Switched model of control circuits for DC-DC switching converters: application to integrated circuits UC1525 and UC1846

Two modelling techniques for power convertor circuits are most commonly used today: the average model, which is very conventional, where voltages and/or currents are applied continuously in a scaling form; and the switched model, where voltages and/or currents are applied for a short fraction of the commutation period. In this paper, the switched model technique and the simulation of PWM control circuits for switched mode DC/DC power converters are described. This model has been developed using Intusoft ISSPICE/286 software, which is based on SPICE2G.6 from the University of Berkeley. SPICE simulation is a halfway step between theoretical circuit design and its practical implementation and allows the reduction of design time and the observation and correction of some unwanted or unpredictable features of the theoretical design. The modelling and simulation techniques are applied to the popular PWM control integrated circuits UC1525 and UC1846. Several parts, which are simulated together with subcircuit lists, including the oscillator, the error amplifier and the comparator, are described. Finally, the efficacy of this model is verified.