The increasing complexity of Power Electronics circuits means that several prototyping phases are required to guarantee that specifications are fulfilled. This has an impact on design cycle times and costs. Most of the redesigns in this area are due to the difficulty to foresee the electromagnetic behaviour of circuits and their compliance with Electro-magnetic Compatibility (EMC) regulations.
The intensive use of magnetic components poses particular modelling problems for the simulation, especially in high frequency applications like power supply systems, with high currents and voltages. High frequency effects in core and windings need to be modelled accurately to predict power losses, and to compute voltage and current wave forms. Parasitic effects from the layout become more critical because of pulsating voltages and currents at high frequencies. More accurate models for magnetic components and for layout parasitics are also needed for simulation of Electromagnetic Interference (EMI), and for simulation of the EMC measurement procedure already during the architectural design of Power Electronics Systems.
POWERCAD tackles these problems by developing advanced tools in the following areas:
- a Magnetic Element Modelling Tool (MEMT), consisting of a tool to design customised transformers and inductors
- a tool to generate magnetic models for the electrical simulation and to generate the field distribution for EMI analysis computation.
- a Parasitics Extraction and Modelling Tool (PEMT), to model and extract parasitic effects such as runtime, dispersion, reflection, crosstalk and radiation in printed circuit boards and thick-film hybrids
- an EMI/EMC Tool (EET) to predict the radiated and conducted noise and compliance with EMC standards.
A state of the art analysis has shown that very few tools exist for power electronics systems. For the parasitics extraction and modelling tool (PEMT) tool, algorithms for integrated circuits can be adapted to thick film hybrids and printed circuit boards (PCBs). Existing hysteresis models can be used for the magnetic modelling, but must be extended to include, for example, eddy current effects in the core. Work on radiation of antennas provides the starting point for electromagnetic compatibility (EMC) simulation.
Based on an in depth requirement analysis, detailed specifications have been worked out. Progress in the different areas can be summarised as follows:
Magnetic modelling tool:
models have been developed for the magnetic core and for the windings. The winding model is already functional for single structures. Simulated winding impedance shows good accordance with measurement. The winding model is being connected to a finite element analysis tool to compute the field distribution on the boundaries.
Parasitics extraction and modelling tool:
preliminary models for simple PCB structures (1 layer, normalised track width and thickness, etc) have been developed, based on transmission line theory. Extraction algorithms for parasitic layout elements were successfully tested.
Electromagnetic interference (EMI)/EMC Tool:
a preprocessing tool extracts and models inductive parasitics (coupling inductance, voltage/current sources) between tracks in the layout. A model for the interaction between loops has been developed based on voltage dependent sources. The EMI/EMC tool computes radiated noise (electromagnetic field generated by the circuit in any point of the space) and conducted noise reinjected to the power source. Good results were obtained for a simplified PCB.
Computer aided design environment:
links between the different tools and links to graphical displays are under development. The interface formats have been defined.
All these models and tools will be included in a simulation environment, and will be validated for telecom applications involving AC/DC and DC/DC converters.