Reconfigurable PWM Amplifier Loop Topology for Load Impedance Control
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Solution Overview
Problem
Existing audio amplifiers, particularly class-D amplifiers, struggle with flexible load impedance control, especially in high Q load resonance scenarios, leading to ripple in the closed-loop transfer function, and lack the ability to switch between current and voltage modes efficiently.
Innovation Solution
A configurable control loop system with a reconfigurable pulse width modulator (PWM) that can switch between voltage-mode and current-mode operations using a digital and analog PWM, incorporating an analog-to-digital converter (ADC) for feedback, allowing seamless transition between modes without significant additional hardware cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage-mode control is used for accurate load voltage control, then Total Harmonic Distortion and Power Supply Rejection Ratio are improved, but the system lacks flexibility for current control with large load impedance variations
Solution Approach 1:
The system dynamically switches between voltage-mode and current-mode control based on operating conditions. A mode selection circuit determines whether to activate the voltage-mode PWM amplifier or current-mode PWM amplifier, allowing the system to adapt its control characteristics to match the specific application requirements and load conditions.
Solution Approach 2:
The amplifier is designed with dual functionality, incorporating both voltage-mode and current-mode control paths within a single device. This multi-functional design allows the same amplifier to serve both voltage control applications (with high THD and PSRR performance) and current control applications (with accurate current control for varying load impedances), eliminating the need for separate amplifiers for different control modes.
2Measurement precision
If current-mode control is used for accurate current control with large load impedance variations, then current control accuracy is improved, but ripple in the closed-loop transfer function increases due to high Q load resonance
Solution Approach 1:
The system dynamically selects between current-mode and voltage-mode control based on load conditions. When operating with high Q load resonance, the mode selection circuit can switch to voltage-mode control to avoid the ripple issues inherent in current-mode control, while still maintaining accurate current control capabilities when load conditions are favorable.
3Adaptability or versatility
If separate voltage-mode and current-mode amplifiers are used to provide mode flexibility, then adaptability is improved, but device complexity and hardware cost increase
Solution Approach 1:
The patent merges both voltage-mode and current-mode control circuits into a single integrated amplifier device. The architecture combines a voltage-mode PWM amplifier and a current-mode PWM amplifier sharing common components such as the PWM modulator, feedback circuits, and power stage, allowing both control modes to coexist in one unified structure rather than requiring completely separate amplifier systems.
Solution Approach 2:
The amplifier incorporates universal design elements that serve both voltage-mode and current-mode operations. Shared components including the PWM modulator, feedback network, and output stage are designed to function effectively in both control modes, reducing the need for duplicate hardware and minimizing overall device complexity while maintaining full adaptability.
4Adaptability or versatility
If reconfigurable PWM with both digital and analog modes is used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The reconfigurable PWM modulator merges digital and analog PWM generation circuits into a single integrated block. The design combines digital signal processing capabilities with analog modulation functionality, allowing the same hardware to operate in both digital PWM mode (for current-mode control) and analog PWM mode (for voltage-mode control) through a unified reconfigurable architecture.
Data Source
Figure 1~2B
Figure 3
AI summary
In accordance with embodiments of the present disclosure, a system may have a configurable control loop technology, wherein the system comprises a first mode control loop, a second mode control loop and a reconfigurable pulse width modulator (PWM) configured to generate an output signal from an input signal. The reconfigurable PWM may include a digital PWM and an analog PWM and may be configured such that when the first mode control loop is activated, the reconfigurable PWM utilizes the analog PWM to generate the output signal from the input signal and when the second mode control loop is activated, the reconfigurable PWM utilizes the digital PWM to generate the output signal from the input signal and the digital PWM receives its input from a digital proportional integral derivative controller.