Download Buck Converter Using 38423/17/2021
Low-power buck converters generally operate between 1 MHz and 6 MHz.
Buck Converter Using 3842 Update Your BrowserFor optimal site performance we recommend you update your browser to the latest version.Update Microsoft Internet Explorer Subscribe Toggle navigation Menu Search Analog Dialogue About 50 Years Archives StudentZone RAQs Resources LT Journal Archive Technical Articles Technical Books FAQs Videos Webcasts Application Notes Analog.com Engineer Zone Wiki Subscribe Subscribe Provide us with your email address to get Analog Dialogue delivered directly to your inbox Follow Us Join our Analog Devices Inc.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.The batterys 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. A simple way to reduce the battery voltage to a lower dc voltage is to use a low-dropout regulator (LDO). Unfortunately, power not delivered to the load is lost as heat, making LDOs inefficient when V IN is much greater than V OUT. A popular alternative, the switching converter, alternately stores energy in an inductors magnetic field, and releases the energy to the load at a different voltage. Its reduced losses make it a better choice for high efficiency. Buck, or step-down converters covered hereprovide lower voltage. Boost, or step-up convertersto be covered in a future articleprovide higher output voltage. Switching converters that include internal FETs as switches are called switching regulators, while devices requiring external FETs are called switching controllers. Most low-power systems use both LDOs and switching converters to achieve cost and performance objectives. Nonoverlapping switch drives ensure that only one switch is on at a time to avoid unwanted current shoot through. The inductor is connected to V IN, so current flows from V IN to the load. ![]() The inductor is connected to ground, so current flows from ground to the load. The current decreases due to the negative voltage across the inductor, and energy stored in the inductor is discharged into the load. When operating in continuous conduction mode (CCM), the inductor current never drops to zero; when operating in discontinuous conduction mode (DCM), the inductor current can drop to zero. The current ripple, shown as I L in Figure 2, is typically designed to be 20 to 50 of the nominal load current. The term synchronous indicates that a FET is used as the lower switch. Buck regulators that use a Schottky diode in place of the lower switch are defined as asynchronous (or nonsynchronous). For handling low power, synchronous buck regulators are more efficient because the FET has a lower voltage drop than a Schottky diode. However, the synchronous converters efficiency at light load will be compromised if the bottom FET is not released when the inductor current reaches zero, and additional control circuitry increases the complexity and cost of the IC. PWM holds the frequency constant and varies the pulse width ( t ON ) to adjust the output voltage.
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