Half Bridge MOSFET Induction Heater Problems
Gabriel35, Mon Aug 31 2009, 10:29PMHi all!
I was trying to build a new IH for me, since i've already got bored with Mazilli ZVS one.
So i created one topic asking about what circuit would be better and easier to build...
When "Tonskulus" showed his "schema3"
I liked it a lot, so i've decided to follow this schematic, but i've made some modifications because i cant find any powerfull IGBTs near here...
And the circuit got this face:
But i'm not certain that everything is alright, and if the IH will work with this schematic, can someone check it and give some clues about it?
The circuit is finished, and i have one 12v , 18v and 45v DC supplys for the IH
When i turn it on, the only thing that heats up a little is the 40106 IC, the rest keeps cool, seems to be not working and i don't know why...
Can you take a look at the circuit and tell if you see something wrong?
I've just noticed that i'll need a Osciloscope for tuning it before the circuit was already finished, and i don't have one osciloscope, so this is a problem, perhaps anybody knows a nice IH circuit that don't need a osciloscope for tuning...?
I got only some 630v capacitors for the tank, but i'm trying to turn it up with only 45vDC so i think it can handle for test purposes, the same for the "weak made" coil and small dissipators on the IRFP's
The tank of "red" capacitors are de 9uF DC blocking capacitors, can it be this kind of capacitors?
As you can see i'm a little confused...
Thank you!
Re: Half Bridge MOSFET Induction Heater Problems
Tonskulus, Tue Sept 01 2009, 06:35PM
First of all, you should check that there is signal on gates of fets. Should be clean squarewave. Again, oscilloscope is nice tool there. However, as you dont have one, you can try this method:
-Remove feedback from trigger.
-Put Amp meter between powersupply and inverter
-Use low voltage for inverter, 24...48V
-Now as you adjust potentiometer ( relaxant oscillator frequency), when it hits resonant freq of tank circuit you should see input current rising rapidly. Maximum current means that it is tuned.
If there is no change in current at all, something is wrong. Its also possible that Zmatch coil has too much inductance..And I can see that you are using toroidal ferrite core for Zmatch? I think its just too much. You should use EI core with variable airgap.
Tonskulus, Tue Sept 01 2009, 06:35PM
First of all, you should check that there is signal on gates of fets. Should be clean squarewave. Again, oscilloscope is nice tool there. However, as you dont have one, you can try this method:
-Remove feedback from trigger.
-Put Amp meter between powersupply and inverter
-Use low voltage for inverter, 24...48V
-Now as you adjust potentiometer ( relaxant oscillator frequency), when it hits resonant freq of tank circuit you should see input current rising rapidly. Maximum current means that it is tuned.
If there is no change in current at all, something is wrong. Its also possible that Zmatch coil has too much inductance..And I can see that you are using toroidal ferrite core for Zmatch? I think its just too much. You should use EI core with variable airgap.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Tue Sept 01 2009, 06:51PM
oh! ok very nice clues!
thank you a lot!
i've checked that
there's 0,00 Amperage when i put the Amp meter between the inverter and the 41,2vDC Supply, even turning the potentiometer.
there's something really wrong...
do you have some clues about the oscilator circuit?
some readings that i should get?
the 12 V+ and GND should go just on VDD and VSS from trigger, or on any other pin of the trigger too?
or do you think that the problem is caused by the zmatch toroidal?
can i make the Zmatch with a flyback ferrite like this ones?
how many turns do you suggest? and what about the gap?
The IRF's don't warm, the only thing that warms is the 40106 trigger, and the thing don't make any noise
one more time, is the schematic that i've posted right?
thanks!
Gabriel35, Tue Sept 01 2009, 06:51PM
oh! ok very nice clues!
thank you a lot!
i've checked that
there's 0,00 Amperage when i put the Amp meter between the inverter and the 41,2vDC Supply, even turning the potentiometer.
there's something really wrong...
do you have some clues about the oscilator circuit?
some readings that i should get?
the 12 V+ and GND should go just on VDD and VSS from trigger, or on any other pin of the trigger too?
or do you think that the problem is caused by the zmatch toroidal?
can i make the Zmatch with a flyback ferrite like this ones?
how many turns do you suggest? and what about the gap?
The IRF's don't warm, the only thing that warms is the 40106 trigger, and the thing don't make any noise
one more time, is the schematic that i've posted right?
thanks!
Re: Half Bridge MOSFET Induction Heater Problems
Proud Mary, Tue Sept 01 2009, 07:28PM
Why not use a self-oscillating half-bridge driver like IR2153?
They cost only a dollar or two depending on whether you buy DIP or SOIC.
Proud Mary, Tue Sept 01 2009, 07:28PM
Why not use a self-oscillating half-bridge driver like IR2153?
They cost only a dollar or two depending on whether you buy DIP or SOIC.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Tue Sept 01 2009, 07:48PM
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
Gabriel35, Tue Sept 01 2009, 07:48PM
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
Re: Half Bridge MOSFET Induction Heater Problems
Proud Mary, Tue Sept 01 2009, 08:21PM
The IR2153D is a slight improvement on the first iteration, I believe.
Proud Mary, Tue Sept 01 2009, 08:21PM
Gabriel35 wrote ...
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
The IR2153D is a slight improvement on the first iteration, I believe.
Re: Half Bridge MOSFET Induction Heater Problems
Tonskulus, Wed Sept 02 2009, 08:50AM
Yes it is self oscillating and not. First of all, it has fixed frequency oscillator so it cant track the resonant frequency of tank circuit. Not very useful and may also lead to mosfet failure if undertuned.
Tonskulus, Wed Sept 02 2009, 08:50AM
Gabriel35 wrote ...
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
like on this one?
if it's self-oscillating, why does it have one potentiometer?
do you suggest some schematic?
i'll try all the way with Tonskulu's schema, if i really can't get nothing from that ill try another circuit...
thank you!
Yes it is self oscillating and not. First of all, it has fixed frequency oscillator so it cant track the resonant frequency of tank circuit. Not very useful and may also lead to mosfet failure if undertuned.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Wed Sept 02 2009, 03:53PM
yes! because of that I'll keep trying your schematic Toni!
What about my questions on 3rd reply?
i'm certain that the problem is on my oscilator circuit but i can't find a mistake on that
I need that help so i can continue the project
thanks!
Gabriel35, Wed Sept 02 2009, 03:53PM
yes! because of that I'll keep trying your schematic Toni!
What about my questions on 3rd reply?
i'm certain that the problem is on my oscilator circuit but i can't find a mistake on that
I need that help so i can continue the project
thanks!
Re: Half Bridge MOSFET Induction Heater Problems
teravolt, Thu Sept 03 2009, 03:57AM
you have replaced the max4428 with one cd40106 wich has a much higher output impedance maby if you dubled up on the 5 remaining inveters there would be more drive. If you are interested you could use this chip
and 2 regular n-chanel fets to drive your GDT. the inputs will have to be one from cd40106 pin2 and the other pin4. with this chip you may have to play with phaseing to get it to oscillate. if you need a tool to check this a logick probe will help
teravolt, Thu Sept 03 2009, 03:57AM
you have replaced the max4428 with one cd40106 wich has a much higher output impedance maby if you dubled up on the 5 remaining inveters there would be more drive. If you are interested you could use this chip
and 2 regular n-chanel fets to drive your GDT. the inputs will have to be one from cd40106 pin2 and the other pin4. with this chip you may have to play with phaseing to get it to oscillate. if you need a tool to check this a logick probe will help
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Fri Sept 04 2009, 04:39PM
Hey!
Now I'm trying the circuit that Karim Ladha developed, using the "same" topology but including a IR2184 MOSFET/IGBT Driver
But i need to ask some questions here:
That Neutral and LIVE inductors, it is one Zmatch for each wire ? or the Matching inductor goes only in one wire ? (Live or Neutral)
and what about the IR2184 Conection Pins, they are not in order on kim's schematic, are them?
i've drawed the conection schema as i think it is correct, can someone say if this is right?
Thank you!
Gabriel35, Fri Sept 04 2009, 04:39PM
Hey!
Now I'm trying the circuit that Karim Ladha developed, using the "same" topology but including a IR2184 MOSFET/IGBT Driver
But i need to ask some questions here:
That Neutral and LIVE inductors, it is one Zmatch for each wire ? or the Matching inductor goes only in one wire ? (Live or Neutral)
and what about the IR2184 Conection Pins, they are not in order on kim's schematic, are them?
i've drawed the conection schema as i think it is correct, can someone say if this is right?
Thank you!
Re: Half Bridge MOSFET Induction Heater Problems
teravolt, Sat Sept 05 2009, 02:17AM
I think your circuit might work, try the schematic on a proto bord if pausible. The device has a little delay in it. I also think that you could dump all the zeners if you are using a regulated supply
teravolt, Sat Sept 05 2009, 02:17AM
I think your circuit might work, try the schematic on a proto bord if pausible. The device has a little delay in it. I also think that you could dump all the zeners if you are using a regulated supply
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Sat Sept 05 2009, 04:02AM
OK! i've mounted it on a PCB,
I'm afraid of killing this IR2184 Driver,(Yes they're expensive) because of that i've asked if the conections were right...
So it means that the design that Karim Ladha drawed is just for reference, the right conections are like i've drawed, alright?
Can I turn just the driver part of the circuit on first, and then the Inverter part? or it can damage something?
Thank you!
Gabriel35, Sat Sept 05 2009, 04:02AM
OK! i've mounted it on a PCB,
I'm afraid of killing this IR2184 Driver,(Yes they're expensive) because of that i've asked if the conections were right...
So it means that the design that Karim Ladha drawed is just for reference, the right conections are like i've drawed, alright?
Can I turn just the driver part of the circuit on first, and then the Inverter part? or it can damage something?
Thank you!
Re: Half Bridge MOSFET Induction Heater Problems
uzzors2k, Sat Sept 05 2009, 10:54AM
I see several mistakes. For one thing, remove the 10k resistors from the input and Vcc pins. "In" is a high impedance input, and Vcc needs access to the full 15V without severe current limiting. Also you've got 15V going into COM or the "common ground". Go through the datasheet again and look at page 5, you seem to have mixed up the pin functions and numbers. Kim has them ordered correctly in his schematic, so just use it for reference.
About the matching inductor, it's two windings on one core, though the schematic says one winding can also be used.
uzzors2k, Sat Sept 05 2009, 10:54AM
I see several mistakes. For one thing, remove the 10k resistors from the input and Vcc pins. "In" is a high impedance input, and Vcc needs access to the full 15V without severe current limiting. Also you've got 15V going into COM or the "common ground". Go through the datasheet again and look at page 5, you seem to have mixed up the pin functions and numbers. Kim has them ordered correctly in his schematic, so just use it for reference.
About the matching inductor, it's two windings on one core, though the schematic says one winding can also be used.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Sat Sept 05 2009, 02:01PM
Oh! yes you are clearly right!
now i've saw the page 5. Kim's drawing is perfectly right...
I'll make the changes
Thank you!
Gabriel35, Sat Sept 05 2009, 02:01PM
Oh! yes you are clearly right!
now i've saw the page 5. Kim's drawing is perfectly right...
I'll make the changes
Thank you!
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Tue Sept 08 2009, 12:46AM
Hi all!
i got some photos of the work...
I need someone to say if the Current transformer and the "Air cored inductor" are right
And the other photos are just for showing the work:
the last one is a IGBT that i've got, rated 1200v and 35A, fullbridge of 6 "mosfets" with built-in free-wheeling diodes
so if I don't have sucess with the IRFP's i'll try this IGBT,
and for the tank capacitors i'll buy 14x 220nF - 1000v capacitors, (the ones on the photos are just for testing purposes)
what do you think?
Thank you!
Gabriel35, Tue Sept 08 2009, 12:46AM
Hi all!
i got some photos of the work...
I need someone to say if the Current transformer and the "Air cored inductor" are right
And the other photos are just for showing the work:
the last one is a IGBT that i've got, rated 1200v and 35A, fullbridge of 6 "mosfets" with built-in free-wheeling diodes
so if I don't have sucess with the IRFP's i'll try this IGBT,
and for the tank capacitors i'll buy 14x 220nF - 1000v capacitors, (the ones on the photos are just for testing purposes)
what do you think?
Thank you!
Re: Half Bridge MOSFET Induction Heater Problems
uzzors2k, Tue Sept 08 2009, 01:31PM
Looks good, just using thicker insulation on the current transformer's primary to avoid arc-over.
uzzors2k, Tue Sept 08 2009, 01:31PM
Looks good, just using thicker insulation on the current transformer's primary to avoid arc-over.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Tue Sept 08 2009, 05:06PM
I've finally turned the heater up...
I got a little "bzz" noise when i put the potentiometer all the way right, it varies from 0.00A to 3,16A (the thing is oscilating)
When I put the potentiometer is all the way right and it gives me 3,16A(pretty low) and the mosfets, the coil and the tank caps warm a little..
The screw (on the work coil) starts to heat a little too
So it seems to be working, but the amperage is still low, (~3,0A) (i'm using 41,2VDC)
Something is limiting the current too much...
Another thing that i've found strange is that, when I turn the potentiometer all the way right and there's no workpiece on the workcoil the amperage is 3,16A and when i put a screw on the work coil it falls to 2,64A
I've noticed that when I tried to turn the inverter part with 36vDC the amperage stayed at 0,00A turning the potentiometer,
so maybe is just a voltage problem, perhaps it need more voltage to excite well...but i'm afraid of trying it with 250vDC because the mosfets heat pretty well now, maybe with 250vDC they can blow... or not?
Any clues?
Thank you
Gabriel35, Tue Sept 08 2009, 05:06PM
I've finally turned the heater up...
I got a little "bzz" noise when i put the potentiometer all the way right, it varies from 0.00A to 3,16A (the thing is oscilating)
When I put the potentiometer is all the way right and it gives me 3,16A(pretty low) and the mosfets, the coil and the tank caps warm a little..
The screw (on the work coil) starts to heat a little too
So it seems to be working, but the amperage is still low, (~3,0A) (i'm using 41,2VDC)
Something is limiting the current too much...
Another thing that i've found strange is that, when I turn the potentiometer all the way right and there's no workpiece on the workcoil the amperage is 3,16A and when i put a screw on the work coil it falls to 2,64A
I've noticed that when I tried to turn the inverter part with 36vDC the amperage stayed at 0,00A turning the potentiometer,
so maybe is just a voltage problem, perhaps it need more voltage to excite well...but i'm afraid of trying it with 250vDC because the mosfets heat pretty well now, maybe with 250vDC they can blow... or not?
Any clues?
Thank you
Re: Half Bridge MOSFET Induction Heater Problems
Steve Conner, Wed Sept 09 2009, 09:32AM
If the max current is at one end, sounds like your pot needs some more range. You should be able to tune through the maximum.
Steve Conner, Wed Sept 09 2009, 09:32AM
If the max current is at one end, sounds like your pot needs some more range. You should be able to tune through the maximum.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Wed Sept 09 2009, 03:46PM
current hits the maximum @ about 7/9 of the pot (i've forgot to mention this detail...)
So i think that the pot is fine
I still think that it need more voltage...
What do you think?
Gabriel35, Wed Sept 09 2009, 03:46PM
current hits the maximum @ about 7/9 of the pot (i've forgot to mention this detail...)
So i think that the pot is fine
I still think that it need more voltage...
What do you think?
Re: Half Bridge MOSFET Induction Heater Problems
teravolt, Thu Sept 10 2009, 03:32AM
have you tried playing with the tank capacitors to increase the circulating current? Tonskulus or anybody does the 100k trimmer change pulse width to the fets
teravolt, Thu Sept 10 2009, 03:32AM
have you tried playing with the tank capacitors to increase the circulating current? Tonskulus or anybody does the 100k trimmer change pulse width to the fets
Re: Half Bridge MOSFET Induction Heater Problems
Tonskulus, Thu Sept 10 2009, 08:54AM
No, does not change pulse width. If input current is too low, Zmatch inductor may have too high inductance.
If tank caps warms, it works.
Tonskulus, Thu Sept 10 2009, 08:54AM
No, does not change pulse width. If input current is too low, Zmatch inductor may have too high inductance.
If tank caps warms, it works.
Re: Half Bridge MOSFET Induction Heater Problems
Gabriel35, Thu Sept 10 2009, 03:50PM
hey!
what happens if i try to turn the inverter part with 250vDC?
are there risks of melting the fets(IRFP460s) ?
changing the inductor, and feeding it with 41,2vDC @ 6A it was capable of warming a screw, that turned untouchable, i think it was about 140ºC
The fets heated pretty well too...(I thought that they would work cool) but i have big dissipators now
Current is limited, the maximum that i could achieve using a very tiny inductor was about 6~8A, so i was thinking
if the amperage is limited to 2,5A
250V x 2,5A = 625 Watts
A acceptable power level, for beggining...
What do you think?
Gabriel35, Thu Sept 10 2009, 03:50PM
hey!
what happens if i try to turn the inverter part with 250vDC?
are there risks of melting the fets(IRFP460s) ?
changing the inductor, and feeding it with 41,2vDC @ 6A it was capable of warming a screw, that turned untouchable, i think it was about 140ºC
The fets heated pretty well too...(I thought that they would work cool) but i have big dissipators now
Current is limited, the maximum that i could achieve using a very tiny inductor was about 6~8A, so i was thinking
if the amperage is limited to 2,5A
250V x 2,5A = 625 Watts
A acceptable power level, for beggining...
What do you think?
Re: Half Bridge MOSFET Induction Heater Problems
paolss, Thu Dec 03 2009, 07:59PM
Hello
I build this circuit also - and it is not lucky for me :)
i burn two ir2184 when i use 4.7ohm resistors from HO/LO to gates of mosfets.
I change resistors to 22ohm and circuit start to working but....
When HO and LO are not connected to gates of mosfets signal is ok.
But when i make connection to mosfets the signal of HO looks like this:
Sorry this is paint - but signal on osciloscope is exactly the same.
Output from CD40106 is also ok - square wave of 50% duty cycle.
Someone can tell me what can be wrong ?
Circuit is from:
Regards
Pawel
paolss, Thu Dec 03 2009, 07:59PM
Hello
I build this circuit also - and it is not lucky for me :)
i burn two ir2184 when i use 4.7ohm resistors from HO/LO to gates of mosfets.
I change resistors to 22ohm and circuit start to working but....
When HO and LO are not connected to gates of mosfets signal is ok.
But when i make connection to mosfets the signal of HO looks like this:
Sorry this is paint - but signal on osciloscope is exactly the same.
Output from CD40106 is also ok - square wave of 50% duty cycle.
Someone can tell me what can be wrong ?
Circuit is from:
Regards
Pawel
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