Class-D RF Power Amplifier Duty Cycle Control for Harmonic Suppression
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Solution Overview
Problem
Existing class-D RF power amplifiers face challenges in minimizing harmonics and preventing shoot-through issues, especially as frequency increases, leading to high power loss and limited frequency operation.
Innovation Solution
A high efficiency class-D RF power amplifier with duty cycle control, utilizing PMOS and NMOS transistors and an integrated low pass filter, where the driving amplifier's output voltage controls the duty cycle of the power amplifier units to prevent shoot-through and suppress harmonics, with a stronger PMOS transistor design to ensure non-overlapping signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-overlapping signal generator is used to prevent shoot-through, then shoot-through is reduced, but power consumption increases and frequency is limited
Solution Approach 1:
The patent extracts the non-overlapping control function from a separate signal generator and integrates it directly into the driving amplifier circuit. The driving amplifier inherently provides non-overlapping drive signals to the push-pull output stage, eliminating the need for an external non-overlapping signal generator and its associated power consumption and frequency limitations.
Solution Approach 2:
The patent combines the driving amplifier and non-overlapping signal generation functions into a single integrated circuit block. The driving amplifier simultaneously performs signal amplification and generates non-overlapping drive signals for the output transistors, reducing component count and power consumption while extending frequency operation.
2Reliability
If a non-overlapping signal generator is used to prevent shoot-through, then shoot-through is reduced, but frequency operation is limited
Solution Approach 1:
The patent removes the frequency-limiting non-overlapping signal generator from the system and replaces it with a driving amplifier that naturally provides non-overlapping outputs without frequency constraints. This allows the amplifier to operate across a wider frequency range including higher frequencies.
Solution Approach 2:
The driving amplifier uses dynamic voltage control to manage the switching of output transistors. By controlling the voltage levels and timing within the driving amplifier itself, the circuit achieves non-overlapping operation that adapts to various frequencies without relying on fixed-frequency feedback mechanisms.
3Use of energy by moving object
If class-D amplification is used to achieve high efficiency, then power efficiency is improved, but harmonics and out-of-band emissions increase
Solution Approach 1:
The patent introduces an integrated low-pass filter as an intermediary between the class-D power amplifier stage and the output. This filter suppresses harmonics and out-of-band emissions generated by the switching operation, allowing the system to maintain high efficiency while meeting spectral emission requirements.
Solution Approach 2:
The driving amplifier serves multiple functions simultaneously: it amplifies the input signal, generates non-overlapping drive signals for the output stage, and controls the duty cycle to manage harmonic content. This multi-functionality maintains efficiency while addressing spectral requirements.
Data Source
AI summary
A class-D RF power amplifier (PA) architecture with duty cycle control has improved power efficiency while suppressing even-order harmonics. An inductor and capacitor (LC) low pass filter (LPF) can also be integrated on-chip to further suppress harmonics and provide impedance transformation between the PA and load. This eases the design for customers and reduce their bill of materials cost. The LPF can also match the PA to the load impedance to improve efficiency. The harmonic levels can also be controlled by adjusting the duty cycle of the PA output.