Table of Contents
Foreword vii
Preface ix
Acknowledgments xi
1 Fundamentals of Audio Amplification 1
1.1 Introduction 1
1.2 Principles of sound and audio amplifiers 2
1.3 A brief history of audio amplifiers 4
1.4 Sound pressure level 5
1.5 Loudspeaker transducers 7
1.5.1 Electromagnetic speaker 7
1.5.2 Piezoelectric speaker 9
1.6 Performance metrics of audio amplifiers 11
1.6.1 Total harmonic distortion plus noise 13
1.6.2 Signal-to-noise ratio 15
1.6.3 Power supply rejection ratio 16
1.6.4 Power supply intermodulation distortion 18
1.6.5 Power efficiency 19
1.7 Audio amplifier classification 23
2 Principles of Class-D Audio Amplifiers 27
2.1 Class-D amplification 27
2.2 Advantages and disadvantages of class-D amplifiers 29
2.3 Class-D output stage power losses 30
2.4 Open loop class-D amplifiers with pulse-width modulation 33
2.5 Layout and printed circuit board recommendations 55
2.6 Typical applications 57
2.6.1 Commercial class-D audio amplifiers typical specifications 59
3 Closed Loop Architectures for Class-D Amplifiers 61
3.1 Closed loop architectures 61
3.2 Pulse-width modulation 64
3.3 Sigma-delta modulation 72
3.4 Self-oscillating modulation 78
3.5 Comparison between modulation schemes 87
4 Class-D Circuit Design Techniques 89
4.1 System implementation 89
4.2 Compensator design 90
4.3 Pulse-width modulator 97
4.4 Class-D output stage design 100
4.5 Output filter 107
4.6 Current and voltage sensor techniques 108
5 Power-Supply Noise Rejection Enhancement for Class-D Amplifiers 115
5.1 Power-supply noise in class-D amplifiers 115
5.2 Power-supply noise modeling in class-D amplifiers 117
5.2.1 Single-ended load 118
5.2.2 Bridge-tied load 119
5.3 Feed-forward power-supply noise cancellation technique 121
5.3.1 System analysis 122
5.3.2 Circuit implementation 125
5.4 Design tradeoffs and methodology 129
5.4.1 Implementation tradeoffs 130
5.4.2 Design procedure 131
5.5 Simulation results 133
5.6 Experimental results with KFPSNC technique 135
5.7 Final remarks 143
6 Sliding-Mode Control for Class-D Amplifiers 145
6.1 Motivation for non-linear controllers 145
6.2 Class-D amplifier with sliding mode controller 146
6.2.1 Controller design with linearity enhancement 149
6.2.2 Architecture of class-D amplifiers with SMC 153
6.2.3 Switching frequency with SMC 158
6.2.4 Design of building blocks 163
6.2.5 Experimental results of CDA with SMC 165
6.3 Integral sliding-mode control for class-D amplifiers 167
6.3.1 Class-D architecture with ISMC 168
6.3.2 Integral sliding mode controller 170
6.3.3 Experimental results of CDA with ISMC 172
6.4 Final remarks 175
7 Class-D Output Stage for Piezoelectric Speakers 177
7.1 Motivation for piezoelectric speakers 177
7.2 Class-D amplifier efficiency for piezoelectric speakers 179
7.3 Class-D architecture for piezoelectric speakers 180
7.4 Stacked-cascode H-bridge output stage 186
7.5 Experimental results for PZ speakers 194
7.6 Remarks on piezoelectric speakers 200
Appendix A Harmonic Distortion in Open-Loop Class-D Amplifiers 201
Appendix B Fundamentals of Sliding Mode Control 211
Appendix C Switching Frequency of Class-D Amplifiers with Sliding Mode Control 223
Bibliography 229
Index 239