Hi everybody! It is no secret that the switching power supply consumes a large current at startup. This is due to the input capacitors of the power supply, the larger the capacity, the greater the starting current.
Here I decided to put together a soft start scheme! Let's consider the scheme!
It consists of several radio components! This is a 0.47μm input quenching capacitor, a low-power diode bridge, a smoothing capacitor, a 12-15 volt zener diode, a transistor with a strapping, and a 12 volt relay itself. The principle of operation is to delay the relay. Initially, after turning on the power supply, the voltage of 220 volts passes through a powerful limiting resistor of 22-47 Ohms. and after about a second, the relay trips and closes the circuit. the response time is set by the capacitor (according to scheme C7), the larger the capacity, the longer it takes to operate.
Tests conducted on a pulsed power supply and on an incandescent lamp! More details in the video:
PCB Link