A linear assisted DC/DC converter for Envelope Tracking and Envelope Elimination and Restoration applications

In recent years, there has been a great effort in the development of fast and efficient DC/DC converters in order to follow the envelope of communication signals for increasing the efficiency of Radio Frequency Power Amplifiers by using techniques such as Envelope Tracking and Envelope Elimination and Restoration. However the bandwidth and slew rate required by modern communication signals is higher than the maximum slew-rate achievable by switching DC/DC converters made for these purpose. The slew rate of these switching DC/DC converter can be improved by combining it with the use of a linear stage, thus establishing a trade-off between slew rate and overall efficiency. This paper presents a simple way of combining the use of both a switching DC/DC converter, the Multiple Input Buck Converter, and a linear stage to obtain slew-rates above 100 V/μs, with a moderate decrease in the overall efficiency (81% efficiency tracking the envelope of an EDGE standard signal). Finally, a prototype of the complete system (including the digital control for both stages) is presented in this paper.