Applied Embedded Electronics

Chapter 4. Power Systems

Providing system power can be a simple matter, but for complex systems it can turn into a significant design issue. Power and ground (P&G) are common to an entire system and can be a smoky failure point, a common path for noise into the entire system, or a path where the power demand in one place affects the performance someplace else.

Safe AC power, safe failure scenarios, regulatory compliance issues, suitable noise levels on power, controlled up/down power cycles, and stable power under highly variable loads are all part of a reliable system. Understanding the options available among power converters and how to configure the power system is the goal. Designing an AC/DC converter from scratch is rarely necessary, as many off-the-shelf converters are available that are easily implemented into a system.

After initial AC/DC power conversion, additional items such as local regulation, multiple voltages for different circuits, high-frequency bypassing, selective device decoupling, power monitors, and power cycling controls are commonly needed. In addition, several source-power scenarios exist: disposable battery, battery with charging capability, external AC/DC converter, or AC/DC converter inside the system.

This chapter discusses all of these and highlights their similarities and differences.

Split Phase AC Mains Power

What does AC mains power consist of? In the United States at the residential level (Figure 4-1), the AC power grid feeds a local step-down ...