Delayed gradual lighting with protection function

The circuit of the delayed gradually brightening lamp is shown in the figure below.

The right half of the circuit consists of a single-phase thyristor 3CT1A/600V trigger diode D7 and auxiliary circuits R3, R2, C2, and R1. When the charging voltage of C2 reaches the trigger voltage of D7, 35V, D7 breaks down to generate a trigger pulse, turning on the thyristor and allowing current to flow through the incandescent lamp. This part of the circuit is a typical thyristor voltage regulation circuit.
The charging circuit composed of R1 and C1 with a time constant of 10 to 20s makes the current through C2 increase as the voltage on C2 rises, so that the time for C2 to reach the trigger voltage of D7 will gradually decrease from 8ms to 1ms, thereby making the voltage conduction angle through the incandescent lamp gradually increase from 30 to 165. This process takes about 10s, and the incandescent lamp gradually lights up during this process. The larger the value of C2, the longer the delay time. R4 and D5 ensure that whenever the thyristor is turned on, when C2 discharges to 2V, the thyristor voltage passes through zero and turns off, and C2 starts charging again. The function of D6 is to ensure that C1 is not charged when the voltage at point A in the circuit shown in the figure below is lower than 30V, so as to avoid the incandescent lamp waiting time too long to start powering on.

When the power switch K is turned off, C1 charges C2 through R2, so that the thyristor can still conduct. As the voltage of C1 gradually decreases, the conduction angle of the thyristor gradually decreases, and the brightness of the incandescent lamp gradually dims until it is turned off.
The power of the incandescent lamp is between 25W and 40W. If the power is 60W to 100W, the thyristor should be replaced with (2A to 3A)/600V.
The above circuit can also be used for energy-saving lamps, but the following changes must be made:
R1 increases from 27k to 47k. R2 increases from 27k to 67k. D6 changes from a 30V transient suppression diode to a 68V transient suppression diode, and C1 changes to 470u-680u/200V.
After the above changes, the circuit at this time is equivalent to the voltage of the energy-saving lamp gradually increasing from AC 120V to 220V, and its brightness will increase from 20% to 100%.