An Efficient and Accurate Time Step Control Method for Power Device Transient Simulation Utilizing Dominant Time Constant Approximation

An accurate metric for the time step control in the power device transient simulation is proposed. This metric contains an exponential term of the dominant time constant of the whole device structure derived from the matrix exponential term of the linearized device state equation. The proposed metric allows larger time step widths than the conventional metric of second order approximation of the local truncation error. It focuses on the dominant part of the transient response and its truncation error approximation is more accurate. In the transient device simulation, box integration method and backward Euler method are used for spatial and temporal discretization, respectively. The discretized nonlinear device equations are solved by using Newton iteration whose initial guess is given by the approximated solution of the linearized device state equation by using the dominant time constant. Total calculation time of the transient simulation of a silicon power DMOSFET by using the proposed method decreases down to 27% of that by the conventional method with keeping the current accuracy of the dominant transient response.