On the design of observers robust to load variations for synchronous converters

Due to the ever growing concern on energy efficiency issues, synchronous rectification gained increasing attention in recent years. In the semiconductor industry fast controllers developed for DC-DC converters are typically based on inductor current measures. In this context system costs and performances strictly depend on the current sensor and its proper design. In this paper we present a sensorless synchronous approach based on a current observer. The same observer formulation is valid for the three standard DC-DC converters, simplifying its design for different configurations. Furthermore the designed observers are proven to be robust against load variations, the most uncertain parameter of the control law. Our sensorless approach has been tested in a cascade PI structure for buck, boost and buck-boost converters. Numerical results show its good performances in these different scenarios.