coll circuit

Primarily there are two AC mains voltage levels that are specified by countries across the globe. These are 110V and 220V. The USA works with a 110V AC mains domestic line while European countries and many Asian countries supply a 220V AC to their cities. Folks procuring imported gadgets from a foreign region having a different mains voltage specs find it difficult to operate the equipment with their AC outlets because of the huge difference in the required input levels.

Though there are 220V to 110V converters available for solving the above issue, these are big, cumbersome and immensely costly.

The present article explains s few interesting concepts which can be possibly implemented for making compact, transformerless 220V to 110V converter circuits.

The proposed homemade converters can be customized and dimensioned as per the gadget size so that these may be inserted and accommodated right inside the particular gadget. This feature helps to get rid of the big and bulky converters and helps to keep away from the unnecessary mess.

CAUTION: ALL THE CIRCUITS DISCUSSED HERE HAVE POTENTIALS OF CAUSING SEVERE LIFE AND FIRE HAZARDS, EXTREME CAUTION IS ADVISED WHILE GETTING INVOLVED WITH THESE CIRCUITS.

All these circuit diagram have been developed by me, lets learn how they can be constructed at home and how the circuit functions:

Using Only Diodes

The first circuit will convert a 220V AC input to any desired output level from 100V to 220V, however the output will be a DC, so this circuit may be used for operating a foreign equipment which might be employing an AC/DC SMPS input power supply stage. The converter will not work with equipment incorporating a transformer at its input.


As we all know that a normal diode, like a 1N4007 drops 0.6 to 0.7 volts across it, when a DC is applied, means that many diodes put in series would drop the relevant amount of voltage across them.
In the the proposed design, in all 190 1N4007 diodes have been used and put in series for acquiring the desired level of voltage conversion.
If we multiply 190 by 0.6, it gives around 114, so thats pretty close to the required mark of 110V.

However since these diodes require an input DC, four more diodes are wired up as a bridge network for the initially required 220V DC to the circuit.
The maximum current that can be drawn from this converter is not more than 300 mA, or around 30 watts.

Using a Triac/Diac Circuit

The next option presented here has not been tested by me, but looks good to me, however many will find the concept dangerous and very undesirable.
I designed the following converter circuit only after doing a thorough research regarding the involved issues and have confirmed it to be safe, but its my personal point of view, if you find it undesirable better do not try this.

The circuit is based on the regular light dimmer switch circuit principle, where the input phase is chopped at the particular voltage marks of the rising AC sine wave. Thus the circuit can be used for setting the input voltage at the required 100 V level.
One big issue involved with this circuit is back EMF that might be generated  from the transformer of the gadget, this might instantly fry the triac or the diac. Although sufficiently advanced and high power components have been included in the design, an effective snubber circuit stage was felt imperative and therefore the RC network across the triac has been stationed.

The pot shown in the circuit should be adjusted for obtaining the required 110V at the output terminals.
A 500 watt iron element coil resistance may be introduced in series with the load for extra safety.

Alternatively a simpler version of the circuit can be made, where the main high triac is operated via a cheap light dimmer switch for the intended results.

Using an Autotransformer Cocept

The last circuit in the order is perhaps the safest from the above because it uses the conventional concept of transfering power through magnetic induction, or in other words here we employ the age old autotransformer concept for making the desired 110V converter.
However here we have the freedom of designing the core of the transformer such that it can be stufed inside the particular gadget enclosure which needs to be operated from this converter. There will be always some space in gadgets like an amplifier or other simlar systems, which allows us to measure the free spave inside the gadget and  customize the core design.

I have shown the use of ordinary steel plates here as the core material which are stacked together and bolted across two of the sets.
The bolting of the two sets of lamination provides some sort of looping effect, generally required for efficient magnetic induction across the core. The winding a single long winding from start to end, as shown in the figure. The center tap from the winding will provide the required approximate 110 V AC output.