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Output inverter bridge for welding TIG machine?

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Coper

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I have TIG weding machne , but only DC and need AC for welding aluminium and pulse for any precise works.
My idea is add on output full bridge for chnging polarity and or make pulse.

Technical
current is 150A max
switching frequency 400Hz max

As transistor in to bridge I think IPT012N08N5 80V 300A 1,2mOhm, for controlling bridge any MCU STM32F3 with full bridge PWM

I'm looking for a suitable driver for High and low side MOSFET , for charging 13nF input gate capacitor.
Do you recommend suitable drivers with sufficient current?
 

It will be, on the other hand, switching current is 150A, Qoss 208nC and no-load voltage may be 50V. For mimimising switching lost we need mimimise switching time
if we want to open transistor on 40ns we need more than 5A driver current.
For example 6A driver for low side is not problém, but 6A driver for high side with transformerles desig may is problém.
 

In DC mode the bridge must be in "static state" and this eliminates a simple transformers MOSFET driver.
May be I use full isolated digital driver with DC/DC PS.

Yes max switching spoeed is 400Hz , but current is 150A and becouse trnsoisto have SMD HSOF case I will have to invent a PCB that will transfer 150A.
 

You should start to design the transistor heat sinking. 150 A (27 W conduction losses in static operation) won't work on any kind of regular PCB. I guess, you better switch to conventional transistor packages.
 

On the bridge it is even 2 * 27W, but I thing it is not problem , yes must be used heatsink and fan.
 

For clarification. conductivity losses can be reduced by using a pair of transistors 8pcs in full bridge. The question is whether it is economic, because 57W is only 1,5% of total power.
Cool the transistors is nit problem, this make old PC CPU heatsing.
I see the bigger problem in PCB losses. at least on cheap 70um pcb from china, may be add an soldem 0.3mm copper foil
 

conductivity losses can be reduced by using a pair of transistors 8pcs in full bridge.
That's an option. It's still rather difficult to interface the SMD transistor package to a heatsink. You can e.g. use massive thermal vias and mount the PCB on top of the heatsink.

Besides special thick copper designs, multilayer stack-ups with many (e.g. 6 or 8) 70 um layers are an effective way to make high current PCB.

I wonder if screw amounted MOSFET modules and copper bars are a more simple solution in this case.
 

I played with a PCB layout and her is my first design in early alfa version.
I remember, I do not want to produce it in big but in a few pieces
Motherboiard is FR4 with 70um coper, on golden surfaces it is soldered aditional 0,3mm coper foil.
Center rectngle is 40x20mm on top i.e. resistance approximately under 100u Ohm, the same is on Bottom side.
MOSFET 2x IAUT300N08S5N012 i.e. typical Rdson on pair 500uOhm.
As connector on every ports 2x brass screw 4 or 5mm with 2pcs oring connector on every screw.
Transistors will of course have a heatsing and a fan.

What do you think?

. TIG.png
 

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