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Simple Audio modulated SSTC

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Marko

Mon May 15 2006, 02:08PM

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

Hi williamn,

(sorry for offtopic) please answer PM when you arraive, if you can

I just blew topload on my small class E coil (visible in 'spectacular failures').

I didn't manage to audiomodulate it yet but I got it working reliably for several hours on a school showoff, it turned off just few times because visitors liked to harras it by drawing arcs (I had no NE555 kicker')

I used 7667 driver with antenna and single IRFP150, at about 1Mhz. I admit I only got some crappy 1,5cm sparks because input was just 18V, but it was quite low in noise, perfect for audiomodulation.

It also stays quite cool for the frequency it works at.

I also intend to add a boost converter into the coil so I can run the class E stage on high input voltages. The idea is to try audiomodulating the feedback of boost converter and variate voltage on the class E stage modulating the output.

Some sort of class D amplifier.

This way I get a neat 'solid state variac' powered from low voltage, and a way for audiomodulation.

I don't know how good is qualiti going to be but it's far more efficient than simple linear modulation of power rail with enormous losses.

Good luck with your coil!

teravolt

Mon May 15 2006, 08:09PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

at digikey they sell IXDD414CI 14A mosfet driver in a TO-220-5 package for around 3$ ea.

HV Enthusiast

Mon May 15 2006, 09:43PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

One thing which helps with audio modulation and output power / heat dissipation is to run the coil with 50% deadtime. The TL494 chip allows this quite easily and this doesn't affect sound quality much.

Plasmaniac

Wed Jun 07 2006, 05:34PM

Registered Member #206 Joined: Sat Feb 18 2006, 03:17PM
Location:
Posts: 72

*reanimating thread*

I use a PLL in my tiny audiomodulated SSTC. Its Fres is around 1.4MHz and for some reason, my UCCs dont even get slightly warm. The quality is pretty low. I think I have to build a little pre-amp for my audio source.

(12V input, the coil itself is 55mm long, I've allready blewn 2 secondaries but no semiconductors (pretty disturbing))

At the moment, I'm trying some higher input voltages for my faked fullbridge(2MOSFETs, 2primaries -> even if both are on they dont blow the silicon off each other). At 26V I have some nicer sparks but the FETs get very warm. I have to make a bigger heatsink and then push the power up to 120V in 12V steps, assuming nothing happens (I think the MOSFETs wont stand more than 60V without a larger primary and the coil itself will die at 48V

)

I feed the audio source in my VCO's input, in parallel with the comparators output, so the coil gets a little out of tune and changes its output. Right now I'm getting the idea of putting my ipod direcly in series with the comparator. Like that, I wont't have to build any pre-amp (ipod's output ~0.3V ?). Wait... now im noticing its not a very good idea... but let's see...

My secondary is getting warm. Too warm for just 12V. It will set itself on fire or just melt away, especially when I'm using it for 10 sec at some hundereds of watts, just like the two coils before this one did, but I've allready made 3 new coils. Also the coil I'm using right now is really ugly and I'm actually just waiting for it to get broken

The new secondaries also have nicer break out points made from 1mm thungsten electrodes

Another cool fact: I can hear my coil on the radio. The quality is amazing if i put a big torid on the coil (no sparks).

EDY19

Wed Jun 07 2006, 07:10PM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408

I've never seen that dual primary "fullbridge emulator" thing before. That may be worth some more research... looks interesting!

Plasmaniac

Wed Jun 07 2006, 07:21PM

Registered Member #206 Joined: Sat Feb 18 2006, 03:17PM
Location:
Posts: 72

I used it for my flybacks, so why not use it for SSTCs. Unfortunately I can't use it for DRSSTCs, but in SSTCs it has many advantages:

- lower cost
- higher effeciency (a fullbridge uses 2 MOSFETs in series, I'm using just one -> half the voltage on a faked bridge)
- safer (they can't blow each other, as mentioned before)
- no need for a GDT or any other galvanic(al?) isolation (I hope you know what I'm trying to say xD)

The only disadvantage:

- You have to make 2 primaries

EDY19

Wed Jun 21 2006, 06:08PM

Registered Member #105 Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408

Bringing back an old thread- do you have a schmatic for the 555 part- what values did you use for the resistors and capacitors to get this frequency range and 50% duty cycle?

teslacoolguy

Tue Nov 13 2007, 05:34PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

you think i can do the same thing with

an have the audio input on pin 5 of the 555 and gnd to gnd along with a small amp in series with it like 50 miliwatt or something

Dr. Dark Current

Tue Nov 13 2007, 05:54PM

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

teslacoolguy wrote ...

you think i can do the same thing with

an have the audio input on pin 5 of the 555 and gnd to gnd along with a small amp in series with it like 50 miliwatt or something

no its not possible the 555 is just an interrupter running at low freq (few 100 hz or so)

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