VapCap DIY Induction Heating : Bits 'n' pieces

[babunja]

Just checked on wikipedia, iQos works by heating the device in which a "cigarette" (a stick of glycerin soaked tobacco ) is inserted, the one using induction is Illuma.
I don't own an iQos, but maybe it can be hijacked to be a heat source for weed, the problem being how to check temperature

yes but I would like to replicate iqos don't buy it to modify it, then it heats up yes but I would like to replicate iqos don't buy it to modify it, then it heats up to 350 degrees which is too much for the weed

 

[Gomaruana]

Adjustable Resonance Induction Heater ( 12 V ) with TTL ( or CMOS ) PWM signal input
( from a microcontroller ,for example )





As the previous circuit ,but with a different MOSFET gate driver
( UCC2720x High Frequency, High-Side and Low-Side Driver )
and a single channel signal inverter
( MC74VHC1GT04 Inverting Buffer / CMOS Logic Level Shifter )
at the Low-side gate input signal ( LI ) in order to invert the High-side gate input signal ( HI ) ,allowing the use of a single input PWM TTL ( or CMOS ) signal .
The two 10K resistors are used to securely drop the signal to ground ( VDC ) ,
when LOW .

http://www.onsemi.com/pub/Collateral/MC74VHC1GT04-D.PDF

http://www.ti.com/lit/ds/symlink/ucc27200.pdf




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(...)

UCC2720x Application Information

To effect fast switching of power devices and reduce associated switching power losses, a powerful gate driver is employed between the PWM output of controllers and the gates of the power semiconductor devices. Also, gate drivers are indispensable when it is impossible for the PWM controller to directly drive the gates of the switching devices. With the advent of digital power, this situation is often encountered because the PWM signal from the digital controller is often a 3.3-V logic signal which cannot effectively turn on a power switch. Level shifting circuitry is needed to boost the 3.3-V signal to the gate-drive voltage (such as 12 V) to fully turn on the power device and minimize conduction losses. Traditional buffer drive circuits based on NPN and PNP bipolar transistors in totem-pole arrangement, being emitter follower configurations, prove inadequate with digital power because they lack level-shifting capability. Gate drivers effectively combine both the level-shifting and buffer-drive functions. Gate drivers also find other needs such as minimizing the effect of high-frequency switching noise by locating the high-current driver physically close to the power switch, driving gate-drive transformers and controlling floating power-device gates, reducing power dissipation and thermal stress in controllers by moving gate charge power losses from the controller into the driver. (...)

More info about MOSFET gate drivers and high frequency MOSFET switching :

http://www.ti.com/lit/ml/slua618/slua618.pdf

Also search for " TK5Q65W_application_note_en_20180726%20.pdf "

This is really interesting to me, I also came across this board;

Piernas's Fast ZVS Mazzilli Driver

This modified driver is capable of working at much higher frequency than the original. It's very useful if you are looking for high voltage. This is because, in a regular ZVS driver, if you want higher voltage, you have to feed the driver with higher DC voltage, but this also increases the...

hackaday.io

I'm thinking about doing a soft start by running it at a high frequency when powered on, the amperage should stay low and when the metal is inserted we could gradually increase power by dropping the frequency closer to the resonant frequency.

I'm trying to build a 20v 10a induction heater that is very safe, fast and isn't too hard to make a custom pcb for.

 

[jackrod]

This is really interesting to me, I also came across this board;

I've been getting interested in induction heater design too . After looking into it, the common circuit used on the cheap blue "12V ZVS" etc modules is kind of crazy, right? It makes sense that the MOSFETs get killed commonly, given that there is no gate driver. And if the work coil and capacitors fail to start oscillating, both transistors can get turned on at the same time, and you basically get a dead short. I thought ElectroBoom explained these issues pretty well in this video and article.
https://www.electroboom.com/?p=1198

It does seem like some external control is needed to make the induction heaters safer. I assume it is what is in the ispire wand or other commercial products. This video shows a digitally controlled induction heater, using a really simple delay in a microcontroller.

That way, out of control switching can be controlled. But you could use the same thing to control the drive frequency to whatever you want.

I'm thinking about doing a soft start by running it at a high frequency when powered on, the amperage should stay low and when the metal is inserted we could gradually increase power by dropping the frequency closer to the resonant frequency.

This is a cool idea for detecting the metal. You mean a frequency just slightly off of the natural frequency of the empty coil, and capacitor(s)? When the metal is inserted, the natural frequency should drop. So maybe you would actually want the driven frequency to be below the natural frequency, and then the power would increase as the metal is inserted, which might be easier to detect. Maybe once it reaches a certain point, you can go back to "locking on" to the oscillation, like the regular ZVS.

There are some articles on better ways to do induction heating if you search "parallel resonant inverter" on google. A little bit over my head, I'm not an EE. There are some interesting strategies for avoiding crazy power spikes, varying the power level, etc. But using a real gate driver, adding some protection to keep the whole thing from shorting out, maybe some thermal protection, could be a lot safer for sure. Let us know if you build anything cool!