IOT

# Transformerless Power Supply – 220V AC to 9V DC

In this project, A transformerless power supply for low-current applications will be developed. We can think of a transformerless power supply is just a voltage divider network that divides the 220V AC input voltage into the lower DC voltage that we need. A few diodes are used to rectify the AC voltage and control it to the greatest possible voltage. DC-DC Converter circuit has already been discussed. However, we shall now perform the AC-to-DC conversion.

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The cost of a transformer is eliminated with transformerless power supplies, making them particularly cost-effective. The size and cost of transformers make them prohibitive. LED lights, lamps, laptop and phone battery chargers, hair dryers, and toys all operate at lower DC voltages, such as 5V or 9V or 12V or 15V. It is, therefore, necessary to reduce the 220 volts or 110 volts AC in order to reduce DC.

The transformerless power supply is perfect for powering low current demanding logic devices and microprocessor circuits.

Hardware Required

Design considerations

Capacitive and Resistive are two forms of transformerless power supply. The low heat dissipation and very low power loss of the capacitive type make it more efficient than the resistive kind. Such a power source is suitable for circuits that just need a few milliamperes of current.

We need to think about a few things before we start developing a power supply. A steady current can be maintained in the resistor by connecting a non-polarized capacitor and a resistor in series with the AC power line. The capacitor’s reactance should be greater than the resistor’s resistance in this scenario.

The value of capacitor C dictates how much current flows via resistor R. Circuit current will increase when Capacitance increases. The reactance of capacitor C, which is about to decline, determines how much current it can carry (X). The X-Rated capacitance’s current value is defined as:

IRMS = VIN /X

An important consideration is the choice of the voltage-reducing capacitor. A capacitor’s reactive capacitance is used to calculate the output voltage. The following formula calculates the capacitor’s Reactance:

We have used a 0.47uF capacitor and the frequency of mains is 50 Hz hence the Reactance X is:

X = 1 / 23.14500.4710-6 = 6.77 Kohm

Now we can calculate the current (I) in the circuit:

I = V/X = 230/6775 = 34mA

Transformerless Power Supply Circuit

The input voltage was 220V AC mains. For your own protection, you can connect a fuse. To rectify the 220V AC, a number of diodes are used. We used two 1N4007 diodes as a half-bridge rectifier in this circuit. Two resistors are commonly used to provide a voltage divider in a DC circuit. The path’s current is defined by the sum of these factors.

To keep the voltage at 9V, we utilized a Zener Diode 1N4739A at 9V. Depending on your desired output voltage, a specific Zener diode is required for either a 5V or 12V Zener. The output voltage can be measured with our Homemade Voltmeter.

Proteus was used to model the circuit. Below is a simulated image.

Project PCB Gerber File & PCB Ordering Online

When a breadboard isn’t an option and you’d rather use a PCB for your project, this is the PCB for you. Use EasyEDA online Circuit Schematics and PCB designing tool to design PCB Board for Transformerless Power Supply. Below is a picture of the PCB.

The Gerber File for the PCB is given below. You can simply download the Gerber File and order the PCB from https://www.nextpcb.com/