Thyristor VS (triode/Field-effect transistor)

Thyristor VS (triode/Field-effect transistor)

Thyristor is a special type of diode, abbreviated as a Thyristor rectifier element. It is a high-power semiconductor device with a four layer structure of three PN junctions, generally composed of two thyristors connected in reverse. Its function is not only rectification, but also as a contactless switch to quickly connect or cut off circuits, achieving the inversion of direct current into alternating current, converting alternating current of one frequency into alternating current of another frequency, and so on

The Thyristor diode can be simulated using two transistors with different polarities (P-N-P and N-P-N). When the gate of the Thyristor is suspended, both BG1 and BG2 are in the cut-off state. At this time, there is basically no current flowing through the load resistor RL in the circuit. When a positive pulse voltage is input to the gate, BG2 is turned on, causing the base potential of BG1 to decrease. Therefore, BG1 begins to turn on, and BG1's turn on further increases the base potential of BG2, causing the base potential of BG1 to decrease, After this positive feedback process, BG1 and BG2 enter a saturated channel on state. The circuit quickly transitions from a cut-off state to a channel on state, and even if the gate does not trigger a pulse, the circuit will remain in the channel on state due to the positive feedback effect. If reverse voltage is applied to both the anode and cathode at this time, the circuit will quickly shut down due to both BG1 and BG2 being in a reverse bias state, In addition, if the resistance value of the load resistor RL is increased to reduce the circuit current, the base current of BG1 and BG2 will also be reduced. When it decreases to a certain value, due to the positive feedback effect of the circuit, the circuit will quickly flip from the on state to the off state, and we call this current the maintenance current. In practical applications, we can short circuit the anode and cathode of the thyristor through a switch to achieve the turn-off of the thyristor.