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PLL DRIVER CIRCUIT QUESTIONS *EDIT*

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Dr. Dark Current

Sat Nov 23 2013, 06:34PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

You set the VCO range so that the coil's resonant frequency falls within it. More on setting the range, see the CMOs 4046 data sheet.

The decoupling caps are absolutely necessary. If you don't use them, then you have no idea how switching electronics work.

twist2b

Sat Nov 23 2013, 06:41PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
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Posts: 117

Stormy - before I do the math for that design... I don't know why my head got stuck with mosfets, I see you are willing to update your design and I kind of love it because it's so simplistic... you should but this on instructables when you are done! Anyways, why not:

MOSFETS have P = I^2R losses so it will get REALLY hot and if your circuit isn't tuned perfectly they will melt till they don't work (I have done this.. haha)
meanwhile IGBT's have a power loss of P = IV and I have been told (not tried this myself) that IGBT's weaker than the one I just put here have produced 27" sparks... yeah they can handle a lot of stress.
What do you think?

Regardless this design is going to be great and I am really excited for you.

Edit - also, just something always safe to do when using IC's is putting .1uF near the ic from the +12 to GND... it filters out changes and makes sure you get 12V ALWAYS to the chip... it's not 100% necessary but those caps run you like a dollar for 50 so it's work the investment for the chip to last longer.
So use 3 and put them near each chip.

StormInABottle

Sat Nov 23 2013, 06:45PM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect it has on the rest of the circuit.
The Wikipedia page does not really provide information on what values / voltage they should be. Neither does it provide information on where to place it.

twist2b

Sat Nov 23 2013, 06:55PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
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Read my edit.
KISS method here haha.... just remember that capacitors RESIST the change in voltage and inductors RESIST the change in current... so decoupling is just the amount necessary.

TwirlyWhirly555

Sat Nov 23 2013, 06:57PM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

For the driver I made i used 0.1 uF ceramic and 100uF electrolytic decoupling capacitors , voltage is above supply voltage . place them as close as possible to the Gate drive ICs and 4046 IC's

Dr. Dark Current

Sat Nov 23 2013, 07:04PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Just now I meant the power caps, which you put right next to each bridge leg. Those are usually low-inductance polypropylene film caps, such as the WIMA MKP10 series.
Of course, the low voltage electronics need decouplig too.

twist2b

Sat Nov 23 2013, 07:12PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
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OH YEAH! Good call man, I would suggest 10uF polypropylene. (they are expensive :( ) but you suggest you would like to go all the way up to 240V on your variac sooooo yeah GET THEM, NECESSITY :P

StormInABottle

Sat Nov 23 2013, 07:35PM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

The only WIMA MKP10 caps i can access are 0.47 UF 400 volt ones.
What about ECQ-E6684KF ? I 've had really good experience with those.

I also found those smexy igbts.

Those would be cheaper than mosfets. Would allow more watts to be squeezed through my bridge. Would those do good in switching instead of mosfets?
Also
I would like to thank you guys again for the help.
I will get to editing the circuit later. I am tired now X_X

Dr. Dark Current

Sat Nov 23 2013, 08:20PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

For your low frequency, I would definitely go for IGBTs. If you can't find MKP10 caps, look for MKP4, the "MKP4 DC LINK" series are pretty good decoupling caps.
And you absolutely need IGBTs with diodes. Try the FGH60N60SMD, it is from the top of the line of IGBTs available today.

twist2b

Sat Nov 23 2013, 09:11PM

Registered Member #2086 Joined: Tue Apr 21 2009, 02:33AM
Location:
Posts: 117

If you are worried about price I see no issues with the IGBT's you linked to.

scroll down to "
Characteristics of plastic film materials for film capacitors" And you will see that at higher frequencies PP are best suited for the job... All film types technically "work" but we want results eh? :P

EDIT - BETTER YET:

,d.cWc

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