基于GaN器件的模块化多电平包络跟踪电源

Modular Multilevel Envelope-tracking Power Supply Based on GaN Devices

包络消除与恢复EER(envelope elimination and restoration)技术是一种提高变包络幅值调制的射频功放效率的有效手段,其核心装置是高跟踪精度、高带宽和高效率的包络跟踪电源。为提高其带宽、效率和跟踪精度,提出了一种结构模块化的多电平包络跟踪电源电路。首先,由2个半桥单元层叠构成一个三电平子模块,并由1路独立直流电源供电;再将多个三电平子模块的输出串联后采用载波移相PWM进行调制,从而可得到多电平的输出电压。由于通过增加输出电压电平数提高了等效开关频率,并减小了阶梯电压,因此可有效提高带宽和跟踪精度。针对每个三电平子模块内部2个直流电容的电压不平衡问题,提出了一种微调PWM信号占空比的平衡控制方法。采用氮化镓GaN(gallium nitride)器件搭建了1台最大功率500 W、开关频率1 MHz和带宽400 kHz的五电平包络跟踪电源样机,实验结果验证了该电路拓扑及控制方法的有效性和可行性。

Envelope elimination and restoration(EER)technique is an effective method to improve the efficiency of radio-frequency power amplifier with non-constant envelope modulation,whose key equipment is a high tracking precision,high bandwidth,and high efficiency envelope-tracking power supply.In order to improve its bandwidth,efficiency and tracking precision,a multilevel envelope-tracking power supply circuit with a modular structure is proposed in this paper.First,two half-bridge cells are stacked to form a three-level sub-module,which is powered by an isolated DC source.Then,several three-level sub-modules are series connected and further modulated by phase-shifted PWM(PSPWM),thereby obtaining multilevel output voltage.Due to the increase in equivalent switching frequency and reduction in stair voltage by increasing the number of voltage levels,the bandwidth and tracking precision can be improved effectively.A capacitor voltage balancing method based on the fine adjustment of the duty ratios of PWM signals is also proposed to solve the problem of capacitor voltage imbalance between two DC capacitors within each three-level sub-module.A five-level envelope-tracking power supply prototype based on gallium nitride(GaN)devices with 500 W peak po-wer,1 MHz switching frequency and 400 kHz bandwidth was designed,and experimental results verified the effectiveness and feasibility of the proposed circuit topology and its control method.