Switching 240V to 120V converter? - Page 1
Forum section: electronics / general

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 28, 2016, 07:52:26 am
content: While browsing deals on Amazon, I came across this interesting gadget:https://smile.amazon.com/dp/B01E140XWA/It's a power strip that has a built in 200W step down converter. That itself isn't interesting until you realize that the unit is clearly too small and too light to contain a 200W transformer. It's designed for electronics so it isn't just a simple triac or SCR. My best guess is that it's rectifying the AC and then running an inverter from it.

author: Ampera
author_rank: Super Contributor
timestamp: November 28, 2016, 08:18:58 am
content: Quote from: NiHaoMike on November 28, 2016, 07:52:26 amYou know, BigClive did something like this, but instead of it just being like a Triac, it was a proper transformer for light loads.Watching it now, will reply.EDIT: Yea, so it's just a tiny transformer. Nothing like a proper 900W one like some of the 120-230 units I have laying around the house (They have an I/O range, but that's how I use them), but that one seems fine for like a cellphone charger, or a lighter application, while the Triac mode is just for restive loads.I have doubts that this is using any inversion technology, that seems like it would take a lot, but if this is the case, I will immediately purchase as many as they have, because that is the cheapest bloody inverter I have ever seen-40 bucksAlright, but it serves mutliple functions, so that can be justified slightly.Nah, I don't even think the circuitry would fit. It would be a starry dream to have very very portable mains voltage conversion....Or for the US to switch to 230v50, but billions of dollars in house to house changes, basically rewiring every single house in America, or finding a compromise, yea not going to ever happen.

author: bktemp
author_rank: Super Contributor
timestamp: November 28, 2016, 10:09:45 am
content: Quote from: blueskull on November 28, 2016, 09:49:26 amThat would be my guess also.From what I can see on this video, there is probably a PFC stage (transformer near mains inlet) generating a regulated DC voltage from 90-260VAC followed by the modified sine wave inverter (I can't see it, but there seems to be a lot of stuff on the other side of the pcb).

author: Ampera
author_rank: Super Contributor
timestamp: November 28, 2016, 11:28:41 am
content: Quote from: bktemp on November 28, 2016, 10:09:45 amThat's actually pretty damn cool. 200W inverter for 40 bucks, plus AC-DC transformer? Not bad. I never thought an inverter could fit in such a tight space.Yeah, I'm more of a computer engineer, software at best. Made a pretty swish 486 tho.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 28, 2016, 04:30:14 pm
content: What's interesting is, one can actually build a buck converter that runs at constant duty cycle, using bidirectional synchronous switches, to convert AC to any ratio (determined by the duty cycle) above or below. Some filter caps smooth out the pulsations and EMI on both sides, and you're done.The pictured solution is probably even smaller than this method -- despite the isolation transformer. Go figure!Tim