Multi-Level Envelope Tracking with Split DC and AC Supply Paths
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Solution Overview
Problem
Existing multi-level envelope tracking systems suffer from efficiency degradation due to both DC and AC currents being circulated through switches of the modulator and/or a common filter, resulting in power losses from DC resistance and significant switching losses.
Innovation Solution
The implementation of a multi-level envelope tracking system with separate DC and AC paths, where the DC path carries at least 75% of the energy provided to the power amplifier, and the AC path includes a filter with a series inductor and shunt capacitor to reduce switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If both DC and AC currents are circulated through switches of the modulator and a common filter, then the system can provide power to the power amplifier, but efficiency degrades due to power losses from DC resistance and significant switching losses
Solution Approach 1:
The patent segments the power delivery path into separate DC and AC current paths. The DC path delivers bulk power through a DC-friendly filter with low DC resistance, while the AC path handles envelope tracking variations through an AC-optimized filter. This segmentation allows each path to be optimized for its specific function, reducing overall power losses without requiring a completely complex system redesign.
Solution Approach 2:
The patent introduces separate DC and AC filters as intermediary components between the modulator and the power amplifier. These filters act as mediators that selectively handle different current components: the DC filter handles the bulk DC current with minimal resistance, while the AC filter handles the AC envelope tracking current with optimized AC characteristics. This intermediary approach resolves the contradiction by adding components that enable more efficient overall system operation.
2Device complexity
If a common filter is used for both DC and AC paths, then the system structure is simplified, but the filter must accommodate both DC and AC requirements, leading to suboptimal performance
Solution Approach 1:
The patent divides the filtering function into two separate filters: a DC filter optimized for low DC resistance and a AC filter optimized for AC signal characteristics. This segmentation allows each filter to be independently optimized for its specific function, preventing the compromise that would result from using a single common filter for both DC and AC paths.
Solution Approach 2:
The patent applies local quality optimization by designing the DC filter with properties specifically suited for DC current (low DC resistance) and the AC filter with properties optimized for AC signals. Each filter has tailored characteristics that match its specific function, rather than using a generic common filter that must compromise to serve both functions.
3Loss of energy
If the modulator switches handle both DC and AC currents, then the switching losses increase significantly, but separating the paths requires additional components
Solution Approach 1:
The patent segments the current handling function so that the modulator switches primarily handle AC envelope tracking currents rather than the full DC+AC composite current. By separating the DC and AC paths with dedicated filters, the switching devices operate in a more efficient regime with reduced switching losses, despite the addition of separate filter components.
Solution Approach 2:
The patent introduces separate DC and AC filters as intermediary components that prepare and condition the currents before they reach the modulator switches. These intermediary filters reduce the burden on the switching devices by pre-filtering and conditioning the currents, thereby reducing switching losses even though additional components are added to the system.
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
This configuration enhances the overall efficiency of the envelope tracking system by reducing switching losses in the AC path and providing a high-efficiency path for low-frequency energy content, while also relaxing size and DC resistance constraints of the modulator's switches.
Implementation Method 1
a first filter coupled between the modulator output voltage and the power amplifier supply voltage, and a second filter coupled between a DC voltage and the power amplifier supply voltage
Data Source
AI summary
Multi-level envelope tracking systems are disclosed. In certain embodiments, a method of envelope tracking includes amplifying a radio frequency signal using a power amplifier, supplying power to the power amplifier using a power amplifier supply voltage, generating a plurality of delay-controlled regulated voltages based on controlling a delay of a plurality of regulated voltages using a controllable delay circuit, generating a modulator output voltage at a modulator output of a modulator, providing filtering using a first filter coupled between the modulator output and the power amplifier supply voltage, and controlling activation of a plurality of switches of the modulator based on an envelope of the radio frequency signal. The plurality of switches are each coupled between the modulator output and a corresponding one of the plurality of delay-controlled regulated voltages.