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

Guidelines for X capacitor design in switch-mode power supplies:
Referencing 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)
Referencing the 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)

Referencing the 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)
Typically, two-stage X capacitors are used: 0.47uF for the first stage, 0.1uF for the second stage, and 0.47uF for the single stage. Currently, there is no convenient calculation method available. (The size of the capacitor is not directly related to the power of the power supply.)

Guidelines for Y capacitor design in switch-mode power supplies:
Earth = PGND (or CHGND)
Referencing the AD1118 Y Capacitor Placement Principle:
1. Mains Input L/N Line to Earth: (2 472/250V Y2)
2. The Two Lines of the Mains After the First-Class Common Mode Choke: (2 472/250V Y2)
3. The Low Voltage End of the Rectifier Bridge Output (Primary Low Voltage Side of the Transformer) to Earth: (1 222/250V Y2)
4. Six Sets of Low-Voltage DC Output 88V: (1 103/1KV Y1 Each)
5. Six Groups of 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)

Referencing the Design of AD1043:
1. Mains Input L/N Line to Earth: (2 222/250V Y2)
2. Two Lines of the Mains After the First Common Mode Choke: (2 472/250V Y2)

Referencing the Design of Kangshu Electronics:
1. Mains Input L/N Line to Earth: (2 102/250V Y2)
2. The Two Lines of the Mains After the Second-Level Common Mode Choke: (2 102/250V Y2)
3. The Low Voltage End of the Rectifier Bridge Output (Primary Low Voltage Side of the Transformer) to 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)

Referencing the Design of MW S-145-12:
1. Two Lines of the Mains After the First Common Mode Choke: (2 222/2kV Y1)
2. The Low Voltage End of the Rectifier Bridge Output (Primary Low Voltage End of the Transformer) to Earth: (1 222/2kV Y1)
3. 12V Low Voltage DC Output GND to Earth: (1 103/1KV Y1)

Referencing the Design of MW S-200-12:
1. Mains Input L/N Line to Earth: (2 472/250V Y2 Not Installed)
2. Two Lines of the Mains After the First Common Mode Choke: (2 472/250V Y2)
3. The Low Voltage End of the Rectifier Bridge Output (Primary Low Voltage End of the Transformer) to Earth: (1 222/250V Y2)
4. PFC Output High Voltage End to Transformer Primary Ground: (1 103/2kV Y1)
5. 12V Low Voltage DC Output to Earth: (1 103/1KV Y1)
6. 12V Low Voltage DC Output GND to Earth: (1 203/1KV Y1)

Based on the above descriptions, the Y capacitor design rules are as follows: (these can be selected as needed)
1. Mains Input L/N Line to Earth: (2 222/250V Y2)
2. The Two Lines of the Mains After the First-Class Common Mode Choke: (2 222/250V Y2)
3. The Low Voltage End of the Rectifier Bridge Output (Primary Low Voltage Side of the Transformer) to Earth: (1 222/250V Y2)
4. Transformer Primary Low Voltage End to Transformer Secondary Low Voltage End: (Share One 103/1kV Y1)
5. Low Voltage Side DC Output to Earth: (1 103/1KV)
6. Low Voltage Output Side GND to Earth: (1 103/1KV)