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Automatic power module layout design

Fig. 1. Automatic layout design process for power module.
It has been shown that the parasitic parameters in a module have a detrimental influence on the switching loss and the dynamic behavior. This phenomenon is exaggerated when the density increases, because a higher switching rating leads to faster variations. A literature survey also shows that only manual layout designs have been created so far. The main dissatisfactions with manual layout design are the design speed and the limited choice of candidates. Manual design is always an experience-based process which lacks consistency. The automatic layout of a design is highly preferred during the iterations.

The power module layout design is an iteration-based comparison with a much smaller number of components and simpler placement and routing. However, unlike the fitness evaluation in the VLSI design, power module layout design requires a parasitic parameter extraction process. Based on these characteristics, the genetic algorithm (GA) is chosen as the automatic design algorithm. As shown in Figure 1, in the automatic layout design, there are two loops utilizing GA. The outer loop is the placement loop, in which the components are placed and evaluated based on the design results of the inner loop, which is the routing loop. The outer loop provides the layout of the components in the inner loop. With certain components positioned, the inner loop physically connects the components based on the electrical connection. The routing process is implemented by GA, and an analytical equation-based parasitic parameter calculation method is utilized during the fitness evaluation step. After several iterations, the best individual routing result and its fitness is passed on to the outer loop. The outer loop uses these routing results as the criteria for fitness in placement evaluation.

In the example studies shown in Figure 2, the best solution found through manual design is similar to that found with automatic design. Design results are also verified by Ansoft Q3D. The design results prove that automatic design has advantages in power module layout.

Fig. 2. Example of automatic layout design