In many applications, one is limited to a fixed DC voltage source, and a regulated output voltage range is required which extends from less than to greater than the input voltage magnitude. A DC-to-DC converter may be utilized to provide this extended range of output voltages. This extended range is provided through the use of a transformer in the converter, and the appropriate design of the turns ratio permits the selection of any desired output voltage range; however, transformers are costly and relative to the converter circuitry quite large in size.
These particular size and cost limitations may be overcome by the use of a switching regulator, which utilizes a two-terminal inductor as an energy storage device. The switching regulator has many advantages; it is easy to design, may be embodied in integrated form with perhaps the exception of the need for a discrete energy storage inductor and a discrete filter capacitor, is small in size and is very power efficient. However, it has the limitation that it cannot provide a continuous up/down voltage output range traversing the input voltage magnitude without inverting the polarity of the DC output voltage relative to the DC input voltage polarity. Hence voltage regulator designs that needed an extended range of controlled DC output voltage without inverting the polarity of the input voltage were forced to utilize the DC-to-DC converter which utilizes a transformer.