How can I remove this warning:Estimated channel modulation for data extrapolation must be greater than zero. Use linear extrapolation.

Hello, when simulating this N-Channel MOSFET model, an extrapolation error appears: Estimated channel modulation for data extrapolation must be greater than zero. Use linear extrapolation

I have checked the lookup tables, and they are correct. How can I perform linear extrapolation in Simulink?

Regards, and thank you very much.

Answer 1

[MULI]

Hi @Ignacio,

I understand that you are facing an extrapolation error while simulating N Channel MOSFET model.

• The issue arises because the MOSFET simulation relies on a lookup table (3D, temperature-dependent) for interpolating data such as Ids (drain-source current) versus Vds and Vgs
• When the data in the lookup table is not smooth or contains any discontinuities, the simulator encounters challenges during extrapolation or interpolation, leading to this warning.
• To resolve this issue, make sure that the tabulated drain-source currents Ids are smooth and differentiable across all dimensions (Vds, Vgs and temperature).
• The “smoothdata” function removes noise and smoothens transitions in your data by applying techniques like moving averages. You can refer to the below documentation link for more information on this function: https://www.mathworks.com/help/releases/R2024a/matlab/ref/smoothdata.html
• You can also plot the lookup table data (Ids Vs Vds and Vgs) before and after smoothing to ensure gradual transitions.

[Ignacio]

Hi,

I have used the smoothdata function, but now the warning is :

At time 1.911928e-09, one or more assertions are triggered. Tabulated drain-source currents, Ids(Vgs,Vds,T) has resulted in a current in opposition to the applied voltage. Consider modifying the tabulated data to ensure that all operating points are contained within the data, and that the signs of the currents and voltages are consistent. Clipping the current to zero. The assertion comes from:

Block path: MSCSM170DUM039AG_Simulink_Model/Sic Mosfet

Assert location:

o (location information is protected)

o (location information is protected)

Ungroup 19 similar

Component:Simulink | Category:Model warning

[MULI]

Hi @Ignacio,

• Ensure that the tabulated data for Ids(Vgs,Vds,T) is accurate and covers all the operating points of your simulation.
• Check for any inconsistencies in the sign or magnitude of the current values relative to the applied voltages.
• If the simulation operates outside the range of your tabulated data, consider expanding the data range to include these points