The first place to talk about Y capacitors
Y capacitor common pitch is 10mm, leaving the pad in the middle of the gap is 8mm, the middle is best not to take the line;
Do not take the middle line, of course, is where to place upper and lower plates, left for strong power, the right for the weak, the strong electric power terminal GND is the best, the best weak-side GND GND pin near the transformer;
For input ground, there are three Y, is a luxurious place;
Y capacitors connected to GND terminal adapter based on "no Y capacitor power" design reference, then back capacitor is the same reason I want it.
Difficult to see that this figure should be the primary current loop is the shortest , and we can refer to , more suitable for 5 ~ 40W power adapter.
Beyond high-powered , follow or two points:
1, the main current loop is best not to use the jumper , the jumper must be used if you need to add on the casing above the jumper if you have components , then , need to glue points
2 , in the limited flat area where a safe distance as bold and , if not bold , you need to add auxiliary solder layer
Point 3 , the signal ground and power ground
Take flyback PWM control , the distinction between the two places is actually to let PWM chip from interference , that is, the chip needs to auxiliary power , the ground should be connected to the auxiliary on -chip power supply filter capacitor , and should not be connected to the large the capacitor ;
Half-bridge or full-bridge and other , if the control chip and non-isolated input , then the same with the flyback , if it is isolated ( for example, some have standby auxiliary power ) , you should add 1 to 3 on the power supply capacitor 0.1uF .
4 , the input LC filter
Elaborate here only say for those 85 ~ 264V wide voltage switching power supply
1, input X capacitor package size, because X capacitor size have been standardized , the time when the certification if you need to increase the X capacitor , if the package is small, it is very troublesome , so the X capacitor must do in the beginning of the design preparation, rather big point , do not small , can save money in other places where the province do not ;
2 , varistors, varistor some without jacket , and with a jacket size to a larger size , so as with the X capacitor , need to set aside more room ;
3, L, common mode and differential mode , the design needs to verify whether the differential mode for low-power generally do not increase ;
4, NTC / PTC, a negative temperature coefficient, a is a positive temperature coefficient, two of the inrush current prevention effect are
Put a figure .
1 ) AC power line , two lines before the fuse minimum safe distance of not less than 6MM, two-wire and chassis ground within the machine or the minimum safety distance of not less than 8MM.
2 ) fuse after traces requirements: zero , FireWire minimum creepage distance of not less than 3MM.
3 ) The minimum area of low pressure in the high pressure zone and creepage distance not less than 8MM, less than or equal 8MM 8MM 's . Shall open 2MM security slot.
4 ) high-pressure high-pressure warning area should have silkscreen logo , that triangle exclamation point , including ; high pressure area must live with silk box, box section shall be not less than 3MM wide screen .
5 ) The minimum safe distance between the positive and negative high voltage rectifier filter is not less than 2MM
