The role of X capacitor and Y capacitor on computer power supply

A regular computer power supply manufacturer must have a rectifier bridge, a main control module, a main capacitor, a transformer, various MOS tubes, etc. Among them, the EMI module contains X capacitors and Y capacitors. Why are there safety regulations X and Y on the power supply? What about capacitors? Their role is great.

The general switching power supply AC power input is divided into three terminals: FireWire (L) / Neutral (N) / Ground (G). A capacitor connected in parallel between the live line and the neutral line is generally referred to as an X capacitor. Capacitors that are connected between the live and ground lines and between the neutral and ground lines are generally referred to as Y capacitors.

EMI design is a very important part of the circuit, and X capacitors and Y capacitors are important components. A typical regular power supply has both EMI and secondary EMI. The EMI circuit of the power supply utilizes some of the characteristics of inductive and capacitive components to filter out harmful electromagnetic interference in electrical or electronic engineering. To put it simply, it acts to filter impurities, just like a filter. With these two levels of EMI filter circuit, it can filter out the high frequency clutter and the in-phase interference current from the power grid well, and also weaken the electromagnetic radiation generated in the power supply to a very low limit, so that the leaked electromagnetic radiation It does not affect the human body or other equipment.

The X capacitor is a type of safety capacitor. The capacitor is divided into an X capacitor and a Y capacitor. The X line is between the zero line of the live line. The X capacitor is used in the power supply filter to filter the power supply and filter the differential mode interference. The Y capacitor is used to eliminate common mode interference. Capacitors that are also connected between the two lines of the power line and the ground (L-E, N-E), are generally in pairs. Based on the current limit of the leakage current, the value of the Y capacitor cannot be too large. The X capacitor Y capacitor is a guaranteed capacitor. The difference is that the X capacitor is connected to both ends of the input line to eliminate differential mode interference. The Y capacitor is connected between the input line and the ground line to eliminate common mode interference.

Someone has done experiments, take the X power supply on the power supply and test it. It is found that removing the X capacitor mainly affects the MEI circuit of the power supply, especially the ripple effects of +5V and +3.3V are very large, +5V and + 3.3V due to the lack of X capacitors, the ripple breaks through the standard upper limit, which is easy to cause damage to hardware such as hard disk, memory, keyboard and mouse. Many small manufacturers often cut corners in these places in order to save costs. What is abnormal, but a long time will cause a devastating blow to the computer.

If you have technical questions, please contact us and we will try our best to solve it for you.