The Digital Control Loop

This chapter introduces the main blocks in the digital control loop around a switched-mode power converter and provides an overview of the design issues the digital scenario brings in from a system-level standpoint. It explains that digital control of a switched-mode power converter differs from analog control in two aspects: time quantization and amplitude quantization. The chapter commences with an introduction on the digital control loop. It then moves on to introduce the characteristics and modeling of the main blocks in the digital control loop, the analog-to-digital (A/D) conversion, the digital compensator, and the digital pulse width modulator (DPWM). This is followed by a discussion on loop delays introduced by the time quantization and the sampling processes in the digital controller. Finally, the chapter discusses the limitations of this approach, using averaged models in the digital design.