Digitally controlled DC-DC converter for RF power amplifier

This paper describes design and implementation of a digitally controlled DC-DC converter that provides a dynamically adjustable supply voltage for an RF power amplifier (RFPA). The techniques employed in the design include a combination of constant-frequency continuous conduction mode and a variable-frequency discontinuous conduction mode to achieve very high converter efficiency over a wide range of output power levels. The variable-frequency converter control is accomplished using a simple current-estimator circuit, which eliminates the need for current sensing. An FPGA-based digital controller implementation allows programmability of the mode transition and other controller parameters. In the complete experimental system, which consists of the digitally controlled DC-DC converter and a class-E RFPA operating at 10 GHz, experimental results show that the overall system efficiency is significantly improved over a wide range of RFPA output power levels, e.g. from 22% to 65% at a low power level.