Class-D Amplifier PWM Control for Audio Distortion Reduction
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Solution Overview
Problem
Class-D amplifiers face challenges in reducing audio distortion, particularly due to unsupported voltages and stray magnetic fields inducing noise in low power electronic devices.
Innovation Solution
The proposed Class-D amplifier incorporates a PWM controller that generates pulse signals to drive currents in multiple drivers, with a sensing resistor to monitor voltage drops. If the voltage drop exceeds a threshold, the PWM controller sequences control of the pulse signals and switches the voltage supply to prevent unsupported voltages and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Class-D amplifier operates with high power output, then audio signal quality improves, but voltage drops across sensing resistors increase causing audio distortion
Solution Approach 1:
The patent applies preliminary action by proactively switching the voltage supply to the first driver before the voltage drop causes audio distortion. The PWM controller monitors the voltage drop across the sensing resistor and switches the voltage supply to an increased voltage level when the drop approaches a threshold, preventing the driver from reaching unsupported voltages that would cause distortion.
Solution Approach 2:
The patent implements feedback by continuously monitoring the voltage drop across the sensing resistor and using this information to control the PWM generator and voltage supply switching. The PWM controller adjusts the voltage supply to the first driver based on the real-time voltage drop measurement, creating a closed-loop system that maintains optimal operating conditions.
2Manufacturing precision
If Class-D amplifier uses multiple voltage supplies to prevent distortion, then audio quality improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the PWM controller to perform multiple functions: generating PWM signals for the first and second drivers, monitoring voltage drops across sensing resistors, and switching voltage supplies to multiple drivers. This multi-functional approach consolidates control logic into a single controller, reducing overall system complexity despite the presence of multiple voltage supplies.
Solution Approach 2:
The patent uses the PWM controller as an intermediary that mediates between the power supply system and the output drivers. The PWM controller manages the switching between different voltage supplies and coordinates the operation of multiple drivers, simplifying the control architecture by centralizing the intelligence in a single control component rather than distributing complexity across multiple components.
Data Source
AI summary
A class-D amplifier having an output driver with a first, second, and third driver, the output driver having a first output coupled to the first and third drivers, a second output coupled to the second driver; a sensing resistor coupled in series between the first driver and the first output; and a pulse width modulation (PWM) controller coupled to the inputs of the drivers and configured to receive an audio input signal; control a PWM generator to generate a first pulse signal and a second pulse signal based on the audio input signal and a power supply input; determine a voltage drop across the sensing resistor; and, responsive to the voltage drop being greater than a threshold, sequence control of the first pulse signal to the first driver and switch a voltage at the first driver to an increased voltage based on the voltage drop.