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Yes, you can have the phasing of the GDT primary wrong which will cause issues. Either swap the UCC chips in their sockets or reverse the phasing of the GDT primary.
If you think the primary may be out of phase it is important to make sure you have the high and low side phases of the GDT secondary correct, you don't want to cross conduct and blow it all up!
Be aware that GDTs can be funky when it comes to certain duty cycles, mine never seem to like anything too far from 50%.
Oh and while you're tinkering, be sure to have those decoupling caps on the ICs, they are NOT optional.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
well i swapped the output of the ucc chips to the GDT and it didnt do anything for the bridge, it still wont switch any power O.o and i cant figure out why. The ticking sound from the driver board is causing a florescent tube to light up when placed inside the coil but still the half bridge wont switch, Im not sure what the problem is, I checked the phasing of the GDT and most of the traces(DMM) , there also dont appear to be any splits on the copper. both FETs were brand new and i believe i tested them, if they were bad wouldnt they just short out and pop or heat a lot ??
If one (or both) gate is dead but the DS junction is fine (happens when you exceed Vgs) then that transistor will simply never turn on, and that can cause the symptoms you're experiencing.
Well test them first. Remove them and measure the resistance between all pin combinations, nothing should be shorted <1k ohms. Just remember that a charging capacitance looks like a short for a short while so don't "tap and move on" with the dmm leads.
Then check your DC blocking caps in the bridge. Then check the DC blocking cap on the GDT primary. Check the gate resistors, etc.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
ZakWolf wrote ...
I think I blew all or my decoupling caps, there all tantalum caps and they dont handle ripple very well or at all.
UPDATE: Turns out there was a short on the 3rd and 4th pin on the 555 time, I replaced the .1uf caps with ceramics but i dont have any 1uf caps... I tried to power up the board with the gdt load and the 74hc14 got super hot.
Can the driver not run without the decoupling caps for the UCC chips????
Im a noob to SSTC design and circuity, its painful
You absolutely need decoupling capacitors on the rails of the UCC. I generally use a 0.1uF ceramic and then either a 10uF tantalum (low ESR) or electrolytic (low ESR, high ripple current) - depending on the load and frequency i'm driving.
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SSTC 5 troubleshooting
