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IR2110 H-Bridge Inverter for Induction Heater

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mohiuddinHimel

Mon Jan 02 2012, 07:18PM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

Hi,

I was designing a High Power High frequency Induction Heater inverter. I've choose H-bridge configuration for the inverter
and IR2110 gate drivers to drive the bridge. As the IR2110 is a half-bridge driver i'll use two of them to drive the both sides.
I've done a rough circuit(just drawing). As i dont know much about power electronics i wonder if there is any mistake.

Any kind of advice, recommendation, and any kind of error that should be fixed in my circuit will be highly appreciated!!!

Also i've some questions:

1) what is the use of C3 n how i'll calculate the value?
2) Exactly which back EMF protection Diode should i use as D' ?
3) Do i need to use an opto-isolator for high side nMosfets?

The intended frequency is 150KHz and the Mosfet's are N-type.

PLz help!!

Inducktion

Mon Jan 02 2012, 07:27PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

1. I don't know what the purpose of C3 is unfortunately.

2. Most Mosfets have body diodes already built in them. Check the speed of them, if it's faster than say, 200 nS you're fine and don't need an external one. The faster the better.

3. You do not need to use an opto-isolator if the gate driver has high side driving. However, it could be useful to prevent your logic from exploding in case your mosfets fail.

The Lightning Stalker

Mon Jan 02 2012, 09:43PM

Registered Member #4230 Joined: Sat Nov 26 2011, 05:50AM
Location: Socketville
Posts: 53

That looks pretty sweet to me. I was looking for a single chip solution like this, except that it would drive all four transistors. To answer your questions:

1. C3 is a filter cap for the low side driver driver portion of the chip. It helps isolate the low side driver portion of the chip from any switching noise on the ground and 15V supply rails. It also stores some energy close to the chip for when it demands current to charge the gate of the low side MOSFET. This should be at least a 100nF ceramic type. If you're seeing funny stuff on the low side (or both) gates when the circuit is running, try using bigger ones. If you have to go a lot bigger (above like 1uF), you'll probably be forced to use solid tantalum.

2. Like Dr. Duck says, you may not need any. I think something like the RURG8060 may be a good place to start looking if you need these, but I'm not sure if they're up to snuff at this frequency. You may need something even bigger at really high power levels.

4. The short answer is no. The circuit as drawn works fine assuming nothing goes wrong. I agree with Dr. Duck on this as well, but the place to put the optoisolators, if you use them, would be before the PWM input. It might not be a bad idea to use a couple temporarily during testing to avoid frying your PWM circuitry, but keep in mind they will add delay that may need to be compensated for.

Marko

Mon Jan 02 2012, 10:15PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Any kind of advice, recommendation, and any kind of error that should be fixed in my circuit will be highly appreciated!!!

Yep, there is, a parallel LC fed by a voltage fed inverter is a certain instant mosfet death. You should look into "LCLR" , "Series" or current-fed topology IH's.

For all but the current fed ones, you're going to need some sort of feedback loop to keep your work coil current at safe levels when the workpiece is not present.

This is a simple project you might want to have a look at:

Dr. ISOTOP

Tue Jan 03 2012, 05:02AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Dr. Pork wrote ...

For all but the current fed ones, you're going to need some sort of feedback loop to keep your work coil current at safe levels when the workpiece is not present.

Bleh, feedback is overrated; mine ran open-loop and never blew up

The IR2110 is probably not going to drive transistors big enough for induction heating.
Also, you should look into using a matching transformer, or LCLR.

mohiuddinHimel

Fri Jan 06 2012, 10:59PM

Registered Member #4254 Joined: Sat Dec 10 2011, 09:36PM
Location: Dhaka, Bangladesh
Posts: 27

Dr. Pork wrote ...

This is a simple project you might want to have a look at:

I really like your circuit! it made my life lot more easier dude! even now i want to try this one first!! but several questions

1) Can i use 1N4937 diodes as "fast didoes" in your circuit? because it is the fastest possible diode in my country.
2) Is it mandatory that both of the inductors have to have same value? i'll make them with ferrite toroids and wound enamel insulated wire around them.
3) for the power supply can i use 24VDC (220 Vac to 12Vac transformer, 400 watt, rectified and voltage doubled by two big caps)?
4) What determines the frequency of this oscillator?? simple f=1/(2pie*sqrt-root(LC)) ?

Marko

Fri Jan 06 2012, 11:37PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

1. 1N4937 should work, yes.

2. Just wind the same number of turns on both of them! Use yellow toroids from PC power supplies. Do not use ferrite toroids.

3. Should work, providing your doubler caps are large enough.

4. What you said - and the L is inductance of the work coil, not chokes as some people think. In my case the circuit resonates with a 4uF cap at about 100kHz.

Marko

Patrick

Sat Jan 07 2012, 03:00AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

why is there a 1k resistor from gate to emitter? some of my IC's datasheets show them being used too.

Daedronus

Sat Jan 07 2012, 03:36AM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

Patrick wrote ...

why is there a 1k resistor from gate to emitter? some of my IC's datasheets show them being used too.

Makes sure they don't turn on by accident while the driver is unpowered?
It doesn't take much to turn on a mosfet, just touching the gate is enough.

Dr. ISOTOP

Sat Jan 07 2012, 03:57AM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

Patrick wrote ...

why is there a 1k resistor from gate to emitter? some of my IC's datasheets show them being used too.

It's a pulldown resistor, there largely as a safety measure.
If the driver fails you don't want the gate to stay charged and make the transistor go boom.

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