Multi-Mode DC-DC Converter for RF Power Amplifiers
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Solution Overview
Problem
Existing DC-DC converters for RF power amplifiers face efficiency limitations in envelope tracking due to current sharing between slow and fast converters, and struggle to provide dynamic voltage levels higher than battery voltage without dedicated boost converters, especially in power level tracking mode where low capacitance leads to high voltage ripple.
Innovation Solution
A multi-mode, dynamic DC-DC converter architecture featuring a slow and fast converter in parallel, with a link capacitor interposed between the fast converter and the RF power amplifier, allowing the fast converter to regulate the voltage at the power input node and the slow converter to regulate the voltage across the link capacitor, preventing current sharing and enabling voltage boost without a dedicated boost converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a parallel architecture with slow and fast converters is used, then the bandwidth and dynamic response are improved, but current sharing between converters causes efficiency degradation
Solution Approach 1:
A link capacitor is introduced as an intermediary element between the fast converter and the RF power amplifier. This capacitor blocks DC current sharing between the slow and fast converters while allowing the fast converter to regulate the voltage at the power input node. The link capacitor thus mediates the interaction between converters, preventing harmful current sharing while maintaining the benefits of parallel architecture for bandwidth and dynamic response.
2Power
If a dedicated boost converter is added to provide voltage higher than battery voltage, then the voltage level capability is improved, but the device complexity increases
Solution Approach 1:
The link capacitor serves multiple functions: it blocks DC current sharing between converters, enables voltage boosting above battery voltage at the RF power amplifier input, and provides energy storage for dynamic response. By making the link capacitor multi-functional, the patent eliminates the need for a dedicated boost converter, thus achieving high voltage capability without increasing device complexity.
Data Source
AI summary
A multi-mode, dynamic, DC-DC converter supplies a dynamically varying voltage, as required, from a battery to an RF power amplifier (PA). In envelope tracking mode, a fast DC-DC converter generates a dynamic voltage that varies based on the amplitude envelope of an RF signal, and regulates the voltage at the PA. A slow DC-DC converter generates a steady voltage and regulates the voltage across a link capacitor. The fast and slow converters are in parallel from the view of the PA, and the link capacitor is between the fast converter and the PA. Because different nodes are regulated, no current sharing is possible between the converters. The link capacitor boosts the dynamic voltage level, allowing a maximum dynamic voltage at the load to exceed the battery voltage. In power level tracking mode, the fast converter is disabled and the link capacitor is configured to be in parallel with the load. The slow converter directly regulates the PA, and the link capacitor is in parallel with (added to) an output capacitor. Multiple wireless network standards may be supported, allowing for the sharing of RF circuits.