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.