thyristor
Silicon Controlled Recfier (SCR) is a high-power electrical component, also known as a thyristor. It has the advantages of small size, high efficiency and long life. In the automatic control system, it can be used as a high-power driving device to realize the control of high-power equipment with low-power control. It has been widely used in AC and DC motor speed control system, power regulation system and servo system.
Thyristors are divided into two kinds: unidirectional thyristors and bidirectional thyristors. Bidirectional thyristor is also called TRIAC, or TRIAC for short. The bidirectional thyristor is structurally equivalent to two unidirectional thyristors in reverse connection, and this thyristor has a dual pilot pass function. Its on-off state is determined by the control pole G. Adding a positive pulse (or negative pulse) to the control pole G can make it forward (or reverse) conduction. The advantage of this device is that the control circuit is simple and there is no reverse voltage problem, so it is particularly suitable for AC contactless switch use.
Working principle
Structural element
The thyristor is a P1N1P2N2 four-layer three-terminal structural element with a total of three PN junctions. When analyzing the principle, it can be regarded as composed of a PNP tube and an NPN tube, and its equivalent diagram is shown in the figure on the right. Bidirectional thyristor: Bidirectional thyristor is a silicon controllable rectifier device, also known as bidirectional thyristor. This device can realize the contactless control of alternating current in the circuit, and control the large current with small current. It has the advantages of no spark, fast action, long life, high reliability and simplified circuit structure. From the appearance, the bidirectional thyristor is very similar to the ordinary thyristor, and also has three electrodes.
However, in addition to one of the electrodes G is still called the control pole, the other two electrodes are usually no longer called the anode and cathode, but collectively referred to as the main electrodes TI and T2. Its symbol is also different from ordinary thyristors, which is drawn by connecting two thyristors together, as shown in Figure 2. Its model is commonly used in our country as "3CTS" or "KS"; Foreign data are also represented by "TRIAC". The specifications, models, shapes and electrode pin arrangement of bidirectional SCR vary according to the manufacturer, but most of its electrode pins are arranged from left to right in the order of T1, T2, G (when observed, the electrode pins are down, facing the side marked with characters).
thyristor
Thyristor (Thyristor) is short for crystal thyristor, also known as thyristor rectifier, previously referred to as thyristor; In 1957, the United States General Electric Company developed the world's first thyristor product, and commercialized it in 1958; The thyristor is a PNPN four-layer semiconductor structure, which has three poles: anode, cathode and control pole; Thyristors have the characteristics of silicon rectifier devices, and can work under high voltage and high current conditions, and its working process can be controlled, and it is widely used in controlled rectifier, AC voltage regulation, contactless electronic switch, inverter and frequency conversion electronic circuits.
