Controlling IGBTs via a microcontroller

[stube40]

Anyone have any suggestions how to drive an IGBT via a microcontroller? I'm trying to drive a STGE200NB60S with an Atmel AVR CPU.

The AVR can run at both 3.3V and 5V and the gate threshold of the IGBT is 3V, so in theory I could just connect up an go. But, i cant help thinking that it can't be that simple, can it?

Also, if anyone has any suggestions where I can source low numbers (<= 5) of the 64-lead TQFP version of the AVR (id AT90CAN128-16AU or AT90CAN128-16AI) then I'd love to hear them - Digikey dont do the TQFP package.

[Alex Tsekenis]

No, it is not that simple. In fact, you could do a research degree on this. But some deviation from perfect is acceptable.

I see the IGBT you are using is a power device. Generally, driving an IGBT is like driving a MOSFET. In you case is a big MOSFET with 1.56nF of gate capacitance.

Do a search on driving high power IGBT or Mosfet with MCU.

You say threshold is 3V. Have a look at figure 1 of the datasheet on ST. You will need to charge the gate up to 10-15V to fully turn on the device. At the threshold voltage the igbt will merely be conducting.

Another consideration is how quickly you can deliver gate charge to the gate capacitance. You thus need a high current driver for this device that has a high gate capacitance. The current required will be porportional to the frequency you will be switching the igbt at.

The MCU is not capable of such outputs. You can use external transistor amplifiers controlled by the MCU to drive the gates, but I think even better is to use a so called 'low-side mosfet driver' Have a look on IRF, National, Micrel, Linear, Analog, Microchip, you will find a lot of devices. I came across a Microchip app. note a while ago on selecting the right driver for your application.

What is your application by the way?

Regarding the MCU, the only thing on Farnell was 1455065 which is not yet in stock and very expensive. Nothing on RS. Atmel does samples, possibly you could try that. Also search under Contact Us>sALES Support and select your region. There are many other distributors but this looks like a low demand part. Consider finding an alternative that is in stock. Elektor Electronics (the magazine) very very recently published a massive list of retailers that you could find useful.

[stube40]

What is your application by the way?

Thanks for your advice - I need 4 of these IGBTs to switch a 150V / 40A DC power source in a H-bridge formation - hence only 2 will ever be on.

Effectively, I will switch 2 of them on for approx 20ms then off for 80ms, then switch the other 2 (ie reverse the output polarity) for 20ms then off again for 80ms - and so on in an endless loop. In other words, switching at 10hz with a 20% duty cycle.

When I decide to switch one on I would ideally like it to go on within 1ms.

By the sounds of it, the IGBT I selected may not be the best choice although I am certainly talking about low switching speeds