Dynamic Common-Mode Voltage Circuit for Low-Loss Class-D Audio
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Solution Overview
Problem
Class-D audio power amplifiers experience high static power consumption due to fixed common mode voltage, leading to inefficiencies in energy usage, especially when no audio is playing or at low to medium power levels, as the inductor ripple current remains significant and the common mode voltage leaves unused power consumption margins.
Innovation Solution
A common mode voltage dynamic modulation circuit that adjusts the common mode voltage based on a preset static bias and the normalized swing of the audio signal, incorporating an anti-clipping-off feedback adjustment module to maintain optimal voltage levels, reducing the PWM duty cycle and minimizing inductor ripple current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fixed common mode voltage is used at 1/2 of full swing, then the PWM duty cycle is maintained at 50%, but static power consumption is high and inductor ripple current remains large
Solution Approach 1:
The patent applies dynamics by transitioning from fixed common mode voltage to dynamic common mode voltage adjustment. The common mode voltage is continuously adjusted according to the instantaneous amplitude of the audio signal, allowing the system to adapt to varying signal conditions and minimize power consumption while maintaining stable operation.
Solution Approach 2:
The patent changes the parameter of common mode voltage from a fixed value (1/2 of full swing) to a dynamically variable parameter that adjusts according to the audio signal amplitude. This parameter change enables the system to optimize power consumption by reducing the common mode voltage when the audio signal amplitude is low, thereby reducing inductor ripple current and static power consumption.
2Ease of operation
If fixed common mode voltage of PVDD/2 is used, then the output signal swings around 1/2 of power supply voltage, but power consumption is wasted when volume is small or medium
Solution Approach 1:
The system dynamically adjusts the common mode voltage based on the instantaneous amplitude of the audio signal. When the volume is small or medium, the common mode voltage is reduced accordingly, eliminating the waste of power consumption that occurs with fixed common mode voltage while maintaining the ability to swing the output signal effectively when needed.
Solution Approach 2:
The patent employs feedback by continuously monitoring the audio signal amplitude and using this information to adjust the common mode voltage. This feedback mechanism ensures that the common mode voltage is optimized for the current operating condition, reducing power consumption during low to medium volume operation while preserving full output signal swing capability when high volume is required.
3Reliability
If high common mode voltage is maintained, then the PWM duty cycle remains at 50%, but inductor ripple current losses increase
Solution Approach 1:
The patent makes the common mode voltage dynamic rather than fixed, allowing it to adjust in real-time according to the audio signal amplitude. This dynamic adjustment reduces inductor ripple current losses by lowering the common mode voltage when high voltage is not needed, while maintaining PWM modulation stability through continuous adaptation to signal conditions.
Solution Approach 2:
The common mode voltage parameter is changed from a constant high value to a variable parameter that changes according to the audio signal amplitude. This parameter change directly reduces inductor ripple current losses by minimizing the voltage across the inductor when the audio signal amplitude is low, thereby reducing energy loss while maintaining reliable PWM operation.
Data Source
AI summary
The disclosure provides a common mode voltage dynamic modulation circuit, a method thereof and a class-D audio power amplifier. The modulation circuit includes: a signal input terminal and a common mode voltage dynamic adjustment module. The signal input terminal is used to receive an audio signal and output a differential audio signal to the common mode voltage dynamic adjustment module. The common mode voltage dynamic adjustment module is used to dynamically adjust a common mode voltage of the differential audio signal according to a preset static common mode bias and a normalized processing result of a swing of the audio signal, track an amplitude of an input audio signal in real time and obtain a continuously adjusted common mode voltage.