In Soft Start Circuit Board, there are many different parts. For HIFI fans, this means bad sound ... ...
Less is more ... I will show you a simple, inexpensive Soft Start Circuit. The one and only one drawback is ... ... you have to control it manually each time you switch on the equipment.
For the 220V a.c. supply at home, the rated overload current of the MCB is 10A, 20A or 32A. Therefore, we have to keep the starting current of the equipment, e.g. transformer, within 10A.
Moreover, smaller current can prolong the life of the switch, give you a safer circuit, use cheaper parts ... ...
I = V / R
- I - current
R = V / I
modified to R must be larger than V / I, R > V / I
R > 220V / 10A
R > 22 ohm
In other words, if a 22 ohm resistor connect to the equipment in series, the current will be no more than 10A and the MCB will not trip.
Of course, we can use a larger resistor because we can further reduce the current and use a High Resistance, Low Wattage resistor.