The symbols & I-V characteristics of the Power Diode Thyristor, SITH, GTO, MCT, TRIAC, LASCR.

 TRIAC                 

A TRIAC (triode for alternating current also bidirectional triode thyristor or bilateral triode thyristor ) is a three terminal electronic component that conducts current in either direction when triggered.

TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction.

Most TRIACs can be triggered by applying either a positive or negative voltage to the gate (an SCR requires a positive voltage). Once triggered, SCRs and TRIACs continue to conduct.

Symbols & Characteristics

LASCR

Light activated SCR (LASCR) or a Photo SCR is just an ordinary SCR except that it can also be light triggered.

Most LASCRs have a gate terminal for being triggered by an electrical pulse just as a conventional SCR.

The LASCRs find many applications including optical light controls, relays, phase control, motor control and a large number of computer applications.

The maximum current (rms) and power (gate) ratings for LASCRs commercially avail-able are about 3 A and 0.1 W.

Symbols & Characteristics

Question

 Draw and explain (i) the symbols and (ii) I-V characteristics of the following.

• Power diode
• Thyristor
• Static Induction Thyristor, SITH
• Gate Turn Off Thyristor, GTO
• MOS-controlled Thyristor, MCT
• TRIAC
• Light Activated Silicon Controlled Rectifier, LASCR

Symbols & Characteristics

IGBT

It is a voltage controlled four-layer device with the advantages of the MOSFET driver and the Bipolar Main terminal. Its switching times can be controlled by suitably shaping the drive signal. This gives the IGBT a number of advantages: it does not require protective circuits, it can be connected in parallel without difficulty .

The IGBT is presently one of the most popular device in view of its wide ratings, switching speed of about 100 KHz a easy voltage drive and a square Safe operating area devoid of a Second Breakdown region.

Symbols & Characteristics

MOSFET

A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor (MOSFET) designed to handle significant power levels. Compared to the other power semiconductor devices, such as an insulated-gate bipolar transistor (IGBT) or a thyristor, its main advantages are high switching speed and good efficiency at low voltages.

The power MOSFET is the most common power semiconductor device in the world, due to its low gate drive power, fast switching speed, easy advanced paralleling capability, wide bandwidth, ruggedness, easy drive, simple biasing, ease of application, and ease of repair.

In particular, it is the most widely used low-voltage (less than 200V) switch.

Symbols & Characteristics

Symbols & Characteristics

Question

 Draw and explain (i) the symbols and (ii) I-V characteristics of the following.

• Power BJT
• Insulated Gate Bipolar Transistor, IGBT
• Metal Oxide Semiconductor Field Effect Transistor, MOSFET
• Static Induction Transistor, SIT

What Are The Advantages Of IGBT Over BJT, MOSFET?

IGBT has

1. Lower turn on and turn off times than BJT
2. Lower on state conduction losses than MOSFET
3. Excellent safe operating area

Comparison between Thyristor and Transistor

The thyristor is a four-layer device while the transistor is a three-layer device. Rating of a transistor is always in watts while that of a thyristor is in KWs i.e. thyristors having better power handling capacity. A thyristor needs only a pulse to make it conducting and thereafter it remains conducting. On the other hand, a transistor needs a continuous current for keeping it in a conducting state. A thyristor is used only as a switching device whereas a power transistor is required to operate in the active region in many application. Therefore the internal power losses in power transistors are in the range of several hundred watts and the rating of an SCR is in the range of kilowatts.

Power Converter Topologies

APPLICATION

Applications of power electronics range in size from a switched mode power supply Applications of power electronics range in size from a switched mode power supply in an AC adapter Applications of power electronics range in size from a switched mode power supply in an AC adapter, battery chargers, audio amplifiers, fluorescent lamp ballasts.

DC/DC converters are used in most mobile phones to maintain the voltage at a fixed value. AC/DC converters (rectifiers) are used every time an electronic device is connected to the computer, television etc.

In power distribution networks AC/AC converters may be used to exchange power between utility frequency 50 Hz and 60 Hz power grids.

DC/AC converters (inverters DC/AC converters (inverters) are used primarily in UPSDC/AC converters (inverters) are used primarily in UPS or renewable energy systems or emergency lighting systems. Power electronics Devices used in electric vehicles hybrid electric vehicles (HEVs), consist mostly of dc/dc converters for battery charging and dc/ac converters to power motor.