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Switching power supply must follow the principle of high-frequency circuit wiring when designing PCB layout
The switching power supply works in high frequency and high pulse state, which belongs to a special kind of analog circuit. The principle of high-frequency PCB circuit wiring must be followed when PCB layout.
1. Layout: The pulse voltage connection should be as short as possible, in which the input switch tube is connected to the transformer, and the output transformer is connected to the rectifier tube. The pulse current loop is as small as possible, as the input filter capacitor is positive to the transformer to the switch tube and the return capacitor is negative. The output part of the transformer output terminal to the rectifier tube to the output inductor to the output capacitor return to the transformer circuit X capacitor should be as close as possible to the input terminal of the switching power supply, the input line should be avoided parallel to other circuits, should be avoided. The Y capacitor should be placed on the chassis ground terminal or FG connection end. Keep a certain distance between the common touch induction and the transformer to avoid magnetic coupling. If it is not easy to handle, add a shield between the common-mode inductor and the transformer. The above items have a greater impact on the EMC performance of the switching power supply.
Generally, two output capacitors can be used, one close to the rectifier tube and the other close to the output terminal, which can affect the output ripple index of the power supply. The parallel effect of two small-capacity capacitors should be better than one large-capacity capacitor. The heating device must be kept a certain distance from the electrolytic capacitor to extend the life of the whole machine. The electrolytic capacitor is the key to the life of the switching power supply. For example, the transformer, power tube, and high-power resistor must be kept away from the electrolysis, and there must be a space for heat dissipation between the electrolysis., It can be placed in the air inlet if conditions permit.
Attention should be paid to the control part: the connection of the high impedance weak signal circuit should be as short as possible, such as the sampling feedback loop, and the current sampling signal circuit, especially the current control circuit, should be avoided during processing. Accident.
The above is the introduction of the principle of high-frequency PCB circuit wiring when the switching power supply design PCB layout. Ipcb also provides PCB manufacturers and PCB manufacturing technology.
