Single-Ended Class-D Amplifier Control for Pop-Free Output
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Solution Overview
Problem
Single-ended output class-D amplifiers are prone to generating 'popping' sounds due to rapid changes in output voltage when the power supply is turned on/off or a shutdown signal is activated, which detracts from audio quality and is particularly problematic under high voltage conditions.
Innovation Solution
A pop-free single-ended output class-D amplifier design that includes an input signal generator, reference voltage generator, gain-adjustable stage, pulse width modulation module, low-pass filter, and logic controller, with controlling methods to manage the gain, reference voltage, and pulse width modulation to prevent spikes and ensure smooth voltage transitions, utilizing a mute switch, fast charging circuit, and inside feedback path to stabilize the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single-ended output class-D amplifier is used to reduce device complexity and power consumption, then the amplifier achieves higher power efficiency and lower heat generation, but the output voltage changes rapidly during power supply transitions causing popping sounds
Solution Approach 1:
The patent applies preliminary action by controlling the output voltage to rise and fall smoothly during power supply transitions before the actual power change occurs. The logic controller manages the reference voltage and PWM module to ensure gradual voltage transitions, preventing sudden changes that would cause popping sounds while maintaining the high power efficiency of the single-ended output class-D amplifier architecture
2Speed
If the output voltage is allowed to change rapidly for fast response, then the amplifier responds quickly to signal changes, but popping sounds are generated during power supply transitions and shutdown
Solution Approach 1:
The patent applies dynamics by implementing adaptive control of the output voltage based on the operating state. The logic controller dynamically adjusts the reference voltage and PWM duty cycle according to whether the amplifier is in normal operation, power transition, or shutdown state. This dynamic control ensures fast response during normal operation while preventing popping sounds during transitions by smoothing voltage changes
3Object-affected harmful factors
If additional control circuits are added to prevent popping sounds, then the popping noise is reduced, but the device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the logic controller to perform multiple functions: it generates the PWM signal, controls the reference voltage, manages the shutdown sequence, and prevents popping sounds during transitions. By consolidating these control functions into a single controller, the patent reduces the need for separate control circuits while still effectively preventing popping sounds
Data Source
AI summary
A pop-free single-ended output class-D amplifier includes: an input signal generator for generating an input signal; a power supply for supplying input power; a reference voltage generator for generating a reference voltage; a gain-adjustable stage for generating an amplified signal according to the reference voltage and adjusting a gain of the single-ended output class-D amplifier; a pulse width modulation module for outputting a pulse width modulation signal according to the reference voltage, the amplified signal, and the input power; a low-pass filter for low-pass filtering the pulse width modulation signal to generate an output voltage; and a logic controller for generating at least one control signal to control the reference voltage generator, the gain-adjustable stage, and the pulse width modulation module according to the input power, the reference voltage, and the pulse width modulation signal.