Note that the switching regulator operation can be continuous or discontinuous. Buck converter topology and operating waveforms. The current decreases due to the negative voltage across the inductor, and energy stored in the inductor is discharged into the load. The inductor is connected to ground, so current flows from ground to the load. In Phase 2, Switch A is open and Switch B is closed. The current increases due to the positive voltage across the inductor. The inductor is connected to V IN, so current flows from V IN to the load. Nonoverlapping switch drives ensure that only one switch is on at a time to avoid unwanted current “shoot through.” In Phase 1, Switch B is open, and Switch A is closed. Typical low-power portable system.īuck regulators consist of two switches, two capacitors, and an inductor, as shown in Figure 2. Most low-power systems use both LDOs and switching converters to achieve cost and performance objectives. Switching converters that include internal FETs as switches are called switching regulators, while devices requiring external FETs are called switching controllers. Boost, or step-up converters-to be covered in a future article-provide higher output voltage. Buck, or step-down converters-covered here-provide lower voltage. Its reduced losses make it a better choice for high efficiency. A popular alternative, the switching converter, alternately stores energy in an inductor’s magnetic field, and releases the energy to the load at a different voltage. ![]() Unfortunately, power not delivered to the load is lost as heat, making LDOs inefficient when V IN is much greater than V OUT. A simple way to reduce the battery voltage to a lower dc voltage is to use a low-dropout regulator(LDO). The battery’s usable output varies from 3 V to 4.2V, while the ICs require 0.8 V, 1.8 V, 2.5 V, and 2.8 V. ![]() These devices typically require several independent supply voltages, each usually different than the voltage supplied by the battery or external ac-to-dc power supply.įigure 1 shows a typical low-power system operating with a Li-Ion battery. ![]() Smartphones, tablets, digital cameras, navigation systems, medical equipment, and other low-power portable devices often contain multiple integrated circuits manufactured on different semiconductor processes. How to Apply DC-to-DC Step-Down (Buck) Regulators Successfully
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