Envelope Tracking Supply Paths to Cut Modulator Switching Losses
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Solution Overview
Problem
Multi-level envelope tracking systems face efficiency degradation due to both DC and AC currents being circulated through switches and a common filter, resulting in power losses and significant switching losses, especially when the source impedance is high.
Innovation Solution
Implementing a multi-level envelope tracking system with separate DC and AC paths, where the DC path carries at least 75% of the energy through a DC path filter and the AC path through an AC path filter, allowing for reduced switching losses and enhanced efficiency by relaxing size and resistance constraints of the modulator's switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If both DC and AC currents are circulated through switches and a common filter in multi-level envelope tracking systems, then the system can provide power to the power amplifier, but power losses and switching losses increase significantly
Solution Approach 1:
The patent divides the single common filter into separate DC path filter and AC path filter, and separates DC and AC current paths. This segmentation allows DC current to flow through the DC path filter while AC current flows through the AC path filter with DC blocking capacitor, preventing both currents from circulating through the same switches and filter, thereby reducing power losses and switching losses in the modulator switches.
Solution Approach 2:
The patent extracts the DC current path from the AC current path by introducing a DC blocking capacitor in series with the AC path filter. This extraction ensures that DC current flows only through the DC path filter and not through the AC path switches and capacitor, eliminating the harmful interaction between DC and AC currents in the same circuit elements and reducing overall power losses.
2Device complexity
If a common filter is used for both DC and AC paths, then the system structure is simplified, but the filter size and resistance constraints become significant
Solution Approach 1:
The patent segments the common filter into separate DC path filter and AC path filter with different design optimizations. The DC path filter can be designed with larger inductors and capacitors optimized for DC current handling, while the AC path filter uses smaller components optimized for AC signal processing. This segmentation allows each filter to be sized appropriately for its specific function rather than being constrained by the requirements of both DC and AC paths.
3Power
If high source impedance is used in the envelope tracking system, then power delivery is improved, but switching losses in the modulator increases
Solution Approach 1:
The patent extracts DC current from the modulator switch path by providing a separate DC path with DC blocking capacitor. This allows the modulator switches to operate primarily with AC current at lower impedance, reducing switching losses, while still achieving high power delivery through the combined parallel paths with appropriate impedance matching.
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 overall system efficiency by providing a high-efficiency path for low-frequency energy content and reducing the size of the DC path filter components, while the AC path filter includes a series DC blocking capacitor to minimize DC current through the AC path.
Implementation Method 1
both DC and AC currents being circulated through switches and a common filter, resulting in power losses and significant switching losses
Implementation Method 2
the AC path filter includes a series DC blocking capacitor to minimize DC current through the AC path
Data Source
AI summary
Multi-level envelope tracking systems with separate DC and AC paths are provided. In certain embodiments, an envelope tracking system for generating a power amplifier supply voltage for a power amplifier is provided. The envelope tracking system includes a multi-level supply (MLS) DC-to-DC converter that outputs multiple regulated voltages, an MLS modulator that controls selection of the regulated voltages over time based on an envelope signal corresponding to an envelope of a radio frequency (RF) signal amplified by the power amplifier, an AC path filter coupled between an output of the MLS modulator and the power amplifier supply voltage, and a DC path filter coupled between a DC voltage and the power amplifier supply voltage.