How does the switching power supply circuit not interfere with others and how is it not interfered by others?
The thermoelectric part of the commonly used switching power supply has a dedicated anti-interference filter circuit. Because it is unknown, it generally does not attract attention. As for the specific location, it is the circuit behind the fuse and varistor. This combination is not easy to break, but it is essential. Today let's talk about some common sense here.
This part of the circuit is not complicated and is generally composed of capacitors and inductors. Speaking of which, it is necessary to mention some basic knowledge - filter circuits. Anyone with a little knowledge of weak electricity knows that capacitors and inductors can form an LC structure or π structure filter circuit. , the Lc circuit can be composed of an inductor and a capacitor, and the π filter circuit is composed of two capacitors and an inductor. Because the structure resembles a π shape, it is vividly called a π filter circuit.
The characteristics of the anti-interference circuit of the switching power supply, which is composed of inductors and capacitors, are very obvious. It generally consists of an inductor that looks like a small transformer and two square safety capacitors. It is basically not broken here, especially because there are very few inductors. In the event of an open circuit fault, because the inductor is connected in series in the circuit, there is no short circuit. Unless the mains power is particularly stable, safety capacitors rarely burn out and short circuit.
The main function of this filter circuit is to filter out interference pulses from the power grid, prevent interference pulses from impacting the switching power supply components, and also prevent oscillation pulses generated by the switching power supply during operation from being sent back to the power grid, which will affect other electrical appliances using the power grid. cause interference.
At this point, you will know why the capacitors here are called safety capacitors. For the safety of the power grid and power supply, it is stipulated that the switching power supply must be equipped with this filter circuit, just like the compensation capacitor in the electrical cabinet. Capacitors and inductors together form a protective wall, which not only protects the switching power supply itself from damage, but also protects it from causing interference to the power grid.
