BCI simulation model
Large current injection is a non-intrusive, conductive sensitivity test method. Electromagnetic interference is injected into the cable through inductive coupling and transmitted to the equipment under test.
The model includes a line impedance stability network (LISN), a parameterized injection clamp model and two power lines for the DUT.
The 3D model is as follows:
The cable is placed on a 5cm thick dielectric plate (polystyrene). Zmin is set as the electrical boundary simulation ground plane, and Xmin and Xmax are also set as the electrical boundary to set the cable port. In addition, the model also includes an injection clamp port for exciting interference signals.
According to the test standard, the simulation frequency range of the model is set to 1 MHz to 400 MHz.
The disturbance level of BCI test is specified in ISO 11452-4:
Generally, in order to obtain the required interference, the injection clamp and calibration device are used to calibrate the signal source before the BCI test. This process can be realized by simulation. The good news is that in the BCI model of CST, this step can be omitted. The required excitation signal is directly placed in the model and can be found in the navigation tree.
This signal is a level 1 excitation signal. The current generated on the fixture during calibration is as follows:
If the disturbance level needs to be adjusted, it can be realized by post-processing the above excitation signals.
Run the AC task included in the model to obtain the voltage and current results of two power lines and LISIN terminals under level 1 interference. The circuit model also contains LISN sub-circuits. For those who are interested in this, please review the simulation example 115: Introduction to the “doll” modeling (sub-circuit) function of circuit simulation.
Simulation case
For BCI simulation, the complete simulation process can be divided into three parts: simulating the BCI injection clamp, simulating the PCB board, and combining the BCI injection clamp and PCB in the circuit to obtain the current and voltage values during the large current injection. This can save simulation time, and only part of the simulation needs to be changed to modify the model.
In the circuit model, BCI model and PCB model are combined on the schematic diagram, and probes can be added at the chip end and connector end to simulate the voltage and current induced during interference injection.
The simulation results are shown in the figure below. In this example, the influence of decoupling capacitance on induced voltage and current is also compared and analyzed:
In addition, we can also set a field monitor to directly observe the surface current and field distribution on the PCB.
Summary:
CST 2023 provides BCI current injection clamp model and excitation signal source.
BCI model and PCB model can be combined on schematic diagram to effectively simulate BCI test.
