| Popis: |
Modern energy transmission and signal reproduction techniques rely upon power amplifier (PA) architectures that must operate with high efficiency. Current-source PAs are linear but inherently inefficient; switch-mode PAs are efficient-yet-nonlinear systems, often lacking an efficient means of amplitude modulation (AM) for power transmission. A promising technique for addressing these problems involves replacing the fixed PA supply voltage V_dd with a controlled, variable voltage provided by a dynamic power supply. High-efficiency envelope tracking and amplitude modulation can thereby be provided to both current-source and switch-mode PAs, respectively. This work presents a pulse-width modulated (PWM) dc-dc buck converter for use as the core power stage of a dynamic supply. Although buck converters typically function as fixed-output supplies, this work provides new theoretical dc analysis for operation wherein the output voltage is controlled and variable over a wide, continuous range. A new design procedure for the variable-output PWM dc-dc buck converter is derived. The new dc analysis and design procedure are verified experimentally. Open-loop ac characteristics, such as transient response, frequency response, and dynamic modulation efficiency are assessed via simulation and experimental measurements. The variable-output buck converter is found to operate as designed, with bandwidth dependent upon a sufficiently high PWM switching frequency f_s. Within this bandwidth, minimal modulation distortion is observed, measured efficiency is greater than 90%, and supplied power-on-demand is verified. |
