Power Devices

Introduction: Semiconductors

Consider the conductivity of three common materials.
Copper, a good conductor, has a conductivity of 0.59 × 106 S/cm;
Glass, a common insulator, may range between 10-16 and 10-13 S/cm;
While silicon and germanium (semiconductors) have conductivity that varies from 10-8 to 10-1 S/cm. As the conductivity of them is in between conductor and insulator they are called as semiconductor.

What is meant by Power semiconductor devices or Power Devices?
Semiconductor devices which have high voltage and current ratings are called as power semiconductor Devices. They are used in power circuits (ie, high voltage circuits). To withstand the high voltage and current rating, the construction of the power semiconductor device differs from signal level semiconductor device.
Comparison between signal diode and power diode structures will make us to understand about this concept. Click here to know more about it.

Power semiconductor devices are the heart of modern power electronic equipments. It is essential to be familiar with the abbreviations and symbols of power devices. 

The power devices are classified based on various parameters like turn ON/OFF capability, voltage withstand capability etc. 

Various power devices like Power Diodes, Power Transistor,  Silicon Controlled Rectifiers(SCR), MOSFETIGBTMCTTRIAC, DIAC etc. are elaborately discussed in various posts. 

Applications of Power Devices
Power Devices are used in wide-ranging applications. Here we are giving few samples only.

  • Industrial applications mainly consist of two areas, motor control and power supplies. The motors which are controlled vary from the very large, as used in steel mills, to the relatively smaller ones, such as in machine tools. 
  • Consumer applications cover many different areas in the home, such as audio amplifiers, heat controls, food mixers and security systems
  • Transportation applications, the largest being motor drives for areas such as electric vehicles, locomotives and fork-lift trucks. Non-motor drive applications like traffic signal control, vehicle electronic ignition and vehicle voltage regulation.
  • Aerospace and defence applications include VLF transmitters; Power supplies for space and aircraft; and switching using solid state relays and contactors.

Future Trends in Power Devices

  • Depending on the applications, the power range processed in power electronic range is very wide, from hundreds of milliwatts to hundreds of megawatts.
  • So it is very difficult to find a single switching device type to cover all power electronic applications.
  • Today’s available power devices have huge power and frequency rating range as well as diversity.
  • Their forward current ratings range from a few amperes to a few kilo amperes, blocking voltage rating ranges from a few volts to a few of kilovolts, and switching frequency ranges from a few hundred of hertz to a few megahertz.
  • The Power Semiconductor devices are different from the signal level semiconductor devices in terms of their structure, voltage and current handling range etc.
  • In Power electronics applications they are used in non linear switching mode not as a linear amplifiers.