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Old 11-05-2015, 07:00 PM   #2295 (permalink)
MPaulHolmes
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Quote:
Originally Posted by e*clipse View Post
Paul - wiring questions for the gate drivers

- what IGBT's did you design the version one ACControlAndDriver board for?

- the connector for DESAT - on the physical board, it's just a small hole. Does this line up with a pin, or do you run a wire?

- Can I just run separate gate resistors to each individual mosfet from the control transistors (for example Q1 and Q9) ?

- For each mosfet, should there be a corresponding diode to the emmitter ( for example D1)

- How is the output voltage controlled?? How is the +15 , -8.2 V set? Does the Attiny/ transformer do this?

- E*clipse
ACControlAndDriverBoard is designed to plug right into 600v 50amp igbt half bridges up to 1200v 600amp IGBT half bridges. The pin spacings are the same for all of them.
Powerex Product: CM600DY-12NF

So, no wiring is required for the gate and emitters. The collector is either the B+ tab, which requires a wire, or is the high side emitter tab (E1 = C2). So, a wire is intended to be used for C1 and C2 holes (for desat detection).

Yes, you can run multiple resistors. For this design, it's 2 gate resistors per IGBT. One for turn on and one for turn off. So, you would have 3 turn-on resistors going to the 3 separate mosfets and 3 turn-off resistors going to the 3 separate mosfets. There's around 8 amps (continuous!! lol) of drive current available for those npn and pnp package transistors, so I'm sure you could probably do 12amp peak.

The reason there is the NPN -PNP totem pole arrangement is because this was required to boost the 2.5amp from the SOIC driver, but still maintain the soft turn-off feature of the driver when desat is encountered. If we just dumped those, and put a regular old mosfet/igbt gate driver in place of the npn-pnp totem pole, a desat event would turn off the igbts in like 8nsec, which would possibly destroy them.

A separate back to back zener diode pair for each mosfet would work, but the 500amp controller just uses one TVS diode right at the gate driver (before the gate resistors). However, Otmar says the protection diodes should be right at the legs of the igbts or mosfets (if we are talking to-247).

The input voltage is 24v. The attiny pushes and pulls the gate drivers, which cause the output to be close to 24v too, after it gets rectified. Then, you do this:

+24v ------------- 3k resistor ----------< 8.2v zener ---------- 24v ground

Then, we call +24v "+15v", and we call the spot between the 3k resistor and the 8.2v zener cathode "emitter", and we call the 24v ground "-8.2v". The output voltage is limited to no more than a total of +24v by a 24v zener from +15v down to -8.2v (also known as +24v down to 24v ground). There is no regulation on the output voltage other than keeping it <= 24v. The voltage drops as the current increases, but in practice, the current just never goes all that high, so the voltage doesn't sag much on the output. Generally, the real voltages for switching are around -8.2v up to 15.8v or something like that. Sometimes 15.3v, etc...
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Last edited by MPaulHolmes; 11-07-2015 at 10:58 AM..
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