 Halfbridge anti parallel diodes?
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Lekky1
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Sun Mar 15 2009, 10:18AM
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Registered Member #1592
Joined: Thu Jul 17 2008, 06:58AM
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Posts: 11
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Hello all.
I have nearly completed my second version of a single stage halfbridge coil gun & need some advice on choice of IGBT's..
I have two to choose from: FHGTG27N120BN or FGL60N100BNTD.
The FGL60N100BNTD is a 60A/1000V device with an integral anti parallel diode & the FHGTG27N120BN is a 72A/1200V device, but has no anti parallel diode incorporated.
I am using a cap bank charged to 300V.
Are antiparallel diodes a necessity with halfbridge switching topology?
I have searched the wiki & googled the topic, but have found no clear answer.
Any help will be greatly appreciated! 
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hotcrazyfruit
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banned on 5/26/2009
Registered Member #1877
Joined: Mon Dec 22 2008, 02:03AM
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Posts: 147
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well... the arent a nessesity, but they sure wouldent hurt anything. i would recommend getting the 72 amp one, and just putting an anti parralel diode with it. so you can have a higher current rating. if i understand igbt's right...
edit: YES an anti parralel diode IS nessary. i didnt read that you were building a coil gun. and an anti parralel diode will keep the bank from charging to a negative polarity. which will seriously screw them up. this is because the ring bank effect from the coil, it isnt nessesary when you discharging it into stuff, like ic's and micro controllers. xD LED's are esspecially fun to blow up with 5 kj
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