 Zeners and Gate Drive Transformers..
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si2030
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Tue Sept 23 2008, 03:08PM
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Registered Member #1571
Joined: Wed Jul 02 2008, 03:26AM
Location: Bendigo Victoria Australia
Posts: 44
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Hi all,
This question relates to the gate drive voltage of the IGBTs I am using. I have spent some time examining Steve Ward's material (excellent site) and I need a little hand with the configuration of the gate drive transformer. I want to use the same configuration Steve uses, that is, using CAT5 cable and having the transformer configured 1:2.
The IGBT's in question are irgp50b60pd1 which have a maximum gate drive voltage of 20Volts. If I use the configuration as outlined in Steve Wards schematics and run 12 volts into the trasformer with a 1:2 ratio then I whould get 24 volts out. Wont this just tax the zeners (I intend using 20volt zeners) at the gate on every cycle? or do I run the gate at a higher voltage like 24V.. should I alternatively run the input for the transformer at say ~10 volts (LM317) causing the output for the GDT to be 19-20volts? whats the best approach here to use given its a full bridge?
Simon
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Sulaiman
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Tue Sept 23 2008, 06:57PM
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Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
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In general;
- igbt gate voltage is nominal and quite a bit of overvoltage can be tolerated
- increasing the gate drive voltage for an igbt isn't really a good idea as the ON resistance isn't very much lower with an overdriven gate, and the most difficult part of igbt operation - turning off fast - will be worse.
- do not try to drive the gates with a voltage higher than your zener voltage, something will smoke.
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