The world is now fully habituated with the electrical and electronic devices, with which we could we could perform various day to day tasks with much ease. Hence it is very important to develop devices that are error free and fast responding, with much higher efficiency. As the portable electronics industry progressed over the years, different requirements evolved such as increased the battery lifetime, small and cheap systems, brighter, full color displays and a demand for increased talk time in cellular phones. A continually increasing demand from power systems has placed power consumption at a premium. To carry on with these demands engineers have worked towards developing efficient conversion techniques and also have resulted in the subsequent formal growth of an interdisciplinary field of Power Electronics. However it comes as no surprise that this new field has offered challenges owing to the unique combination of two major disciplines of electrical engineering: electronics and power. By the name, DC-DC Converters mean the input is DC and the output is also DC. The two basic DC-DC Converters are Buck and Boost Converters. Semiconductor devices like Bipolar Junction Transistor (BJT) and Metal Oxide Semiconductor Field Effect Transistor (MOSFET) are used as switch devices, because of which they are operated at higher frequencies. Inductors and Capacitors arranged in different positions in these circuits acts as the filters. The resistance acts as the load in the circuit, which can be varied to study these converters in various conditions. The different types of input dc sources are used like battery, renewable energy sources etc. The converter is operated at different frequency levels to identify and improve the response of the converters at all situations.
DC-DC converters are high-frequency power conversion circuits that use high-frequency switching and inductors, transformers, and capacitors to smooth out switching noise into regulated DC voltages. DC-DC converters come in non-isolated and isolated varieties. There are many types of DC-DC Converters. But the two basic types are — Buck and Boost Converter. A buck converter steps a voltage down, producing a voltage lower than the input voltage. A boost converter steps a voltage up, producing a voltage higher than the input voltage.
Buck Converter
A buck converter is a step down DC-DC converter consisting primarily of inductor and two switches (generally a transistor switch and diode) for controlling inductor. It fluctuates between connection of induction to source voltage to mount up energy in inductor and then discharging the inductor’s energy to the load. When the switch pictured above is closed (i.e., ON-state), the current flowing through inductor linearly rises. The diode doesn’t allow current to flow through it, since it is reverse-biased by voltage. When the switch is opened (i.e., OFF-state), diode is forward biased and the inductor current which was rising in ON case, now decreases.
Boost Converter
A boost converter (step-up converter), as its name suggest step up the input DC voltage value and provides at output. This converter contains mostly a diode, a transistor as switches and at least one energy storage element. Capacitors are usually added to output so as to perform the function of removing output voltage ripple and sometimes inductors are also combined. During the ON period, switch is made to close its contacts which results in increase of inductor current. During the OFF period, switch is made to open and thus the only path for inductor current to flow through the fly-back diode ‘D’ and the parallel combination of capacitor and load. This enables capacitor to transfer energy gained by it during ON period.
These 2 are the basic DC-DC Converters, using which other converters including Buck-Boost Converter and Cuk Converter are designed and built. Adding to this, various other converters are in the process of fabrication.
To know more, read my research paper in ResearchGate
DC-DC Converters : A Study of Technology
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