Principle of artificial power supply network
①The filter consists of inductor L1 and capacitors C1, C2, whose function is to prevent RF interference signals from being transmitted from the power supply to the equipment under test, and at the same time, to prevent the interference signals from the equipment under test from entering the power supply, thus providing isolation.
②Isolator rhyming capacitor C3 is used to isolate the power supply voltage and prevent it from adding to the measurement side, for different interference frequency selection of different capacitors. Thus, the RF interference signal can be coupled to the measurement/signal end.
③Controller is accomplished by a push-button switch, which controls the measurement at the time of measurement. Among them, the "line selection" switch controls the "ground" and "between the lines", which is selected according to the measurement needs during the measurement. Another set of switches controls the frequency range and the attenuator, and the frequency range buttons are selected according to different interference frequencies during measurement. Press the attenuator button before measurement, when measuring the interference signal, in general, should not use the attenuator, only in the interference signal is too large, and more than in the disturbed field strength meter range can be used only when the 20 dB attenuator.
④20 dB attenuator by the "pedestal" network, its characteristic impedance is 50 Ω, in the measurement of interference signals, the attenuator on the test instrumentation to provide security protection circuitry to prevent interference pulses due to the large and burn equipment. Therefore, before the test must be the attenuator down, when the interference signal in the interference field strength measurement instrument has enough readings, it should be disconnected from the attenuator so that the signal through, so that the attenuator can be removed from the introduction of the error, thereby improving the measurement accuracy.
5 analog hand in order to reproduce the effect of the user's hand, the ungrounded hand-held electrical equipment for interference measurements should be connected to the analog hand for measurement. The measurement circuit adopts the circuit recommended in publication CISPRl4, and the measurement method also adopts the method recommended in publication CISPRl4.
Features of the artificial power network
1, you can manually select the test phase line, can also be automatically switched through the software;
2, the frequency range of 9kHz -30MHz, can be used for DC -63Hz power conduction test;
3, in line with the CISPR16-1 standard, can be tested in accordance with EN, CISPR, FCC, ETS, VCCI and VDE standards;
4, built-in ammeter, can be in accordance with the requirements of CISPR 14-1 switching operation and EUT absorbed current measurements, for the measurement of intermittent interference and the matching of the clicks sound analyzer;
Artificial Power Supply Classification of Artificial Power Networks
There are V-type and △-type artificial power networks; V-type artificial power networks are used to measure asymmetrical voltages, and △-type artificial power networks are used to measure symmetrical and asymmetrical voltages.
Symmetrical Voltage: the radio frequency harassment voltage between the two wires, often referred to as the differential mode voltage
Unsymmetrical Voltage: the voltage between the wires or terminals and the specified ground reference
Unsymmetrical Voltage: the voltage between the two wires or terminals and the specified ground reference
Asymmetrical Voltage Voltage: The RF voltage between the electrical midpoint of two wires and the reference ground, also known as the **** mode voltage
Artificial power supply network role
1, for the 50Hz utility to provide access. Because the inductance on this side of the grid is very small (50μH), not enough to form a large impedance at the utility frequency, the utility can be unimpeded to provide power for the test article, while the capacitance on the side of the grid (1μF) can further attenuate the interference signal from the grid.
2, isolate the RF electromagnetic harassment generated by the work of the switching power supply under test (measurement frequency of 0.15MHz ~ 30MHz). Utilizing the high impedance of the network inductor under RF, it can prevent the RF nuisance signals generated by the switching power supply from entering the power grid.
3. Through the coupling capacitor (0.1μF) near the side of the switching power supply to transfer the RFI signal generated by the switching power supply into the receiver.
4. Stabilize the impedance. As the impedance of each power grid is different, making the switching power supply nuisance voltage values also vary. For this reason, the standard specifies a uniform impedance (50Ω) to facilitate the intercomparison of test results.
Requirements for artificial power supply networks
The purpose of using an artificial power supply network is to connect the network between the receiver power plug and the power supply, so that between the two ends of the receiver power supply, there is a specific high-frequency impedance, and at the same time isolate the power supply in order to use an unbalanced input interference measurement instrument to measure the symmetrical interference voltage and the asymmetrical interference voltage.
The network shall also include a filter section to filter out RF interference present in the power supply system. If necessary, an auxiliary filter should also be added.
The impedance of the filter should be high enough in the frequency range being measured so that it does not affect the impedance characteristics of the network. It is required that the impedance between the ends of the power supply AB as well as the AB ends connected