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Classic transformers for 220v to 110v or similar (with 50-60hz) are very large and expensive for high power (say 2000W).

For regulating current, a dimmer can be used (and most of the search results return this) but the voltage wave peak is not reduced if I understand correctly.

For DC-DC or AC-DC switching regulators are used, and at least in principle one could use a high power AC to DC and then an inverter to get AC again. But I guess many of the parts in the middle could be omitted for this particular application (hopefully reducing the size and costs).

I'm looking for a relatively simple/inexpensive circuit used to convert mains 220V to 110V. It doesn't have to be a perfect sine wave, but the idea is that devices like a TV would work (not only motors and heaters).

Summary:

  1. Why aren't there commercially available consumer (non industrial) implementations of this idea?
  2. Is it viable to do so (reducing size and costs compared to iron transformer)?
  3. Any sample circuits there?

Please correct me if I'm missing something.

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  • \$\begingroup\$ 2 kW may be feasable economically, but if weight isn't a problem, it will be a hard selling point. You can build one. There are plenty of inverter eval kits for washing machines and the like on the market. \$\endgroup\$ – winny Apr 5 '18 at 9:26
  • \$\begingroup\$ Don't know what you mean by "very large and expensive" but any builders merchant or tool store in UK/Europe sell isolating transformers for the job, usually yellow, tough/waterproof enough to use on building sites, at reasonable prices. \$\endgroup\$ – Brian Drummond Apr 5 '18 at 10:07
  • \$\begingroup\$ There are commercially available implementations of this idea. They're called Travel Power Converters (not just adaptors), and I can go down to my local Walmart or Target or whatever and buy one off the shelf - in fact I did exactly that a few months ago ... \$\endgroup\$ – brhans Apr 5 '18 at 11:29
  • \$\begingroup\$ @brhans I don't think that's it. They suggest using for heaters and motors, which makes me suspect they are like dimmers (SCR, turning on and off existing sine wave but not reducing the actual voltage, only average power). But yes, as you mention they are much lighter and cheaper. Are you sure this can be used to plug in a TV? \$\endgroup\$ – Alejandro Pulver Apr 6 '18 at 10:36
  • \$\begingroup\$ @BrianDrummond by "very large" I mean 10kg instead of 3kg for instance. Like this one. \$\endgroup\$ – Alejandro Pulver Apr 6 '18 at 10:37
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Regarding the second and third parts of your questions: In essence, motor drivers (variable frequency drivers etc) are very similar to what you are trying to do. You just need somewhat different control software (and perhaps some external coils, I believe that many VFDs rely on the motor inductance for filtering, but don't quote me on that, I am not an expert on these devices). UPS systems also sometimes use such devices. They still generally work by switching to DC first, just because it is easier to work with (even your AC-DC power brick will go from AC to high voltage DC, which it turns into much higher frequency AC, which it then sends through a tiny transformer to turn that back into DC - so it is AC->DC->AC->DC!)

The reason they are not readily availabe for consumer is because there is little demand. This is for two reasons:

  • Most people don't move between 220/230/240 V regions and 110 V regions. Hence you won't be selling a lot of these devices.
  • A lot of modern electronics uses either a switchable mains transformer where you can select the voltage with a small switch (or sometimes an internal jumper), or use switching AC/DC supplies that can work on a wide range (100 V - 250 V) of input voltages - in both cases removing the need to use a setop down/step up transformer. So even if we did move between the two, you won't be needing one in most cases. Apart from simple devices such as a kitche mixer, I cannot think of a single device in my house that would need to have an external transformation of 110 V to 240 V or vice-versa.
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