Recently, there was a notice issued by China Consumers Association about the failure of computer radiation harassment to exceed the standard, which easily affected the equipment in the power grid and eventually caused the computer to crash. The main reason is that the radiation disturbance of computer power terminals exceeds the limits set by national standards, and such disturbances may interfere with the normal operation of other electronic devices, especially high-sensitivity electronic devices. With the development of science and technology, more and more digital and high-speed electrical and electronic equipment are widely used in various fields of society. While promoting social development, electromagnetic interference generated along with the application of electrical and electronic equipment is also given to society. Brought electromagnetic pollution problems. While electromagnetic pollution and water pollution, air pollution is called the three major sources of pollution in today's society. With the increasingly prominent electromagnetic interference problem, the International Radio Interference Special Committee (CISPR) has issued CISPR-16, CISPR-15, and the European Standards Committee has issued standards such as EN55015 and EN55022. These measures and standards are designed to regulate electromagnetic interference limits and other specifications for point electronics to reduce the social problems associated with electromagnetic interference.
Electromagnetic interference EMI (ElectromagneTIc Interference), there are two types of conducted interference and radiated interference. Conducted interference refers to the coupling (interference) of signals on one electrical network to another electrical network through a conductive medium. Radiated interference refers to an interference source that couples (interferes) its signal to another electrical network through space. In high-speed PCB and system design, high-frequency signal lines, integrated circuit pins, various types of connectors, etc. may become radiation interference sources with antenna characteristics, which can emit electromagnetic waves and affect other systems or other subsystems in the system. normal work. As we all know, EMC's testing target is electrical and electronic equipment, and lighting equipment as an important part of it, naturally there are corresponding constraints. For example, the FCC certification in the United States and the CE certification in the European Union have proposed related test items for LED lighting equipment. When talking about electromagnetic interference, there are generally two sources of interference; one is conducted interference, mainly because the interference signals generated by electronic devices interfere with each other through conductive media or public power lines, and FCC certified conducted interference scans for LED lamps The test frequency starts from 0.15MHz to the end of 30MHz. The conducted interference scan test frequency in CE certification starts from 9KHz to 30MHz. Another type of interference is radiation interference, which mainly means that the interference signal generated by the electronic device transmits the interference signal to another electric network or electronic device through spatial coupling. The FCC certification space radiation interference scanning test frequency of the LED lamp starts from 30MHz to 1GHz. At the end, the space radiation interference scanning test frequency in CE certification starts from 30KHz to the end of 300MHz.
In the lighting industry, there are two methods for testing EMI in the 9KHz-30MHz band. One is to use Antenna (antenna) and EMI receiver, which are based on CISPR15, EN55015, GB17743. For low-frequency magnetic field devices that may be generated by lighting fixtures, the three-loop antenna specified in CISPR16-1-4 is required to measure the low-frequency magnetic field radiated disturbance. It is mainly tested by a three-ring antenna and an EMI receiver. The test is carried out in a shielded room. Note: The three-loop antenna converts the low-frequency magnetic field components in the X direction, Y direction and Z direction into RF signals, and transmits them to the EMI receiver through the coaxial switch three channels for measurement; the other is to use the LISN test method, which is required for testing. It is performed by EMI receiver + artificial power network + LISN and test software. The conducted disturbance test system is used to measure the disturbance generated by the power port of the lamp and the luminaire under normal working conditions. The LISN realizes the isolation, sampling, impedance matching of the RF signal, and provides the electrical path for the EUT, and the EMI receiver measures the RF signal. And finally analyzed, processed and judged by EMI testing software. The test should be carried out in a shielded room.
At the same time, the CDN method was adopted in the EMI test in the 9 kHz-300 MHz band. Another method of testing the radiated electric field disturbance of the illuminating device, namely the CDN common mode terminal voltage method, is also provided in the CISPR 15, EN55015 and GB17743 standards. Adopt CDN method, mainly including EMI receiver, CDN and attenuator. The test can be carried out in a shielded room.
For the EMI test, the International Special Committee on Radio Interference (CISPR) has issued CISPR-16 radio interference and anti-interference measuring instrument specifications. For the lighting industry, the International Radio Interference Special Committee also proposed CISPR-15 electronic lighting and related equipment radio interference. Characteristic limits and measurement methods, and countries have also introduced various types of EMI lighting inspection specifications according to their national conditions, such as EN55015-2007 from the European Union and GB17743-1999 from China. For EU countries, the EN55015 standard (citing CISPR-15) is suitable for traditional lighting equipment with luminaire frequencies exceeding 100 Hz, such as incandescent lamps, fluorescent lamps, self-rectifying energy-saving lamps, etc. Usually the frequency of such equipment does not exceed 30 MHz, and the corresponding radiation interference limits are shown in Table 1. However, for the emerging LED lighting industry, the frequency usually exceeds 30MHz. It is clearly stated in the CE certification that the scanning frequency is from 30MHz to 300MHz.
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