Power Supplies Study Notes for Electronics and Communication Engineering

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Power supplies are essential components in electronic devices that convert electrical energy from a source (AC or DC) into the required voltage and current levels to power electronic circuits. They play a crucial role in providing stable and regulated power to ensure proper functioning of electronic systems.

In this article, you will find the Study Notes on Power Supplies which will cover the topics such as Unregulated, Linear regulated, switching and ripple-regulated. These study notes are helpful in GATE, ISRO, ESE, and other exams preparation.

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Power Supplies

There are mainly 4 types of power supplies: unregulated, linear regulated, switching, and ripple-regulated.

Unregulated Power Supply: An unregulated power supply consisting of a transformer, rectifier, and low-pass filter.

  • Exhibit a lot of ripple voltage and other AC “noise” superimposed on the DC power.
  • If the input voltage varies, the output voltage will vary by a proportional amount. The advantage of an unregulated supply is that it is cheap, simple, and efficient.

Linear regulated Power Supply: A linear regulated supply is simply a (unregulated) power supply followed by a transistor circuit operating in its “active,” or “linear” mode.

  • A typical linear regulator is designed to output a fixed voltage for a wide range of input voltages.
  • It simply drops any excess input voltage to allow a maximum output voltage to the load. This excess voltage drop results in significant power dissipation in the form of heat.
  • If the input voltage gets too low, the transistor circuit will lose regulation, meaning that it will fail to keep the voltage steady.

Switching Power Supply: A switching regulated power supply (“switcher”) is an effort to realize the advantages of both brute force and linear regulated designs (small, efficient, and cheap, but also “clean,” stable output voltage).

Switching power supplies work on the principle of rectifying the incoming AC power line voltage into DC, re-converting it into high-frequency square-wave AC through transistors operated as on/off switches, stepping that AC voltage up or down by using a lightweight transformer, then rectifying the transformer’s AC output into DC and filtering for final output.

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Ripple regulated Power Supply: A ripple-regulated power supply is an alternative to the linear regulated design scheme: a “brute force” power supply (transformer, rectifier, filter) constitutes the “front end” of the circuit, but a transistor operated strictly in its on/off (saturation/cutoff) modes transfers DC power to a large capacitor as needed to maintain the output voltage between a high and a low set point. As in switchers, the transistor in a ripple regulator never passes current while in its “active,” or “linear,” mode for any substantial length of time, meaning that very little energy will be wasted in the form of heat.

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