Modification of an HV supply 12V DC to 220V AC - Page 1
Forum section: electronics / beginners

author: pranavAppu
author_rank: Newbie
timestamp: February 09, 2017, 11:44:10 am
content: I have built an HV power supply using a 12V DC input. I'm sending the circuit diagram of it. I want it to modify it to work on my mains supply for more power.I used a 2N3055 Transistor, 1 47ohm 2watt resistor, a flyback from an old TV.My mains power supply rates 220V 15A.*My question is : What do I want to do to make it suitable for an 220V AC input?*Sent from my Lenovo S850 using Tapatalk

author: Arjan Emm
author_rank: Regular Contributor
timestamp: February 09, 2017, 12:09:27 pm
content: What's the question exactly?A 2n3055 is rated 60V, just enough to withstand the inductive spikes in this schematic at 12V.

author: Seekonk
author_rank: Super Contributor
timestamp: February 09, 2017, 03:10:20 pm
content: You might get more power if you had fewer turns of feedback.

author: james_s
author_rank: Super Contributor
timestamp: February 09, 2017, 04:26:35 pm
content: You'd need to completely redesign it, much higher voltage transistor, more turns on the primary, it's possible to make a self-oscillating converter like that but it's much easier to take a different route.I built a version of thishttp://uzzors2k.4hv.org/index.php?page=multiinvertera few years ago and it has proven very robust. Careful though, it's easy to blow flyback transformers with so much power on tap.

author: Benta
author_rank: Super Contributor
timestamp: February 09, 2017, 06:51:58 pm
content: That's the nastiest converter I've ever seen. It's guaranteed to kill all radio and TV reception within half a mile.Considering the spikes generated from stray inductance (when the core saturates), I'm surprised that the 2N3055 has survived.Did you really try it in practice?

author: james_s
author_rank: Super Contributor
timestamp: February 09, 2017, 10:43:36 pm
content: Quote from: Benta on February 09, 2017, 06:51:58 pmI've built one, when I was about 14. It does work just fine, although yes I'm sure it emits all sorts of RF noise. It's like a Tesla coil, fun but not something meant to run continuously.

author: radiogeek381
author_rank: Regular Contributor
timestamp: February 10, 2017, 01:05:53 am
content: Quote from: pranavAppu on February 09, 2017, 11:44:10 amThere are likely quite a few readers who are very very concerned that you're taking ona very dangerous task without even a rudimentary understanding of the hazardsof your undertaking.You clearly are an ambitious and imaginative person. You may even do great things.But this isn't one of them.If you want to make a mark or build something useful, start with some projects that willteach you useful lessons. Getting killed by a flyback transformer is not a useful lesson.If energy conversion is interesting to you, build some heaters. Experiment with low temperatures.Buy some peltier coolers. Experiment with solar, or LiPo cells.If building a big energy discharge apparatus is really really what you want to do, thenlearn enough about it that you can reason on your own through the circuit design andthe safety considerations. Start with low voltage primaries (as you have) and thoroughlyunderstand all the effects, both first order and second order (as you havenot). Andnote that with high-energy designs, the "second order" effects can present first orderdangers. You need to understand the fundamentals. Until you do, you're just screwingaround with high voltages and putting yourself at risk. That's not engineering, its irresponsible.Sure, you may complete this project without killing yourself. But to what benefit?Do it right. Start from the beginning. Learn the principles. Build something that youunderstand.

author: pranavAppu
author_rank: Newbie
timestamp: February 10, 2017, 02:13:46 am
content: Can you give me a schematic ?Quote from: james_s on February 09, 2017, 04:26:35 pm*written by :PranavAppu/

author: james_s
author_rank: Super Contributor
timestamp: February 10, 2017, 07:15:56 am
content: Quote from: pranavAppu on February 10, 2017, 02:13:46 amI'm not going to design it for you, I've got my own projects to work on. I posted a link to a complete design that works, it's not self oscillating but it's effective and robust.

author: ebastler
author_rank: Super Contributor
timestamp: February 10, 2017, 11:25:36 am
content: Quote from: james_s on February 09, 2017, 10:43:36 pmjames_s , I think Benta's comment was directed at the OP's design in the initial post, not yours.

author: james_s
author_rank: Super Contributor
timestamp: February 10, 2017, 04:36:47 pm
content: Quote from: ebastler on February 10, 2017, 11:25:36 amThat's the one I was talking about, the self oscillating converter with a single 2N3055, it's been around since the early 80s at least. Often called a Tesla coil although it's not really one but it does produce a similar effect.

author: Vtile
author_rank: Super Contributor
timestamp: February 10, 2017, 05:06:13 pm
content: Quote from: james_s on February 10, 2017, 04:36:47 pmFirst single transistor battery to 72V "HV" converter (ala joule thief) I have seen is from 50's (tube)radio amateur book, to convert battery voltage suitable to "pocket tube radios". Not 1:1 as it did have 11nF worth of capacitors parallel the transformer and a bit modified wiring. OC76 were the transistor.