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Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Bushman wrote ...
When I connect the secondaries of the GDT to the half-bridge circuit and turn on the modulator the UCC37321 cooks and dies within 1 or 2 seconds. The UCC37322 has only fried once. Trying to understand if the half-bridge circuit is somehow overloading the GDT and causing the gate driver to be driven too hard or could it be something else on the driver circuit? The other question is how to debug this without frying a driver IC on every test? Getting expensive!
After re-reading this, i can definately point to a problem on the secondary side of the gate transformer.
1. First, the 10//10 parallel primary winding - Did you ensure that the proper phasing was followed when paralleling the primary turns?
2. Is the secondary windings terminated properly?
3. Are the IGBTs in backwards?
4. Are the diodes properly installed and of the correct type on the gate circuit? I would try removing them to see if one of those diodes is shorted etc...
5. Is the 10uF capacitor which is used for series decoupling a yellow tantalum capacitor?
It definately points to a short circuit on the transformer secondary side. You just need to isolate where it is occuring.
Registered Member #6038
Joined: Mon Aug 06 2012, 11:31AM
Location: Salado, TX
Posts: 248
Thanks for the debug suggestions - very helpful. Totally agree it's not the circuit design. Clearly an error in construction or faulty component. Answers:
1) believe the phasing is correct on the GDT - output looks good on the scope too 2) Secondary windings terminated as per schematic 3) Need to check this to be certain - i am using the T0-247 package so could be a mistake. 4) Diodes are installed correctly and exact type as specified. Tested in place seem ok, but have not removed them and tested. 5) 10uF is a yellow tantalum
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
Bushman wrote ...
Thanks for the debug suggestions - very helpful. Totally agree it's not the circuit design. Clearly an error in construction or faulty component. Answers:
1) believe the phasing is correct on the GDT - output looks good on the scope too 2) Secondary windings terminated as per schematic 3) Need to check this to be certain - i am using the T0-247 package so could be a mistake. 4) Diodes are installed correctly and exact type as specified. Tested in place seem ok, but have not removed them and tested. 5) 10uF is a yellow tantalum
Will test those suggestions - thanks
Same here except I'm using the SOT-227B miniBLOC I'm going to rewind my GDT as well as re-install the the 5.1 2W gate resistors and 1N5819's.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Make sure you are driving at a low duty cycle too. Those chips have to deliver a lot of power to the IGBTs and if you have modulator set for a high duty cycle, the driver chips will overheat. Duty cycle should generally be less than 10%.
Registered Member #7267
Joined: Tue Oct 16 2012, 12:16AM
Location: Detroit, Michigan
Posts: 407
teravolt wrote ...
Bushman, Physics Junkie, do you have pictures of your setup
scroll down to the bottom...
EasternVoltageResearch wrote ...
Make sure you are driving at a low duty cycle too. Those chips have to deliver a lot of power to the IGBTs and if you have modulator set for a high duty cycle, the driver chips will overheat. Duty cycle should generally be less than 10%.
Im driving tests at 250us and 100hz PRF. During operation my duty cycle will be 2% or less
teravolt wrote ...
nice work I noticed that your coupling capacitor is a tantalum you should replace it with a bypoler chip cap
Pretty sure it is supposed to be tantalum, your referring to the yellow 10uf cap correct? As EVR pointed out, no components need to be changed. Anyways, why do you say not tantalum?
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Gate Driver Problem
