Abstract：To improve spectrum utilization efficiency, 5G systems widely employ high-order modulation and transmission technologies such as QAM and OFDM for radio frequency (RF) signals, resulting in signals with high peak-to-average power ratio (PAPR). The mainstream envelope tracking (ET) power supplies employ the switch-linear hybrid (SLH) architecture, combining linear amplifiers and switching converters (SCs) in series, parallel, or series-parallel configurations to enhance the efficiency of RF power amplifiers. The power spectral density (PSD) of RF signals is primarily concentrated in mid-to-low frequency bands. High-efficiency switching converters are utilized to track and supply most power components. At the same time, linear amplifiers compensate for high-frequency components that switching converters cannot track, enabling the system to achieve both high efficiency and excellent linearity. However, the wide slew rate distribution of high PAPR RF signals requires constructing multiple SC circuits with different inductance values in SLH ET power supplies to respond to varying voltage slew rate (SR) signals. As a single inductance value only covers a narrow SR range, discrete inductors need to be built to achieve the exact amounts of the corresponding SCs. Therefore, traditional discrete inductor-based designs significantly increase system complexity. This paper proposes a coupled-inductor cooperative control strategy to reduce the number of discrete inductors and enhance fitting accuracy by optimizing inductance configuration. According to divided slew rate intervals, winding quantities and their turn numbers can be designed to get the required inductance values on a single magnetic core. Based on the coupled inductor, the mutual inductance effect during parallel operation generates amore reasonable equivalent inductance distribution. Thus, the coupled inductor can track both low SR envelope signals and high SR transient signals through parallel-connected inductors, further improving tracking accuracy. The operating ranges of SR in coupled inductors significantly impact ETPS efficiency: (1) Inductor L1 with a relatively large value covers 40% probability of SR signals; (2) L2 with approximately half of value handles 45% probability of SR signals; (3) The remaining 15% extreme SR signals are addressed by parallel equivalent inductance Leq. Optimized fitting accuracy and efficiency are achieved by adjusting inductance coverage ranges. Unlike SC configurations with discrete inductors, the ETPS based on coupled inductors exhibits richer operational modes due to the mutual induction voltages between windings. The mutual induction voltages accelerate the establishment of the output voltage during circuit turn-on and enable rapid energy recovery during turn-off, significantly enhancing tracking efficiency. Taking a dual-winding coupled inductor (L1 and L2) as an example: L1 is a large inductor and L2 a smaller one, with winding turns N1 and N2, respectively. When switch controlling L1 is turned on, the coupling between L1 and L2 induces an opposing electromotive force (EMF) across L2. Since L1 and L2 simultaneously supply power to the load during this phase, the envelope signal tracking is accelerated, reducing the output current demand on the linear amplifier. During the turn-off of the switch controlling L2, the coupling effect generates a reverse EMF across L1. As a result, the energy stored in the inductors rapidly feeds back to the power supply rather than being dissipated through the linear amplifier, thereby improving tracking efficiency. A prototype ETPS was developed and tested with 64-QAM OFDM signals under the IEEE 802.11a standard, featuring a 10.07 dB PAPR, a 20 MHz bandwidth, and a 57 W peak power. Compared with discrete inductor solutions, the coupled-inductor ETPS improves efficiency from 73.86% to 80.83%.
周岩, 李淼, 沈天明, 杨宗政. 基于耦合电感协同控制的高带宽包络线跟踪电源设计[J]. 电工技术学报, 2025, 40(24): 8015-8024.
Zhou Yan, Li Miao, Shen Tianming, Yang Zongzheng. Design of High Bandwidth Envelope Tracking Power Supply Based on Coupled Inductors Collaborative Control. Transactions of China Electrotechnical Society, 2025, 40(24): 8015-8024.
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