Power Electronics is concerned with the control and conversion of electrical power using semicondcutor devices such as diodes, transistor, thyristor etc. commonly known as switches.
It covers a very wide range of power level from a few wats as for example in the power suppliers for electronics equipment to gigawatts for large dc transmission scheme (HVDC)
AC to DC : Rectifiers
AC Mains 230Vrms to DC Voltage for Computer, Handphones, Electronic equipment, Microprocessors, IC’s etc
DC to DC: Choppers
Step up or Step down of a DC Voltage, similar to transformer for AC voltages or to produce a variable DC voltage from a fixed constant sources, speed control of DC Motor
DC to AC: Inverters
Variable Speed AC drives, Induction Motor, Brushless DC Motor, Interface between battery and AC Network or Grid
Parts of a Switching Device
Converter with switches
This convertor can be a rectifier/Chopper or Invertor. It is made up of switches (diodes, transistor, MOSFETs, Thyristor). The converter has an input voltage (eg AC input for rectifier) and the switches modifies this input and the switches modifies this input voltage to produce a “raw” or “unfiltered” output voltage at PQ (ie. Vpq in Figure above)
Load
The load is the device that the converter need to supply. It can be a resistor of a heating element, a DC motor, an AC motor or even IC devices or a microprocessor on a printed circuit board. It need a specific voltage (eg. a constant voltage for ICs, a variable DC level for a variable speed DC motor or a variable frequency sine wave current for an AC motor).
Output Filter
The filter removes the switching component in the output voltage Vpq. Consider the rectifier example.
Important idea in power electronics: The load receives practically only the “averaged” component of the signal Vpq coming from the converter (n the presence of a suitable filter) and the switch are used to control this “averaged component”
| Controllable | ON | OFF |
| Power Diode | – | – |
| Thyristors | Yes | – |
| Power BJT | Yes | Yes |
| Power Mosfets | Yes | Yes |
| GTOs, IGBT, IGCT | Yes | Yes |
Active Devices generally are your semiconductor device where you can control the turn on or turn off characteristics
Passive Devices generally are non semiconductor device such as resistor that would turn on and off based on its inhibited material characteristics.
