Definition of Power Supply, functions, classifications, and how it works

By | August 16, 2021

Definition of Power Supply

Power Supply is a circuit that is most important for electronic systems. Power supply is an electronic device or device that functions to convert AC current into DC current to power other hardware devices. The AC source is an alternating voltage source, while the DC voltage source is a direct voltage source.

Power supplies must effectively isolate the internal circuit from the mains network, and usually must be provided with automatic current limiters or breakers in the event of an overload or short circuit. If, in the event of a power supply fault, the DC output voltage increases above a maximum safe value for the internal circuit, the power must automatically be disconnected.

Power Supply Function

Power Supply functions as a converter from AC (Alternating Current) voltage to DC (Direct Current) voltage, because computer or similar equipment hardware can only operate with DC current. The power supply is generally in the form of a box that is placed on the back of the casing. The amount of electricity that the power supply can handle is determined by its power and is calculated in Watts.

Power supply power ranges from 150 watts to 350 watts. For 150 watts of power it is rare because it is only used for simple computers without many additional components. Meanwhile, if in a computer that has several components, for example: CD-ROM, CD-RW, and uses a lot of hard disks, it is recommended to use a power supply of 300 watts or greater.

A poor/damaged power supply function can result in an uneven DC voltage and a lot of ripples. If used for a long period of time will cause damage to computer components, such as hard drives.

Power Supply Classification

In general, Power Supply can be classified into 3 major groups, namely based on its function, based on its mechanical form and also based on its conversion method. The following is a brief description of the three groups. The following are some classifications of power supplies:

  1. Power Supply Based on Function (Functional)

Based on its function, power supply can be divided into regulated power supply, unregulated power supply and adjustable power supply.

  • Regulated Power Supply is a Power Supply that can maintain a stable voltage and electric current even though there are changes or variations in the load or power source (Input Voltage and Current).
  • Unregulated Power Supply is a Power Supply whose voltage or electric current can change when the load changes or the power source changes.
  • Adjustable Power Supply is a Power Supply whose voltage or current can be adjusted as needed by using a Mechanical Knob.
  1. Power Supply Based on Shape

For Electronic equipment such as Televisions, Computer Monitors, Desktop Computers and DVD Players, the Power Supply is usually placed inside or integrated into these devices so that we as consumers cannot see them directly. So only an electrical cable that we can see from the outside. This Power Supply is called the Internal Power Supply (Built in).

However, there is also a stand-alone power supply that is outside the electronic devices that we use, such as cell phone chargers and laptop adapters. There is also a stand alone Power Supply which is large and can be adjusted according to our needs

  1. Power Supply Based on Conversion Method

Based on the conversion method, power supplies can be divided into linear power supplies, which convert the electrical voltage directly from the input, and switching power supplies, which must convert the input voltage to AC or DC pulses first.

The table below is a general comparison between Switching Power Supply and Linear Power Supply :

How Power Supply Works

Electric current that we use in homes, offices and factories in general is generated, sent and distributed to their respective places in the form of alternating current or AC current (Alternating Current). This is because the generation and distribution of electric current through alternating current (AC) is the most economical way compared to direct current or DC (Direct Current).

However, the electronic equipment that we use today mostly requires DC current with a lower voltage for its operation. Therefore, almost every electronic equipment has a circuit that functions to convert electric current from AC current to DC current and also to provide a voltage that matches its Electronic circuit.

The circuit that converts AC electric current to DC is called a DC Power Supply or in Indonesian it is called a DC power supply. DC Power Supply or Power Supply is also often known by the name “Adapter”.

A DC Power Supply or Adapter basically has 4 main parts in order to produce a stable DC current. The four main parts include Transformer, Rectifier, Filter and Voltage Regulator.

Before we discuss further about the working principle of DC power supply, we should know the basic blocks that make up a DC power supply. Below is a DC Power Supply (Adapter) Block Diagram in general.

The following is a brief explanation of the working principle of the DC Power Supply (Adapter) in each block based on the block diagram above.

  1. Transformer (Transformer/Transformer)

Transformer (Transformer) or abbreviated as Transformer used for DC Power supply is a Step-down type Transformer that serves to lower the electrical voltage according to the needs of the Electronic components contained in the adapter circuit (DC Power Supply).

The transformer works based on the principle of electromagnetic induction which consists of 2 main parts in the form of a winding, namely the primary winding and the secondary winding. The primary winding is the input of the transformer while the output is the secondary winding. Even though the voltage has been lowered, the output of the transformer is still in the form of alternating current (AC current) which must be processed further.

  1. Rectifier (Wave Rectifier)

Rectifier or wave rectifier is an electronic circuit in a power supply that functions to convert AC waves into DC waves after the voltage is lowered by a step down transformer. Rectifier circuit usually consists of a diode component. There are 2 types of Rectifier circuits in the Power Supply, namely “Half Wave Rectifier” which only consists of 1 diode component and “Full Wave Rectifier” which consists of 2 or 4 diode components.

  1. Filter (Filters)

In the power supply (adapter) circuit, the filter is used to even out the current signal coming out of the rectifier. This filter usually consists of a capacitor (Condenser) component of the type Electrolyte or ELCO (Electrolyte Capacitor).

  1. Voltage Regulator (Voltage Regulator)

To produce a steady and stable DC Voltage and Current (direct current), a Voltage Regulator is needed which functions to regulate the voltage so that the Output voltage is not affected by temperature, load current and also the input voltage from the Output Filter. Voltage Regulators generally consist of Zener Diodes, Transistors or ICs (Integrated Circuit).

In a sophisticated DC Power Supply, the Voltage Regulator is usually also equipped with Short Circuit Protection, Current Limiting or Over Voltage Protection (protection against overvoltage).

Types of Power Supply

In addition to the above classification, Power Supply can also be divided into several types, including DC Power Supply, AC Power Supply, Switch Mode Power Supply, Programmable Power Supply, Uninterruptible Power Supply, High Voltage Power Supply. The following is a brief explanation of the types of Power Supply.

1. DC Power Supply

DC Power Supply is a power supply that provides voltage and electric current in the form of DC (Direct Current) and has a fixed Polarity, namely Positive and Negative for the load. There are 2 types of DC supply, namely:

a. AC to DC Power Supply

AC to DC Power Supply, i.e. DC Power Supply which converts AC power supply voltage into DC voltage required by Electronic equipment. AC to DC Power Supply generally has a transformer that lowers the voltage, a diode as a rectifier and a capacitor as a filter.

b. Linear Regulator

Linear Regulator serves to change the fluctuating DC voltage to a constant (stable) and usually lowers the DC input voltage.

2. AC Power Supply

AC Power Supply is a power supply that converts an AC voltage level to another voltage level. For example AC Power Supply which lowers the AC voltage from 220V to 110V for equipment that requires 110VAC voltage. Or vice versa from 110V to 220V AC voltage.

3. Switch-Mode Power Supply

Switch-M. ode Power Supply (SMPS) is a type of Power Supply that directly rectifies and filters the AC input voltage to get a DC voltage. The DC voltage is then switched ON and OFF at a high frequency with a high frequency circuit so as to produce an AC current that can pass through the High Frequency Transformer.

4. Programmable Power Supply

Programmable Power Supply is a type of power supply whose operation can be controlled by Remote Control via Analog or digital Input interfaces such as RS232 and GPIB.

5. Uninterruptible Power Supply (UPS)

Uninterruptible Power Supply or often referred to as UPS is a Power Supply that has 2 sources of electricity, namely electric current that comes directly from the AC input voltage and the battery contained therein. When the mains is normal, the Input voltage will simultaneously charge the battery and provide electric current for the load (electrical equipment). But if there is a failure at the AC voltage source such as a power outage, the battery will take over to provide voltage for the electrical/electronic equipment concerned.

6. High Voltage Power Supply

High Voltage Power Supply is a power supply that can produce high voltage up to hundreds or even thousands of volts. High Voltage Power Supply is usually used on X-ray machines or tools that require high voltage.