Abstract: A method using a computer program for numerically simulating an electrical circuit, in a computer system, having a plurality of nodes and a plurality of circuit elements. A circuit description of the electrical circuit together with tstart and tstop times of a time interval are read into the computer system with at least one input value of the electrical circuit for at least one specific time in the time interval. Voltage values and/or current values at the nodes of the electrical circuit are calculated in the selected time interval using table-based models for the circuit elements. From these voltage values and/or current values, a simulation time tn in the time interval [tstart; tstop] under consideration is selected at which system equations are determined describing the circuit elements by physical formulas and dynamic effects of the elements are described by differential equations.

Abstract: A simulation is carried out in a computer system in which a circuit description of an electrical circuit having a plurality of nodes and a plurality of circuit elements is present. First, voltage values and/or current values at the nodes of the electrical circuit are calculated in a selected time interval using table-based models for the circuit elements. From these voltage values and/or current values, simulation times tn are determined in the time interval [tstart; tstop] under consideration at which system equations of the circuit description are determined and calculated. These system equations describe the circuit elements using physical formulas and do not describe the dynamic effects of the circuit elements using differential equations.

Abstract: A simulation apparatus for a system has at least one analog and at least one digital element, in particular an electronic system. The simulation apparatus has an apparatus for solving differential algebraic equation systems based on a one-step method for automatically producing a data record with a simulation event. A detector is provided for automatically determining that a threshold value has been exceeded within one time step in the simulation event. The detector determines whether the simulation event is greater at the end of the respective time step than a predetermined tolerance of the respective threshold value. The detector automatically reduces the time step if the tolerance is exceeded, until the tolerance is undershot, in order to determine the point at which the threshold value is exceeded. A transformation device uses values calculated previously for this purpose. It is thus possible to simulate mixed digital-analog systems particularly efficiently.

Abstract: A system relationship function is defined which describes the “external response” of a set of coupled linear components in an electrical circuit. A differential equation system is defined for the set of coupled linear components, and a predetermined number of eigenvalues are determined for the homogeneous differential equation system. An error is indicated for the eigenvalues which is caused by ignoring those eigenvalues which have not been determined within the homogeneous differential equation system. If the error is less than a given setpoint error, then the system relationship function is produced from the differential equations which are described by the determined eigenvalues. If the error is greater than the limit, then further eigenvalues are determined, for which an error is in turn determined. This method is continued iteratively until the error is less than the limit.