Power Electronics Circuits

Power Electronics is branch of Electronics in which we normally control High Power loads for instance motors through semiconductors devices, Power Electronics is responsible to reduce sizes, cost of many systems, hence increasing overall efficiency  of  system.


Below is the generalized Block Diagram of any Power Electronics system.

A simple Power Electronics system is consist of Power Converter Controller and Obviously Load

Now a days Power Electronics is very widely used in many Electronics Systems, some of applications are used in Solar Power Generation systems, Wind Turbine Systems ,  Electric Vehicles and very new technology Fuel Cells.


There are many devices used in Power Electronics, one thing for sure they all are Semi Conductor Devices. Following is complete list of devices that are used in Power Electronics system for Different Purposes. 

1. Diodes
2. Silicon Controlled Rectifiers (SCR)
3. Thyristors
4. Gate Turn Off Thyristors (GTO)
5. Triac
6. Bipolar Junction Transistors (BJT)
7. Power MOSFET
8. Insulated Gate Bipolar Junction Transistors ( IGBTs)
9. MOS-Controlled Thyristor
10. Integrated Gate Commutated Thyristor

 Above are list of devices that we use in power electronics system, now we will discuss them in very brief manner just to get idea what do they do when installed in Power Electronics System.


 
1- Diode

 Diode is device which only allows current to pass in only one direction, there is depletion layer in between cathode and anode which expands when connected in reverse polarity hence blocking the current and when it is connected in Forward manner( Anode with Positive Terminal and Cathode with Negative Terminal of Battery) i.e Depletion layer is decreased hence providing conduction path for Current to flow.

Simple diodes are used in mostly uncontrolled AC to DC converters Half wave Rectifiers , in which output cannot be controlled.


2- Thyristors
 
These are the diode which can be turned off and on by giving pulsating DC on its gate, and output can be controlled to our desire. 
The more detail of Thyristor will be discussed in SCR's topic.











 3- Silicon Controlled Rectifier (SCR)

 The SCR is one of the type of thyristor, The working and structure of SCR is almost same as normal diode but it has one difference, until or unless we give give voltage to Gate of SCR it will not conduct in any direction, Gate is like power on button of diode. By turning on and off  gate we can control overall average of DC output which cant be done in simple Diode.

SCR are mostly used in controlled  AC to DC converters Half Wave Rectifiers , its output can be controlled by Controlling Firing Angle (Alpha).




4- TRIAC


TRIAC is combination of two SCRs connected in anti-Parallel state, so what is advantage of having two anti Parallel SCR,, as we know single SCR will only give Half Wave Output , so if we want our power to be Full Wave then we will use TRIAC, consider it as Diode Rectifier Bridge but advantage is that we can control the output of its Output unlike Bridge. Pulsating DC can be used turn on and off the device to get desired average DC Value.







5- Bipolar Junction Transistor (BJT)

BJT is widely used device in Electronics world, i think BJT helped revolutionize the world, The Computer you use has millions of transistors in its CPU, we will later discuss in detail about BJT and its circuit now here with very brief detail, BJT is most basic type of transistor which can work as a Switch, Amplifier and voltage controlled voltage device. It is reknown for its High Current and voltage Gain and Very High Power Ratings as compared to other Type of Transistors.


6-MOSFET

MOSFET stands for Metal oxide Semi-Conductor Field Effect Transistor, it is modernly most used type of Transistors, because of its very high Input Impedance and very Low Output Resistance its Widely used in Electronics systems and constantly replacing old type of transistors i.e BJTs. There are many type of FETS, Like EMOS, CMOS , D-type.





We will discuss all these devices again in in Following Circuits of Power Electronics:


Types of Circuits in Power Electronics: 

1.  Diode Rectifiers ( Uncontrolled Rectifiers )
2. AC to DC Converters ( Controlled Rectifiers )
3. AC to AC Converters (Voltage Control Variac)
4. DC to DC Converters ( DC Choppers )
5. DC to AC Converters ( Inverters )
6. Switches

Now We will soon discuss Everyone of these Categories of Circuits Stay Tuned, Bookmark Us. 

Ask Questions if you couldn't understand something. We will be Glad to Answer.