Bidirectional thyristor stepless dimmer

When turning on the light, close the switch S, and the 220V alternating current charges the capacitor C2 through RP1, RP2 and R. When the voltage
at both ends of C2 reaches the turning voltage of the bidirectional trigger diode VD, VD and the triac VS conduct one after another, causing the controlled lighting Lamp H
gets electricity and shines. When the alternating current crosses zero and reverses direction, vs turns off itself, C2 begins to reverse charge again, and the above process is repeated. It can be seen that
in each cycle of alternating current, vs is symmetrically conducted once in the positive and negative half cycles. If the resistance value of RPI is adjusted,
the charging rate of capacitor C2 will be changed, thereby causing the vs trigger conduction time to move forward or backward in any half cycle, that is,
the vs conduction angle is changed, and the corresponding voltage applied to both ends of the lamp H is changed. The average voltage also changes accordingly, so the purpose of stepless dimming can be achieved.