Envelope Tracking Power Supply with Split-Path Bandwidth Control
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Solution Overview
Problem
Current tracking power supplies for wireless communication systems, particularly those using variable envelope modulation technologies, face challenges in meeting high bandwidth and efficiency requirements due to limitations in semiconductor technology, leading to output noise and distortion that affect Adjacent Channel Power Ratio (ACPR) and Peak-to-Average Power Ratio (PAPR).
Innovation Solution
A tracking power supply system that combines a basic voltage output unit with a linear amplifier in series and a switch tracking current source in parallel, where the linear amplifier outputs a high-precision, high-bandwidth signal and the basic voltage output unit provides high-efficiency, low-bandwidth and low-precision signals, with the switch tracking current source reducing the output current of the linear amplifier to improve overall efficiency and reduce power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common switching power supply is used for envelope tracking, then the device complexity is reduced, but the bandwidth requirement cannot be met due to limitations of semiconductor technology and switching frequency
Solution Approach 1:
The power supply is segmented into two independent paths: a switching power supply path for high-efficiency operation and a linear amplifier path for high-bandwidth tracking. This segmentation allows each path to be optimized for its specific function, resolving the contradiction between complexity and bandwidth performance.
Solution Approach 2:
The system dynamically switches between switching power supply mode and linear amplifier mode based on the envelope signal characteristics. When high bandwidth is required, the linear amplifier is activated; when efficiency is prioritized, the switching power supply operates. This dynamic adaptation resolves the bandwidth-complexity contradiction.
2Measurement precision
If a linear amplifier is used to amplify the envelope signal, then the bandwidth and precision requirements are met, but the efficiency is reduced due to power loss
Solution Approach 1:
Instead of using the linear amplifier for the entire envelope signal amplification, it is used only partially - specifically for the high-frequency components that require precise tracking. The switching power supply handles the majority of the amplification, thus reducing overall power loss while maintaining necessary precision.
Solution Approach 2:
Different quality requirements are applied to different frequency components of the envelope signal. High-frequency components receive high-precision linear amplification, while low-frequency components use efficient switching power supply amplification. This local differentiation resolves the contradiction between precision and energy loss.
3Speed
If the switching frequency is increased to meet bandwidth requirements, then the bandwidth is improved, but the output noise and distortion increase causing out-of-band spectrum spread and affecting ACPR
Solution Approach 1:
The linear amplifier serves as an intermediary for high-frequency envelope components, isolating the switching power supply from directly amplifying these components. This prevents the switching noise and distortion from being modulated onto the carrier, thus improving ACPR while maintaining the necessary bandwidth through the linear amplifier's high-frequency response.
Data Source
Figure 1~2A
Figure 2B
Figure 3
AI summary
A tracking power supply, a method for controlling a power supply, and a communication apparatus are disclosed. The tracking power supply includes: a basic voltage output unit, configured to provide a basic voltage; and a compensation voltage output unit, configured to provide a compensation voltage. The compensation voltage output unit and the basic voltage output unit are connected in series so as to provide a voltage which is the sum of the basic voltage and the compensation voltage for a load.