Electric power supply has become a daily necessity of our daily lives. The electrical power that we are receiving in our daily life is 230V 50Hz AC supply. However, using power electronics converting circuits I am using this energy by converting it to specific form and range as required. These converters Power Electronics circuits are step-down and step-up converters, voltage stabilizer circuits, AC to DC, DC to DC, DC to AC converter circuits and so on. We use a microcontroller every day to supply 5V DC. This 5V DC power supply circuit is obtained from 230V AC supply using AC to DC converter.

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Power supply circuit

Typically, this circuit is used to control the load supply capacity. This circuit is called as power supply circuit. There are also different types of power supply circuits such as switched mode power supply, variable power supply, DC controlled power supply etc. They are classified according to different criteria.

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AC to DC converter

There are various types of power electronics converters for conversion from AC to DC such as rectifier, inverter, voltage regulator, F to V converter, cycloconverter etc. The power electronics converter used to convert from AC to DC is called a rectifier circuit. The maximum number of electrical circuits use DC power for their operation and our microcontrollers (6051 microcontrollers) require 5V DC controlled power supply.

There are various techniques by which 230V AC power can be used to convert 5V DC power using different techniques. Typically, step-down converters convert the input voltage to a low output voltage. Let’s discuss the functionality of 230V AC to 5V DC converter.

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There are 4 steps to convert AC to DC

Step-up transformers are used to raise the voltage level and step-down transformers are used to lower the voltage level. Thus, it can be said that the 230V AC power supply is converted to 12V AC using a step-down transformer.

Step-down TransformerSource

Step-down transformers have two windings, one primary and the other secondary winding. The secondary winding has more turns than the primary winding. We know that the law of transformer Faraday's electromagnetic induction works on the basis of principle.

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Initially, 230V AC power is stepped down to 12V AC but 5V DC is the required power. So, this stepped-down output has to convert 17V AC power to DC power and then convert it to 5V DC. AC to DC converter rectifier 17V is used to convert AC to DC and there are different types of rectifiers such as half-wave, full-wave and bridge rectifiers. Bridge rectifiers are more commonly used than half-wave, full-wave and bridge rectifiers.

AC to DC Converter Circuit Diagram

The four diodes are connected in the form of an integrated bridge which is called a rectifier of the bridge. We know that the diode drives only on one side (only during forward bias), while on the other side it is closed (during bias). The diode is usually uncontrolled i.e. whenever the anode voltage is higher than the cathode, it starts conducting until the end voltage is lower than the cathode.

In the upper circuit, diodes D2 and D4 are operated during the positive half-cycle of the power supply, and diodes D1 and D3 are operated during the negative half-cycle of the power supply. Thus, the input AC power output is corrected to DC power; However the DC output power is referred to as pulsating DC and not pure DC. However, due to the internal resistance of the diodes a voltage drop of 1.4V occurs and thus, the peak voltage of the rectifying circuit remains close to 15V.

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15V DC can be controlled to 5V DC using a step-down converter but before that, pure DC power needs to be converted. Authentic DC power is obtained from pulsating DC using filter circuits. C-filters are frequently used for smoothing.

Smoothing Filter to obtain Pure DC

The capacitor is used to store energy in the circuit. When the input voltage increases from zero to its peak value and, the peak value of the input voltage decreases from zero, power can be transmitted from the capacitor. Thus, pulsating DC is converted to pure DC using this charging and discharge process of the capacitor.

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The 15V DC output voltage is controlled using DC voltage regulators such as IC 78XX where the last two digits represent the value of the XX-output voltage. Here let’s discuss IC7805, which is used to maintain a constant 5V DC output even if the input changes DC voltage.

IC 78XX DC Voltage Regulator Internal Diagram

The figure above shows the block diagram of the IC7805 DC voltage regulator. The IC consists of an operating amplifier that acts as an error amplifier, the Zener diode that provides the voltage reference, as shown in the figure below.

Zener Diode as Voltage Reference

The transistors are used to dissipate excess energy because the heat and the heat sink are used for heat protection.

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