Looking for an ac power supply circuit diagram. - Page 1
Forum section: electronics / projects

author: avitsur
author_rank: Contributor
timestamp: December 09, 2023, 02:17:22 pm
content: I'm looking for an ac power supply that can work like a variac ranging from 0-230vac.

author: Martinn
author_rank: Frequent Contributor
timestamp: December 09, 2023, 02:34:11 pm
content: Power level?Frequency?

author: Ian.M
author_rank: Super Contributor
timestamp: December 09, 2023, 02:37:50 pm
content: ...Why a Variac isn't suitable?

author: avitsur
author_rank: Contributor
timestamp: December 09, 2023, 03:54:04 pm
content: Two reasons. I don't have one and it's bulky.

author: Ian.M
author_rank: Super Contributor
timestamp: December 09, 2023, 04:33:15 pm
content: What you are asking for is a function generator driving an overload protected power amplifier. At typical AC mains voltages and currents said power amplifier wont be small, cheap or easy to design. Its only *worth* doing vs a Variac if you need variable frequency.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 09, 2023, 04:43:03 pm
content: Quote from: avitsur on December 09, 2023, 03:54:04 pmIf you don't have one, you can buy one (or steal one).As for bulkiness, you haven't given any size or weight specifications.

author: bdunham7
author_rank: Super Contributor
timestamp: December 09, 2023, 05:01:17 pm
content: Quote from: avitsur on December 09, 2023, 03:54:04 pmUnless you only need a very small amount of power (signal level) acquiring a Variac, plus an isolation transformer if needed, is going to be the simplest, cheapest and most compact solution. What is your intended use of the supply?

author: mariush
author_rank: Super Contributor
timestamp: December 09, 2023, 05:17:14 pm
content: If you would be fine with less fine control, you could just buy a 230v - 230v toroidal transformer and unwind it to create lots of taps on the secondary side, like for example every 5v AC - 46 taps.Then buy yourself a bunch of mechanical relays and code something that takes out or puts in secondary windings.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 10, 2023, 11:28:58 am
content: hello avitsur,it is an interesting topic, I once designed and made a such instrument,what i needed :a 230V AC RMS clean SINE, constant frequency, constant voltage output,no matter how much mains voltage variations, only 100watt needed.how i did it:crystal controlled microcontroller made the 50Hz / 60Hz selectable mains frequency from sine table and pwmmains transformer bridge and caps, just classis high voltage supplythen a 100W audio amplifier board and heatsinks, i went for linear class AB for cleanest result.then a step up transformer, since the audio amp cant deliver 230V but the amp can deliver 30Voltso a step up fra 30 to 230 is needed.feed back : i really wanted global feedback (from output of step up transformer) this way i could get zero output impedance,however this is not possible the normal way, due to phase shiftings in loads and in transformer,my next will be class D amp, and output rectified and then level feedbackedthis way it should be stable and low impedance.Performance : this does outperform a variac in voltage resolution, distortion stability, BUTsize and cost : it is bigger, more heawy, and more expensive over a variac, and a variac can deliver much more power pr weight.