Feed-Forward Envelope Tracking With Charge Pump and Buck Regulation
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Solution Overview
Problem
Existing envelope tracking systems for power amplifiers face challenges in scaling for higher frequencies due to large solution area on the PCB and inefficiencies in analog control loops, particularly in cellular and WLAN/WiFi applications.
Innovation Solution
A feed-forward envelope tracking system using a capacitive charge pump for adjustable boost and an inductive buck DC/DC converter for step-down regulation, eliminating the analog control loop and leveraging capacitors for efficient voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an analog control loop is used for envelope tracking, then the power amplifier supply voltage can be controlled to track the signal envelope, but the solution area on the PCB becomes large and the system does not scale for higher frequencies and carrier aggregation
Solution Approach 1:
The patent replaces the analog control loop (mechanical/electrical continuous system) with a digital feed-forward envelope tracking system. The digital system uses a digital signal processor to calculate the envelope signal and control the power amplifier supply voltage through digital-to-analog conversion, eliminating the need for large analog components and reducing PCB area while improving scalability to higher frequencies
Solution Approach 2:
The patent introduces a digital signal processor and digital control architecture as an intermediary between the envelope detection and power amplifier control. This digital intermediary enables precise envelope tracking with reduced hardware footprint by processing envelope signals digitally and generating control signals for the power amplifier supply voltage regulation
2Reliability
If an analog control loop is used for envelope tracking, then voltage regulation can be achieved, but the system efficiency decreases and the complexity increases for higher carrier aggregation levels
Solution Approach 1:
The patent replaces the energy-inefficient analog control loop with a digital feed-forward system that calculates the required supply voltage based on the envelope signal. This digital approach reduces power consumption by eliminating continuous analog signal processing and using digital computation only when needed, thereby improving system efficiency while maintaining voltage regulation accuracy
Solution Approach 2:
The patent implements feed-forward control where the envelope signal is calculated in advance and used to pre-determine the power amplifier supply voltage. This preliminary action eliminates the need for continuous feedback and correction, reducing energy consumption and system complexity while maintaining accurate voltage regulation
3Power
If an inductor-based DC/DC converter is used for voltage regulation, then voltage conversion can be achieved, but the height and board space increase
Solution Approach 1:
The patent replaces the inductor-based DC/DC converter with a capacitor-based voltage regulation system. The digital feed-forward control drives capacitor-based voltage generation, eliminating the need for large inductors and reducing the converter height and board space while maintaining the required voltage conversion capability for envelope tracking
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate PA supply voltage at high frequencies with reduced board space and height, supporting higher frequencies and faster switching without the limitations of analog control loops.
Implementation Method 1
A feed-forward envelope tracking system using a capacitive charge pump for adjustable boost
Implementation Method 2
an inductive buck DC/DC converter for step-down regulation
Data Source
Figure 1~1A
Figure 1B
Figure 2
AI summary
Systems, methods, and circuitries are provided for generating supply voltages for a power amplifier in a digital envelope tracking system. In one example, a voltage generation circuitry converts a source voltage into a supply voltage based on a target voltage. The voltage regulation circuitry includes an adjustable boost circuitry that multiplies the source voltage to generate an input voltage having a voltage equal to or greater than the source voltage and a step-down regulator circuitry that regulates the input voltage to generate a regulated output voltage having a voltage that is less than or equal to the input voltage. A voltage splitter circuitry is coupled to the regulated output voltage and is configured to generate at least one derived output voltage from the regulated output voltage. A supply modulator provides a selected one of the at least one derived output voltage to a power amplifier.