Nonlinear Average Current Control Using Partial Current Measurement

This paper presents a nonlinear average current control method which regulates the true average of the inductor current by using the switch current as the feedback signal. The method is simple and requires no compensator design. Unlike existing average current control where the control bandwidth is limited to about one tenth of the switching frequency, the proposed control method has no limitation by the switching frequency and is very insensitive to switching noise. It combines the advantages of both peak current and linear average current control while overcoming their limitations. It can be used in both buck- and boost-derived topologies for a variety of applications requiring precise control of the input or output current, including battery charging using buck-derived topologies and power conditioning for solar and fuel cells using boost-derived topologies. Numerical simulation and experimental measurement results are presented along with theoretical development and analysis to demonstrate the operation principle and performance of the control method. Performance and general control characteristics of the method are also compared with existing linear average current control by using an averaged model. Switch current sensing methods for use with the control are also reviewed.