Читать книгу Origin of Power Converters - Tsai-Fu Wu - Страница 28

Based on the natural law, Faraday's law, there exists only voltage source, and the output load is usually supplied with voltage form. Thus, the source and load can be configured by the circuit shown in Figure 2.1a. To control the power flow from the source to the load, a control gear or a switch is adopted to link the source and load, as shown in Figure 2.1b. Since source voltage V_i is not necessarily always equal to load voltage V_o, there might exist an inrush current through the switch when switch S₁ is turned on. An inductor is therefore inserted in series with the switch, as shown in Figure 2.1c, to limit current slew rate. However, when switch S₁ is turned off, there is no path for inductor current to flow continuously, resulting in high voltage spike imposing on the other components. Thus, a freewheeling diode D₁ is introduced to provide a path for the inductor current, as shown in Figure 2.1d, and it is the buck converter. How to prove that the buck converter is the origin of converters is left for later discussion.