What is SMPS? | Functions | Types | Working | Benefits - Electrical C & V


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28 April 2020

What is SMPS? | Functions | Types | Working | Benefits

What is SMPS?

Switched Mode Power Supply or "SMPS" is a type of power supply unit (PSU), which converts unregulated AC or DC voltage into regulated DC using switching devices. SMPS uses a switching regulator to convert one form of electricity into another form.

What is SMPS? | Functions | Types | Working | Benefits
Process of SMPS

For example, the electricity that comes to our homes is an alternating current (AC). But sensitive equipment like computer requires stable and efficient power supply. Therefore, SMPS is used to provide power to the various components of the PC, which converts AC into static energy. We call it direct current (DC).

What is SMPS? | Functions | Types | Working | Benefits
SMPS is also called Switching Mode Power Supply. These electronic devices include a combination of diodes and MOSFETs such as inductors, capacitors, and semiconductor devices. SMPS is used for power supply in almost all our home electronic devices.

The SMPS in a computer is a piece of hardware, which is fitted like a back inside the case. If you open the computer, you will see a tin can in the backside. In a computer, its job is to provide usable power for its various parts like RAM and motherboard. Let us understand in detail what are the main functions of SMPS.

Functions of SMPS

1. It works to supply power from source to load to start electronic devices.

2. SMPS converts a wall-voltage AC power to lower voltage DC power.

3. Despite the difference in I / P voltage, it provides reliable output by regulating electric power.

4. Different components inside the computer require different amounts of electric power. SMPS provides power to each part as per its requirement.

Main Types of Power Supply in Electrical Circuits

How important is the power supply for any electronic system. But it is not necessary that one type of power supply unit is used for power supply in all electronic devices. Actually, it cannot be done because all the devices demand different voltage power. That is why the power supply in electrical circuits is classified into various types.

1. Unregulated Power Supply

This type of power supply equipment does not have voltage regulators. They are designed to produce specific voltage. These are a type of block wall charger that transforms AC into a small package of DC. But the output voltage provided by them is not constant. In this, AC is converted to DC with a combination of transformer, rectifier and filter.

However, due to its simplicity, it is the cheapest and most reliable for low power requirements. But they are not used in most of the devices due to lack of clean voltage. It is also called linear power supply.

2. Regulated Power Supply

They have a voltage regulator, due to which the output voltage is always clean. It has the ability to convert unregulated alternating current to stable direct current. Their main function is to deliver a constant voltage to a device or circuit. This ensures that the voltage changes in the input do not affect the output. This is why we get constant voltage.

In this, AC is converted into pure DC with the help of step down transformer, bridge rectifier, DC filter and regulator. We also call it Switch Mode Power Supply. Regulated power supply is used in most electronic devices.

Types of SMPS

1. DC to DC Converter
2. DC to AC Converter
3. Fly back Converter
4. Forward converter

1. DC-DC Converter

In this type of SMPS, high voltage DC is obtained from a DC power source. After this this DC power is usually switched in the 15KHz-5KHz range. It is then placed in a step-down transformer, which has a frequency of 50Hz. Now the output received from this transformer is further fed into the rectifier.

Now the rectified output power received is used as the source for the load ie electronic device. In this, the Puls regulate the switching power supply output using Width Modulation. This switch is operated by the PWM oscillator. By doing this indirectly the step-down transformer automatically comes under control.

That is why the output is controlled by the PWM. Now because the output voltage and PWM signals are inversely proportional to each other. So the maximum power is passed through the transformer when the duty cycle is longer. Conversely, if the duty cycle is short, the power dissipation in the transformer is also reduced.

2. AC-DC Converter

In these SMPS, the main AC is converted to DC with the help of rectifier and filter. MOSFET transistors are used to perform the switching process. This transistor consumes low on-resistance, while it can resist high current. In this, the frequency of switching is kept so that it is less for a normal person.

PWM is also used to control the switching process. In this, the level of AC voltage is fed down to the transformer. The output from the transformer is then rectified and smoothed by giving it to another rectifier and filter. In this, the o / p voltage is controlled by comparing the reference voltage with the feedback circuit.

3. Flyback Converter

This type of SMPS has very low output power. This is a much simpler circuit than the rest of the SMPS circuit. They are used for low power applications. The unregulated i / p voltage is converted to preferred o / p voltage with consistent results using MOSFET. The switching frequency is about 100KHz.

4. Forward Converter

These are similar to flyback converter. However, in this type of SMPS, other methods are used to control the switch. It is also called DC-DC buck converter. It has a transformer, which is used for scaling and isolation. In addition to the diode, the capacitor also has an inductor attached. If the switch turns ON, i / p is given for the primary winding of the transformer.

Parts of Computer SMPS

Rectifier:- This part converts AC power to DC, which we call diode.

Capacitor:- filters unregulated DCs converted by rectifiers and converts them to smooth DCs.

Transformer:- A transformer controls the incoming voltage by up and down.

Voltage Regulator:- It controls the DC output, so that the right amount of power, volts and watts can be given to the computer hardware.

Hit Sink:- Absorbs heat when the transistor is heated.

Fuse:- This protects the circuit from heavy voltage.

Transistor:- Its function is to switch the power.

Choke Coil:- It works to smooth the received DC current.

By reading the parts mentioned above and their functions, you can understand the working of an SMPS very well. So let's now know about its connectors. Because with their help, we are able to supply power to different parts of the computer.

How's SMPS works

Let us know how SMPS converts AC into DC and makes it usable for electronic devices. In this process, AC power is first input into the SMPS with the help of wire. After which the NTC, with the help of fuse, line filter and capacitor, stabilizes it slightly and gives it to the rectifier and filter. The rectifier and filter convert it from AC to DC.

In this step, the output DC current received is given to the switching transistor. In which DC current is once again converted to more clean AC current with the help of NPN transistor and switching cycle. Even the process takes place in the primary circuit of the SMPS.

This current is then given to the rectifier and filter present in the second part of the circuit, which again converts the AC current to very pure DC current. By repeatedly changing the current, we get stable DC power. The rectifier and filter output are connected to the starter transformer and amplifier. This is where the wire comes out to power electronic devices.

Benefits of SMPS

Its biggest advantage is that SMPS gives stable current for all electronic devices according to their 
requirement. So that there is no defect in those devices. The design of SMPS is quite simple and the size is also very small, so that it does not take up much space. No matter how many variations in your input voltage, SMPS ensures that the output voltage will be exactly constant and regulated. An SMPS is cheaper than the rest of the power supply.

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