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The buck–boost converter is a type of DC-to-DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude. It is equivalent to a flyback converter using a single inductor instead of a transformer.〔(The Flyback Converter ) - Lecture notes - ECEN4517 - Department of Electrical and Computer Engineering - University of Colorado, Boulder.〕 Two different topologies are called ''buck–boost converter''. Both of them can produce a range of output voltages, from an output voltage much larger (in absolute magnitude) than the input voltage, down to almost zero. ; The inverting topology : The output voltage is of the opposite polarity than the input. This is a switched-mode power supply with a similar circuit topology to the boost converter and the buck converter. The output voltage is adjustable based on the duty cycle of the switching transistor. One possible drawback of this converter is that the switch does not have a terminal at ground; this complicates the driving circuitry. Neither drawback is of any consequence if the power supply is isolated from the load circuit (if, for example, the supply is a battery) because the supply and diode polarity can simply be reversed. The switch can be on either the ground side or the supply side. ; A buck (step-down) converter combined with a boost (step-up) converter : The output voltage is typically of the same polarity of the input, and can be lower or higher than the input. Such a non-inverting buck-boost converter may use a single inductor which is used for both the buck inductor and the boost inductor,〔("Non-inverting Buck-Boost Regulator" (p.9) )〕〔(ST AN2389: "An MCU-based low cost non-inverting buck-boost converter for battery chargers" )〕〔 Motorola Semiconductor. ("Application note AN954: A Unique Converter Configuration provides step-up/down functions" ). 1985. "... a unique step-up/down configuration can be created ... which still employs a single inductor for the voltage transformation." 〕 sometimes called a "four-switch buck-boost converter",〔 Haifeng Fan. ("Wide VIN and High-Power Challenges with Buck-Boost Converters" ). 2015. 〕 it may use multiple inductors but only a single switch as in the SEPIC and Ćuk topologies. The rest of this article describes the inverting topology. == Principle of operation == The basic principle of the buck–boost converter is fairly simple (see figure 2): *while in the On-state, the input voltage source is directly connected to the inductor (L). This results in accumulating energy in L. In this stage, the capacitor supplies energy to the output load. *while in the Off-state, the inductor is connected to the output load and capacitor, so energy is transferred from L to C and R. Compared to the buck and boost converters, the characteristics of the buck–boost converter are mainly: * polarity of the output voltage is opposite to that of the input; * the output voltage can vary continuously from 0 to (for an ideal converter). The output voltage ranges for a buck and a boost converter are respectively to 0 and to . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Buck–boost converter」の詳細全文を読む スポンサード リンク
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