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Registered Member #588
Joined: Sat Mar 17 2007, 11:06AM
Location: UK
Posts: 93
Hi, I am new to sstcs and high power electronics in general, however I have drawn up what I think is a halfbridge sstc schematic, I wanted to have some kind of feedback so I don't have to tune it but I have no idea how to do it. Anyway the schematic is here: Do you think it would work? The pic chip give an output like a flip-flop. The component values I have not given because I haven't calculated it yet. Thanks,
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Here are some observations; 1) The KBL04 bridge rectifier for 230Vac is too puny for my liking, I'd use the highest current cheap bridge rectifier I could get e.g. KBPC3504 400V 35A (GBP 1.60 from Maplin UK) 2) I'd add a line filter (rfi) to the 230Vac input 3) If the HVDC capacitor is large (>= 1000 uF) you will probably need a current inrush protection device 4) There is no need for diodes across the two half-bridge capacitors 5) I'd put FAST diodes across the half-bridge transistors 6) Your entire gate-drive circuit is complex and wrong Have a look how others do it. 7) The 7812 regulator isn't required, it will probably cause more trouble than it's worth, just use a suitable voltage transformer and capacitor.
It's VERY easy to blow up SSTC transistors, like you said, there's no feedback control of frequency. I suggest you copy a simple/proven SSTC design before designing your own - saves sorrow and cash!
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
why do you use such a complex gate driver one ucc3732 and one ucc37321 would be a lot simpler to use. I started with this sstc circuit it's really easy to understand and to buid. Now it should work
Registered Member #887
Joined: Sun Jul 08 2007, 10:24PM
Location:
Posts: 2
Don't want to hijack the thread or anything but I was thinking of trying out the same miniSSTC you've provided a link to, so hopefully this is still ontopic. I'm new to sstc stuff too, have only built a DC coil based on a MOT before.
Anyway, looks like the SSTC5 schematic shows some capacitors placed between chip +ve power rail and the common -ve rail, which I think are decoupling capacitors? The 0.1uF ones like C2 and C14. What kind of capacitors are good for decoupling - they're not polarised in the schematic so I was guessing polyester MKT ones or maybe ceramics?
Any assistance appreciated, I tried searching for decoupling and came up with lots of hits but not really any guidance for what to use. Cheers anyway.
Registered Member #588
Joined: Sat Mar 17 2007, 11:06AM
Location: UK
Posts: 93
I guess I was trying to run before I can walk... again... Tom540, your schematic is a little confusing as there are several 555 timers up top with only the power connected... I think I will go with steve's minitesla circuit.
Next time I will try to design my own again! and fail!
Registered Member #588
Joined: Sat Mar 17 2007, 11:06AM
Location: UK
Posts: 93
Ah right, ok.
I have a question about GDTs now, I have seen some designs where one of the secondarys is crossed over, I am guessing this is to invert it, but what about the ones that don't? Is the aim to push and pull current in ither direction of the GDT pimary to power each FET, right?
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SSTC help
