, D2 in first diagram. What is purpose of those diodes?
The gates of the respective MOSFETs are grounded and switched OFF through these diodes, when the opposite MOSFETs conduct. This gives rise to the required high frequency oscillations.
Great article Swagatam, I am studying this circuit. can We design 2KW induction heater with voltage rating 318 V (With low current rating) with same topology/ Mazzilli driver circuit ? What modifications we need to make for it (Deciding rating of components)? If you have documents/ research papers related to this, please share….
Thank you Omkar, yes that seems possible. You will have to upgrade the MOSFET rating accordingly, along with the coil wire thickness, and finally use a power supply which can supply the required amount of current for the 2kw output
Okay, Can you give me some hints to start and find ratings of all components. Like I have voltage and power rating of 318 V and 2kw. From this I will get approx input current. Now should I select resonant frequency as 27 KHz and calculate L and C values (same as full bridge) and go further on use other approch to start finding ratings?
If I analyze voltage and current waveforms for all components in 48V, 1200W model. will it help to design circuit?
please give me hints to start…..
318V induction heater may not be available easily, you will have to select from 12V or 24V or units.
Hii,
I am trying to design 318V,2KW induction heater using same topology. As voltage between drain and source will be very high I am using IGBTs instead of mosfets(Using same gate driver circuit around 12 to 20 V). Will IGBTs support this topology?
What other changes I need to do (I am using heat sinks to reduce over heating and changing component ratings according to voltage rating) to switch IGBTs properly?
Hi, I think IGBTs will also work since their gate triggering is identical to mosfets. Alternatively you can also try using 500 V mosfets for the same, which can make things easier.
However I am not sure what other changes may be required for a 318V switching. I guess the number of turns of the work coil will need to changed accordingly.
Hii, I have simulation of this circuit in LTspice, it is working fine with 48V(With same components) and 318V(with modifying some values). I have hardware of this board, replaced mosfets with 650V, 20A and given 24V supply( Kept gate voltage 12V as it is). After switching it ON circuit was drawing very high current and MOSFETs got heated a lot in very less time also input voltage dropped to 8V. What can be the reason and how to tackle this problem?
Hi, if the circuit is drawing high current it means the LC circuit is not resonating or there may be some other serious technical issues. I don’t think the above designs are suitable for 318 V operation. The circuit can be much complicated than this, and might require an H bridge mosfet configuration with a separate H bridge driver oscillator circuit.
I am not an electronic engineer but I have very little experience in the works, so, my main work is mechanical engineering but I can not create my workshop now because i am struggling to make an induction heater to forge metals and it is not sold in my locality.
So can you help tell me how I can make it in other ways without all these plenty materials like MOSFETs etc, that I don’t understand? For instance I try connect an induction coil to a welding machine, there was magnetic field in the coil and it heated a small iron very poorly for me, but the most heat was on the coil as it bridge the welding machine. So I don’t know if there is any other way. But I would prefer the one I can connection to AC power supply and not that DC to be converted to AC though inverter because my problem is that inverter but I have electricity in my place.
There’s only one method of building an induction heater which is explained in the above article, and it the most efficient and the correct method of implementing induction heating.
Hi,
Thank you very much for prompt answer.
I’ll try to do so …
Kind regards.
YT
You are welcome!
Hello,
I bought “standard” mini ZVS heater 5-12V, 120W. It operates good for heating of different metal elements introduced in the coil L1 with the frequency around 200 kHz. However for my heating process I need the frequency 20-50 kHz. Is it possible to change the resonant frequency of my heater to lower values?
Thanks in advance for support.
YT
Hi, it can be probably done by adjusting the coil turns and the parallel capacitor values, however I do not have the information regarding its calculations.
Hello i see that you say we can calculate the frequency from the formula but what i don’t understand is based on what do you chose the coil and the capacitors??Because you just calculate it and suddenly you have the frequency and from the formulas you can’t get the answer for this.
Hello, I did not build this circuit…I bought it ready made. If you are having problems calculating the parts, you can also buy one from the market and then compare the practical results with the formula results.
Hello Swagat
what is the Henry value in main heater coil L1 in ZVS mini 120watt module that is available in the market? I want to put a another coil of same value to make it a cooker.
thanks
J K barik
Hello JK, sorry I do not have any information regarding the inductance value of the coil.
Hello Swagat as you say is :
( the easiest way is to restrict the input supply current to the desired lower level.)
But how do I lower the current ?
Pl answer.
thanks
Hello JK, you will have to locate from where the induction heater is getting the power. It is probably from an SMPS power supply which could be modified so that its current output is reduced appropriately.
Otherwise you can replace the SMPS with a lower rated SMPS, or a lower rated transformer power supply
Hello Swagat
I have an induction cooker. It is ON/OFF type means 1000watt/ 0watt. When it is ON it consumes 1000watt. I want to reduce. So what should I do? Reduce voltage by capacitor network ; put a low value capacitor in series or reduce coil and tank capacitor? what is most easy method to do? I want some 200 watts.
thanks
J K barik
Hello Jk, the easiest way is to restrict the input supply current to the desired lower level, any other optimization in the circuit can be dangerous for the circuit.
Bonjour,
Quelle fréquence pour fondre du bronze ?
Cordialement,
Dear Swagatam,
Your article is very useful for me, thank you and may god bless you.
Yan
It is my pleasure Yan, wish you all the best!
Hi Swagatam,
Thanks for all the helpful information on induction heating circuits. Not being well versed in electronics, I am trying to better understand what’s happening in your version of the Induction Noobheater circuit diagram, especially mosfet switching and the timing in the circuit.
In the section on the functioning of a Royer oscillator, point 4 says “Let’s imagine T1 turns ON first. When this happens, due to heavy current flowing through T1, its drain voltage tends to drop to zero, which in turn sucks out the gate voltage of the other mosfet T2 via the attached schottky diode.”. I’m not sure I’m thinking about this correctly, so I’m hoping you can correct or confirm my assumptions and answer some questions. My assumptions on point 4 are:
– Before mosfet T1 turns on, the voltage on the drain of T1 is positive (from point 1) because there’s a small timing delay in turning on T1, so the T1 drain voltage is initially positive. The T2 drain voltage is also initially positive.
– IRF540N mosfets are being used, which are N channel, making the current flowing to the gate of T1 negative.
– The negative current flowing out of the T1 gate causes the voltage signal on the gate to drop from positive to zero.
– Are these assumptions correct?
– What is the force responsible for sucking the positive gate voltage out of T2 via the schottky diode? In my limited understanding, I would have thought that a zero voltage on the T1 drain would not have an effect on the T2 gate voltage.
In point 6, it says “However, this is the moment when the L1C1 tank circuit comes into action and plays a crucial part. The sudden conduction of T1 causes a sine pulse to spike and collapse at the drain of T2. When the sine pulse collapses, it dries down the gate voltage of T1, and shuts it down. This results in a rise in voltage at the drain of T1, which allows a gate voltage to restore for T2. Now, its the turn of T2 to conduct, T2 now conducts, triggering a similar kind of repetition that occurred for T1.”
– Is it true that up until this point, the tank circuit has not had an effect on the mosfets?
– is the sine pulse spike a voltage or current spike?
– My understanding of tank circuits is that the inductor in the circuit reacts to a change in current from the capacitor by creating a voltage opposing the direction of that current, thereby charging up the capacitor with the opposite polarity from what it had before. Does the sudden conduction of T1 create the change in current that causes the creation of the voltage from the L1 inductor which causes the spike?
– Could you help me understand why the collapsing of the sine pulse would dry down the gate voltage of T1, why this would result in a rise in voltage at the drain of T1, and why this would allow the gate voltage to be restored on T2? I feel like I’m missing some crucial knowledge.
Sorry for asking so many questions.
Thanks again.
Sorry Randy, Due to lack of time I am unable to analyze your question and reply to it. The above article was written a long time ago and don’t remember the explanations very well. I will have to read the article again, then recall the details, and then compare it with your analysis which can take a lot of time, and presently due to work load I am unable to dedicate time for lengthy questions.
Thanks for your reply and I understand. I have to say I’m very impressed with your knowledge and explanations. Maybe you could respond to some basic electronics timing information that I’ve been studying and confirm/correct my thinking. It may help clear up some of the mystery I have about circuits in general. I was always under the impression that electrons move very quickly in a circuit and that has created some confusion/ambiguity in my mind about voltages and current at various points in a circuit. However, recently I found some articles about electron drift velocity and voltage. To my surprise, I’ve read that electrons in a circuit tend to move very slowly – on average, somewhere in the neighborhood of 1 meter per hour! According to these articles, what makes a current appear to be so quick is that the electric fields supplying the force to move these particles move at nearly the speed of light. These fields signal to a large number of electrons in the circuit to start moving at virtually the same time. Even though the electrons move very slowly, there are so many of them that the number crossing a given cross sectional area per unit time tends to be large, which can generate in a large current. As the voltage increases, the electron drift velocity increases, resulting in a higher current.
Can you tell me if this information is accurate?
I am so glad to have a truly inquisitive visitor like you, and I appreciate that!
Since all the other online sources are confirming with the details that you have provided so it must be correct… although it sounds very strange since we always believed that electrons travel at the speed of light?
But these facts are something which are very difficult to simulate in our minds, therefore again it may be difficult for me to provide the correct interpretation or my personal opinion regarding the subject.
Thanks! I’m in the same boat. I have seen some circuit simulation videos on youtube, but they don’t seem to really address this apparently huge difference in velocity between charged particles and electric field voltage. Like many people, I’m a visual learner, so I’m hopeful that a visual simulation will be available at some point that will help. (Maybe one already exists and I just don’t know about it.)
You are absolutely correct, thanks for your valuable feedback!
Hi Randy, can I ask if your questions are solved? cuz I’m also the one who want to know that 🙂
Thank you, Swagatam
Thank you so much Swagatam, for your prompt reply.
It looks like matching the LC frequency may be an issue. Would it be a better option to use a 555 with a 2N3055 as in your other circuit, so the frequency can be adjusted?
I have no way to measure the inductance of any coil.
Is there any way to connect the work coil to the circuit and use a multimeter to find out if the LC is matched?
Will a pancake coil wound using insulated 3/20 wire work?
You are welcome Srikant, you will have to buy an inductance meter for checking and matching the inductance values precisely. IC 555 will not give you proper results. You can try the pancake coil only after matching the pancake coil’s inductance with the existing coil inductance.
Hi Swagatam,
This is one of the best pages on the net discussing induction cooker circuits.
Im interested in making a low wattage cooker of 500W. The difficult part seems to be making the work coil.
Would these circuits work with the ready induction cooker coils available for sale on Amazon?
Do you think any any modifications to these circuits are needed, if so what?
Would all the circuits here work with a commercial work coil?
Thanks.
Thank you Srikant,
You can use any type of work coil with any shape provided it matches the inductance value of the original work coil. Suppose the original work coil inductance is 10 mH, then the new work coil inductance must be also adjusted to this 10 mH value, and then integrated with the circuit.
Good day Sir, please how can zvs model can be modified to use 96v,10amps to make more efficient and reduce drawing current.
That might require a lot of calculations for the inductors
OK Sir, thanks.
I saw fairly used induction cooker being sold in my neighborhood. Please does it have much difference with new cooker in terms of efficiency and latest development.
Hi Seun, as long as the parts are not worn out or degraded, the old ones will also be good enough, and efficient.
Thanks so much Sir, I saw 6.1kw(title, in foreign language) at the back of an induction cooker, please what can it signify.
6.1 kw can be 6.1 kilowatt
Sir, is that the power consumption rate, that is too high
Yes, the purpose is to design an Induction heater that produces variable power output (from around 100 watts to 1000 or 1200 watts).I want to use this circuit in an automated appliance (that I want to design).
You can try applying the 3rd last design from the following article, to control current and wattages for the induction heaters:
https://www.homemade-circuits.com/universal-high-watt-led-current-limiter/
Hi Swagatam,
Is it possible (1) to design circuit with variable power, having 10 to 12 power settings, (2) To produce multiple circuits using the same design and they all give same power output (10-12 settings) ?
If this is possible, then I am looking to get such a circuit designed, for a project that I am working on.
(post note: I am exploring possible ways to get such a circuit designed, the other ways to produce variable power was by using a microprocessor (such as 555) and changing the frequency, but looks like this is tedious to design and operate)
Thanks
Dinesh
Hi Dinesh, for what purpose do you need this power supply, is it for induction heater? because the above article is regarding induction heater…
Super.
Pozdrawiam.
How can we make a variable power Induction circuit, for example a circuit that can deliver power from 100 watts, 200 watts, ….. upto 1000 watts (10 power settings) ?
The consumer induction heater are not good for the purpose, as they control output power just by switching on/off the coil (full power has continuous power in coil, where as minimum power has around 5 sec power in duration of 25 sec – which is not good for my purpose)
It can be simply done by using a power supply with an adjustable current output. By reducing the input power supply current you can reduce the output power of the induction heater and vice versa.
Hi. I love the clear explanation you gave concerning the Induction heater.
I just built my circuit with all the components, except for the gate 12v zener diode, because I’m using a 12v, 18Ah battery power source. When I switched power ON, I put an iron nail into the coil, but it doesn’t heat up at all. The whole copper coil heats up(as a result of current passing through), but the nail doesn’t heat up, looks like it doesn’t induce any current on the nail, I tried using other metals and materials, but it’s still the same. Pls do you know why it is like that, I really have interest in getting this heater to work. Thanks.
Hi, thanks, what inductor value did you use for L1, L2, L3??
Sorry for the late reply. Actually, I built the circuit with a center tapped coil which was about 7 turns of 1mm copper wire with 20mm internal diameter. For L2, I wound 34 turns of 0.5mm coil on a toroid of around 18mm external diameter. My capacitor was 330nF(334) metalized pp, 400v. But this time around, only one part of the coil heated red hot after some seconds, but the work metal in the coil doesn’t heat up, except for the little heat from the coil. I’ve tried changing the capacitor’s value to 660nF, 1.5uF, 3.16uF(combination), and as small as 47nF, but all the same. I will be glad to hear from you soon. Thanks Mr. Swagatam.
The coils should be exactly as given in the picture. L2 should be built over a 25mm torroid, or the inductance should be around 2mH
The circuit was successfully built but overheating was observed in the capacitors
Is there a suggestion
In my experiment it did not heat much, did you assemble the parts exactly as given in the original prototype?
What advice would you give
Note that the file also warms up a little and the rest of the components are not hot
hi
I want t oask if the middle object (for example, the same drill bit) is rotating, will it still heat up?
Does it also depend on the rotation speed?
thank a lot
Yes it will still become hot according to me….
Did you have any experience or not ?
If I have a simple DC voltage withe required current , will it still heating up ?
the original scheme calls for fast diodes rated 400v+ , how can the bc547 even work??/
in the schematic only 12V is involved, not 400V….and the BC547 is rated to handle over 100 MHz frequency
Hi Swagatam,
i just love ur enthusiasm. My best wishes with u for ur future endeavour.
Could u pls let us know how domestic indiction cooker works, how much frequency and how much voltage is there. Can we make mini version of domestic induction heater with this cirucit which runs on AC 230V what changes we need to do for that.
Thanks in advance.
Thank you Arpit, The working concept is quite the same as explained in the above article, expect that a H-bridge design is typically used in commercial units. Nevertheless, you can easily make a mini version by modifying the first concept explained in the above article, by converting the existing coil into a flat spiral coil, and by matching the inductance values so that they are exactly similar.
If dimensions of L1 ( Working coil)inside dia. 19 mm increased to 150 mm whether circuit will still work
It may work, but the number of turns might need to be increased.
Hi!
I need a help.
Can we use the circuit of induction cook top, to heat metal externally. I am of with the view, of replacing the flat coil that comes with the induction cook top with the spiral coil formed of copper, as with shown in all tutorials. Thank You
Hi, I won’t recommend that. It is a lot better to buy the second design explained in the above article from the market, which is much easier and cheaper to implement.
Hi, I made a first attempt of the induction heather with the Mazzili driver concept version and it was unsuccessful. Reviewing the info and comparing the simple drawing and the original one, I found something that caught my attention. The original drawing shows the symbol of Zener diode arranged as voltage regulators and in the simple version of the drawing the diodes are shown as fast recovery diodes. In my first construction attempt I used a couple of fast recovery diodes and one of the mosfet become hot as soon as I turned on the power supply.
My question is; the diodes are arranged as voltage regs or as blocking elements ?
Thank in advance for your attention and for your kind response to my question.
Hi, the 1N4007 diodes shown in the first diagram were probably used for simplicity and for cost cutting. These are also used in the original diagram as D3, D4. The function of these diodes are to ground the gate of the opposite MOSFETs alternately, to trigger and sustain the oscillations. The 12 V zener shown in the original diagram is for regulating the gate voltage of the MOSFET to 12 V in case higher input supply voltages are used
Hi there, thank you for your response. Regarding the problem that I described to you about one of the mosfit get hot as soon as the power is on, I think, is in a cold solder in one of diodes what perhaps inhibit the oscillation of the circuit. I´ll let you know the result of the new circuit.
No problem, Thanks for letting us know.
Can FGA60n65 IGBT be used in place of IRFP260 mosfet in a induction heater circuit. thank you
Please check and compare their datasheet information regarding VDs and ID.
Sir. I have a bajaj induction cooker 1400w coil and body with ceramic plate but no motherboard to operated this. (I got this from bhangarwala)Can you design a simple circuit for me so I can use this for cooking food.
I have a 95w HP laptop charger. Is this power supply sufficient enough, I have a single p channel igbt ,coils and some caps
Shankar, you can buy any standard ZVS based induction circuit like the one explained in the first example above.
and then try replacing the coil with your coil, and see if the circuit locks in to your coil. The power supply will depend on the circuit and the coil specification, and the intended load power.
thank u sir ,suggest me an power circuit of 1500w 24 to36 voltsdc from ac220v induction heater supply beacuse an low capacity eats the power like any thing
D Ramesh, you will need a 0-24V, 62 amps transformer, 100 amp bridge rectifier and 10000uF/50V filter capacitor to build it. I do not have a SMPS design for such huge power suply.
d ramesh ,dear sir will a small curcible can be used of 25mm dia nor circuit will dammage
Hi, You can use a 25mm diameter iron load with the shown circuits.