Switching power supply electromagnetic compatibility test technology
(1) Measuring instruments
Considering the characteristics of switch mode power supplies, they are all composed of electronic circuits. During steady-state operation, the power supply does not generate sparks, arcs, or gas discharges, nor does it produce the unique "clicking" noise interference of household appliances. Only periodic voltage, current, and their harmonics are generated. Therefore, it is recommended to use a spectrum analyzer. Within the testing frequency range specified by the standard, it is sufficient to use a spectrum analyzer with a frequency range of 10kHz to 1000MHz or higher.
(2) The LISN access method is the same as before
(3) Antenna
The use of a Giecht transverse electromagnetic wave chamber (GTEM chamber) with upper and lower bottom plates and internal partitions functions similarly to a receiving antenna, so the receiving antenna used in the final test configuration is eliminated.
(4) Test site
Due to the small size of the switch mode power supply, it is expected to be accommodated in the recently developed Giecht transverse electromagnetic wave chamber (GTEM chamber), and the operating frequency range of the chamber is also sufficient to meet the needs of general testing.
Although this testing site has not been recognized in CISPRll and GB4824 standards, the TEM chamber method has been adopted as the standard test method for testing the radiated emission characteristics of electronic/electrical components/modules in the CISPR25 standard for testing the radio interference characteristics of automotive electronic/electrical components. The GTEM cell is a development of the TEM cell, with a large experimental space and no contradiction with the frequency range used, thus it has been increasingly applied.
(5) Testing method
For radiation testing between 10kHz and 1000MHz, GTEM chambers and spectrometers are used for testing. To ensure the repeatability and comparability of the test results, the position where the EUT is placed for each test should be fixed.
Regarding the polarization testing issue: Due to the fixed position between the partition inside the chamber and the upper and lower bottom plates, it can only be achieved by rotating the EUT so that several faces of the EUT face the partition in sequence.
