A Linear Assisted DC/DC Converter for Envelope Tracking and Envelope Elimination and Restoration Applications

In recent years, there has been a great deal of focus on the development of fast and efficient dc/dc converters in an effort to follow the envelope of communication signals for increasing the efficiency of RF 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 are higher than the maximum ones achievable by switching dc/dc converters made for this purpose. The slew rate of these switching dc/dc converters 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 enhanced data rates for GSM evolution (EDGE) standard signal]. Finally, a prototype of the complete system (including the digital control for both stages) is presented in this paper.