An interactive computer-based learning tool with multiple sessions is proposed in this paper, which teaches students to think and helps them recognize the merits and limitations of simulation tools so as to improve their practical abilities in electrical circuit simulation based on the case of a power converter with progressive problems. The common problem of fast simulation and differential equation solver convergence are discussed in detail for the simulation of nonlinear power electronic circuits. Another special ratio for ripple restriction is proposed, taking practical work into consideration. Some design and simulation tradeoffs for corresponding problems are also presented. Such a learning tool can improve students' programming skills and inspire their interest in practical work as well. The practical tests--carried out at the Aichi Institute of Technology, Toyota, Japan, and Southeast University, Nanjing, China--validate the effectiveness of the learning tool. (Contains 2 tables and 12 figures.)