How to solve the electromagnetic noise generated by the switching power supply?

Issue Time:2006-09-01
Switching power supplies are widely used in electronic equipment of all walks of life because of their small size, light weight and high efficiency. However, when the switching power supply is in working condition, it will generate strong electromagnetic noise, which will cause instability to its own work. Then, how to solve this situation? Shenzhen Lianyunda Xiaobian believes that we can start from the following two aspects.

一.EMI problem

The EMI problem of switching power supplies is reflected in radiation and conduction, which is the main electromagnetic compatibility problem of switching power supplies.

1. The radiation problem of the switching power supply is solved by: 
(1)adjusting the filter circuit of the input terminal, such as increasing or changing the common mode inductance of the input terminal; 
(2)changing the MOS drive resistance; 
(3)adjusting the RCD buffer circuit; 
(4)outputting a common mode inductor; 
(5)MOSFET parallel connection A small absorption circuit; 
(6)switching tube loop is as small as possible; 
(7)transformer, output diode, output smoothing electrolytic capacitor constitutes the circuit loop as small as possible. 
(8)can be magnetic beads on the rectifier tube; 
(9)adjust the absorption circuit parameters of the rectifier tube; 
(10)can change the impedance of a secondary side across the Y capacitor branch; 
(11)transformer copper foil.

2, switching power supply conduction problem solution: 
(1)adjust the input filter circuit, such as differential mode interference can adjust X capacitor, add differential mode inductance, adjust the differential mode inductance; for common mode interference can adjust the common mode inductance, add Y Capacitor; 
(2)change MOS drive resistance; 
(3)adjust the position of the Y capacitor between the secondary side and the parameter value; 
(4)switch tube loop as small as possible; 
(5)transformer, output diode, output smoothing electrolytic capacitor composed of circuit ring as much as possible small. 
(6)output terminal connected to a common mode inductor; 
(7)adjust the absorption circuit parameters of the rectifier tube;

二.EMS problem

The EMS problem of switching power supply is mainly harmonics and surges, and the EFT, radiation immunity, and conducted immunity are generally matched with the whole system. Once these parts have problems, they are treated as system-level problems. of.

1. Switching power supply harmonics: 
(1)Add PFC correction circuit; 
(2)Add power filter.

2, surge: 
(1)increase the thermistor; 
(2)increase the varistor; 
(3)increase the air discharge tube.

Switching power supply as the power supply center of the whole system, it is very important to choose the right manufacturer. Shenzhen Lianyunda Electronics Co., Ltd. specializes in research and development of switching power supply, factory direct sales, focus on details, finely crafted, stable performance, brand quality is guaranteed.

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