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Very High Voltage Piezoelectric Power Supply - Digitaly Variable - Lightweight SMT

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Uriah

Wed Sept 12 2007, 07:54AM

Registered Member #898 Joined: Sun Jul 15 2007, 07:50AM
Location:
Posts: 20

Waiting on the Surface mount components, and have a couple questions regarding.

HOW CAN I SIMPLY FABRICATE A SMALL WORK AREA THAT IS STATIC SAFE???

Also, what is the formula to define the capacitance depending on voltage and current input? In this case the discharge capacitor (3.46kV at

This is tricky, because of the adjustable discharge, this capacitor must be charged fully when selected frequency dictates the discharge through the IXEL40N400. I am assuming keeping the current constant no matter the voltage in order to accomplish this. Am I correct is this assumption?

In the DDS circuit should I change anything because I am using kHz ranges not MHz??? The one I am looking at is from 0-25Mhz output with 0.1Hz steps. This will fit my needs perfectly. Because I can change the frequency suddenly I will use another DDS to control the IGBT Driver circuit. I am thinking each of the SMD circuits I'll need to make will be 3in x 1in stacked. This way all five boards can be potted with super corona dope and enclosed in a ceramic package. The ceramic enclosure is lightweight and strong, with a conductive GND surface to make sure there is no static build up on the ceramic. The five SMD boards are as follow. (1)Piezo DDS/adjustable amp, (2)IGBT DDS/IGBT driver,
(3)MOSFETs & voltage regulator circuits, (4)MICROPROCESSOR to compute all the I/Os, and (5)Data Log (BLACKBOX) EEPROM with over 5MB of space for hours or recording.

I am using a ceramic PCB board from IXYS who makes the IXEL40N400 IGBT and driver IC. The product is called DAB or Direct Aluminum Bonded. It is a 1mm ceramic substrate able to withstand 10kV with .3mm of a range of special conductors. There is DCB and DAB types, DCB is copper bonded and DAB is for aerospace or lightweight applications. The ceramic spreads heat rapidly for SMD power components. The case may be where there is no need for thermo electric cooling. I think these boards are amazing. Here is the PDF ATTACHED!!!

Super Corona Dope will be used for everything until the pulse transformer. 4kV/mm breakdown!

Best regards,
Uriah

]1189583682_898_FT28407_direct-copper- bonded_dcb_alumina_substrates.pdf[/file]

Steve Conner

Wed Sept 12 2007, 08:44AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Just buy an anti-static mat and anti-static wrist strap to make your "work area".

Since you are using lower frequencies, you can use a lower frequency reference oscillator than the examples in the DDS datasheet. This will give you finer step sizes, as well as making the DDS chip run cooler and saving power. You may need to redesign the anti-alias filter, though.

How much is it going to cost to fabricate this thing on direct aluminium bonded PCB?

thedatastream

Wed Sept 12 2007, 11:27AM

Registered Member #505 Joined: Sun Nov 19 2006, 06:42PM
Location: Yorkshire!
Posts: 329

Bergquist T-Clad

is abot 7 times more expensive than 1.6mm double sided 1oz FR4 IIRC

It does the job though...

Uriah

Fri Sept 14 2007, 05:48PM

Registered Member #898 Joined: Sun Jul 15 2007, 07:50AM
Location:
Posts: 20

So how do I go about redesigning the anti-alias filter?

-Uriah

Steve Conner

Fri Sept 14 2007, 06:36PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Multiply all inductances and capacitances in the datasheet filter design by the ratio you want to change the frequency. So if the filter was 40MHz, and you want to change it to 10MHz, just make all the inductors and all the capacitors 4 times bigger. That is fairly basic electronics: if you didn't know it, are you sure you're up to a complex mixed-signal project like this?

Uriah

Fri Sept 14 2007, 07:21PM

Registered Member #898 Joined: Sun Jul 15 2007, 07:50AM
Location:
Posts: 20

Well honestly, I hope so. I'm headed to college in Feb 08 for electrical engineering. Some things like this just do not make sense yet.

Thank you.

-Uriah

Marko

Sat Sept 15 2007, 01:38PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

All I now want to say is truth, and that is, I don't think you have enough experience/tools/technology to build such a circuit.
I actually don't know *anyone* in the world who does with the current status of things.

If you wanted to reduce weight, you use thinner copper and plastic foil instead of fiberglass board.

Apart from that, have you calculated the required size of battery in order for such a thruster to be able to do anything at all? I believe weight of the circuit will be completely insignificant in comparison to it.

Before you waste huge amounts of money into something that has a poor chance to work at all, you need to do something called prototyping.

You relaxedly build a HV supply on protoboard and test it on model or scale model of your plane.

Then you measure thrust. Power input. Calculate how many batteries you need for same power

Even at that point you may realize that situation is hopeless and that thrust/weight ratio of the batteries alone is way too low for any use, and plane would do better simply as a glider.

If you from other side manage to get light enough batteries and drive working efficintly enough, and feel some chance for it, you go into the wind tunnel experiments.

You are still using your prototyped HV supply!

After you are done and completely confident and your plane is practically flying, the very last step is this what you've opened the thread about - building and insulating a small, compact and lightweight HV supply.

Yup, I'm saying that it's the very last thing you should do, when your plane is flying.

And at that point you'll have so much experience that you'll not even come to asking such questions or wasting money.

Marko

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