Inductor design for PWM buck converter operated as dynamic supply or amplitude modulator for RF transmitters

Pulse-width modulated (PWM) DC-DC buck converters can play a critical role in high-efficiency power management systems when operated as dynamic power supplies or amplitude modulators. However, no analysis or design methodology currently exists for a buck converter used as variable-output supply in continuous conduction mode (CCM). This paper describes a key difference in analysis and design for this application, namely the method for determining the optimum inductance value. New inductor design equations, different from those derived for fixed-output CCM buck converters in the existing literature, are presented and verified through simulation of an example design.

I. Introduction

Dynamic power management is an important technique for improving the performance of modern communication systems [1]–[7]. The transmitter section typically consists of a radio-frequency power amplifier (RF PA) that must supply amplitude modulation (AM) and/or phase modulation. The RF PA should also operate with high efficiency and low signal distortion.