Variable-Frequency PWM Audio Amplifier for Low-Power Efficiency
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Solution Overview
Problem
Class D power amplifiers face inefficiencies at low output power situations, where they fail to maintain high power efficiency due to increased power loss.
Innovation Solution
An audio amplifier design that adjusts the frequency of an oscillating signal based on the input audio signal's distribution and a reference voltage to generate a PWM signal, reducing power loss by varying the modulation frequency, thereby enhancing power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If class D power amplifier uses fixed frequency PWM modulation, then high power efficiency is achieved at high output power, but power efficiency deteriorates at low output power
Solution Approach 1:
The patent applies dynamics by making the PWM modulation frequency variable rather than fixed. The frequency modulation depth is dynamically adjusted according to the input signal amplitude, allowing the system to adapt to different output power levels and maintain high efficiency across the entire operating range.
Solution Approach 2:
The patent changes the modulation frequency parameter dynamically. By adjusting the frequency deviation based on input signal characteristics, the system optimizes the switching frequency to minimize power losses at different output power levels, resolving the contradiction between fixed-frequency efficiency and adaptability.
2Use of energy by moving object
If class D power amplifier operates at low output power, then energy consumption is reduced, but power efficiency deteriorates due to increased relative power loss
Solution Approach 1:
The system dynamically adjusts the PWM frequency based on the instantaneous input signal amplitude. At low output power levels, the modulation frequency is reduced, which decreases switching losses and maintains efficient operation, thereby resolving the contradiction between low energy consumption and power efficiency.
Solution Approach 2:
By changing the modulation frequency parameter in response to input signal strength, the system optimizes the trade-off between energy consumption and power efficiency. The frequency modulation depth is varied to ensure that even at low power levels, the amplifier operates efficiently.
Data Source
AI summary
A high efficiency audio amplifier is disclosed. The high efficiency audio amplifier includes an input end for receiving an input audio signal, an output end for outputting an output audio signal, a signal generator coupled to the input end for determining a frequency of an oscillating signal according to the distribution of the input audio signal and a reference voltage, and generating the oscillating signal accordingly, a waveform transformer coupled to the input end and the signal generator for comparing the input audio signal with the oscillating signal to generate a pulse width modulation (PWM) signal, a pre-drive circuit for generating a pre-drive signal according to the PWM signal, an output stage coupled to the pre-drive circuit for generating an output signal, and a filter coupled to the output stage for filtering the output signal to generate the output audio signal to the output end.