Abstract: The buck/boost converter successfully addresses the challenge of regulating a 12V from the wide input-voltage swing associated with the sealed lead-acid battery. You can't derive a regulated 12V output from a 12V lead-acid battery by using a simple boost converter because it it can't accept an input voltage that is greater than its output voltage. Conversly, a buck converter is a combination of buck and boost circuitry that successfully addresses the challenge of the wide input-voltage swing associated with the seales lead-acid battery. The circuit of the MAX641 is a buck/boost converter that provides 100mA at 12V and accepts 8V to 16V inputs. Both ends of the circuit's inductor are switched by separate power MOSFETs, which the MAX641 drives directly via ist LX and EXT outputs. These outputs operate out of phase, the the p- and n-channel FETs turn on at the same time. When both n- and p-channel FETs turn off, the two Schottky diodes steer the coil's discharge current to the 12V output. A slight drawback of this circuit is that the converter's efficiency is less that that of a pure busk or boost converter, becuase the two MOSFETs and two diodes increase losses in the charge and discharge current paths. Nevertheless, the circuit still delivers 100mA at a respectable 70% efficiency figure. An additional benefit of this type of circuit is that you can control its operation with a TTL-level signal. Overriding the VFB input with a high-level TTL signal (such as the diode-coupled inverter output shown) fools the MAX641's internal feedback cicuitry into thinking that the output is too high, so the chip turns off both MOSFETs. The circuit's idle current is around 400µA. 相关型号   APP 411: Jul 09, 1998 MAX641 5V/可调、10W、CMOS、升压型、开关稳压控制器 完整的数据资料 (PDF, 1.9MB) 免费样品 自动更新 需要自动接收最新发布的应用笔记吗？请订阅EE-Mail™ (English only)。 我们期待您的反馈！ 喜欢？不喜欢？有待改善？或为我们提供建议？请与我们联系 — 我们将根据您的意见或建议改善我们的工作。 网页评价或提供建议   下载，PDF格式 (28kB)  AN411, AN 411, APP411, Appnote411, Appnote 411