D类音频放大器基本知识英文版.pdf

AN-1071 International Rectifier • 233 Kansas Street, El Segundo, CA 90245 USA Class D Audio Amplifier Basics by Jun Honda Jonathan Adams What is a Class D Audio Amplifier -Theory of Operation Topology Comparison (Linear vs. Class D) Analog Audio to PWM Conversion PWM to Analog Audio Conversion Analogy to Sync-Buck Converter Power Loss in MOSFET Topology Comparison (Half Bridge vs Full Bridge) Major Cause of Imperfection THD and Dead Time Audio Performance Measurement Shoot through Prevention Power Supply Pumping EMI Consideration Conclusion 1 AN-1071 What is a Class D Audio Amplifier - non-linearity of Class B designs is overcome, Theory of Operation without the inefficiencies of a Class A design. Efficiencies for Class AB amplifiers is about A Class D audio amplifier is basically a switch- 50%. ing amplifier or PWM amplifier. There are a num- ber of different classes of amplifiers. We will take Class D – This class of amplifier is a switching a look at the definitions for the main classifica- or PWM amplifier as mentioned above. This tions as an introduction: class of amplifier is the main focus of this appli- cation note. In this type of amplifier, the switches Class A – In a Class A amplifier, the output de- are either fully on or full