Transformerless power supply 


The Transformerless Power supply type explained at this post uses AC main voltage and without proper caution isolation, you may cause injury when you directly come in contact with it.

Transformerless power supply Introduction

Transformerless Power supply building for a particular device is always the hardest task as you know about electronics, there are different power supply circuits are available for different applications and they ensure very calculated variations at its working and building.

When we consider about to build a good power supply circuit, first of all, we need to know. what is the specific application of the device?

Then, what range of output power supply circuit needs to provide?

 And. what all are the functions we need to implement at the power supply circuit? And last what type of enclosure and cost need to design? Satisfying these conditions are the main challenges you need to go through its project designing.

But today I need to talk about the tiny applications-based power supply for applications like minute charger, emergency light, torchlight, etc… These appliances should not have a bigger enclosure to provide complicated circuits.

For a proper explanation about the circuit and its dangerous face, here we add many tiny practical circuits and calculations.

1.   AC line tester circuit designing

2.   Capacitive dropper circuit

3.   Transformerless power supply circuit using reactance

4.   Two different circuits of transformerless power supply

Ac line tester circuit

This is a much tiny application, a very small amount of power is required to work a LED, but the selection of the right component in a theoretical way is good for a beginner.

So our tiny load utilizes only a very small amount of current, it is around 12mA to 15mA, and at the first condition, we provide only 15v for calculating the resistor value.

Ac line tester circuit diagram

Ac line tester circuit
Ac line tester circuit

R=V/I = 15/5

= 3kovalue

For the next practical experiment, we try to provide 220volt AC into our circuit, so first of all we need to calculate what value of resistance we have to provide at this point.

Ac line tester circuit diagram

Ac line tester circuit
Ac line tester circuit
 R=V/I = 217/5

= 43.4kohms

So we need a 45.4kohms resistor to drop a 230 volt AC to work a 3vLED. 

The AC line tester circuit is worked properly at the experiment, you can check yourself without any mishandling.


Next, we need to extend is a simple circuit in two more tiny applications, especially here we use resistors for dropping a large amount of current and turn that into your desired level with a single component circuit arrangement. 


But this vision will fail at its theoretical calculations about efficiency, usage of these compounds like resistors will drop out remaining power into heat.


Pr = V.I = 217 × 5

= 1.085W

Here shows its exact power loss or heat loss happened at the resistor it’s around 1.085W of power is lossing

Here, Pled = 3v× 5mA

  = 0.017W

This is the power we provide into LED, it’s only 0.017 watts, and the remaining power is losses as heat at resistance.


Efficiency = 0.017/1.085

 = 1.6%

Only a 1.6 percentage efficiency is provided by this particular current circuit arrangement.

Conditions to drive a LED

·   For a DC circuit, we need a switching switch element or active component to drive an LED.

·   But for an AC circuit, it is possible to drive LED with a capacitor combined with it.

Capacitive power supply 

So let us try to build a tiny power supply with a capacitor

For that, we need to calculate the value of the capacitor which is to implement at the circuit wish to build.


Circuit diagram

Ac line tester circuit
Ac line tester circuit

The same steps need to follow in the capacitor-based Circuit also, for calculating capacitance


Reactance property

Reactance is the property shown by a capacitor, technically resistance and reactance are the same because the property of opposing is termed as resistance and also blocking property of a capacitor at a circuit is called reactance.


Capacitive reactance = Xc

We need to calculate Xc or capacitive reactance for circuits’ future development.

 Xc = 1/2πFc

   C = 1/2πFc

       = 1/2π×50×^/5×45.400ohm

       = 0.0701uf


The practical arrangement of this circuit using a single capacitor will become a big failure.


so after a long search, we found a circuit using few components to drive a power supply without a transformer.

Capacitive dropper circuit for transformerless power supply

When we always consider about to build tiny circuits like to power LED or tinkling circuit, mostly all of us search for a switching mode power supplies which can provide much softer and smoother DC into our


But it will cause more enclosure space to arrange this circuit with that minute circuit, so here we are trying to build a capacitive dropper or transformerless power supply circuit arrangement for solving this problem.


Generally, transformerless power supply devices are named after the most dangerous circuits to build and use. It is true in the sense, so we try to project’s its dangerous nature and also we try to suggest a safer way to complete this project done.


Capacitive dropper circuit Circuit diagram


Capacitive dropper circuit for transformerless power supply
Capacitive dropper circuit for transformerless power supply
Capacitive dropper circuit Components used

Resistor    1Mohms

Capacitor. 224/400v



Zener diode

This is our initial project for dropping High voltage AC into low voltage without using a transformer.

Capacitive dropper Circuit operation

Very few components are deployed to make a small power supply, instead of diodes, we are using bridge IC at the rectifier section.


We don’t need an explanation to know about the working of the circuit because the main components in this arrangement are RC NETWORK.


Capacitive dropper Circuit diagram

Capacitive dropper circuit
Capacitive dropper circuit

Transformerless power supply Modified circuit

The capacitor used in this project is not like usual capacitors because the transformerless power supply is basically a voltage divider circuit, it takes 220v from ACmains and divided it down to your desired voltage range.


Actually, capacitors block a certain amount of voltage at its plates, this is the common principle of a capacitor, and selecting the right value of the capacitor at this circuit is the main thing.  

Polyester Capacitor for X-rated capacitor

These are the capacitors used to build the transformerless power supply circuit, it is because of its high voltage and current capacity, polyester is the dielectric used at these capacitors.


Because of its high range of tolerance these types of capacitors had the ability to withstand high voltage ranges.


After completing connections, we try to check its working, it is good but here and were some sort of problems are spotted with its safety and correct working, so we are been forced to the modified circuit this circuit.


transformerless power supply circuit
transformerless power supply circuit
Transformerless power supply Components used

Resistors        1Mohms


Capacitors.      224/400V



Zener diode

VDR (Metal oxide varistor) 230v range


transformerless power supply Working and circuit explanation

The circuit shown in the figure is much safer than the first circuit, because of its usage of so many different components to prevent overpower circulation.


We mentioned the working of the polyester capacitor or x rated capacitor and resistor (R1), (RC network) resistor works as a blender component that is, it will produce a path for discharging energy from the capacitor.


R2 is the resistor that works for over rush protection system that is, it will be used as a prevention component to prevent AC current rush towards rectifier or regulator circuits.


The VDR (voltage-dependent resistor) or MOV (metal oxide varistor), this is a special type of resistor used to oppose overvoltage passing into the circuit.


Basically, it is an electrical resistance that varies its value with the applied voltage. Then it is a nonlinear device that provides accurate suppression of voltage variation.


The working condition of VDR works as high resistance at low voltage and low resistance at high voltage.


And after step down of voltage at the capacitor, a fixed amount of voltage passes through the rectifier and producer DC output current.


But both these transformerless circuits provide output current around 25mA and 12v of DC, so next, we try to make a different circuit that can produce a 500mA of output current.

How to make transformerless power supply 230v AC to 12v and 5-volt dc High ampere 500mA

Special about the circuit is that normal transformerless power supplies are built to drive LEDs without the heavier component transformer, but these circuits are limited drive LEDs unto 20 to LEDs, RC network using a polyester capacitor and regulator circuit arrangement.

But this circuit will be more different, we can drive 100 to 150 LEDs because it can produce high current output.

Transformerless power supply Components used

Polyester capacitor.    474K/250v – 2nos

Diode.      1N4001 – 4nos

Irf840 MOSFET.  – 1nos

Capacitor 330uf.  – 2nos

Resistor 1k and 3.3k

Regulator IC. 7815

 transformerless power supply-Circuit diagram

transformerless power supply 230v AC to 12v and 5-volt dc
transformerless power supply 230v AC to 12v and 5-volt dc 

Circuit explanation and working

This is our schematic diagram, instead of using one polyester capacitor here we use two capacitors for voltage suppression, this arrangement also provides to increase current output.


The calculated number of capacitor usage in the circuit will increase the amount of current produced by the circuit, but a standardized X-rated capacitor will be a must.


X2 and X3 capacitors are the types that are available at the market, its size will increase with the increase of capacity.


After the suppression of voltage, the voltage should have to convert into DC using a rectifier arrangement, here it is a bridge rectifier circuit using diodes but also we can use bridge IC for this process.


Next MOSFET and voltage divider arrangement, further uplifting of current happens at this MOSFET, voltage dividers are necessary for GATE voltage supply for triggering, and this section is completed by D5 diode at the top, for the opposition of reverse current back to the rectifier and capacitor network.


C3 Capacitor for filtration and regulation IC for the regulation of DC output than a C4 Capacitor for filtration and protection for regulated IC.


If you need to change the voltage regulator, you need to change it by changing the resistance value at the voltage divider section.

R1. =. 7812. = 3.2k

R2.  = 7809. = 2k

R3. =. 7805. = 1k 

These are the calculated resistor value for the changing circuit diagram.



In this schematic arrangement, we fixed to voltage ranges that are 12 volt and 5-volt dc with a 500mA.


 Check the output values after assembling using a multimeter, we can assure the 12v and 5v dc output, but the amount of current will be different at the output.



Transformerless power supplies are called the capacitive reactance based limiting current device, it’s applications are very much limited in the professional level.


Low profile for this circuit arrangement is due to its dangerous to face at non-isolated application, normal switch mode power supplies are less dangerous because of its usage of a transformer in the circuit.


We consider transformerless power supply, we continuously mentioned about its safety concern, it is because of the connection of neutral wire.


(Connections of the neutral wire and phase are directly into its output, so there is no separate connection between neutral and output, if any high current passing happened the whole circuit will be affected).


Another property always keeps in mind that is about the ground wire installation at your home, that is ground wire connection at home should be proper because the chance of getting shocked is increased into 75 percent and this is happened by when we reverse the power cable connection into the AC mains, the circuit will work normally but chances of getting shocked will be higher when we directly contact with the circuit.

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