In a small digital camera, two cell structure has become mainstream. There are two common AA batteries (alkaline or Ni-MH) or a lithium laptop battery. Sometimes the camera will be designed at the same time with two batteries. This structure will give power designers a special challenge, because, some time will need to upgrade the battery voltage to generate a specific voltage (for example, 3.3 V). In other times, we must reduce the battery voltage to generate the same voltage. This requires a l / buck (or buck / boost) design. In the old design of the camera, sometimes the use of anti-IP (based on transformer) designed to solve this problem, huge, very clumsy and inefficient - often less than 70 percent efficiency.

With multiple groups of the output of integrated design can be very easy to get buck / boost converters, used only to boost the power supply for the buck converter can be. This method in the past hp laptop battery have not been widely used to solve the buck / boost problems, because it requires a separate buck and boost a high level of efficiency, can get enough of efficiency. However, the current mode boost and buck converter can reach 95 percent of the efficiency of the composite efficiency to 90 percent, far better than flyback and SEPIC design can achieve the target.

Under what circumstances the manner in which the construction of buck-boost converter depends on the battery type. 2 AA batteries work in the 1.8 V to 3.6 V, and a lithium battery work in the 2.7 V to 4.2 V. Single lithium battery-powered design will need to buck / boost converters produce 3.3 V. Use two AA batteries of the design may also be used buck / boost converter, because the DSP nuclear power (typical for the 1.5 V or 1.8 V) when the F2024B is heavy because not enough voltage headroom and not directly from the battery-powered . In both cases, can even grade through the DC-DC converters are highly efficient buck / boost converters. 3.3V power supply through the first boost to 5 V (VSU 5V, Figure 2), and then to 3.3 V buck by (VM 3.3V, 2). 1.8V power supply can also use the same 5 V-driven buck converter input (PVSD) and received. Of course, single-use lithium batteries, used in the relief core power directly from the battery-driven (as shown in Figure 2).

Compact digital camera could use a smaller F2299A. Of course, the smaller the battery to a higher efficiency requirements. In addition, smaller batteries can not be as large as the battery supply peak load, power management system must be shut down frequently do not have the power to extend battery life. When power again opened, it should not draw the battery voltage will pull down the high current. Figure 2 shows the integrated power to gradually raise the controlled rate of all imported and therefore the commencement of converters, the input inrush current was reduced to a minimum. It also ensure that the output to predict the way up to facilitate the power sequencing