Devices & Control Mechanism Used In Power Electronics

EEE and ECE Engineering studies are comprised of several engineering subjects which includes power electronics, power systems, control systems, electrical machines, VLSI, embedded systems, and so on. Power electronics is the basic subject in which several power electronic devices such as SCR, TRIAC, DIAC, MOSFET, IGBT, converters, motor drivers, inverters, DC drivers, etc., are used in designing various circuits and projects using different control mechanism like firing angle control, PWM control, and so on.

SCR-Thyristor is a three terminal controlled rectifier which is made of silicon (silicon is typically used), hence also termed as silicon controlled rectifier or SCR. The operation of SCR can be controlled by controlling delay in giving the triggering pulse to the gate terminal which is called as firing angle control. In power electronics the converters such as dual converter, cycloconverter and so on are designed using thyristors and can be controlled using a control mechanism such as firing angle control.

A triac can be defined as two thyrsitors connected in anti-parallel direction and having only one gate terminal. Thus, as there are two thryistors connected in the opposite direction, the triac can conduct in both the directions, i.e., for both polarities of voltage applied by giving a triggering pulse to the gate terminal. Hence, it is also termed as full wave Thyristor.

In AC control circuits, for triggering the thyrsitors and triacs a bidirectional trigger diode is typically used which is called as DIAC. It can be formed by connecting two diodes in anti-parallel direction (cathode of one diode is connected to cathode of other diode), and appears like TRIAC without gate terminal and PNP transistor structure without base terminal.

In this article, we gathered opinions of a few technical experts on devices and control mechanism used in power electronics.

Naresh, M.Tech(Embedded Systems)
R & D, Content Writer

The power electronic devices plays major role in the real time industries which is used to control and convert the electrical energy. The silicon control rectifiers (SCRS), Thyristors find many uses in electronics, and in particular for power control. These devices have even been called the pillar of high power electronics. Thyristors are able to switch a large amount of power and are accordingly used in a wide variety of different applications.

Thyristors even finds uses in low power electronics where they are used in many circuits from light dimmers to power supply over voltage protection. The term SCR or silicon controlled rectifier is often used synonymously with that of thyristor – the SCR or silicon controlled rectifier is actually a trade name used by General Electric. The power support is an important concept which pretends to explain the customer oriented strategy implemented by Power Electronics.

Sampath Kumar, M.Tech (VLSI) & B.Tech (ECE)
Technical Content Writer

Power electronics deal with the switching electronic circuits in order to control the energy flow. There are various components used in power electronics such as Diodes, Schottky Diodes, Power Bipolar Junction Transistors, MOSFETs, Thyristors, Silicon Controlled Rectifier (SCR), Gate Turn-Off Thyristors, Insulated Gate Bipolar Transistors Gate-Commutated Thyristors.

In Thyristors (power electronics), firing angle is one type of control mechanism It is the phase angle of the voltage at which SCR turns ON. There are two methods of turning an SCR, one is by applying a voltage or by applying a gate current across the SCR till it becomes greater than the breakover voltage.

Viswanath Prathap, M.Tech (EPE) & B.Tech (EEE)
Technical Content Writer

Power electronics devices can be classified into different types based on their control mechanism such as uncontrolled, half-controlled, fully-controlled power electronic devices. In general, diodes are termed as uncontrolled power electronic devices (it conducts based on the voltage at its terminals) as we cannot control the operation of diode with any control system. Thyrsitors can be treated as half-controlled devices because we can trigger or switch ON thyristor by applying a gate pulse, but for turning OFF thyristor a power circuit or control mechanism such as by using commutation methods. The power electronic devices such as MOSFET, IGBT, etc., are termed as fully-controlled devices as they can be turned ON and OFF by using control signals.

The power electronics devices can be further classified into various types such as current driven power electronics devices (Thyristor, Giant Transistor, GTO, etc.,), voltage driven power electronics devices (MOSFET, IGBT, IGCT, SIT, MCT, etc.,), pulse triggered devices (thyrsitors), level triggered devices (MOSFET, IGBT, IGCT, SIT, MCT, etc.,), unipolar devices (power MOSFET), bipolar devices (IGBT, GTO, IGCT, MCT, GTR), composite power electronics devices (IGBT, MCT).