Envelope Tracking Supply With Separate DC and AC Paths
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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 separate DC path and AC path through distinct filters, where the DC path carries at least 75% of the energy, relaxes size and resistance constraints of the modulator's switches, reducing switching losses and enhancing overall system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If both DC and AC currents are circulated through switches and a common filter, then the envelope tracking system can be implemented with a unified structure, but power losses and switching losses increase significantly
Solution Approach 1:
The patent divides the envelope tracking system into separate DC path and AC path, each with its own filter. The DC path includes a DC filter for filtering DC currents, while the AC path includes an AC filter for filtering AC currents. This segmentation allows DC and AC currents to be processed independently, reducing power losses and switching losses associated with circulating both currents through a common filter and switches.
2Device complexity
If both DC and AC currents are circulated through switches and a common filter, then the system can be simplified, but switching losses increase significantly
Solution Approach 1:
The patent segments the system into separate DC and AC paths with distinct filters. The DC path processes DC currents through a DC filter, while the AC path processes AC currents through an AC filter. This segmentation eliminates the need for switches to handle both DC and AC currents simultaneously, significantly reducing switching losses while maintaining system functionality.
3Volume of stationary object
If a common filter is used for both DC and AC paths, then the filter size can be reduced, but the resistance constraints of modulator switches become more stringent
Solution Approach 1:
The patent divides the filtering function into separate DC filter and AC filter. The DC filter is optimized for DC current filtering with appropriate inductance and capacitance values, while the AC filter is optimized for AC current filtering. This segmentation allows each filter to be designed with relaxed resistance constraints, making the modulator switches easier to manufacture with standard resistance values.
4Loss of energy
If separate DC and AC paths with distinct filters are implemented, then switching losses are reduced, but the device complexity increases
Solution Approach 1:
The patent implements separate DC and AC paths with distinct filters to reduce switching losses. The DC path includes a DC filter connected to the DC current source, and the AC path includes an AC filter connected to the AC current source. While this segmentation increases device complexity compared to a common filter approach, the reduction in switching losses and power losses provides net system efficiency improvement.
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 approach enhances the efficiency of the envelope tracking system by providing a high-efficiency path for low-frequency energy content and reducing the size and complexity of the filter components, leading to lower switching losses and improved power amplifier efficiency.
Implementation Method 1
The DC-to-DC converter is configured to generate the DC voltage with a different pulse-width modulator sequence relative to each of the plurality of regulated voltages
Implementation Method 2
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
Implementation Method 3
the envelope tracker further includes a plurality of decoupling capacitors each coupled between ground and a corresponding one of the plurality of regulated voltages
Implementation Method 4
the first filter includes at least one series inductor and at least one shunt capacitor
Implementation Method 5
the first filter further includes a DC blocking capacitor in series between the modulator output voltage and the power amplifier supply voltage
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.