What is a bidirectional thyristor?

What is a bidirectional thyristor?

Bidirectional thyristor(TRIAC)is a new type of semiconductor device developed on the basis of one-way thyristor,which is composed of NPNPN five-layer semiconductor material the three electrodes of the semiconductor device are the main electrode T1,the main electrode T2 and the gate G,respectively.The anode and the cathode of the bidirectional thyristor have the performance of bidirectional conductivity,and the internal circuit of the bidirectional thyristor can be equivalent to a combination tube composed of two reverse parallel thyristors the internal structure,equivalent circuit and circuit symbols of the bidirectional thyristor are shown in Figure.The volt-ampere characteristics of bidirectional thyristors are shown in Figure.Good performance of the bidirectional thyristor, its forward and reverse characteristic curves have good symmetry.The two way product network is opened to the number liquor,that is,regardless of the door.Time plus positive or negative fine hair voltage,all can Bidirectional thyristors are in positive and negative directions in two directions,so two-way thyristors have four trigger states.

When the voltage of the gate G and the main electrode T2 relative to the main electrode T is positive (Vr2 > Vn,Vc>Vn) or the gate G and the voltage of the main electrode T1 relative to the main electrode T2 is negative (V PI

When the gate G and the main electrode T1 are positive (V tau 1> V tau 2,VG> V tau 2) or gate G and the voltage of the main electrode T2 relative to the Ti electrode of the main electrode is negative (Vr2),the direction of the thyristor is the anode and the cathode is the anode.

Whether the polarity of the voltage between the main electrode T1 of the bidirectional thyristor and the main electrode T2 is positive or reverse,as long as the gate G and the main electrode T (or T2) are added with different positive and negative triggering voltages to meet the necessary trigger current,the thyristor can trigger a low resistance state.At this time,the pressure drop between the main electrode T and T2 is about 1. V.

Once the thyristor is turned on, even if the trigger voltage is lost, the conduction state can also be maintained. When the current of the main electrode T1 and T2 decreases to the maintenance current or the polarity of the voltage between T and T2, and there is no trigger voltage, the bidirectional thyristor can be turned off automatically, and only the trigger voltage can be reapplied. When the trigger pulse size or time on the gate G changes, the conduction current will change accordingly.