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Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
How would i go about figuring out the max frequency an IGBT can handle based off of rise and fall times? Is it okay to go faster than it? Because I'm trying to build a Royer based induction heater, with protection, and all that fancy stuff, but I can't choose which igbt to go with. The circuit oscillates around 70-80 khz, measured with my oscilloscope. I don't want them to blow up, heh.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Inducktion wrote ...
How would i go about figuring out the max frequency an IGBT can handle based off of rise and fall times? Is it okay to go faster than it? Because I'm trying to build a Royer based induction heater, with protection, and all that fancy stuff, but I can't choose which igbt to go with. The circuit oscillates around 70-80 khz, measured with my oscilloscope. I don't want them to blow up, heh.
It's a matter of power loss that you can tolerate in the IGBT, based on how good your heatsinking is and the efficiency you want (if you care about efficiency that is).
Assuming the oscillator turns the IGBT's fully on then fully off then you'll dissipate some power in the on-state equal to Vce,sat*Ic, and you'll dissipate none in the off-state, and you'll dissipate some in the rise and fall region equal to the integral of the voltage*current on the IGBT over the rise/fall time. You can make simplifying assumptions like a current that linearly ramps up to the on-state value and voltage that similarly ramps down linearly, and you would have a guess for how much power was dissipated. Or to take it to the extreme, you take the supply voltage * on-state current * rise time to get a maximum value for power dissipated during the rise time.
Or you can just just take a rough guess and say that to minimize power dissipation in the IGBT you want the total rise and fall time to be no more than 10% of the period, where the period in seconds is 1/frequency, 14microseconds at 70kHz. Then you would say you want IGBT's with a rise/fall time under 1.4microseconds. Or to be safer you say 5% and buy IGBT's with a rise/fall better than 700ns.
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How to figure the max frequency of an IGBT?
