In this post we will unravel a few homemade crude 220V to 110V converter circuits options which will enable to user the user use it for operating small gadgets with a different voltage specs.
An SMPS circuit is the recommended option for building this converter, so for an SMPS 220V to 110V converter design you can study this concept.
However if you are interested in easier albeit crude 110V converter versions, you may definitely take a tour across the various designs explained below:
Why we Need 220V to 110V Converter
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, let's learn how they can be constructed at home and how the circuit functions:
Using Only Series 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.
CAUTION: Diodes will dissipate a lot of heat so make sure they are mounted on a suitable heatsink.
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 that's 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.
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 a Triac/Diac Circuit
This light dimmer option presented here has not been tested by me, but looks good to me, however many will find the concept dangerous and very undesirable. It was taken from an old book.
The actual author of this circuit says that he designed the following converter circuit only after doing a thorough research regarding the involved issues and have confirmed it to be safe.
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.
The ratio of the resistors R3/R5 in the circuit has been precisely adjusted for obtaining the required 110V at the output terminals across the load L1.
Using Capacitive Power Supply
A 100uF / 400V capacitor can be seen introduced in series with the load for extra safety.
The following image suggests how a simple high value capacitor can be used for achieving the intended 220V to 110V output. It is basically a triac crowbar circuit where the triac shunts the extra 110V to ground allowing only 110V to come out across the output side:
Using an Autotransformer Concept
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.
Using Triac with Transistors
The next circuit has been taken from an old elektor electronic magazine which describes a neat little circuit for converting 220V mains input to 110V AC. Let's learn more about the circuit details.
The shown circuit diagram of a transformerless 220v to 110v converter utilizes a triac and a thyristor arrangement for making the circuit successfully work as a 220v to 110v converter.
The right end of the circuit consists of a triac switching configuration where the triac becomes the main switching element.
The resistors and the capacitors around the triac is kept for presenting perfect driving parameters to the triac.
The left section of the diagram shows another switching circuit which is used to control the switching of the right hand side triac and consequently the load.
The transistors at the extreme right of the diagram are simply there to trigger the SCR Th1 at the right moment.
The supply to the entire circuit is applied across the terminals K1, via the load RL1 which is in fact a 110V specified load.
Initially the half wave DC derived through the bridge network compels the triac to conduct the full 220V across the load.
However in the course, the bridge starts getting activated causing an appropriate level of voltage to reach the right hand section of the configuration.
The DC thus generated instantly activates the transistors which in turn activates the SCR Th1.
This causes short circuiting of the bridge output, choking the entire trigger voltage to the triac, which finally ceases to conduct, switching off itself and the entire circuit.
The above situation reverts and restores the original state of the circuit and initiates a fresh cycle and the system repeats, resulting in a controlled voltage across the load and itself.
The transistors configuration components are so selected that the triac is never allowed to reach above the 110V mark thus keeping the load voltage well within the intended limits.
The shown "REMOTE" points must be kept joined normally.
The circuit is recommended for operating resistive loads only, rated at 110V, below 200 watts.
Another Design for Resistive Loads
The design conditions were that this circuit must perform without having specific adjustments, and the price of parts must be low. The apparent specifications of the circuit should be:
- It must detect mains zero crossings
- It must be able to count four mains cycles and switch a triac
- It must include triac to control the load
- It must include a built-in power supply
Beginning with the 4rth requirement, the least expensive power supply could be built using a mains dropper resistor. The reality that the circuit contains floating 'Live' AC is not important here since it doesn't require to be fine-tuned once constructed. Considering that the basic circuit necessities could be completed using CMOS ICs, the current consumption of the design are low.
Triacs typically wouldn't trigger perfectly through a positive trigger voltage and a negative load voltage, thus in order to avoid this issue a negative supply voltage was considered in this 220V to 110V converter circuit. Nothing at all in the circuit depends on analogue voltage ranges, therefore certain amount of ripple on the power supply is not a crucial thing. A Zener in parallel with an electrolytic capacitor helps in regulating the supply.
Power = V2/R = 2202 / 22K = 48400 / 22K = 2.2 watts
Due to the fact we have a diode in series with the resistor, nonetheless, this power is fed only for 50 % of the time, consequently the power wasted through heat is 1.1 watts, that is not way too significant.
The Zener diode ZD1 restricts the voltage negative peaks to -10V, and C1 filters the voltage to some degree. The current output that is obtained from this power supply network is somewhat harder to estimate, although it is feasible!
Returning back to the explanation, now, the Schmitt trigger NAND gates IC1a and IC1b constitute an cost-effective zero-crossing detector circuit network. During the time the mains voltage is positive, each inputs to IC1b have logic 1 and its output at pin 4 will be as a result logic 0.
Therefore while pin 2 is at low logic, pin 3 of IC1a could just be logic 1. At this point as the mains voltage deviates down in the direction of zero the voltage drops below the Schmitt limit, which causes the pin 4 of IC1a to turn logic 1.
However since the voltage on pin 1, IC1a, is consistently 10V more positive than the voltage on pins 5 and 6 (since pin 1 is hooked up between Live and Neutral while pins 5 and 6 are connected between Live and the -10V supply line), each inputs to IC1a for some moment of time becomes logic 1 and its output turns logic 0.
The pin 1 voltage subsequently drops under the Schmitt limit very fast, such that, with one input low, IC1a output yet again turns to logic 1.
On the other hand as the mains voltage moves up from the negative peak, the two inputs IC1b both turn low, causing pin 4 to be high. Pin 1, which continues to be 10V more positive, crosses the threshold before pins 5 and 6, causing both inputs to go high briefly, and IC1a output turns low.
Shortly after IC1b turns low, it causes IC1 to return back to a logic 1 output.
The overall impact of the above functioning is to produce small low-going pulses on the IC1a output, that straddle the mains zero-crossing point.
In the meantime, the IC1 pin 3 produces a supply that turns positive right before the negative-going mains zero crossings.
Due to this reason, it could be ideally applied to clock the IC 4013 which is a dual D-type flip-flop, and is employed here to count to four complete mains AC cycles.
Using a D-type flip, the Q output turns into the logic state that was on the D input right before the clock edge, on a positive clock edge. If this logic state is supplied back from the Q output, the D-type switches states on each clock edge.
IC1c decodes the 4013's Q outputs to provide a logic 0 output for one full mains cycle out of four. This is gated together with the mains zero-crossing signal in IC1d; using a couple of diodes and a resistor.
IC1d acts as a NOR gate, allowing the transistors to switch on and activate the triac only at a time when each of the above mentioned voltages are at logic 0.
This is crucial, since if the triggering current was left switched on during the cycle, the required current would surpass the supplied 4.9mA!
This relates to another fascinating point: when a power supply is insufficient, CMOS outputs can perform weird stuff. If the power supply goes below 2V, the 4093 output may flip to logic 1, irrespective of the instructions supplied by its inputs.
If the triggering transistors could turn on under these circumstances, the power supply would never get beyond this voltage, leaving some engineers with mysteriously non-functioning circuitry.
As a result, a 4k7 resistor from the base to the negative supply has been incorporated to stop the transistors from turning on until the logic has sufficient power to function properly!
A sufficient switch ON current must also be given for the triac.
Considering that the Darlington pair of transistors switches on to drop roughly 1V, and that the triac demands a total of 1V to trigger, the trigger current is = 8 / 150 ohms = 53.3mA, which is sufficient for most triac specifications.
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