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

Guidelines for X Capacitor Design in Switching Power Supplies:

Referencing the AD1118 X Capacitor Placement Principles:

• Before the Common Mode Choke: 105/275VAC (MKP/X2)
• After the Common Mode Choke: 474/275VAC (MKP/X2)

Referencing the MW SP200-12 X Capacitor Placement Principles:

• Before the Common Mode Choke: 1uF/275VAC (MKP/X2)
• After the Common Mode Choke: 0.33uF/275VAC (MKP/X2)

Referencing the MW S145-12 X Capacitor Placement Principles:

• Before the Common Mode Choke: 0.22uF/MKP-X2-250VAC/275VAC (GS-L)
• After the Common Mode Choke: 0.1uF/MKP-X2-250VAC/275VAC (GS-L)

Typically, two-stage X capacitors are used, with 0.47uF for the first stage, 0.1uF for the second stage, and 0.47uF for the single stage. At present, 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 Switching Power Supplies:

Earth = PGND (or CHGND)

Referencing the AD1118 Y Capacitor Placement Principles:

• Main Input L/N Line to Earth: (2 472/250V Y2)
• Two Lines of Main After First-Class Common Mode Choke: (2 472/250V)
• Low Voltage End of Rectifier Bridge Output (Primary Low Voltage Side of Transformer) to Earth: (1 222/250V)
• Six Sets of Low-Voltage DC Output 88V Pair to Earth: (1 103/1KV Y1 Each)
• Six Groups of Low-Voltage Output Auxiliary Power Supply AGND (Transformer Secondary Low-Voltage End) to Earth: (Share One 103/1KV Y1)
• Transformer Primary Low Voltage End to Transformer Secondary Low Voltage End: (Share One 103/1kV Y1)

Referencing the Design of AD1043:

• Main Input L/N Line to Earth: (2 222/250V Y2)
• Two Lines of Main After First Common Mode Choke: (2 472/250V Y2)

Referencing the Design of Kangshu Electronics:

• Main Input L/N Line to Earth: (2 102/250V Y2)
• Two Lines of Main After Second-Level Common Mode Choke: (2 102/250V Y2)
• Low Voltage End of Rectifier Bridge Output (Primary Low Voltage Side of Transformer) to Earth: (1 332/250V Y2)
• 12V Low Voltage DC Output to Earth: (1 223/1KV DISC Y1)
• Transformer Primary Low Voltage End to Transformer Secondary Low Voltage End: (222/250V Y1)

Referencing the Design of MW S-145-12:

• Two Lines of Main After First Common Mode Choke: (2 222/2kV Y1)
• Low Voltage End of Rectifier Bridge Output (Primary Low Voltage End of Transformer) to Earth: (1 222/2kV Y1)
• 12V Low Voltage DC Output GND to Earth: (1 103/1KV Y1)

Referencing the Design of MW S-200-12:

• Main Input L/N Line to Earth: (2 472/250V Y2 Not On)
• Two Lines of Main After First Common Mode Choke: (2 472/250V Y2)
• Low Voltage End of Rectifier Bridge Output (Primary Low Voltage End of Transformer) to Earth: (1 222/250V Y2)
• PFC Output High Voltage End to Transformer Primary Ground: (1 103/2kV Y1)
• 12V Low Voltage DC Output to Earth: (1 103/1KV Y1)
• 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 (can be selected as appropriate):

• Main Input L/N Line to Earth: (2 222/250V Y2)
• Two Lines of Main After First-Class Common Mode Choke: (2 222/250V Y2)
• Low Voltage End of Rectifier Bridge Output (Primary Low Voltage Side of Transformer) to Earth: (1 222/250V Y2)
• Transformer Primary Low Voltage End to Transformer Secondary Low Voltage End: (Share One 103/1kV Y1)
• Low Voltage Side DC Output to Earth: (1 103/1KV)
• Low Voltage Output Side GND to Earth: (1 103/1KV)