source:Other information release time:2023-06-28 Hits: Popular:PCB Assembly company
PCB radiated EMI interference can come from a non directional emission source and an unintentionally formed antenna. Conductive EMI interference can also come from a radiation EMI interference source or be caused by some circuit board components. Once your circuit board receives conductive interference, it will reside in the PCB trace of the application circuit. Some common sources of radiated EMI interference include components discussed in previous articles, as well as switch mode power supplies, connecting wires, and switch or clock networks on PCB boards.
Conductive EMI interference is the result of the normal operation of switching circuits and the combined action of parasitic capacitors and inductors. Figure 1 shows some EMI interference sources that may enter your PCB trace. Vemi1 originates from switching networks, such as clock signals or digital signal traces. The coupling mode of these interference sources is through parasitic capacitance between traces. These signals bring current spikes into adjacent PCB traces. Similarly, Vemi2 originates from a switching network or from an antenna on a PCB. The coupling mode of these interference sources is through parasitic inductance between line traces. This signal introduces voltage disturbances into adjacent PCB traces. Every three EMI sources come from adjacent wires within the cable. The signals propagating along these wires can generate crosstalk effects.Solar Energy System
Switching power supply generates Vemi4. The interference generated by the switching power supply resides on the power line trace and appears in the form of a Vemi4 signal.
During normal operation, switching mode power supply (SMPS) circuits provide opportunities for the formation of conductive EMI. The "on" and "off" switching operations within these power sources will generate strong discontinuous currents. These discontinuous currents exist at the input end of the buck converter, the output end of the boost converter, and the input and output ends of the flyback and buck topology. The discontinuous current caused by switch action will generate voltage ripples, which propagate to other parts of the system through PCB traces. The input and/or output voltage ripple caused by SMPS can endanger the operation of the load circuit. Figure 2 shows an example of the frequency composition of a DC/DC buck SMPS input operating at 2 MHz. The Fundamental frequency composition range of SMPS conducted interference is 90 – 100 MHz
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