Fuzzy Logic in Power Supply Applications

In modern microelectronics technology, a high-performance power supply is one of the key factors. Very small steady-state error and fast settling time have to be coupled with short-circuit protection and soft start-up to avoid current and voltage overshoot. To achieve the above goals a two-stage power supply is needed. A DC/DC power- conversion stage is necessary after a coarse AC/DC rectifier, in order to eliminate disturbance, and obtain a precise supply voltage needed to ensure correct operation. Complex integrated circuits have been developed to realize this second DC/DC stage. However in these circuits, more sophisticated features are added to conventional control laws by means of additional circuitry, e.g., external capacitive elements. Nevertheless, we can expect this additional complexity to be reduced if we design the control law with a more sophisticated technique, like a fuzzy control, which can take articulated input-output correspondence into account while keeping computational complexity to a reasonable level. As fuzzy logic relies more on the understanding of the system’s behavior than on precise mathematical modelling, we may foresee not only a reduction in the implementation complexity, but also an increase in the sophistication and robustness of the control policies. In this chapter we will discuss the application of fuzzy logic to some implementations of DC/DC converters.