Application of MATLAB-PSPICE Co-Simulation in EMI analysis

Software simulations are key in circuit designs. They allow the designer to see the outputs of his or her design early and gives freedom to modify the circuit at the design stage if modification is required. In electromagnetic Interference (EMI) analysis, software have a very great role to predict the EMI emissions of a converter or other devices, so that the Electromagnetic Compatibility(EMC) of the device will be assessed at the design stage and avoid failure of products since so many EMC regulations are being applied.

Among the available commercial software, the application of MATLAB and PSpice software virtually will be discussed in this blog. MATLAB is a very powerful software. It allows the user to design different control schemes and also offer different signal visualization options. Therefore, its use in the electrical design is vital. In the other side PSpice allows the user to design a circuit by considering datasheet information and paracitic elements by downloading and easily integrating different circuit component PSpice models from manufacturers to the PSpice software library. This allows to design a circuit which perform nearly practical.

Recently the use of the two powerful simulation softwares (MATLAB and PSpice) virtually is introduced in PSpice using Co-simulation feature. The Co-simulation feature allows to design a circuit as close as practical representations in PSpice software (with all paracitic elements and datasheet information) and use MATLAB SIMULINK for signal visualization and control system implementation. This has a very great advantage specially in EMI analysis, since both the accurate modelling of devices is required to accurately predict the EMI emissions and alternative control schemes are required to reduce the EMI emissions.

A simple set-up is presented in this blog to show the application of MATLAB-PSpice cosimulation in the analysis of the output voltage harmonics of the boost DC-DC converter. First the boost converter is modelled in PSpice by considering non ideal circuit parameters i.e. non ideal MOSFETS, diodes and parasitic elements as shown in Fig.1. Next the cosimulation set up is implemented in SIMULINK as shown in Fig.2 

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Figure 1. Circuit model of boost converter in PSpice including parasitics

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Figure 2. Cosimulation set-up in SIMULINK.

The PSpice system block in Fig.2 represents all the circuits modelled in PSpice Software. When double clicking (left click) on this block, it gives the options as shown in Fig.3., which allows to choose the desired input and output parameters. The spectrum analyzer block in the right side has many useful features for EMI analysis i.e. it is possible to set resolution bandwidth and other parameters, to see the frequency spectrum. 

In this set-up first the output voltage of the boost converter is compared when the circuit is run in PSpice (as shown in Fig.4) and in SIMULINK Cosimulation (as shown in Fig.5). As it can be seen clearly, the output voltage wave form is the same in both cases (in Pspice and Cosimulation) which proofs that one can use cosimulation to run nearly practical simulations as that of PSpice software. Next the output voltage harmonics of the DC-DC converter is analyzed. The spectrum Analyzer displays the output voltage harmonics with peaks at discrete multiple of the switching frequency (in this case the switching frequency is 35KHz) as shown in Fig.6. 

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Figure 3. Options in PSpice System block to choose the input/output parameters.

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Figure 4. Output voltage of the boost converter modelled in PSpice software.

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Figure 5. output voltage of the boost converter when it is run in SIMULINK Cosimulation.

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Figure 6. Frequency spectrum of the output voltage harmonics.

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