What is a triac and how does it work?
A bidirectional thyristor is a triac, which is an abbreviation of a thyristor, sometimes called a thyristor. Before understanding the bidirectional thyristor, first understand the unidirectional thyristor. It is a high-power semiconductor switching device. They all have three electrodes, namely anode A, cathode K, and control electrode G.
The unidirectional thyristor can be seen as consisting of three PNs, forming a PNP transistor and an NPN transistor, as shown below
Therefore, the thyristor must meet two conditions:
1. Indirect forward voltage of thyristor anode and cathode;
2. The forward voltage is also connected between the control electrode and the cathode.
A bidirectional thyristor can be viewed as a combination of two unidirectional thyristors in reverse parallel. The difference between a bidirectional thyristor and its unidirectional is its trigger control characteristics. As long as a trigger signal is added to its control electrode G, whether this signal is positive Both the negative and the negative can be turned on, so there is no anode or cathode in the bipolar thyristor electrode. We generally call this electrode T1 electrode and T2 electrode. The electrode on the P-type semiconductor is the T1 electrode and on the N-type semiconductor. The electrode is a T2 electrode.
Thyristors are generally used for AC signal control, such as motor control and dimming circuits.