Bidirectional thyristor trigger circuit working principle diagram

5V, 35pF, bidirectional ESD protection diode

Two-way thyristor trigger circuit working principle diagram The voltage regulator circuit is mainly composed of a RC phase shift circuit and a bidirectional thyristor. These two parts of the circuit are drawn separately (above), and R5, RP and C5 form a RC phase shifting circuit.
When the power switch S is closed, the AC power supply voltage is charged to the capacitor C5 through R5 and RP. When the voltage across the capacitor C5 rises to a voltage slightly higher than the turn-over voltage of the bidirectional trigger diode ST, the ST and the triac VS are sequentially turned on, and the load RL is obtained. Electrical work.
When the AC power supply voltage crosses zero, the triac turns itself off, and then C5 is reversely charged by the power supply, repeating the above process. When analyzing the circuit, you should realize that the trigger circuit works in the AC circuit. The positive and negative half cycles of the AC voltage will send positive and negative trigger pulses to the control pole of the triac, so that the tube is in the positive and negative half cycles. Conducted symmetrically once.
Changing the resistance of RP changes the charging speed of C5, which changes the conduction angle of the triac, and changes the AC voltage on the load RL accordingly, realizing AC voltage regulation.