Integrated Digital Class-D Audio Amplifiers (AC149-101-0)

SynopsisSwitch mode Class-D audio power amplifiers can achieve significant power efficiency improvement over the conventional linear topologies such as Class-A or Class-AB. However, Class-D audio amplifiers are sensitive to modulator non-linearity, power stage non-idealities and power supply noise. This course serves as an introduction for anyone interested in learning the basic concepts and circuit design for analog and digital Class-D audio amplifiers. 

Part I of the course begins with an introduction to the differences between linear and switching audio amplifiers. The advantages and complexities of class-D power amplifiers will be described. Analog and digital PWM sampling methods will then be introduced. The pros and cons of analog vs. digital PWM modulation will be discussed. Special emphasis will be placed on the digital signal processing path, including over-sampling, pre-distortion and delta-sigma modulation that are required to minimize the distortion of the digital PWM signal. Examples of typical digital signal processing architectures for Class-D audio power amplifiers will be illustrated with MATLAB exercises.

Part II of this course will focus on actual circuit design and implementation of integrated digital Class-D audio amplifiers. Discussion will begin with a brief introduction to power semiconductor devices and how they can be integrated into a suitable CMOS compatible Power IC fabrication processes. System partition, choice of output stage configurations, gate drivers and protection circuits will then be discussed. In particular, half bridge, H-bridge, level shifting, dead-time control, over temperature and over current protection circuits will be covered. Spice simulation examples of the output stage IC will also be used as exercise and demonstration. The complete design flow of the integrated digital class-D power audio amplifier will then be discussed. The course will conclude with measurement techniques and a survey of recently published digital class-D power audio amplifiers.

What You Will LearnWe expect that, after attending this short course, the audience will gain understanding of basic concepts and the design challenges in the practical implementation of integrated digital Class-D audio power amplifiers.

Who Should AttendThis course aims at design and sales engineers with interest in consumer electronics. Basic understanding of undergraduate-level electronics circuit design is assumed.

PrerequisiteParticipants must have understanding of basic electronics at diploma or degree levels.

Course MethodologyFor each of the topic covered, the participants are first taught the basic concepts. After that its practical implementation is then covered. Software tools are used to illustrate the concepts and techniques.

Course Duration2 days, 9am - 5pm

Course StructurePart I
1. Introduction to Audio Amplifiers

• Linear Amplifiers - Class A and Class AB
• Switching Amplifiers - Class D
• Critical Performance Specification for Hi-Fi Audio Amplifiers

2. Analog and Digital Sampled PWM Signals

• Digital Modulator Design
• Definitions and conventions
• Modulation Techniques
• Modulator Architecture

3. System Design and Implementation

• PWM Modulator
• Delta-Sigma Modulator
• PWM Distortion Analysis
• PWM Linearization Techniques
• Up-sampling and Interpolation
• Full System Verification
• Additional Considerations
• Design Methodology

Part II
4. Power IC Fabrication Processes

• Integrated Power Devices
• Device performance and trade-off parameters
• MOSFET vs. Bipolar Power Transistors
• Breakdown Voltage
• Ron, Gate Charge, FOM
• Isolation Techniques: Self, Junction, and Dielectric Isolation
• Smart Power IC Processing Technologies: HVCMOS, BCD
• Smart PIC Output Drivers
• Design Considerations: Power Efficiency, Distortn and Reliability
• Half-Bridge, H-Bridge and Gate Driver and level shifter design
• Protection Circuits: Over-Temperature Protection, Over-current Protection
• Power MOSFET Design and Layout
• Packaging: Die Attachment, Wire Bonding, High Pin-count Packages

5. Audio Performance Measurements

• Commonly Used Audio Amplifier Measurements
• Ideal Operating Condition
• THD+N vs Output Power and Power Supply Noise Rejection Measurements

6. Survey of Current Class-D Audio Power Amplifiers

Course Instructor(s)Assoc Prof Dr Ng Wai Tung

Wai Tung Ng is an Associate Professor and the Associate Chair, Undergraduate Studies, Electrical & Computer Engineering, University of Toronto. His current research work covers a wide spectrum, ranging from advanced MOS and RF BJT/HBT device designs, power management circuit, integrated SMPS (Switched-Mode Power Supplies), smart power integrated circuits and fabrication processes. After he obtained his Ph.D. degree in 1990, Dr. Ng joined Texas Instruments, Dallas TX to work on LDMOS power transistors for automotive applications. In 1993, Dr. Ng joined the University of Toronto where he established the Smart Power Integration & Semiconductor Devices Research Group. He has extensive experience in working with the industry to modify standard CMOS technology for smart PIC applications. Prof. Ng also serves on the board of directors for the Auto21 Network Centre of Excellence in Canada, where he is also an active researcher in automotive electronics.