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Increasing the efficiency of Radio Frequency Power Amplifiers has growth in importance due to the widespread use of wireless communications. Efficiency enhancement techniques such as Envelope Tracking and Envelope Elimination and Restoration use DC/DC converters to track the envelope of the signals being transmitted. These envelopes often have very high bandwidth and slew rate, challenging the design of fast and efficient tracking converters. Furthermore, traditional second order output filter design techniques applied to tracking converters lead to very high switching frequencies and thus low efficiencies. This paper analyzes the use of higher order filters to improve the dynamic response of tracking converters without increasing the switching frequency, thus maintaining high efficiency operation. This approach can be combined with a multiphase architecture to further increase the achievable bandwidth. Experimental results that demonstrate the effectiveness of the proposed approach are shown using a 2-phase multiple-input buck converter operating in open loop with a fourth order Bessel output filter. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]