This component also suppresses any surges that may occur when the switch opens. As soon as the switch opens, the inductor reverses the voltage at its ends and sends the diode into conduction.In other words, the switch is in normal conduction, and the current normally flows from the voltage generator to the load. The capacitor is therefore charged with this current. When the switch is closed, the current normally flows through it and does not pass through the diode, which is inversely polarized.We can now observe the operation and function performed by the electronic components in the two phases of DC/DC converter operation, i.e., when the switch is in the on position and in the off position: Usually, the use of a large output capacitance reduces this problem significantly.įigure 2: Step-down converter with resistor and inductor as load It may be affected by oscillations, deliberately amplified in the figure. v(out) is the output signal lower than the input signal.As can be seen, it is affected by peaks and oscillations that make the signal saturated with interference. v(d) is the signal present at the ends of the diode.v(sw) is the rectangular signal (pulse train) supplied by the system controlled by the electronic switch.v(in) is the DC input voltage and supplies the entire conversion circuit.On the oscillograms in the figure, the following signals can be observed: The output is an average voltage, between 0 V and V s, according to the parameters set by the signal’s “on” percentage. The electronic switch generates a rectangular signal with a non-zero voltage value and an appropriate duty-cycle parameter. Its operation is quite simple: A DC voltage V supplies the circuit. The output filter network consists of an inductor L, a capacitor C, and a load resistor R. It mainly consists of a MOSFET as SW switch and a diode D. This DC/DC converter provides an output voltage lower than the input voltage. Step-down DC-DC converter with resistor and inductor as loadįigure 2 shows a step-down circuit’s generic schematic and operating principle with an LC-type load. The switching frequency is higher than the ultrasonic frequency (>20 kHz). The basis of the switching circuit is an electronic switch (a BJT, MOSFET, or other) that alternately switches on and off at a very high frequency (see Figure 1). In theory, it would be possible to lower the input voltage by using a large power resistor or power divider, but the energy wasted unnecessarily in heat would be enormous, and such a solution would return only a few percentage points of efficiency. Modern technology today encapsulates the entire complex circuit structure in a single enclosure. A step-down, or buck, converter is a DC/DC power converter that reduces the input voltage and provides a lower output voltage. In DC/DC switching circuits, appropriately driven electronic switches and components are used to store energy, allowing it to be converted. With DC/DC conversion, it is quite easy to have sophisticated power supplies, with the possibility of working with different supply voltages according to one’s needs. The conversion of DC voltage into another DC voltage is used in various power applications, such as the control of electric-vehicle motors and other applications in which it is necessary to continuously vary the speed of rotation while keeping the torque and force parameters intact. Its transformation is somewhat more complicated and requires special strategies and methodologies and extremely complex electronic components. Unfortunately, it is not so simple for DC voltage. A transformer is sufficient to raise or lower the alternating mains voltage very easily and safely. One of the main reasons why electricity is distributed in the alternating form in homes is the simplicity of the transformation. Varying the voltage of a direct-current source - DC/DC converter In this chapter, we will see which methods are most commonly used. The variation of the voltage can be either increasing or decreasing. The DC/DC converter is a complex device whose task is to carry out a DC voltage transformation from one level to another. Often, the need to convert one DC voltage into another in the industrial, medical, or even household field lies at the heart of many applications.
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