How does the switching power supply circuit not interfere with others
The thermoelectric part of the commonly used switching power supply has a special 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 the varistor. This combination is not easy to break, but it is essential. Let’s talk about some common sense here today.
This part of the circuit is not complicated. It is generally composed of capacitors and inductors. Speaking of this, it is necessary to mention a little basic knowledge-filter circuit. Anyone with a little weak current knowledge knows that capacitors and inductors can form an LC structure or a 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 is similar to the shape of π, it is vividly called a π filter circuit.
The characteristics of the anti-interference circuit composed of inductors and capacitors of the switching power supply are very obvious. It is generally composed of an inductor with the same appearance as a small transformer and two square safety capacitors. Basically, it will not be damaged here, especially with very little inductance. There is an open circuit fault, because it is connected in series in the circuit, so there is no short circuit in the inductor. Unless the mains power is particularly stable, safety capacitors are rarely burned and short circuited.
The main function of this filter circuit is to filter out the interference pulse from the power grid, prevent the impact of the interference pulse on the switching power supply components, and also prevent the oscillation pulse generated by the switching power supply during operation from being sent back to the power grid, which is harmful to other electrical appliances using the power grid. cause disturbance.
Speaking of this, I know why the capacitor here is called a safety capacitor. 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 electric cabinet. Capacitors and inductors together form a protective wall, which not only protects the switching power supply itself from being damaged, but also protects it from causing interference to the power grid.
