SSTC help
Munkey, Sun Jul 08 2007, 03:27PMHi,
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,
Re: SSTC help
Sulaiman, Sun Jul 08 2007, 04:08PM
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!
Sulaiman, Sun Jul 08 2007, 04:08PM
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!
Re: SSTC help
Dalus, Sun Jul 08 2007, 04:17PM
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
Dalus, Sun Jul 08 2007, 04:17PM
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
Re: SSTC help
Munkey, Sun Jul 08 2007, 04:24PM
Sulaiman, ill redesign my circuit then post it again.
Dalus, Your link doesn't work....
Munkey, Sun Jul 08 2007, 04:24PM
Sulaiman, ill redesign my circuit then post it again.
Dalus, Your link doesn't work....
Re: SSTC help
lardembargo, Mon Jul 09 2007, 12:08AM
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.
lardembargo, Mon Jul 09 2007, 12:08AM
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.
Re: SSTC help
Tom540, Mon Jul 09 2007, 01:59AM
Heres the circuit i always use
]1183946250_487_FT28058_sstc_logic.pdf[/file]
Decoupling caps are either poly or Tantalum 35v or 50v.
Tom540, Mon Jul 09 2007, 01:59AM
Heres the circuit i always use
]1183946250_487_FT28058_sstc_logic.pdf[/file]
Decoupling caps are either poly or Tantalum 35v or 50v.
Re: SSTC help
Munkey, Mon Jul 09 2007, 06:40AM
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!
Munkey, Mon Jul 09 2007, 06:40AM
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!
Re: SSTC help
Tom540, Mon Jul 09 2007, 07:05AM
Yeah those are just to show the power connections for the digital parts without having them near the actual part.
Tom540, Mon Jul 09 2007, 07:05AM
Yeah those are just to show the power connections for the digital parts without having them near the actual part.
Re: SSTC help
Munkey, Mon Jul 09 2007, 03:30PM
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?
Munkey, Mon Jul 09 2007, 03:30PM
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?
Re: SSTC help
Dalus, Mon Jul 09 2007, 04:48PM
Can you give me a design where the secondary isn't crossed over, I can't remeber any of those designs.
Dalus, Mon Jul 09 2007, 04:48PM
Can you give me a design where the secondary isn't crossed over, I can't remeber any of those designs.
Re: SSTC help
Munkey, Mon Jul 09 2007, 05:29PM
Here:
Also Ive got another question here about steve's mini SSTC- 74CH14 inverter chips, since I cant buy them would any NOT gate work? And would it be wise to put some 15V zeners on the gates of the fets?
Munkey, Mon Jul 09 2007, 05:29PM
Here:
Also Ive got another question here about steve's mini SSTC- 74CH14 inverter chips, since I cant buy them would any NOT gate work? And would it be wise to put some 15V zeners on the gates of the fets?
Re: SSTC help
CT2, Mon Jul 09 2007, 08:27PM
In the schematic you posted (richie's) I think he didn't show them switched just for simplicity sake. One of the windings NEEDS to be oppositely wound, or crossed, or whatever. And if its an H-bridge it gets a little more complicated still. I'm not sure about using any NOT gate, but the zeners are a good idea. My first coil had no zeners on the gates and when I ran it CW the fets exploded presumably because I overvolted the gates and shorted them out.
CT2, Mon Jul 09 2007, 08:27PM
In the schematic you posted (richie's) I think he didn't show them switched just for simplicity sake. One of the windings NEEDS to be oppositely wound, or crossed, or whatever. And if its an H-bridge it gets a little more complicated still. I'm not sure about using any NOT gate, but the zeners are a good idea. My first coil had no zeners on the gates and when I ran it CW the fets exploded presumably because I overvolted the gates and shorted them out.
Re: SSTC help
Munkey, Mon Jul 09 2007, 09:00PM
Oh right, so what about the push/pull through the GDT? or does it just pulse current through the primary in any direction?... I am finding it impossible to find the UCC driver chips, so I need to make another circuit to go inplace of that.
Munkey, Mon Jul 09 2007, 09:00PM
Oh right, so what about the push/pull through the GDT? or does it just pulse current through the primary in any direction?... I am finding it impossible to find the UCC driver chips, so I need to make another circuit to go inplace of that.
Re: SSTC help
CT2, Mon Jul 09 2007, 09:21PM
If you cannot get UCC's (try sampling from TI's website, that's where I get all of mine from) then have a look at other peoples gate drive circuits. The UCC's are used together as an H-bridge, one is inverting and the other one isn't. I can't recomend any other gate drive circuits because all I have used so far is UCC's.
CT2, Mon Jul 09 2007, 09:21PM
If you cannot get UCC's (try sampling from TI's website, that's where I get all of mine from) then have a look at other peoples gate drive circuits. The UCC's are used together as an H-bridge, one is inverting and the other one isn't. I can't recomend any other gate drive circuits because all I have used so far is UCC's.
Re: SSTC help
Josh Johnson, Mon Jul 09 2007, 09:27PM
Digikey has plenty of the UCC37322 and UCC37323
http://dkc3.digikey.com/PDF/T072/P0811.pdf
Josh Johnson, Mon Jul 09 2007, 09:27PM
Digikey has plenty of the UCC37322 and UCC37323
http://dkc3.digikey.com/PDF/T072/P0811.pdf
Re: SSTC help
Munkey, Tue Jul 10 2007, 06:33AM
If I can't get the samples (I hope they ship to the UK) I will make my own GD.
Thanks for the help so far, after ive got the chips and fets ill start building it.
Munkey, Tue Jul 10 2007, 06:33AM
If I can't get the samples (I hope they ship to the UK) I will make my own GD.
Thanks for the help so far, after ive got the chips and fets ill start building it.
Re: SSTC help
thedatastream, Tue Jul 10 2007, 07:03AM
*toot*
All you (n)ever wanted to know about GDTs
TI ship samples to the UK, in nice recycleable packaging too hurrah
thedatastream, Tue Jul 10 2007, 07:03AM
Bacon wrote ...
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?
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?
*toot*
All you (n)ever wanted to know about GDTs
TI ship samples to the UK, in nice recycleable packaging too hurrah
Re: SSTC help
Munkey, Tue Jul 10 2007, 12:35PM
Ill have a go at ordering the UCCs sometime this week.
Great GDT info you have got! So making a GDT is not so simple, I though it is just winding 15-25 turns of any wire around any ferrite core...
Munkey, Tue Jul 10 2007, 12:35PM
Ill have a go at ordering the UCCs sometime this week.
Great GDT info you have got! So making a GDT is not so simple, I though it is just winding 15-25 turns of any wire around any ferrite core...
Print this page