Simple hybrid dimmer circuit

According to electrical principles, when a capacitor is connected to a sinusoidal AC circuit, the maximum values ​​of voltage and current are 90° out of phase. According to this principle, connecting C1 and C2 in series and taking out the difference from the middle is more stable than connecting a resistor and a capacitor in series. In the circuit, D1 and D2 rectify the positive half-wave and negative half-wave of the power supply respectively, and add them to A to trigger and C1 or C2 to charge. W is further used to change the triggering time for phase shifting. As long as the resistance of W is adjusted, the output voltage can be changed. D1 and D2 also play the role of limiting the reverse voltage of the trigger pole to protect the triac.