A buck-boost DC/DC converter delivers a regulated output voltage even when the input voltage is below or above that required by the load. Buck-boost converters adequately serve the needs of battery-powered consumer devices where the required input range is rather narrow; in many cases from 1.8 to 5.5 VDC. However, the situation is different when it comes to industrial and automotive applications where input voltages can vary over a very wide range.
For example, the automotive battery presents one of the most challenging inputs to a power supply. While its nominal voltage can vary from 10.6 to 15 V, depending on the battery’s state of charge, the ambient temperature, and the alternator, cold-crank conditions can push the rail below 4 V and line transients can produce 40 V spikes. That means it can vary from less than 4 V to over 40 V. In addition, experts say that the automotive power rail is also subject to a variety of dynamic disturbances produced by changes in the engine, transitioning loads, and inductive transients in the wiring harness.
To address the needs of industrial and automotive applications, power semiconductor suppliers such as Intersil, Linear Technology, and Texas Instruments, among others, have developed a variety of low-noise, high-performance, wide-input buck-boost DC/DC converters. As a result, a variety of products are available that can help power designers confront the challenges of generating a stable output voltage using a single low-cost inductor, despite very wide fluctuations in the input voltage range.
For more detail: Buck-Boost DC/DC Handles Wide Input-Voltage Range