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Looking at the Fairchild web site, there seems to be many different kinds of IGBTs. At the least, there's PDP, NPT, PT, Field Stop, and Trench IGBTs. The PDP IGBTs seem to be lower voltage but also lower cost.

Which kind would be best for a 120V inverter with a maximum DC bus voltage of 210V and a PWM frequency of 15kHz or so?

That's quite a low bus voltage, and quite a fast switching frequency. Unless you have a good reason to select an IGBT, I would simply use a MOSFET.

Generally speaking (and this is a fairly gross generalisation with all the new devices appearing) IGBTs are slow switching devices that are rated for high voltages and currents. They tend to have high switching losses and low conduction losses, relative to MOSFETS. The low conduction losses are due to them having a saturation voltage, rather than a drain-source resiatance so your loss is VI, rather than I^2R.

One of the reasons why I'm looking at IGBTs is because IGBTs generally have faster inverse (freewheeling) diodes than MOSFETs. With MOSFETs, it would be necessary to use external inverse diodes and design the circuit to prevent the slow internal diodes from operating. I'm also looking at making the design easily modifiable for 240V by simply using higher voltage components and changing the value of some voltage sense resistors.

IGBTs shouldn't have any problems at 15kHz or so. I can further reduce the PWM frequency if that would make the circuit more efficient.

IGBT's don't have any intrinsic diode.  Most IGBT packages have a co-packaged fast recovery diode (FRED) (you should check to be sure that there is a packaged diode if you're depending on one being there).  You can get co-pack MOSFETS as well, or use an external diode.

If you were switching some large amount of inductance dont you need still need a free wheeling diode across the load in addition to one for the switch?


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