MCT-MOS Controlled Thyristor

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MOS Controlled Thyristor

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A SEMINAR ON MOS Controlled Thyristor (MCT):

A SEMINAR ON MOS Controlled Thyristor (MCT) Presenter: Mukesh Kumar 111522 M.E Modular (2011 batch)

Topics covered:

Topics covered Thyristor Two transmitter model of Thyristor MosFET MCT-Intro and construction MCT-Turn-on and Turn-off Advantages and Disadvantages Applications of MCT Conclusion References

Thyristor :

Thyristor Most important type of power semiconductor device. The thyristor, also called a silicon-controlled rectifier (SCR), is basically a four-layer three-junction pnpn device. p n p n Anode A Gate G Cathode C Gate G Cathode C Anode A J1 J2 J3

Thyristor Types:

Thyristor Types Phase-control Thyristors (SCR’s). Fast-switching Thyristors (SCR’s). Gate-turn-off Thyristors (GTOs). Bidirectional triode Thyristors (TRIACs). Reverse-conducting Thyristors (RCTs). Static induction Thyristors (SITHs). Light-activated silicon-controlled rectifiers (LASCRs). FET controlled Thyristors (FET-CTHs). MOS controlled Thyristors (MCTs).

Two Transistor Model of SCR:

Two Transistor Model of SCR Regenerative Action on SCR When a positive current is applied to terminal Gate. Transistor Q2 is biased into conduction, causing its collector current to rise and saturated. The collector current of Q2 cause Q1 is biased into conduction, causing the collector current to rise and saturated. Both transistors are driven into saturation, and the impedance between A and C is very low. The positive current applied to terminal G, which served to trigger the self-regenerative action, is no longer required since the collector of PNP transistor Q1 now supplies more than enough current to drive Q2 The circuit will remain on until it is turned off by a reduction in the collector current to a value below that necessary to maintain conduction

MOSFET:

MOSFET A power MOSFET is a voltage-controlled device and requires only small input current. Switching speed is very high Two types of MOSFETS 1. Depletion MOSFETs ( n-channel and p-channel) 2. Enhancement MOSFETS( n-channel and p-channel)

MOS Controlled Thyristor (MCT):

MOS Controlled Thyristor (MCT) New device that has become commercially available. Basically a thyristor with two MOSFETs built in the gate structure. One MOSFET for turning ON the MCT and the other to turn OFF the MCT. Anode A Gate G Cathode

MCT Turn-on and Turn-off:

MCT Turn-on and Turn-off Turn-on process : By applying negative voltage pulse at gate w.r.t anode. On-FET gets turned-on and off-FET is off. Turn-off process : By applying positive pulse at the gate w.r.t anode Off –FET gets turned-on and on-FET is turned off.

Merits and Demerits:

Merits and Demerits Merits Low forward conduction drop Fast turn-on and turn-off times Low switching losses Low reverse blocking capacity Demerits For higher values of current, the MCT has to be commutate. Gate draws the peak current during turning off. A continuous gate pulse over the entire on or off period is required to avoid ambiguity.

Applications:

Applications Area of ac-dc and ac-ac conversion where the input is 60 Hz ac. Variable power factor operation was achieved using the MCTs as a force-commutated power switch. MCTs are also used in circuit breakers. High power applications such as high power converters. UPS system. Induction heating. Dc-dc converters. Power line conditioners.

Conclusion:

Conclusion The MCT is a power switch with a MOS gate for turn-on and turn-off. It is derived from a thyristor by adding the features of a MOSFET. It has several advantages compared to modern devices like the power MOSFET and the IGBT. In particular, the MCT has a low forward drop and a higher current density which are required for high-power applications.

References:

References M.H. Rashid, Power Electronics: Circuits, Devices, and Applications , Upper Saddle River, N.J.: Prentice-Hall, 2004. Dr. P.S. BIMBHRA, Power Electronics, Khanna Publication S. Yuvarajan, “MOS Controlled Thyristor,” IEEE Trans, on Industrial Electronics 42 :5, 554–558 (Oct. 1995). www.circuitmaniac.com/2009/04/08/mos-controlled-thyristormct/ En.wikipedia.org/wiki/MOS_controlled_Thyristor

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