Created: May 03, 2016
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The boost converter is a step-up DC-DC switching converter. The idea is that the output voltage is much greater than the voltage source. It uses a transistor switch, which in this circuit uses BJT, to pulse width modulate the voltage into an inductor. It also contains a an energy storage element (capacitor and inductor).
Like the buck converter, the boost converter also use NPN transistor to act as a switch. When the switch is close or ON- state, it results in an increase in inductor current and the magnetic field around the inductor starts to build up. The diode D1, becomes reverse biased. However, when open or OFF-state, the only path opened for the inductor current is the flyback diode D1, the capacitor C1, and load R. The inductor current continues to flow through the diode D1, and pushes new energy to the capacitor charging it slightly. The capacitor voltage starts to rise higher than the input voltage. Thus, making the circuit a boost regulator.
Boost converters can be used in hybrid electric vehicles like the Toyota Prius that uses a 500v motor. The car would nearly use 417 stacked cells without the use of the boost converter. This converter can also be used in portable lighting system like the CCFL in devices like flashlights and LCD backlights.