Transformerless Power Supply Circuit Diagram and Safety

All about Transformerless Power Supply.

Transformerless Power Supply: Today we are going to know about Transformerless Power Supply. Nowadays in many electrical and electronic equipment which are low cost, they have a Transformerless power supply system. In this article, I have tried to give you the knowledge about Transformerless Power Supply.

What is a Transformerless Power Supply?

All electrical and electronic equipment that we use in our daily lives need electric power. There are many products we use which are operated in very small DC voltage like 6V DC, 12V DC etc. But in our home 230V, AC supply is given. So a power supply system is installed in our electrical equipment which Steps Down the voltage as the requirement and then converted into DC. In the early days, a Step-Down Transformer was installed for Step Down voltage but nowadays no transformer is installed. A different type of power supply system is there which is described below. So this type of Power Supply System is called a Transformerless Power Supply.

Why Transformerless Power Supply become popular?

• It has a very low cost.
• It required a very small area for installation.
• It gives sufficient efficiency.
• It has a low power loss.

How Transformerless Power Supply works?

The circuit diagram of a simple Transformerless Power Supply is given below. 

As you see in the circuit diagram The Transformerless Power Supply has a series non-polarized capacitor(225J,400V). This capacitor drops the voltage and gives a low output voltage. Now you may say that why we used a series Capacitor, not a Resistor as the Resistor also drops the voltage. I will tell you that as the Resistor losses power (I²R) so we cannot use the resistor.

A 1 mega ohm Resistor is connected across the capacitor because as the capacitor is charged by 230V so it is very dangerous for us. So for the discharge the capacitor, we used a resistor across it.

A Full bridge rectifier circuit using IN4007 diodes is used to convert AC to DC. A 25V, 470 microfarads polarized capacitor is used to remove the ripple factor. 

In the above circuit diagram, the rating of the Zener diode is not given because you can use a Zener Diode of any rating according to your required output voltage. For example, If your required output voltage is 12V then you can use a 12V Zener Diode.

Read also:

• Working of modern LED bulb with transformerless power supply.
• What inside a Mobile Charger? How a Mobile charger works?
• Symbols and ratings on Mobile Charger.Explanation.

Why Transformerless Power Supply is not Safe?

A Transformerless Power Supply is not safe for us because when it is on no load then no current flows through the circuit, therefore, no voltage drop in the capacitor. So when we touch the circuit we will get an electric shock.

The transformerless Power Supply inside an emergency Light:

Here a Transformerless Power Supply circuit inside an Emergency Light is shown below.

Here the circuit is installed on a PCB with SMD resistors, capacitors.

How to Make Transformerless Power Supply?

You can make easily a Transformerless Power Supply in your home. Use the circuit diagram which is given in the "How Transformerless Power Supply works?". The apparatus which are required for making a Transformerless Power Supply is also given in the above circuit diagram. So see the circuit diagram carefully and make the circuit.

Read also:

• Bipolar Output Full Wave Bridge Rectifier with Center Tapped Transformer.
• How a speaker Works?
• How CPU fan Works?BLDC Motor.
• The microphone inside Headphones.

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