Yes, for several projects, I use IGBTs to PWM drive DC motors (24V, 16A) from an SX. I'm using IRG4PC40KD IGBTs from International Rectifier with a max. current of 25A. As this type requires a Vge of 15V to "turn on", I'm using a photo coupler to shift the 0...5V output from the SX to 0...15V on the gate side.
Please find attached the schematic of how I use a photo coupler (OK1) for shifting the IGBT gate drive level. Using the photo coupler also allows to completely isolate the SX side from the power parts (including ground). Right now, I do not make use of the Sense line to detect over-current. This line could be fed into a comparator, powered from the +24_Regulated supply, driving another photo coupler to still keep the SX and power grounds separated.
The schematic also shows two parallel IGBTs for increased output current. Each gate should be driven through a separate resistor (R11, R12), and the common resistor R13 is used to quickly discharge the gates when the photo coupler turns off. R7 and D8 provide the required gate voltage for the IGBTs.
As the IGBTs are used as low-end drivers in this circuit with the motor connected to +24V_Unregulated (MOT_A), and to the IGBT's collectors (MOT_B), their internal flyback diodes do not potect the IGBTs against the motor's reverse voltage when the IGBTs turn off. Therefore a fast switching power diode pair (D7), with both diodes wired in parallel is used to kill such spikes.
I fully agree with the comments you made. In my application, the PWM frequency is around 200 Hz only, so this simple optocoupler setp works fine enough. The maximum current in my application could be handled by just one of these types of IGBTs, so the second one is an additional safety measure.
Ahmet,
ok, I understand, you want to use one of these 7-packs (actually a 6-pack plus one IGBT for the brake function). I've been looking at similar parts as I have a customer request for a frequency converter with variable output frequency. Unfortunately, I did not write any SX code for this project so far, that might be helpful for you. I'm not even sure if I finally will use an SX for this project. A Propeller might be the better choice when it comes to synthesizing the PWM signals for 3-phase sine output.
Ok, for us dummies in the crowd, the expansion of acronyms is handy
So that I don't look like a complete fool next time, IGBT stands for Insulated Gate Bipolar Transistor (I had to look it up). Here is a good article defining the difference between IGBT's and MOSFET's:
I want to use a TC1401N non inverting mosfet driver for my SX project. I am using a 900 volt mosfet and I am switching right now about 450 volts. I am testing the drive circuit with a function generator and before I assemble my prototype board I would like to ask if the opto would be better than the driver I am going to use. I need fast switching from 500 to over 100k at the very least I may need to go to mhz switching. I am driving a resistive load so I am not worried about the kickback.· What do you think Gunther.. is the opto better protection and can it handle the switching speeds I need???? Thanks
ok about the acronyms - I promise to improve on this part next time. Thanks for posting the two links - they provide helpul informations about IGBTs.
Concerning the sixpack - I had expected such a question because I'm living in the "Beer Country". Too bad, this has nothing to do with beer this time . It is an array of IGBTs in one enclosure with three pairs of IGBTs, where one acts as the high-end driver, and the other as the low-end driver. Think of an H-bridge designed to drive three-phase devices, like motors. The seventh IGBT is used to quickly shut down the output voltage when the motor shall stop.
datacps,
for such high switching frequencies, and opto would not be such a good idea. When designing PCBs for high-current applications where the power stage and the controlling parts have common ground, I keep the ground traces or planes of both parts separated, and make an electrical connection at one single point only to avoid that high currents flowing through the ground side of the cirquit mess up the controller side.
There has been a lot of talk about IGBT's and motor control on the OSMC (Open Source Motor Controllers) group. All sorts of motors ans controllers are discussed. It is a good reference for the electronic design and you could always use the SX processor to control the show. You can checkout the group at:
I've built several of the original OSMC controllers and used a set on my old Middleweight Battlebot. Since then there has been some other variants for controlling other motors.
AHMET AKSU
Posts: 62
Comments
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Greetings from Germany,
G
The schematic also shows two parallel IGBTs for increased output current. Each gate should be driven through a separate resistor (R11, R12), and the common resistor R13 is used to quickly discharge the gates when the photo coupler turns off. R7 and D8 provide the required gate voltage for the IGBTs.
As the IGBTs are used as low-end drivers in this circuit with the motor connected to +24V_Unregulated (MOT_A), and to the IGBT's collectors (MOT_B), their internal flyback diodes do not potect the IGBTs against the motor's reverse voltage when the IGBTs turn off. Therefore a fast switching power diode pair (D7), with both diodes wired in parallel is used to kill such spikes.
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Greetings from Germany,
G
I fully agree with the comments you made. In my application, the PWM frequency is around 200 Hz only, so this simple optocoupler setp works fine enough. The maximum current in my application could be handled by just one of these types of IGBTs, so the second one is an additional safety measure.
Ahmet,
ok, I understand, you want to use one of these 7-packs (actually a 6-pack plus one IGBT for the brake function). I've been looking at similar parts as I have a customer request for a frequency converter with variable output frequency. Unfortunately, I did not write any SX code for this project so far, that might be helpful for you. I'm not even sure if I finally will use an SX for this project. A Propeller might be the better choice when it comes to synthesizing the PWM signals for 3-phase sine output.
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Greetings from Germany,
G
So that I don't look like a complete fool next time, IGBT stands for Insulated Gate Bipolar Transistor (I had to look it up). Here is a good article defining the difference between IGBT's and MOSFET's:
http://www.irf.com/technical-info/whitepaper/choosewisely.pdf
And a tutorial on them:
http://www.microsemi.com/micnotes/APT0201.pdf
Gunther, is that "six pack" like beer and the seventh one is for when you slam on the brake when the cop stops you?
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John J. Couture
San Diego Miramar College
ok about the acronyms - I promise to improve on this part next time. Thanks for posting the two links - they provide helpul informations about IGBTs.
Concerning the sixpack - I had expected such a question because I'm living in the "Beer Country". Too bad, this has nothing to do with beer this time
datacps,
for such high switching frequencies, and opto would not be such a good idea. When designing PCBs for high-current applications where the power stage and the controlling parts have common ground, I keep the ground traces or planes of both parts separated, and make an electrical connection at one single point only to avoid that high currents flowing through the ground side of the cirquit mess up the controller side.
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Greetings from Germany,
G
http://groups.yahoo.com/group/osmc/
I've built several of the original OSMC controllers and used a set on my old Middleweight Battlebot. Since then there has been some other variants for controlling other motors.
Robert