Design Rules for X Capacitance and Y Capacitance in Switching Mode Power Supply

Source：http://www.kehong88.comRelease time：2017-01-23 08:53:39Views：

X capacitor design guidelines for switching power supplies:
   Refer to AD1118 X Capacitance Placement Principle:
   1. Common mode choke front: 105 / 275VAC (MKP / X2)
   2. Common mode choke after: 474 / 275VAC (MKP / X2)
   Reference MW SP200-12 X Capacitance Placement Principle:
   1. Common mode choke front: 1uF / 275VAC (MKP / X2)
   2. Common mode choke: 0.33uF / 275VAC (MKP / X2)

Reference MW S145-12 X Capacitance Placement Principle:
   1. Common mode choke front: 0.22uF / MKP-X2-250VAC / 275VAC (GS-L)
   2. Common-mode choke: 0.1uF / MKP-X2-250VAC / 275VAC (GS-L)
   General two-stage X capacitor, the former level with 0.47uF, the second level with 0.1uF; single stage with 0.47uF. There is no convenient method of calculation. (The size of the capacitor capacity and the power of the power is not directly related)

Y capacitor design guidelines for switching power supplies:
   Earth = PGND (or CHGND)
   Reference AD1118 Y Capacitance Placement Principle:
   1. Mains input L / N line to the earth: (2 472 / 250V Y2)
   2. Mains after a common-mode choke after the two lines of the earth: (2 472 / 250V)
   3. Rectifier bridge output of the low-voltage side (transformer primary low-voltage side) of the earth: (1 222 / 250V)
   4.6 group of low-voltage direct-current output 88V1 to the earth: (each 1 103 / 1KV Y1)
   5.6 group of low-voltage output auxiliary power AGND (transformer secondary low-voltage side) of the earth: (share a 103 / 1KV Y1)
   6. Transformer primary low-voltage side of the transformer secondary low-voltage side: (share a 103 / 1kV Y1)

Refer to the design of the AD1043:
   1. Mains input L / N line to the earth: (2 222 / 250V Y2)
   2. Mains after two common-mode chokes on the earth: (2 472 / 250V Y2)

Reference Kang Shu electronic design:
   1. Mains input L / N line to the earth: (2 102 / 250V Y2)
   2. Mains after two common-mode chokes after the two lines of the earth: (2 102 / 250V Y2)
   3. Rectifier bridge output of the low-voltage side (transformer primary low-voltage side) of the earth: (1 332 / 250V Y2)
   4.12V low voltage DC output to the earth: (1 223 / 1KV DISC Y1)
   5. Transformer primary low-voltage side of the transformer secondary low-voltage side: (222 / 250V Y1)

Reference to the design of MW S-145-12:
   1. Mains after two common-mode chokes on the earth: (2 222 / 2kV Y1)
   2. Rectifier bridge output of the low-voltage side (transformer primary low-voltage side) of the earth: (1 222 / 2kV Y1)
   3.12V Low-voltage DC output GND to the earth: (1 103 / 1KV Y1)

Reference to the design of the MW S-200-12:
   1. Mains input L / N line to the earth: (2 472 / 250V Y2 not on)
   2. Mains after two common-mode chokes on the earth: (2 472 / 250V Y2)
   2. Rectifier bridge output of the low-voltage side (transformer primary low-voltage side) of the earth: (1 222 / 250V Y2)
   3.PFC output high voltage side of the transformer primary: (1 103 / 2kV Y1)
   4.12V low voltage DC output to the earth: (1 103 / 1KV Y1)
   5.12V Low-voltage DC output GND to the earth: (1 203 / 1KV Y1)

According to the above description, Y capacitor design rules are as follows: (can be properly selected)
   1. Mains input L / N line to the earth: (2 222 / 250V Y2)
   2. Mains after two common-mode chokes on the earth: (2 222 / 250V Y2)
   3. Rectifier bridge output of the low-voltage side (transformer primary low-voltage side) of the earth: (1 222 / 250V Y2)
   4. Transformer primary low-voltage side of the transformer secondary low-voltage side: (share a 103 / 1kV Y1)
   4. Low-voltage side of the DC output to the earth: (1 103 / 1KV)
   6. Low-voltage output side of the GND to the earth: (1 103 / 1KV)

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