Digital Switching Amplifier PWM with Offset Pulse Compensation
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Solution Overview
Problem
Conventional digital amplification systems using pulse width modulation in digital switching amplifiers suffer from residual noises, heat generation, and pop noises due to switching, which decrease amplification efficiency and can damage speakers.
Innovation Solution
A method and apparatus that divide input audio signals based on their sign, add or subtract a predetermined offset, and perform pulse width modulation on each divided signal to minimize differential output pulse width, especially when the input signal is near zero, using a digital switching amplifier with an offset adder, sign determining unit, inverter, switching unit, and minimum pulse width compensator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional pulse width modulation is used in digital switching amplifiers, then amplification efficiency is improved, but residual noises and heat generation increase
Solution Approach 1:
The input audio signal is divided into positive and negative half-cycles based on its sign. Each half-cycle is processed separately through independent pulse width modulation paths, allowing for optimized control of each polarity and reduction of residual noises while maintaining high amplification efficiency.
Solution Approach 2:
A predetermined offset is added to the audio signal before pulse width modulation, dynamically changing the signal parameters. This offset adjustment minimizes the differential output pulse width and reduces residual noises and heat generation while preserving amplification efficiency.
2Loss of energy
If conventional pulse width modulation is used in digital switching amplifiers, then amplification efficiency is improved, but heat generation increases
Solution Approach 1:
By segmenting the audio signal into positive and negative half-cycles and processing them separately, the system optimizes the duty cycle for each polarity independently. This reduces unnecessary switching and minimizes heat generation while maintaining high amplification efficiency.
Solution Approach 2:
The offset addition dynamically adjusts signal parameters to minimize differential output pulse width, thereby reducing power dissipation and heat generation in the switching amplifier while preserving amplification efficiency.
3Loss of energy
If conventional pulse width modulation is used in digital switching amplifiers, then amplification efficiency is improved, but pop noises occur
Solution Approach 1:
Separating the audio signal processing into distinct positive and negative half-cycle paths allows for independent optimization of each polarity's pulse width modulation, reducing abrupt transitions and pop noises while maintaining amplification efficiency.
Solution Approach 2:
The offset is added to the audio signal before pulse width modulation to preemptively minimize the differential output pulse width. This preliminary adjustment prevents excessive pulse widths that could cause pop noises, while preserving amplification efficiency.
4Object-generated harmful factors
If offset is added to minimize differential output pulse width, then residual noises are reduced, but device complexity increases
Solution Approach 1:
The signal processing is segmented into distinct stages: sign determination, offset addition, and separate positive/negative half-cycle processing. This structured segmentation reduces residual noises through systematic control while keeping the device complexity manageable through modular design.
Data Source
AI summary
There is provided a method and apparatus for output pulse width modulation in a digital amplifier including: a determining step of adding or subtracting a value corresponding to a predetermined offset to or from an input audio signal alternately according to a period of the input audio signal, thereby determining a sign of a resulting value of adding or subtracting; a switching step of outputting the input audio signal to a first port based on the determined sign, or outputting the input audio signal to a second port after inverting the input audio signal into a positive number; an adjusting step of adding a value of a predetermined switching time to the audio signals output from the first port and the second port, and outputting a resulting value of adding; and a modulating step of performing pulse width modulation on the audio signals output from the adjusting step and outputting a first modulation signal and a second modulation signal.