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I saw this video about DIY Induction Heater and I decided to make it by myself in order to learn something from this project.

After finish wiring everything, I connect the power supply and heard/saw a spark. I touched the components and the two MOSFET were super hot. I supposed that I connected something wrong / shortened something so I rebuilt the circuit with new components, with more space between them, and before turning it on, I checked connectivity with a multimeter to verify everything is well connected.

On the second time I also limited my power supply to 3 Amps. When I connected it to the circuit, the voltage of the power supply dropped to 5.4V (because of the 3A limit) and I felt the MOSFETS are becoming again very hot.

I also built this circuit in an online simulator but it seems to behave differently. I couldn't think of any solution, hope you guys can help.

This is the schematic: enter image description here

L2, L3:

Inductance: 100uH, Current Rate: 6A

L1: 3uH. 2mm thick Pure Copper Wire Round Solid Uncoated with 10 turns of 20mm diameter.

Capacitors: 2 x WIMA MKP10 0.33uF (0,33µF 330nF) 400V 5% pitch:22.5mm Capacitor

This is how I connected everything: enter image description here

enter image description here

enter image description here

Power Supply before connecting: enter image description here

Power Supply after connecting: enter image description here

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    \$\begingroup\$ What is the current rating on L2 and L3? What's the calculated inductance of L1? What frequency should it oscillate at? How do the values tie in with the video (that I won't be watching)? \$\endgroup\$ – Andy aka May 1 '18 at 13:21
  • \$\begingroup\$ @Andyaka Edited question \$\endgroup\$ – yanivps May 1 '18 at 13:41
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    \$\begingroup\$ Your simulated inductance is probably miles off. I roughly estimate it has a few micro henries at best and not 100 uH as per your simulation. Go find an inductor calculator on line. \$\endgroup\$ – Andy aka May 1 '18 at 13:45
  • \$\begingroup\$ @Andyaka this is the inductor (how can it be something else than what is written?): ebay.com/itm/… \$\endgroup\$ – yanivps May 1 '18 at 13:51
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    \$\begingroup\$ Not those! The big one. (Referring to the @Andyaka's comment, that is) \$\endgroup\$ – Richard the Spacecat May 1 '18 at 13:52
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Does your circuit oscillate? If not, then both mosfets conduct at the same time and the behaviour is like you presented. Both mosfets dissipate all which is available.

One error which prevents the oscillation or lower its frequency to uselessly low is to use some random parts instead of the proper ones. For example 1N4007 instead of ultra fast UF4007. Another error is to have no supply voltage decoupling and about 20 times too long wiring. Your wiring is a bigger coil than the heating coil.

Make your circuit as compact as the model, use exactly right parts and have some big capacitor between Vcc and GND as near the circuit as possible. Be also sure that theres no connection between the turns of L1, if it's not insulated. Any connection is a short circuit.

Without having an oscilloscope debugging is very difficult because a multimeter shows virtually nothing about oscillations.

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  • \$\begingroup\$ Thank you for you answer. Actually on the first time, I built it as compact as in the video, without wires at all, only with some pieces of silver. All parts that I used are as in the schematics. I didn't really understand the what you said about wires / coils size. And for the inductors, they are insulated. \$\endgroup\$ – yanivps May 1 '18 at 13:56
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    \$\begingroup\$ @yanivps you wrote L1: 2mm thick Pure Copper Wire Round Solid Uncoated. That makes me think the copper is clean with no insulation. Your photo does not show that adjacent turns do not touch each other. Uncompact circuit is itself a big coil which makes all unpredictable. \$\endgroup\$ – user287001 May 1 '18 at 14:00
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    \$\begingroup\$ "One great method to prevent the oscillation..." I think this style of answer is going to be challenging for someone who doesn't already know much about electronics, or for whom English is not a first language. This might not be true of the asker but what about future readers? I would consider rewording your answer is a more straightforward manner without the double-negative wording. \$\endgroup\$ – Glenn Willen May 1 '18 at 18:25
  • \$\begingroup\$ @GlennWillen Ok I'll fix it soon \$\endgroup\$ – user287001 May 1 '18 at 18:42
  • \$\begingroup\$ @GlennWillen Definitely agree with you \$\endgroup\$ – yanivps May 3 '18 at 9:49
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Your loops are far too big thus the 1nH/mm, loop area and orientation with Vgs creates a different resonance where the schematic has changed from Laws of Physics which are never shown in schematics so layout is critical to understanding of laws of physics http://hyperphysics.phy-astr.gsu.edu/hbase/emcon.html#emcon

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problem is there is no real loading of the couter-emf spikes of L2 and L3, but its needed for triggering the opposite gate. So you two choices here I see. One is to stick something like a 1-100 ohm 5W resistor between the the power supply and Vcc connections or a 6A10 diode in series there. either way, you need to keep the reverse spikes in the gate circuit but isolated from the power supply. but the difference between the two is the size of the resistor will effect the reverse current spike amplitude ( the larger the resistor, the bigger the spike) but the trade off will be current capacity. If you need maximum current demand from this circuit, I would go for the diode in series method. Examples: circuit with resistor or circuit with diode

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