Universal AC front end

this is often accomplished by transformer with a 120 / 240 switch on the primary.

this can be followed with a variable linier or switching regulator (or some other means of setting needed voltage)

alternately a simple VARAC followed by a rectifier may fit your needs.

a little more info on what you load is and needs to see would help a great deal.

Most simple voltage multipliers depend upon energy storage devices, usually capacitors, to store energy from one half cycle. Then, using a diode as a passive switch, the capacitor is put in series with voltage derived from another half cycle to get the voltage boost. This type of supply usually has high peak currents and is not usually useful for large amounts of power. A hundred watts is a large amount of power for this application.

It would make more sense to merely rectify 120 VAC with a bridge rectifier and use some kind of a chopper supply with a small high frequency transformer to convert to a voltage of choice.

Bill

-- Ferme le Bush

I would suggest that "most simple voltage multipliers" for an AC supply are transformers, as suggested by Tim.

A simple approach would be a very crude voltage-sensing relay that switched taps on the transformer, when the input voltage passed a threshold. Followed, of course, with the rectifier and whatever smoothing the load required, if any.

Of course this would produce large step changes in output voltage, when the relay operated. If less dramatic steps were needed, a series of taps with appropriate relays and sensing circuits might do the job.

At least the 90W load is unlikely to load the supply to the point where it would exceed the voltage-sensing relay hysteresis!

I would simply try one of the autoranging power supplies that accept 90-265VAC. These do a switch mode boost to about 415 vdc, and then have a down conversion stage with the required line to load isolation.

Years ago I used some nominal 85-140 VAC switch mode power supplies to down convert about 100 vdc from a photovoltaic array to charge 24 vdc batteries. Worked like a charm and was very cost effective. It used to be that some of the Lambda power supplies also carried dc input ratings. Power rating was reduced for the dc input useage. Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz