X capacitor and Y capacitor design rules in switching power supply - Power Circuit - Circuit Diagram

MOS power IC full range

SMD aluminum electrolytic capacitor

Tantalum capacitor

X capacitor design guidelines for switching power supplies:
Refer to the AD1118 X Capacitor Placement Principle:
1. Before the common mode choke: 105/275VAC (MKP/X2)
2. After the common mode choke: 474/275VAC (MKP/X2)
Refer to MW SP200-12 X Capacitor Placement Principle:
1. Before the common mode choke: 1uF/275VAC (MKP/X2)
2. After the common mode choke: 0.33uF/275VAC (MKP/X2)

Refer to MW S145-12 X Capacitor Placement Principle:
1. Before the common mode choke: 0.22uF/MKP-X2-250VAC/275VAC (GS-L)
2. After the common mode choke: 0.1uF/MKP-X2-250VAC/275VAC (GS-L)
Generally two-stage X capacitors, 0.47uF for the first stage, 0.1uF for the second stage, and 0.47uF for the single stage. There is no convenient calculation method at present. (The size of the capacitor is not directly related to the power of the power supply.)

Y capacitor design guidelines for switching power supplies:
Earth = PGND (or CHGND)
Refer to the AD1118 Y capacitor placement principle:
1. Mains input L/N line to the earth: (2 472/250V Y2)
2. The two lines of the mains after the first-class common mode choke are: (2 472/250V)
3. The low voltage end of the rectifier bridge output (the primary low voltage side of the transformer) to the earth: (1 222/250V)
4.6 sets of low-voltage DC output 88V1 pairs of earth: (1 103/1KV Y1 each)
5.6 group low-voltage output auxiliary power supply AGND (transformer secondary low-voltage end) to earth: (share one 103/1KV Y1)
6. Transformer primary low voltage end to transformer secondary low voltage end: (share one 103/1kV Y1)

Refer to the design of the AD1043:
1. Mains input L/N line to the earth: (2 222/250V Y2)
2. Two lines of the mains after the 1st common mode choke: (2 472/250V Y2)

Refer to the design of Kangshu Electronics:
1. Mains input L/N line to the earth: (2 102/250V Y2)
2. The two lines of the mains after the 2-level common mode choke are: (2 102/250V Y2)
3. The low voltage end of the rectifier bridge output (the primary low voltage side of the transformer) to the earth: (1 332/250V Y2)
4.12V low voltage DC output to earth: (1 223/1KV DISC Y1)
5. Transformer primary low voltage end to transformer secondary low voltage end: (222/250V Y1)

Refer to the design of MW S-145-12:
1. Two lines of the mains after the 1st common mode choke: (2 222/2kV Y1)
2. The low voltage end of the rectifier bridge output (the primary low voltage end of the transformer) to the earth: (1 222/2kV Y1)
3.12V low voltage DC output GND to earth: (1 103/1KV Y1)

Refer to the design of MW S-200-12:
1. Mains input L/N line to the earth: (2 472/250V Y2 not on)
2. Two lines of the mains after the 1st common mode choke: (2 472/250V Y2)
2. The low voltage end of the rectifier bridge output (the primary low voltage end of the transformer) to the earth: (1 222/250V Y2)
3. PFC output high voltage end to transformer primary ground: (1 103/2kV Y1)
4.12V low voltage DC output to earth: (1 103/1KV Y1)
5.12V low voltage DC output GND to earth: (1 203/1KV Y1)

According to the above description, the Y capacitor design rules are as follows: (can be selected as appropriate)
1. Mains input L/N line to the earth: (2 222/250V Y2)
2. The two lines of the mains after the first-class common mode choke are: (2 222/250V Y2)
3. The low voltage end of the rectifier bridge output (the primary low voltage side of the transformer) to the earth: (1 222/250V Y2)
4. Transformer primary low-voltage end to transformer secondary low-voltage end: (share one 103/1kV Y1)
4. Low-voltage side DC output to earth: (1 103/1KV)
6. Low-voltage output side GND to earth: (1 103/1KV)