一种开关线性复合包络线跟踪电源的控制策略

在3G移动通信系统中,射频功放的输入信号包络线幅值是变化的,且带宽较高,采用恒定电压给射频功放供电,其损耗将很大。包络线跟踪电源可以使供电电压跟随输入信号包络线的变化而变化,使得功放的功率管压降较小,从而提高系统效率。采用开关电源和线性电源并联构成的包络线跟踪电源,其中高带宽的线性电源用于调节输出电压,低带宽的开关电源提供大部分负载功率,以提高电源效率。针对此结构,本文提出一种PWM电流控制策略,使得开关电源工作频率恒定,并对此控制方法进行改进,引入输出电压前馈支路,进一步减小线性电源电流,提高系统效率。文中最后以跟踪频率小于100kHz的正弦信号给出设计实例,并进行实验验证。

A Control Strategy for Switch-Linear Hybrid Envelope Tracking Power Supply

In the third generation(3G) mobile telecommunication system,the input signal to the radio frequency power amplifier(RFPA) characterizes of non-constant envelope with high bandwidth.Under this condition,constant amplitude power supply to the RFPA will lead to significant power loss.To improve the efficiency of the systems,one of the most promising methods is the envelope tracking technique,which is based on using a high efficiency power supply to provide a varying voltage to the RFPA that tracks the envelope of the transmitted signal.Thus,the RFPA can operate near its theoretical maximum efficiency.For this purpose,this paper adopts a linear amplifier and a switched-mode converter connected in parallel at the output to construct the envelope tracking power supply.The linear amplifier stage features of wide bandwidth and it makes the output voltage follow the envelope of the transmitted signal,and the switched-mode converter features of high efficiency and it provides most of the load current.A PWM current control strategy with constant switching frequency is proposed for the switched-mode converter,and it is further improved by feed-forwarding the output voltage to reduce the current of the linear amplifier,leading to a higher efficiency.The effectiveness of the proposed structure and control strategies are verified by the experimental results from a prototype tracking 100kHz sinusoidal signal.