Cell PhonesComputersConsumer ElectronicsGraphic Design & Video EditingHome Theater & AudioIndustrial TechnologyInternet

Basic Components of a Power Supply Unit

Updated on May 2, 2016
jemuelO profile image

Jemuel is an electronics engineer who also finds passion in writing. He does the writing stuff during his free time and on weekends.

A high voltage power vacuum tube power supply. It is capable of supplying +/- 1500 Vdc with 0 - 100mA output.
A high voltage power vacuum tube power supply. It is capable of supplying +/- 1500 Vdc with 0 - 100mA output. | Source

A power supply is an electronic circuit that converts an ac voltage to dc voltage. It is basically consisting of the following elements: transformer, rectifier, filter and regulator circuits. Power supply units (PSU) are used in computers, amateur radio transmitters and receivers, and all other electronic equipment that use dc voltage as an input. Uninterruptible power supply is a must for computers which holds volatile data from time to time. This prevents corruption of data due to power failure and low voltage.

Transformer

The transformer is a static device that transfers electrical energy from the primary winding to the secondary winding without affecting the frequency. It is used to step-up or step-down the ac voltage level and isolates the remainder of the electronic system from the ac power.

The primary winding of the transformer is connected to an ac voltage source that produces alternating current while the secondary is connected to a load. The primary and secondary windings are not physically connected to each other but due to electromagnetic induction following Faraday's law, there is an induced voltage in the secondary winding. There are three main functions of transformers namely: stepping the voltage up, stepping the voltage down and providing isolation between the primary and secondary circuits.

A simple power supply used in desktop computers. This unit supplies the regulated voltage necessary for computer to operate properly.
A simple power supply used in desktop computers. This unit supplies the regulated voltage necessary for computer to operate properly. | Source

Rectifier

The rectifier is a device used to change the ac power into pulsating dc. The basic rectifier is the diode. This diode is a unidirectional device that operates as rectifier in the forward direction. The three basic rectifier circuits using diodes are the half-wave, full-wave center-tapped and full-wave bridge type.

Filter

The filter of the power supply is used to keep the ripple component from appearing in the output. It is designed to convert pulsating DC from rectifier circuits into a suitably smooth dc level. The two basic types of power supply filters are the capacitance filter (C-filter) and RC-filter. The C-filter is the simplest and most economical filter available. On the other hand, RC-filter is used to reduce the amount of ripple voltage across a capacitor filter. Its primary function is to pass most of the dc component while attenuating the ac component of the signal.

Ripple and Ripple factor

Ripple is the unwanted ac component of the signal after rectification. It is unwanted because it can destroy or damage the load. This is the main reason why filters are installed in power supply - to prevent high ripples. The job of the filter is to smoothen the signal and suppress the ac component or variations. Ripple factor is the ratio of the root mean square of the ripple voltage to the value of dc component at the output voltage. It is sometimes expressed in percentage or in peak-to-peak value. The ripple factor determines the effectivity of a filter being used in the circuit.

A sample full-wave bridge rectifier circuit with RC filter. The filter is used to reduce the ac component of the signal.
A sample full-wave bridge rectifier circuit with RC filter. The filter is used to reduce the ac component of the signal. | Source

Voltage Regulators

A voltage regulator is designed to provide a very steady or well regulated dc output. It is always ideal to have a steady output voltage so that the load will operate properly. The output level is maintained regardless of the variation of the input voltage. The commonly used transistor voltage regulators are the series voltage regulator and the shunt voltage regulator.

Series voltage regulator

The series element controls the amount of the unregulated input voltage that goes to the output as a regulated output. The regulated output voltage is sampled by a circuit that provides a feedback to the comparator circuit and is compared to a reference voltage.


Shunt voltage regulator

The shunt voltage regulator provides regulation by shunting current away from the load to regulate the output voltage.

A typical schematic diagram of LM317. The major component, LM317 IC is used as adjustable voltage regulator.
A typical schematic diagram of LM317. The major component, LM317 IC is used as adjustable voltage regulator. | Source

IC Voltage Regulators

A regulator Integrated Circuit (IC) unit contains the circuitry - the reference source, comparator, amplifier, control device, and the overload protector - inside a single IC. There are also adjustable voltage regulators which allow the user to set the desired output level. Other IC regulators have fixed output values. It is said that IC regulators are superior compared to transistor voltage regulators when it comes to linearity of the output voltage.

© 2014 Jemuel

Comments

    0 of 8192 characters used
    Post Comment

    • profile image

      Amit 2 years ago

      Thanks! very much buddy

    • profile image

      sapinoso,Rebecca 2 years ago

      Thanks a lot!

    • jemuelO profile image
      Author

      Jemuel 23 months ago from Cebu, Philippines

      You're welcome Amit and Rebecca! Hope this helps you.

    • profile image

      Nadia Batool 19 months ago

      This is Nice

    • profile image

      michael 17 months ago

      thankyousomuchsir....i hope this project will be ok:)

    • jemuelO profile image
      Author

      Jemuel 17 months ago from Cebu, Philippines

      You're welcome, Michael. Good luck on your project!

    • profile image

      Koobake 10 months ago

      Thank you so much

    • jemuelO profile image
      Author

      Jemuel 9 months ago from Cebu, Philippines

      You're welcome Koobake!

    • profile image

      BRANDT 8 months ago

      THANK YOU SO MUCH! :)

    • profile image

      alex 5 months ago

      thanks its a good one

    • profile image

      Bhuvana 5 months ago

      so useful

    • profile image

      Evans 4 months ago

      This is soo helpful

    • profile image

      Asmin karkee 7 weeks ago

      Thanks A Lot!!!!!!!!!!!!!!!!

    • profile image

      Mahmud 7 weeks ago

      My question is , in case the fluctuation in input voltage this will reflect in output voltage , and in case if i need to purify the AC voltage (fluctuating ) to pure ac without fluctuation there is any electronic circuit to solve this issue ?

    • profile image

      weerasinghe 4 weeks ago

      Thanks a lot dear!!!,my congratulations!!!

    • jemuelO profile image
      Author

      Jemuel 2 days ago from Cebu, Philippines

      Hi Mahmud. AC voltage do fluctuate, and if you want to convert it into non-fluctuating, it becomes DC. If you meant that you want to convert AC to DC then you can use the rectifying circuit, filter and voltage regulator for steady output.

      Thanks!

    Click to Rate This Article