The series-parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply features high efficiency and high bandwidth. In this structure, two multilevel converters are used to fit the load voltage, and a buck converter is used to track the load current. As the bandwidth and the peak-to-average power ratio (PAPR) of the radio frequency signal continue increasing, the buck converter needs to operate at high switching frequency, resulting in increased power loss and reduced overall efficiency of the ET power supply. In this paper, the step-wave voltages generated by the multilevel converters are multiplexed as the input of the buck converter. Thus, the switching frequency of the buck converter is greatly reduced and the overall efficiency is improved. The optimized design of the number and values of voltage levels of the multilevel converters is given, and an improved control strategy for the multilevel converters is proposed to reduce the equivalent switching frequencies. A prototype is fabricated in the lab for tracking the envelope signal with 10-MHz bandwidth. The efficiency of the proposed ET power supply is improved by 3.34% compared to the one without multiplexing the step-wave voltages.
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Li et al. (2024) studied this question.
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