Managing Power Electronics: VLSI and DSP-Driven Computer Systems

Chapter 4

DC-DC Conversion Architectures

In the first two sections of this chapter, we will discuss in detail two buck converter cases. The first case is a high current buck converter for desktop, handling high current and thus requiring external power MOSFET transistors. The emphasis here will be on the advantages of a specific architecture for this application, called valley control. The second case is a low current buck converter for ultraportable applications. For such low power applications, the power transistors are integrated on board. In this case, the emphasis is on the design methodology and fast time to market. In the third section we will discuss the active clamp, a method to deliver instantaneous power to the load bypassing the output filter. This method is advantageous because the filter slows down the response of a regular buck converter regardless of the speed of the front end silicon. In the fourth section we will discuss battery charger system architecture for notebooks. Finally in the fifth section we will cover the subject of digital power, a new trend of implementing power with digital techniques in place of traditional analog ones.

4.1 Valley Control Architecture

Modern CPUs require very low voltage of operation (1.5 V and below) and very high currents (up to 100 A). Such power comes more and more frequently from the silver box, a power supply device typically used inside a desktop PC box that provides all the necessary offline power to the PC electronics. ...