Boost Converter




A boost converter also known as step-up converter is a power converter with an output DC voltage greater than its input DC voltage. It is a class of switching-mode power supply containing at least two semiconductor switches which includes a diode and a transistor, and at least one energy storage element. Filters made of capacitors (sometimes in combination with inductors) are normally added to the output of the converter to reduce output voltage ripple. Output voltage ripple can be defined as difference between maximum and minimum output current. Large ripple introduces large loses e.g. harmonics, negative sequence current etc..
 A boost converter is sometimes called a step-up converter since it “steps up” the source voltage. Since power  must be conserved, the output current is lower than the source current. The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. When the switch is turned-ON, the current flows through the inductor and energy is stored in it. When the switch is turned-OFF, the stored energy in the inductor tends to collapse and its polarity changes such that it adds to the input voltage. Thus, the voltage across the inductor and the input voltage are in series and together charge the output capacitor to a voltage higher than the input voltage.
The other function of inductor is to avoid any sudden change in current due to the fact that as these converters are generally attached to battery therefore to  ensure the good efficiency of battery , current should be uniform for most of the time. The other function of capacitor is to absorb AC component of supply which generally originates due to switching.