Enhancing the bandwidth of the Multiple Input Buck Converter by means of filter design

The widespread of radio communications has shown the need of increasing the efficiency of Radio Frequency Power Amplifiers. Some efficiency enhancement techniques, such as Envelope Tracking and Envelope Elimination and Restoration, require high efficiency DC/DC converters capable of tracking modern high-bandwidth communication signals. Traditional design techniques of switching power converters lead to a second order output filter comprising an inductor and a capacitor, which require excessive switching frequency to reproduce a signal of a given bandwidth, thus yielding higher losses and lower efficiency. When the converters derive from the Buck family and they are operating in open loop, the use of higher order filters can improve their tracking capabilities without penalizing the efficiency. This paper explores the integration of several families of fourth order filters with a Multiple Input Buck Converter. Design tradeoffs and benefits are considered, and experimental results with different type of filters are shown to validate the analysis.