PMDC Motor Pwm Problems Using Igbt

I am trying to control a 1/3HP 12VDC motor using PWM, which is input into a dedicated IGBT driver(Vout -5 to +12), which then in turn should fire my IGBT. Without the IGBT connected everything seems to work fine, PWM signal is perfect and my IGBT gate drive signal is perfect.

My problem is that when the IGBT and motor are connected it only responds at 85% + PWM. Anything below 85% and the motor is totally off.

Has anyone experienced this before? Here are the links to he IGBT, driver IC, and my schematic.


IGBT-(Way overkill but I had one laying around)


PWM_IGBT.pdf (14 KB)

That IGBT has a total gate charge of 3uC - so with that 2A driver it will take 1.5us or more to switch - you don't say what frequency you are using? Arduino default should be OK.

And where's the schematic?

The frequency is 15kHz, generated by U4 in my schematic posted below. Must not have attached it before.

Can't see anything but ads and popups on that site, please don't link to pop-up sites ITS VERY ANNOYING.

Sorry about that, I was looking for somewhere to post a PDF.

i've got a fuji 1mbi300n that ive been using with a UCC27322 gate drive for a while, and its working great so far all the way up to 30 something kilohertz. first thing i would do is see if you can get an oscilloscope and view the waveform on the gate. second thing, where is your -5v and +12 coming from? do they have a common ground, because they need one, and that should connect to the emitter of the igbt.

Thanks for your reply,

The -5V and +12 have a common ground, which is connected to the emitter of the IGBT. Here are a few screen shots of the gate signal. The last one is of the IGBT actually connected the first two dont have the IGBT connected.

your gate waveform seems pretty similar to the one i saw. have you tested your 12 volt supply? try measuring the voltage under load.

My 12V supply was a deep cell lead acid battery with 100Ah capacity, I dont think that was the issue but il give a shot when I get a chance.

thats really strange. your readings look good and as far as i can see your circuit makes sense. surely there's a loose wire or a bad signal somewhere! ohh the joys of electronics.

Ahh I know! I have the arduino working fine, I figured thats where all my problems would be, not in a simple PWM circuit with no programming!

I have a big MOSFET at home that I am going to try. Hopefully that will work better!