Half-bridge driver for induction heating problem

[Rixen]

Hi all,

Im once again, trying to make an induction heater with a half-bridge driver IC, but im running into problems, I would like if someone could take a look at my diagram and see if im doing something obviously wrong..
If I turn off the 31v rail the IC gate signals look fine, but if I turn it on, the IC gets very hot, the inverter appears to draw alot of current and I must turn it off immediately or im risking my transformer..

The PWM signal is comming from my signal generator, the first part of my circuit is my attempt at making a dead time logic circuit, i've measured it with my scope and it appears to work just fine.

Gate signals from the driver also appear to be OK, are out of phase as they should be and are not cross conducting.

The +15v supply is comming from my bench PSU, the +5v is comming from a LM317 regulator that's fed by the 15v supply, this works fine too, all circuit common are connected..

My resonant circuit consists of a work coil made of 3mm cobber tubing that I made myself, I chose a 100KHz resonant frequency as it is the highest my LCR meter will measure, I used the resonant frequency formula to solve for a value of C, giving me 1,613uF. 1,57uF was the closest I could get to that and that gives me a resonant frequency of 98,9 KHz..

Not sure how to solve for C10, it's just a blocking cap, big enough to not influence the tank circuit is the goal I guess..
Also not sure how to calculate inverter current draw, when driven at resonance it should be very small if im reading things right, not sure, it can wait for now I guess.

The fets are IRLB3036's : https://www.infineon.com/dgdl/irlb3036pbf.pdf?fileId=5546d462533600a40153566033ea2589
The IC is IR2110: https://www.infineon.com/dgdl/ir2110.pdf?fileId=5546d462533600a4015355c80333167e

Here is my circuit diagram, the 31v rail isnt on here.
The 31v supply is comming from a transformer with two 22v secondaries in parallel, running into a bridge rectifier, 1000uF smoothing capacitor, that's it.

I can show the calculations that i've done if it's of any help.

Any help is appreciated guys..

 

[kellys_eye]

The MOSFET driver stage looks all wrong to me.

The sources should be ground and the drains connected across the LC circuit and each drain connected to your supply line via choke (filters) of, say, 100μH. C10 not used/required.

 

[Rixen]

Thanks for the reply

I was trying to replicate the basic circuit shown here: https://www.richieburnett.co.uk/indheat.html
Minus his "matching inductor" whos function I feel is not explained very well, nor how to get a value for it or what is required of it.

But I will disregard that and try the circuit you advice, I just wound the 100uH inductors required.. (I got a question about that later )

Before I start soldering, this is what you want me to do?

 

[kellys_eye]

Yes, that's the basic layout...

 

[Rixen]

Yes, that's the basic layout...

I'll give it a shot.

...I was referring to this circuit

If you mean that the "basic layout" is equal to this one taken from richieburnett.co.uk.. I am officially confused.
They dont look alike to me.

Not to offend or anything ofcourse.

 

[kellys_eye]

Yeah -that circuit relies on critical tuning of the two LC circuits which is probably why your layout doesn't work.

The 'new' arrangement will work and come to resonance as you 'tune' the basic switching frequency through the required point but with no special effort at coupling.