What are the main components of a power supply? From the outside, the power supply is a little bigger than a "brick", but there are a lot of things in its "belly". Disassembling the shell, we can see hundreds of various electronic components and complex interlaced cables, which inevitably makes people dizzy. As the saying goes"Catch the thief first, catch the king". When observing the power supply, we should also pay attention to the following parts.

Primary and secondary EMI filter circuits

Our national CCC certification mandates that the listed power supplies must pass the EMI anti-electromagnetic radiation certification, so qualified power supplies should have EMI filter circuits. A qualified power supply should have a complete primary and secondary EMI filter circuit.

The first-level EMI filter circuit is located at the power interface, and the better-made circuit also has an independent PCB board and inductance coil.

The secondary EMI filter circuit is usually on the main PCB of the power supply and consists of inductors and capacitors.

PFC circuit

PFC circuits are divided into two types, passive and active. The inductance of active PFC is often located in front of the high-voltage filter capacitor. Most of the PFCs currently used are active.

High voltage filter capacitor

Which are high-voltage filter capacitors? general speaking，the highest and largest capacitor in the power supply is (1~2pcs). When comparing capacitors, in principle, it can only be compared with the same type of power supply, When it based on the same power, the capacitance required by the passive PFC power supply is larger than that of the active power supply. When comparing at the same level, we can see the capacity, withstand voltage and temperature resistance of the high-voltage filter capacitor. In theory, the larger the three values, It is better to use active PFC, so the high-voltage filter capacitor with a capacity of 330μF can meet the demand. The voltage resistance value of this capacitor is 400V, and the temperature resistance value is 85°C.

Power topology

The power supply topology has an impact on the conversion efficiency of the power supply.

Inductance coil of low-voltage filter circuit

In the low-voltage filter circuit part, it mainly depends on the inductance coil. We mainly look at the size, number of turns and color of the inductor coil. Naturally, the larger the coil, the more the number of turns, the better; as for the color, theoretically gray, black, light green and yellow from good to bad, the better the inductance, the smaller the loss.

Heat sink

Needless to say, the role of the heat sink, the switch tube and Schottky tube with larger heat generation are often installed on the heat sink. Currently commercially available power supplies generally use aluminum heat sinks, usually the thicker the better; at the same time, in order to expand the heat dissipation area in a limited space, most of the heat sinks are equipped with fins. In theory, the more fins, the better.