High Efficiency Envelope Tracking Power Supply Adopting Power Spectrum Allocation Method

With the development of modern mobile communication,for delivering more data in the limited frequency band,the signal modulation formats featuring with improved spectrum efficiency have been adopted.As a consequence,the envelope amplitude of the radio frequency(RF)signal is no longer constant,and features with large peak-to-average power ratio.The linear power amplifier(PA)suffers from low efficiency when supplied by a constant voltage.Envelope Tracking(ET)technique dynamically regulates the supply voltage to the PA according to the RF envelope,and the voltage difference is greatly reduced,leading to a higher efficiency.ET power supply is the core equipment of the ET technique,and its tracking bandwidth and conversion efficiency have influence on the system efficiency.This thesis is dedicated to the envelope tracking power supply to achieve high efficiency and high bandwidth adopting the power spectrum allocation method.Switch-linear hybrid(SLH)ET power supply is a mainstream structure,which combines the merits of the switched-mode converter and the linear amplifier,and can achieve high efficiency and high bandwidth simultaneously.With the increase of the envelope signal bandwidth,the SLH ET power supply with single switched-mode converter is difficult to achieve higher efficiency.Based on the power spectrum allocation method,this thesis proposes a configuration for the SLH ET power supply,which consists of multiple switched-mode converters with different tracking bandwidth.The SLH ET power supply with two switched-mode converters is taken as an example to illustrate the operating principle.One with low tracking bandwidth is defined as slow switched-mode converter,while the other with high tracking bandwidth is defined as fast switched-mode converter.Aiming at the slow switched-mode converter and fast switched-mode converter,the valley-point current control strategy and quasi critical continuous mode(CRM)current control strategy are proposed,respectively.Finally,a prototype of the SLH ET power supply with two switched-mode converters is designed and fabricated in the lab,aiming for 10 MHz tracking bandwidth,with 20 W average output power and 9.6 V ~ 26.4 V output voltage range.The experimental results are provided to verify the effectiveness of the proposed configuration and the current control strategies.