Created: May 03, 2016
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The figure shown is the basic schematic of a boost converter. Boost converter or step-up converter is a class of switched-mode power supply (SMPS). It is a DC-to-DC converter which primarily steps up voltage from its input supply while stepping down current from its load output. For example, you are to supply 9V to a lamp from a solar panel source but it can only generate up to 1.5V. To answer this problem, you need to boost the generated voltage to the required DC voltage of the lamp by using a boost converter.
This boost converter is designed to have a 30V output voltage with 20mA load current from its 9V input supply. The design contains storage elements and semiconductors (capacitor, inductor, diode and transistor). At the initial “high” period of the square wave on the gate of the MOSFET, the MOSFET conducts which allows current to flow to the terminals of the inductor and starts to store energy in its magnetic field. At this instance, there is a high impedance combination of the diode, capacitor and load which resists current from flowing to right part of the circuit. During the “low” state, as the MOSFET is turned-off, current flows now to the diode, the rapid drop in current causes the inductor to produce a back electromotive force in the opposite polarity to the voltage across it to keep current flowing thus resulting in two voltages in series with each other. This high voltage (Vin + Vl) causes the diode to be in forward biased state allowing the current to flow that also charges up the capacitor to Vin+Vl minus the diode voltage drop to supply the load which results to a higher output voltage than the input supply.
Boost converter can be applied to step-up voltages from DC input sources such as batteries, rectified AC from the main supply, DC solar panels, fuel cells, dynamos and DC generators.