Class-D Amplifier Transition Signal for Start-Up Pop Noise
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Solution Overview
Problem
Single-ended class-D amplifiers generate start-up noise due to rush current when initializing, and conventional methods to address this noise require additional circuitry or control circuits, which are not entirely effective.
Innovation Solution
A class-D amplifier design that utilizes a transition signal during start-up to stabilize the output signal, suppressing pop noise without the need for a mute switch by controlling the duty cycle and drive capability through a switching circuit, interpolator, noise-shaper, and PWM generator, in conjunction with a polarized capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a capacitor is used to remove the DC component of the signal in a single-ended class-D amplifier, then the DC component is removed, but start-up noise (pop or click noise) is generated due to rush current
Solution Approach 1:
The patent applies preliminary action by introducing a transition signal that gradually increases the output voltage during start-up before the audio signal is fully applied. This priming action stabilizes the output signal in advance, preventing the rush current that causes pop noise when the capacitor charges abruptly.
Solution Approach 2:
The transition signal acts as an intermediary between the power-on state and the full audio signal state. It mediates the start-up process by providing a controlled voltage ramp that prevents direct connection of full power to the capacitor-loaded output, thereby eliminating the harmful rush current transient.
2Object-generated harmful factors
If conventional methods are used to address start-up noise, then some noise reduction may be achieved, but additional circuitry such as a mute switch and additional control circuits are required
Solution Approach 1:
The transition signal generator is integrated into the existing amplifier circuitry and serves multiple functions: it controls the start-up transient, works with the existing capacitor to remove DC, and operates seamlessly with the audio signal processing chain. This eliminates the need for separate mute switches and additional control circuits while maintaining noise suppression.
Solution Approach 2:
The amplifier circuit itself generates and utilizes the transition signal through its existing components (switching circuit, interpolator, noise-shaper, PWM generator, and capacitor). The system serves its own start-up noise suppression needs without requiring external mute switches or additional dedicated control circuits, thereby reducing overall device complexity.
Data Source
AI summary
Various embodiments of the present technology comprise a method and apparatus for a class-D amplifier. In various embodiments, the class-D amplifier operates to control an output signal during a start-up state to suppress a pop noise (start-up noise) without the need for a mute switch. The class-D amplifier may utilize a transition signal during the start-up state to prime or otherwise stabilize the output signal to suppress the pop noise.