A power supply is an electrical device, which provides electrical supply to the electrical loads. The power supply transforms the electrical power from a source to the required form of voltage, current, and frequency for the supply of the load. Power supplies are also called power converters sometimes. The main components of a power supply are transformer, rectifier, smoothing component, regulator, etc. There are various types of power supplies.
Power supplies can vary in terms of inputs and outputs. The input of a power supply can be AC or DC, and the output can be AC or DC also. Some of the types of power supplies are variable AC power supply, unregulated linear DC power supply, input transformer, programmable power supply, computer power supply, regulated linear DC power supply, switch-mode power supply, inverters, and uninterruptible power supply or UPS.
AC to DC Unregulated Linear Power Supply
The main components of this power supply are a step-down transformer, filter capacitor, rectifier, bleeder resistor. This power supply is simple, its cost is not high, and it’s very reliable for low power requirements. However, the output voltage of this power supply doesn’t remain constant. With the load current and input voltage, the output voltage varies. Also, for electronic applications, the ripple is unsuitable. If we change the filter capacitor to an LC filter, the ripple will be reduced. But in this case, the cost increases.
The input transformer converts the incoming line voltage into the power supply’s required level. Also, it isolates the line supply from the output circuit. The incoming AC signal becomes raw DC due to the rectifier. The signal is pulsated DC. However, the smoothing capacitor removes the unrequired ripples from pulsated DC. The bleeder resistor or power supply drain resistor has a connection across the filter capacitor. The bleeder resistor keeps the power system supply safe by draining the stored charge.
AC to DC Regulated Linear Power Supply
This power supply has some similarities with the unregulated linear power supply; the main difference is that this power supply has a 3 terminal regulator instead of the bleeder resistor used in the unregulated linear power supply. The power supply’s main aim is to supply the required amount of DC power to the load. As the input of the DC power supply, there’s an AC supply. Different levels of attribute voltages are required for different applications. Nowadays, the output voltages of DC power supplies are accurate. An electronic circuitry regulates this voltage, so the output voltage remains constant over a wide range of output loads. This power supply has an efficiency of around 20% to 25%. CRGO cores or Stalloy are used in this power supply as magnetic materials. This power supply is less complex, bulky, and more reliable. It has a faster-responding capability. Also, the noise level is low.
There are also some disadvantages. This power supply is good for various low power applications. However, it’s not so good for high power applications. A high loss of heat, low-efficiency level, size, etc. are some more disadvantages. While using this power supply in the applications of high power, it needs large components for managing power.
The power supply has components like smoothing component, voltage regulator, series regulator, shunt regulator. Large value capacitors remove the varying voltage level from the DC signal rectified from an AC signal. This process is known as smoothing.
There’s an active (MOSFET or BJT) pass device (series or shunt) in a linear regulator. A high gain differential amplifier controls the active pass device. However, the regulator makes a comparison between the output voltage and a precise reference voltage. Thus it maintains an output voltage at a constant level by adjusting the pass device. Linear power supplies can be of two types.
The series regulator is most widely used. In the circuit, there’s a series element. The control electronics vary its resistance so that for the current taken, the correct output voltage can be generated. The shunt regulator has limited use. Across the load, there’s a variable element. A source resistor has a series connection with the input. When the shunt regulator gets varied, it ensures that there’s a constant voltage across the load.
AC to DC Switch Mode Power Supply
This power supply has components, such as rectifier, series transistor, filter capacitor, transformer, regulator. This power supply is more complicated as compared to linear power supplies. Here, with the regulator and series transistor, the AC voltage gets rectified to an unregulated DC voltage. A constant high-frequency voltage is achieved as the DC is chopped. Thus the transformer dramatically becomes less and allows for a smaller power supply. This power supply has some disadvantages. Firstly, all the transformers need to be custom-made. This power supply has complexities. So, economically low power applications or low production is difficult for this power supply.
DC to DC Power Supply
Sometimes it is necessary to take the main DC voltage within a system and increase or decrease the voltage. The DC to DC converter uses switching regulator circuits for step up or step down conversion. DC to DC power supplies (converters) are available as integrated circuits for low power applications, PCB mounted modules for medium power applications, and fully enclosed power supply for high power use.
Uninterruptible Power Supply (UPS)
This power supply works as a backup power source when there are failures or fluctuations of power. It allows sufficient time for a standby generator to start up or an orderly shutdown of the system. There are power sensing and conditioning circuitry plus a bank of rechargeable batteries in the UPS.
Variable AC Power Supply
This power supply has a transformer for generating different AC voltages. There may be multiple taps or windings in the transformers so that different voltage level selection can be possible. If you prefer continuously varying the voltages, an adjustable autotransformer or variable transformer can be used. There may also be meters with some variable AC power supplies so that you can monitor voltage, current, power, etc.
Programmable Power Supply
This power supply has a remote control facility for operating purposes. The operation takes place via digital interfaces like USB, RS232, GPIB or analog input. However, voltage, current, frequency are the controlled properties of this power supply. Its applications are X-ray generators, fabrication of semiconductors, automated apparatus testing, crystal growth monitoring, etc. There’s an essential microcomputer in this type of power supply. This microcomputer monitors and controls power supply operation. This type of power supply with a computer interface uses protocols of a standard or proprietary communication and language of device control like standard commands for programmable instruments (SCPI).
Inverters – DC to AC Power Supplies
Inverters take a DC voltage, typically from a battery, and convert it to an AC voltage. They are found in solar battery systems to convert the stored DC voltage to a usable AC voltage for home and industrial use. They are also used in boats and campers to convert 12VDC battery to a useable AC supply.
These are the major types of power supplies. We hope this article has helped you to have a basic idea about the power supplies.