Simple dimming pull switch circuit

It is a simple and practical dimmer
pull switch. When using it, you only need to pull
the switch down and the light will turn on; pull it again and the light will
dim; pull it again and the light will go off
. It is very convenient.
    The S in the circle is an l×3 double-control pull
switch, commonly known as a jump-style pull switch. At the i position in the figure, the light E does not light up; after pulling the switch once, the switch is placed
in position ②, the light F is directly connected to the 2ZOV power supply, and the light shines normally; when the switch is pulled a second time, the switch is placed in position
③, and the 220V AC power is rectified by the diode VD. It is connected to the light bulb E. At this time, the voltage at both ends of the light bulb is only
about half of the normal voltage, and the light glows dimly. Pull the switch
for the fourth time to position ①, which means it returns to the original position and the light goes out.
In the dark light state, the actual luminous power P of the bulb is
    P-L"/R - (0.45×220)'/R
    ≈ (20Y: - 30%)P^
where U ~ the voltage across the bulb, that is, the half-voltage Pulsating
    voltage , about 0 4 5 × 220V;