Closed-Loop Audio Amplifier Power Stage for Supply Rejection
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Solution Overview
Problem
Conventional pulse width modulated (PWM) input power stages in audio amplifiers have poor power supply rejection performance due to open-loop configurations, leading to unstable output voltages during transient power supply changes.
Innovation Solution
Implementing a closed-loop power stage with a feedback circuit that regulates the duty cycle of the square-wave signal in response to power supply voltage variations, using a comparator, capacitor, driving circuit, and switching devices to maintain voltage stability and adjust gain through resistor ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an open-loop PWM input power stage is used, then the device complexity is reduced, but the power supply rejection performance deteriorates
Solution Approach 1:
The patent applies feedback by introducing a feedback circuit that samples the output voltage and feeds it back to the control circuit. The control circuit compares the feedback signal with a reference signal and adjusts the duty cycle of the PWM signal accordingly, forming a closed-loop control system that automatically compensates for power supply voltage variations and maintains stable output voltage.
2Ease of manufacture
If an open-loop configuration is used, then the ease of manufacture is improved, but the stability of output voltage during transient phase deteriorates
Solution Approach 1:
The feedback circuit continuously monitors the output voltage and provides real-time correction by adjusting the PWM duty cycle. During transient phases when power supply voltage changes suddenly, the feedback mechanism quickly detects the deviation and modifies the switching duty cycle to restore the output voltage to its set point, ensuring stable operation.
Solution Approach 2:
The patent implements dynamic adjustment of the PWM duty cycle based on real-time feedback conditions. The control circuit dynamically modifies the switching parameters in response to changing load conditions and power supply voltage variations, enabling the system to adapt and maintain stability under varying operating conditions.
Data Source
AI summary
The present technology relates generally to a closed-loop power stage and audio amplifier circuits comprising the same. The present technology further provides a method for controlling an amplifier circuit. The closed-loop power stage is configured to receive a PWM input signal having a first frequency and a first duty cycle, a power supply voltage, and a bias signal related to the power supply voltage, and to output a square-wave signal having a second frequency and a second duty cycle. The closed-loop power stage comprises a feedback loop which is configured to regulate the second duty cycle of the square-wave signal in response to a variation in the power supply voltage. The audio amplifier circuit comprising the closed-loop power stage may have a stable output voltage and thus have good power supply rejection performance.