GATE TURN OFF THYRISTOR (GTO)

Gate turn off Thyristor (GTO) is a power electronics components made with semiconductor construction. In a series of power electronics main function of thyristor is as a switch that can set a series of conditions ON or OFF with certain characteristics. GTO has 3 terminals namely anode, cathode and gate which is composed of four layers of P-N-P-N. This gate can be turned on by giving a positive input signal is switched off by means of a negative input signal. GTO has a low reinforcement during the turn off the negative current pulses and require a process to turn off. Ideally the voltage on the type of the standard GTO (550A/1200V) is equal to 3.4 v.

 

Figure 1.1Symbol and  Example of thyristor

 

Gate turn off thyristor is divided into two types, namely:

1. SymmetricalGTOGTO, whichhasforward-reverseblockingcapability 
2. Asymmetrical GTO GTO, which is the most common type of conductor and has no reverse-blocking.

In the process of switching, GTO there are four phases of the turn-on, on-state, the turn-off and blocking state. the following descriptions briefly from the phases.

1. Turn-on

Figure 1.2 Turn On

The current gate streamed across the junction of D to n + layer. Karen junction is forward biased pn +, then on layer n + p electrons into the base, some of which will be entered into the area of intersection of pn SPCR1 changes that hold the anode voltage is Vd.

2. On-state

Figure 1.3 On State

regenerative processes in turn on just described, gives the number of electrons and holes from the emitter into the base layer of the p and n, which will turn into saturated with charge carriers. the resulting carrier concentration exceeds the concentration dopping p and n, thus causing a voltage when the ability emulate GTO state and high wave thyristor konvensiona

in conditions on state, GTO works the same as other common i.e. thyristor will conduct if the potential at the anode is greater than the potential at the cathode and gate in terminal a positive current is applied then it will awake condition for ON.

3. Turn-off

Figure 1.4 Turn off

turn off the process on this GTO is controlled by a gate is negative. because of its high conductivity in p-base, hole from the anode portion drains into the gate the negative polarization. during storage, the fillamen will go to voltage cathode segment, until eventually the filament becomes off and flow in the anode will fall quickly in this State. both pn and pn + who are maintaining a State of tension. a fillamen flow into the center of the cathode, reducing the active phase Silicon torn on.

4. blocking state

Figure 1.5 Blocking State

during the process of blocking state, GTO as the carriers blocking voltage Vd, applied by an external electrical circuit that produces the SPRC!, space charge while the voltage on gate negetif Vgr. polarity diode D have opposite direction, precedes the (leading) gap on the SPCR2. otherwise stifle the ability of diode pn + positive limited approx. 20V. on the conditions of this GTO worked as a PNP transistor.

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