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Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
The usual reason for bad performance in SSTCs is too low coupling. Most SSTC projects I've seen use way too low coupling.
The choice of Lp and k are very important. In fact I think that one of the main challenges in solid state Tesla coil work is in juggling these two parameters to get maximum power transfer into the resonator.
If Lp is too small, the magnetising current becomes unacceptably high. Although this does not contribute to the supply current of the driver, it does contribute to heating in the switches. It also increases the current ripple seen by the supply reservoir capacitors.
If Lp is too great, then there is little step-up due to transformer action. As a result, the Tesla resonator is not well matched to the driver, and little power is drawn from the driver.
If k is too small, then the load current is dominated by the magnetising current, and little of the current supplied by the driver actually contributes to resonance in the secondary winding.
If k is too great, then there is a risk of electrical flashover. This is due to the close proximity demanded to achieve this degree of pri-sec coupling, and the large sparks that result !
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
radhoo wrote ...
Inducktion wrote ...
Radhoo, could you possibly PM me the schematic for the Armstrong oscillator you used? I would like to adapt it to other purposes.....*rubs hands together*
Sure - You can find the schematics on the page I've posted, but here is the link again: . The circuit diagram is the first picture at the top.
Hey Radhoo. I remade your schematic a little, and wondered if maybe protecting the fet was a good idea? I wonder/hope that this method would work, because it's the same method used in driving the mosfets in a ZVS driver. It would make it so you could input a wider range of voltages safely allowing for a more powerful tesla coil, if you get a better mosfet too.
Not trying to steal the spotlight, but it just ran across my mind.
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
I agree with Anders, take down the voltage a notch and play with your coupling. Maybe add more primary turns if your system is drawing too much. You say your primary is on the same form. Is it below your secondary? That could be the problem. Are your MOSFETs heating evenly?
If anyone builds Induktion's circuit, please replace the MOSFET with a center-tapped fuse and/or consider protective eyewear. It will retain all the functionality without the expense of a MOSFET and possibly an eye.
The zener diode is a good idea, though, but nothing else there. I would use back-to-back zeners to have the negative bias on the gate and waste less power.
And adding a 15 volt supply kind of destroys the simplicity of the circuit... and makes the 3.125V-6.25V biasing supply in the circuit seem kind of redundant.
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
ScotchTapeLord wrote ...
I agree with Anders, take down the voltage a notch and play with your coupling. Maybe add more primary turns if your system is drawing too much. You say your primary is on the same form. Is it below your secondary? That could be the problem. Are your MOSFETs heating evenly?
If anyone builds Induktion's circuit, please replace the MOSFET with a center-tapped fuse and/or consider protective eyewear. It will retain all the functionality without the expense of a MOSFET and possibly an eye.
The zener diode is a good idea, though, but nothing else there. I would use back-to-back zeners to have the negative bias on the gate and waste less power.
And adding a 15 volt supply kind of destroys the simplicity of the circuit... and makes the 3.125V-6.25V biasing supply in the circuit seem kind of redundant.
That's kind of mean, it was just an idea. Why would it blow up?
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
Inducktion wrote ...
ScotchTapeLord wrote ...
I agree with Anders, take down the voltage a notch and play with your coupling. Maybe add more primary turns if your system is drawing too much. You say your primary is on the same form. Is it below your secondary? That could be the problem. Are your MOSFETs heating evenly?
If anyone builds Induktion's circuit, please replace the MOSFET with a center-tapped fuse and/or consider protective eyewear. It will retain all the functionality without the expense of a MOSFET and possibly an eye.
The zener diode is a good idea, though, but nothing else there. I would use back-to-back zeners to have the negative bias on the gate and waste less power.
And adding a 15 volt supply kind of destroys the simplicity of the circuit... and makes the 3.125V-6.25V biasing supply in the circuit seem kind of redundant.
That's kind of mean, it was just an idea. Why would it blow up?
Didn't mean to be mean, t'was mostly in jest. It's just that you've given no way for the FET to turn off...
EDIT: I don't want this to get off-topic, so if you'd like to discuss radhoo's schematic further, Induktion, I'd be happy to discuss this in another thread or via PM.
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How to tune SSTC primary?
