DC PSU to AC sine inverter, Function Generator controlled? - Page 1
Forum section: electronics / projects

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 09, 2020, 03:12:20 pm
content: In my quest to calibrate and test stuff, I find myself needing an AC waveform at various voltages and frequencies.I have a HP 3325A with the 40V P-P option, but that only gets me so far..Basically what I am looking for is an amplifier of sorts that will let me hook up my function generator and a high voltage DC PSU or similar (I have a HP beast capable of nearly 500V for example) and invert the DC to a sine wave at high voltage. The higher voltage output the better but 500VAC or so at a couple kilohertz would be fine for most of my stuff.I can then hook it up to my 34461A Multimeter, set it how I need it then transfer it to the DUT.It doesn't need to supply much current as it will be used mostly for testing multimeters and the like.Should I be looking at just a couple transistors and stuff? Or is there an existing circuit I can easily use or adapt?I'm fine with high voltage as I'm an Electrician across two countries so I know how to handle myself, but I'm sure someone can point straight to a simple(-ish...) way of actually doing this faster than I can figure out google.

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 09, 2020, 03:48:39 pm
content: A surplus MRI gradient amplifier of the smaller rack mount style ?Or a 200 Watt public address amplifier feeding a 440 :24 VAC control transformer backwards ?

author: Someone
author_rank: Super Contributor
timestamp: December 09, 2020, 10:56:41 pm
content: There are "high voltage" amplifiers designed for pairing with function generators that will do exactly what you want, but since its a niche market in a niche market the prices are eye-watering. I'm not aware of any power supplies that have sufficient bandwidth for 500V at kHz but there might be something obscure out there (say, a multimeter calibrator)Reading off an output transformer with a significant load wouldn't be too bad as a reference, but won't be particularly stable.

author: bdunham7
author_rank: Super Contributor
timestamp: December 10, 2020, 12:00:25 am
content: It isn't an easy thing to do if you want it to be accurate and stable, you need some sort of feedback at some point.You can use an audio amplifier driving a transformer into a fixed load, provided you find the right transformer.Or, you can try and find a reasonably priced multifunction calibrator. These put out 1100VRMS @ 1KHz, and something like 120VRMS @ 50KHz. I'm not sure what the linear amplifier included here can do.https://www.ebay.com/itm/Fluke-5100B-With-Wideband-IEEE-Fluke-5220A-Local-Pickup-Only/284095749333?epid=1803363530&hash=item42256d1cd5:g:6zAAAOSwPYNfwPnQ

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 10, 2020, 12:12:31 am
content: Yeah, DC references and calibrators are easy to find, I have like 5 of them from Yokogawa and Fluke, but AC ones are a bit harder to come across.Thanks for the suggestions and keep the ideas coming!At least I have a direction to look now.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 10, 2020, 01:39:16 am
content: If you don't need to source much current, a tube amp will do it easily.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 10, 2020, 06:08:06 am
content: I just found a Fluke 5100B listed here on Yahoo Auctions Japan, I'll keep an eye on it to see how stupid high the bidding goes. Poking around, I found this App Note which looks interesting....Page 11, the 'Son of Godzilla Booster' could be useable for my purposes, the trick will be finding or substituting the transformer... A Triad TY-85

author: bdunham7
author_rank: Super Contributor
timestamp: December 10, 2020, 03:15:59 pm
content: Quote from: TERRA Operative on December 10, 2020, 06:08:06 amFrom the translated page:Please think of it as a repair premise and a junk for parts removal.So in that condition, a typical price here would be $500-600 USD. You're better off buying one in 'repair premise' condition rather than overpaying for one that has been patched up to barely work until the next tantalum cap blows. It will make a nice project that will keep you busy for weeks, and when you're done you'll have a good understanding of how they work. They're sort of fascinating and horrifying at the same time! B/t/w, the air filter is missing off the back of the Yahoo-Japan one, which is a common issue.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: December 10, 2020, 11:43:45 pm
content: Have you thought about a bog stand audio amplifier combined with a transformer?If you use an output transformer from one of those old fashoned glass tube things in reverse you should have plenty of bandwidth.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2020, 12:21:04 am
content: I have used an audio amp to get me up to a few tens of volts, but didn't consider using an audio output transformer. I'll have to see if I can dig one up somewhere for cheap.

author: Someone
author_rank: Super Contributor
timestamp: December 11, 2020, 12:41:23 am
content: Quote from: TERRA Operative on December 11, 2020, 12:21:04 amIf you add transformer isolation at the output of a power amp it ends up like "7. Indestructible, Floating Output Booster" in the AN-272 application note you posted.

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 11, 2020, 04:37:10 am
content: Quote from: TERRA Operative on December 09, 2020, 03:12:20 pmA first one: more powerful, large frequency range, more parts.High-voltage amplifier uses simplified circuitAnd a second one. Low power, 5-30 W max, low-frequency range (<1-10 kHz), less parts.Class AB inverting amp uses two floating-amplifier cellsThe second one is simpler. I used it several times: as it is in that article, and with small variations for lower voltages. (A variation from Leoniv, Minsk.)My second one type, Leoniv-version amp is in an attachment, 60x80 mm PCB.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2020, 07:20:57 am
content: Oh that second one looks nice and simple. If I could get it to handle +/-750V or so, it would be perfect.

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 12, 2020, 05:55:45 am
content: Quote from: TERRA Operative on December 11, 2020, 07:20:57 amWhy not. I think it possibly can do that with those 800V MOSFETs (and low output current), but there is a possibility to use 900V rated MOSFETs, or even 1200V ones.

author: james_s
author_rank: Super Contributor
timestamp: December 12, 2020, 06:11:40 am
content: You could look at the schematic for one of the commercially available AC power sources, or just look for one of the units. I have a California Instruments Invertron 501TC here that I use when I need AC power of an arbitrary frequency. It's essentially just a large audio amplifier driving an output transformer that steps up the voltage.