Electromagnetic compatibility test technology of switching power supply
(1) Measuring instruments
The jamming receiver with quasi-peak and average detectors shall be used, and its performance shall meet the requirements of CISPRL 6-1 or the corresponding national standard GB/T6113.1 (specifications for radio disturbance and immunity measuring apparatus). In the frequency range involved in the standard, two jamming receivers with different frequency bands are generally used, which are 10 kHz ~ 30 MHz and 30 ~ 1000 MHz respectively.
(2) Linear impedance stabilization network
Linear impedance stabilization network (LISN) is also called artificial power supply network. LISN(V-type network) with impedance of 50Ω/50μH should be adopted when conducting interference voltage/current test at power supply terminal, and its characteristics should meet the requirements of CISPRL 6-1 and GB/T6113.1. Connecting LISN has two functions: first, it provides a standard linear impedance for the power input port of EUT at high frequency harmonics, so that when other devices connected to the same power supply change, it will not affect the power input impedance of EUT; Secondly, LISN can filter the EMI from the grid power supply and provide a "clean" grid AC power supply for the switching power supply, which will not affect the measurement results of the conducted interference to EUT itself.
(3) Antenna
A shielded loop antenna is used in the frequency band of 10 kHz ~ 30 MHz. Balanced dipole antenna is used in the frequency band of 30 ~ 1000 MHz.
(4) Test site
There are generally two types of laboratories for EMC testing: one is a comprehensive design and testing laboratory or testing center that has been approved by EMC authorities and certified by the quality system, and has legal testing qualifications. It includes shielding room for conducting interference, conducting sensitivity and electrostatic discharge sensitivity test, anechoic shielding room for conducting radiation sensitivity test, open space for conducting radiation emission test and fully equipped test and control instruments and equipment. The other type is an EMC laboratory with certain testing function established according to the actual needs and funds of the unit. Compared with the testing center, this kind of testing laboratory is small in scale and low in cost, and it is mainly suitable for pre-compatibility testing and EMC evaluation, that is, to make products have the means of self-testing and evaluation before EMC certification.
