Basic DC-DC Converter Theory

Several methods exist to achieve DC-DC voltage conversion. Each of these methods has its specific benefits and disadvantages, depending on a number of operating conditions and specifications. Examples of such specifications are the voltage conversion ratio range, the maximal output power, power conversion efficiency, number of components, power density, galvanic separation of in- and output, etc. In order for the designer to obtain a clear view of the DC-DC voltage conversion methods and their individual advantages and disadvantages, with respect to monolithic integration, the three fundamental methods are discussed in this chapter. The first and oldest method of performing DC-DC voltage conversion is by means of linear voltage converters (resistive dividers), which are explained in Sect. 2.1. The second method is by means of capacitor charge-pumps, as explained in Sect. 2.2. The latter two methods are explained more briefly as this work will mainly concentrate on inductive type DC-DC converters, which are discussed in Sect. 2.3. Power conversion efficiency is in most cases a primary specification for any given energy converter. Therefore, a formal method for the fair comparison of DC-DC step-down voltage converters, in terms of power conversion efficiency, is introduced in Sect. 2.4. This method is referred to as the Efficiency Enhancement Factor (EEF). The chapter is concluded in Sect. 2.5.