Thyristor module is a pnpn four layer three terminal component with three PN junctions. When analyzing the principle, it can be regarded as composed of one PNP tube and one NPN tube, and its equivalent circuit diagram is shown in Figure 1 (a), and figure 1 (b) is the circuit symbol of SCR module.
Figure 1 equivalent circuit diagram of SCR module
Working principle of SCR module
Thyristor module is a four layer three terminal component. It has three PN junctions: J1, J2 and j33. The NP in the middle of the module can be divided into two parts to form a composite transistor of PNP type transistor and NPN type transistor.
(1) When the SCR module bears the positive anode working voltage, in order to make the SCR module turn on, the PN junction J2 which bears the reverse working voltage must lose its blocking effect. The collector current of each transistor is the base current of the other. Therefore, when there is enough gate current Ig flowing into the two transistor circuits, it will produce obvious positive feedback and cause the two transistors to turn on saturated.
Suppose that the collector current of PNP and NPN is mainly IC1 and IC2, the emitter current is IA and IK, and the current amplification factor is IA α 1 = IC1 / IA and α 2 = IC2 / IK, assuming that the reverse leakage current flowing through the J2 junction is ICO, the anode current of the thyristor module is equal to the sum of the collector current and leakage current of the two transistors
Ia＝IC1＋IC2＋ICO＝ α 1Ia＋ α 2Ik＋ICO（1）
If the gate current is Ig, the cathode current of SCR module is IK = Ia + Ig.
Therefore, it can be concluded that the anode current of SCR module is as follows:
(2) Relative current amplification factor of SILICON PNP and Silicon NPN α 1 and α 2 changes sharply with the change of emitter current. When the SCR module bears the positive anode voltage and the gate does not accept the voltage, Ig = 0 in formula (1)（ α 1＋ α 2) It is very small, so the anode current of the SCR module IA ≈ ICO, and the SCR module is in the forward blocking mode; When the thyristor module is under the forward gate voltage, the current Ig flows from the gate g, because enough Ig flows through the emitter junction of the NPN transistor to improve the amplification factor α 2, generate enough collector current IC2 to flow through the emitter junction of PNP, and improve the current amplification factor of PNP α This strong positive feedback process can be carried out quickly.
When α 1 and α 2 with the increase of emitter current（ α 1＋ α 2) When ≈ 1, the denominator in formula (1) is 1 -（ α 1＋ α 2) Therefore, the anode current ia of SCR module is increased. At this time, the current flow through the thyristor module is completely determined by the voltage and loop resistance of the main circuit, and the thyristor module is in the forward conduction mode. After the thyristor module is turned on, 1 -（ α 1＋ α 2) Even if the gate current Ig = 0, the thyristor module can maintain the original anode current IA and continue to turn on, and the gate has lost its function.
After the thyristor module is turned on, if the power supply voltage is continuously reduced or the loop resistance is continuously increased, the anode current IA will be reduced below the maintenance current IH, because α 1 and α The SCR module returns to the blocking mode.
The above is the product introduction of thyristor module supplied by semipower.semipower is a power semiconductor module manufacturer specialized in power electronics. It provides customization, production and processing of power semiconductor module for many enterprises and companies, and also provides OEM or OEM processing business for many companies. The main products are insulated and non insulated power semiconductor modules in various packaging forms, various standard and non-standard power semiconductor modules, etc.
