IGBT gate driver question: HIGH POWER SWITCHING USE CM600HA-24H - Page 1
Forum section: electronics / projects

author: applicanon
author_rank: Contributor
timestamp: September 25, 2018, 09:40:53 pm
content: Hello.I have a project in mind and am in the beginning stages of it.I have a 240VAC tombstone style stick welder that I want to convert into a TIG welder.It currently outputs strictly 60hz AC at a low voltage, high amperage.There is currently no control circuitry at all inside other than a power switch and a big dirty tranny.Here are the parts I have from a scrapped spot welder which I can use on this project:6 large puck style SCRs rated at 600A each.4 large IGBT modules rated at 1200V, 600A, 4300W each. CM600HA-24H8 electrolytic 3300uf x 420v capsLiquid cooled heat sinks for all the power electronicsI was planning on keeping the existing welder transformer for providing mains isolation and to get the voltage level down in the area I'll need it. May need to rewind secondary to get correct voltage, but thats not a problem as I have lots of #12 magnet wire I need to use up.Then I'll use 4 of the SCRs to rectify the AC to DC, and the CAPS to smooth it out.I then want to use one of the IGBT modules to PULSE the DC in order to give the kind of pulsed DC a standard TIG welder outputs, PWM style I guess. I will be using a microcontroller such as an arduino to provide the PWM signals. This part of the project won't be a problem for me.The point I am struggling with is everything between the ARDUINO and the IGBT gate pin. Basically, how to drive the IGBT with the correct source and sink current, and if needed, protect the gate from overvoltage transients etc. (bootstrap zener maybe?)I think a gate driver IC might be a good solution, but there are tons to choose from and I really don't know what to look for when picking one for this specific IGBT, especially considering its size and power draw. I'm hoping someone else has the knowledge or experience with this IGBT or a similar one, and can help me out with a schematic that will work for my application, or a recommendation for a gate driver IC to use.Maybe I've overlooked something simple and one of you can slap me upside the head instead!I've attached the datasheet of the IGBT for anyone who wishes to help!All suggestions welcome

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 26, 2018, 12:06:07 am
content: What would you say your electronics skill level is?The magnetic fields around those IGBTs can smash an Arduino in a fraction of a microsecond. "It seems the best decision is not to play..."You need quite a bit of functionality between here and there, plus design and layout to connect everything up without making the magnetic fields, peak voltages and so on that much worse. A TIG output may be under 100V nominal (assuming HF start is disconnected), but make no mistake, a poorly wired circuit will easily blow those IGBTs on the first cycle.Tim

author: applicanon
author_rank: Contributor
timestamp: October 02, 2018, 04:33:57 am
content: my electronics skill level is high. I'm aware of the possibility that these IGBTs will get cooked if not driven properly. Hence, the reason I am posting this question.I've got the skills and experience to build the thing, just need some help with the gate drive circuit is all.

author: capt bullshot
author_rank: Super Contributor
timestamp: October 02, 2018, 07:29:06 am
content: Thesehttps://gate-driver.power.com/are a simple (but maybe expensive) all-in-one solution for a gate driver. They should have some variants that match your IGBT.Otherwise, for this size of IGBT i'd suggest a gate driver capable of some 5...10A peak current. One can make them up using a standard IGBT driver optocoupler (e.g. from Avago / Broadcom, Toshiba, Vishay, ...) and a complimentary emitter follower pair (available e.g. from Zetex / Diodes). You usually run the driver from a +15V / -5V supply (referenced to the IGBT emitter), capable of supplying 1W ... 5W (depends on the switching frequency).Anyway, if your operating voltage is low enough (<100V) I'd consider using MOSFETs instead of the IGBTs. IGBT have higher conduction losses in low voltage applications than MOSFETs.

author: TasosVL
author_rank: Contributor
timestamp: March 20, 2021, 09:14:29 pm
content: I have done a similar thing and i have used the TLP 250 optocouplers to drive the IGBTs. This will isolate your driving signals from the high power and you will need shielded cables and the PCB where the microcontroller is should be housed inside a grounded metallic box. Also you will need to make an 18V isolated power supply to power the gate driver optocouplers. If you are paralelling the IGBTs use one optocoupler for each IGBT.You need pulsed DC or you need to have AC square wave output?Also your microcontroller can get affected by the EMI and the code can get "stuck" and your driving signals will be unexpected.

author: David Hess
author_rank: Super Contributor
timestamp: March 21, 2021, 06:56:41 pm
content: One of the reasons for isolated drive in high current applications is that the inductance in the source lead is in series with the gate drive so high di/dt will corrupt the gate drive signal. With isolated drive, it is easy to reference the gate drive to a point very close to the source limiting the inductance. Some high current IGBTs and thyristors bring out a separate source, cathode, or terminal connection for exactly this reason.I would try to go with transformer isolation of the gate signals but I am not familiar with the details of TIG welder requirements.Quote from: capt bullshot on October 02, 2018, 07:29:06 amI agree; it seems like power MOSFETs would be a better choice at this relatively low voltage but maybe there are voltage spikes or IGBTs are just more rugged for the same price?