Switch mode power supply pulse group suppression
Switching mode power supply can be used individually as a piece of electronic equipment, but more often switching mode power supply is used as a component with each piece of electronic equipment. Therefore, the switching power supply has its own special characteristics, and the EMC performance of the switching power supply is related to the normal use of each piece of electronic equipment. Because of this, the electromagnetic compatibility of an electronic device is good or bad, the first thing to look at the switching power supply electromagnetic compatibility performance is good or bad.
① Pulse group suppression of switching power supply
In terms of switching power supply, leaving aside the input filter of switching power supply, the suppression effect of switching power supply line itself on the pulse group interference is really very low, the reason is mainly because the essence of the pulse group interference is a high-frequency common-mode interference, and the filter capacitance in the line of switching power supply is aimed at the suppression of low-frequency differential-mode interference and the setting of electrolytic capacitors for the ripple suppression of the switching power supply itself is not enough, not to mention the harmonic components. The electrolytic capacitors are not enough to suppress the ripple of the switching power supply itself, not to mention the suppression effect on the harmonic components of the pulse group interference of more than 60MHz. Therefore, when observing the pulse group waveforms of the input and output of the switching power supply with an oscilloscope, there is no obvious attenuation of the interference.
Considering that pulse group interference is common mode in nature.
As far as the switching power supply is concerned, the use of input filters is an important measure for the switching power supply to suppress the ** pulse group interference.
Secondly, the design of the high-frequency transformer in the switching power supply line, especially the use of shielding measures, has a certain inhibiting effect on the pulse group interference.
Again, the switching power supply primary circuit and the secondary circuit between the cross-connect capacitance, can be from the primary circuit into the secondary circuit of the common-mode interference return to the primary circuit to provide a path, on the
It also has a certain suppression effect on the pulse group interference.
Finally, adding a common mode filter circuit (common mode inductor and common mode capacitor) to the output of the switching power supply can also play a role in suppressing pulse group interference.
In addition, the switching power supply line itself has no inhibiting effect on the pulse group interference, but if the switching power supply line layout is not good, it can aggravate the invasion of the pulse group interference to the switching power supply. In particular, the nature of the pulse group interference is a composite of conducted and radiated interference, even if the input filter is used to suppress the conducted interference components, but the existence of radiated interference around the transmission line still exists, can still penetrate through the switching power supply ** layout (switching power supply primary or secondary circuit layout is too open, the formation of the "large ring antenna (the primary or secondary circuit layout of the switching power supply is too open, forming a "big loop antenna"), sensing the radiation component of the pulse group interference, and thus affecting the anti-jamming performance of the whole equipment.
②Pulse group suppression of switching power supplies, and points to note in pulse group tests of equipment power supplies
When the power supply side of the electronic equipment pulse group immunity test, we should pay attention to the power supply of the anti-interference performance of the equipment, but we should not forget that the essence of the pulse group interference is the fact that the conductive and radiated interference composite, so the power supply part of the measures taken after the failure to pass the test, we should think about it, it will not be other ways to make the interference into the equipment, caused by Equipment power line pulse group immunity test failed the false impression.
