Capacitor Voltage Divider Supply Modulation for Envelope Tracking
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Solution Overview
Problem
Wireless communication devices face efficiency challenges in power amplifiers due to high peak-to-average power ratio (PAPR) and large bandwidth, leading to decreased efficiency and linearity, especially when using envelope tracking (ET) techniques.
Innovation Solution
A voltage dividing capacitor circuit and supply modulator with a DC-DC converter and multiple capacitor voltage dividers are used to generate multiple voltage levels based on stored energy, allowing for efficient power management and selection of optimal supply voltages for power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking (ET) techniques are used to increase power amplifier efficiency, then electrical efficiency is improved, but circuit complexity increases due to the need for multiple voltage levels and switching control
Solution Approach 1:
The voltage divider circuit is segmented into multiple independent capacitor branches (first capacitor branch with first and second capacitors, second capacitor branch with third and fourth capacitors). Each branch can be independently controlled by its own switch, allowing granular voltage level selection. This segmentation enables the circuit to provide multiple discrete voltage levels (e.g., Vbat/2, Vbat/4, 0V) without requiring a complex multi-winding transformer or multiple separate voltage regulators, thus improving electrical efficiency while controlling circuit complexity.
Solution Approach 2:
The circuit employs dynamic switching control where switches (first switch, second switch, third switch, fourth switch) are controlled by control signals to dynamically connect or disconnect capacitor branches. This dynamic reconfiguration allows the power amplifier to receive different voltage levels in real-time based on operating conditions, enabling efficient envelope tracking. The dynamic nature allows the system to adapt to varying power demands without permanent circuit modifications, balancing efficiency gains with manageable complexity through software/firmware control.
2Measurement precision
If multiple capacitor branches with switches are used to provide discrete voltage levels, then voltage control precision is improved, but device complexity increases
Solution Approach 1:
Each capacitor branch is designed with specific local characteristics - the first branch contains first and second capacitors for generating intermediate voltage levels, while the second branch contains third and fourth capacitors for additional voltage levels. Each switch (first through fourth switches) is locally controlled by its own control signal, allowing independent manipulation of each branch. This local quality approach enables precise voltage control by selectively activating specific branches based on the desired output voltage level, achieving high precision without requiring a single complex control mechanism.
Solution Approach 2:
The capacitor branches act as intermediaries between the battery voltage source and the power amplifier. Instead of directly regulating the voltage to the power amplifier, the circuit uses capacitor voltage dividers as intermediary elements to generate discrete voltage levels (Vbat/2, Vbat/4, etc.). These intermediary capacitors simplify the control task by providing pre-defined voltage levels, reducing the complexity of the control system while maintaining precise voltage control capability.
3Productivity
If discrete envelope tracking is implemented with multiple voltage dividers, then power management efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The voltage divider circuit serves multiple functions simultaneously: it acts as a voltage regulator, a power management unit, and a signal generator for envelope tracking. The same capacitor branches and switches that provide discrete voltage levels also function as the core envelope tracking mechanism. This multi-functionality eliminates the need for separate voltage regulation circuits and envelope tracking hardware, reducing manufacturing complexity while maintaining high power management efficiency. The universal design allows a single circuit to handle multiple tasks that would traditionally require separate components.
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 solution enhances the electrical efficiency of wireless communication devices by improving power management and reducing output ripple, leading to increased battery life and performance.
Implementation Method 1
a first capacitor voltage divider including a first flying capacitor and a plurality of first switches, the plurality of first switches connected in series between a first voltage node and a ground node
Data Source
AI summary
A voltage dividing capacitor circuit includes a first capacitor voltage divider and a second capacitor voltage divider. The first capacitor voltage divider is connected to a second voltage node, the first capacitor voltage divider includes a first flying capacitor and a plurality of first switches, the second voltage node coupled to a second load capacitor, the plurality of first switches connected in series between a first voltage node and a ground node, the first voltage node coupled to a first load capacitor, and the ground node coupled to a ground voltage. The second capacitor voltage divider is connected between the first voltage node and the second voltage node, and includes a second flying capacitor and a plurality of second switches, the plurality of second switches connected in series between the first voltage node and the second voltage node.