Hello people.
I have a project building a Half bridge motor controller. I've done some testing and its looking good, but now I want to scale up the project for much more voltage/current. I would like to get a bit of assistance on my calculations as I'm fairly new to mosfets (been using bi-polar for a long time).
Doing some initial calculations on the size of Mosfet driver output I need I came up with a number much smaller then I initially expected.
I have a Astable 555 set at ~16khz which I will use to drive a mosfet driver.
I was thinking of using 12x IRFB3077PbF mosfets. 6 for the high side and 6 for the low side (non-reversing controller) 75V 210A.
Qg = 160typ, 220max nC.
Qrss = 350 pF
Derating them to 60v and 150Amps I calculated the turn on current at around 6.5Amps in 25 nanoseconds.
At 16kHZ and 60v 150A I come up with a power dissipation below 40 watts. With some of the math saying only 3 or 5 watts. I was just punching them in the calculator and not sure if I was calculating right so can only give estimates on the results I got.
So since my frequency is not terribly high, and I probably do not need a perfect 25nS switching slope it was looking as though a 6amp driver would be plenty for 12 of these mosfet. The switching should still be under 150nS and power dissipation would not exceed 40watts per fet
First does this sound right? or was I doing all this math incorrectly?
I was considering using the mosfet driver to drive a pre-output stage using a couple HRF3205s that I have (100Amp 55V).
So with all that can someone recommend me a driver to use or confirm if my rough estimations on the math is correct? Do I require a second stage or not (trying to keep a simple design).
OR if I'm completely off base, let me know, I'm a man I can take constructive criticism.
Another side note. Can mosfets be used in series to raise the total voltage handling? say 2x 75v mosfets in series to handle 150v peak? I did this with other transistors but under if it works for fets.
-TriX-
I have a project building a Half bridge motor controller. I've done some testing and its looking good, but now I want to scale up the project for much more voltage/current. I would like to get a bit of assistance on my calculations as I'm fairly new to mosfets (been using bi-polar for a long time).
Doing some initial calculations on the size of Mosfet driver output I need I came up with a number much smaller then I initially expected.
I have a Astable 555 set at ~16khz which I will use to drive a mosfet driver.
I was thinking of using 12x IRFB3077PbF mosfets. 6 for the high side and 6 for the low side (non-reversing controller) 75V 210A.
Qg = 160typ, 220max nC.
Qrss = 350 pF
Derating them to 60v and 150Amps I calculated the turn on current at around 6.5Amps in 25 nanoseconds.
At 16kHZ and 60v 150A I come up with a power dissipation below 40 watts. With some of the math saying only 3 or 5 watts. I was just punching them in the calculator and not sure if I was calculating right so can only give estimates on the results I got.
So since my frequency is not terribly high, and I probably do not need a perfect 25nS switching slope it was looking as though a 6amp driver would be plenty for 12 of these mosfet. The switching should still be under 150nS and power dissipation would not exceed 40watts per fet
First does this sound right? or was I doing all this math incorrectly?
I was considering using the mosfet driver to drive a pre-output stage using a couple HRF3205s that I have (100Amp 55V).
So with all that can someone recommend me a driver to use or confirm if my rough estimations on the math is correct? Do I require a second stage or not (trying to keep a simple design).
OR if I'm completely off base, let me know, I'm a man I can take constructive criticism.
Another side note. Can mosfets be used in series to raise the total voltage handling? say 2x 75v mosfets in series to handle 150v peak? I did this with other transistors but under if it works for fets.
-TriX-