DC – DC Booster:
Booster converter is a combination of Transistors, diodes, and/or inductor or capacitor. The combination of active electronic elements (diodes and transistors) provides a DC voltage step up (say 1.5 to 9 v) while the combination of passive elements acts as a filter to reduce ripples.
Its basic function is to step up DC voltage because we know that transformers only work on AC circuits.
All DC-DC boosters are choppers however step up choppers are dc to dc boosters.
Chopper is a basically static power electronics device which converts fixed dc voltage / power to variable dc voltage or power. It is nothing but a high speed switch which connects and disconnects the load from source at a high rate to get variable or chopped voltage at the output.
Chopper can increase or decrease the dc voltage level at its opposite side. So, chopper serves the same purpose in dc circuit transfers in case of ac circuit. So it is also known as DC transformer.
Devices used in Chopper:
Low power application: GTO, IGBT, Power BJT, Power MOSFET etc.
High power application: Thyristor or SCR.
These devices are represented as a switch in a dotted box for simplicity. When it is closed current can flow in the direction of arrow only.
Step down Chopper:
Step down chopper as Buck converted is used to reduce the input voltage level at the output side. Circuit diagram of a step down chopper is shown in the figure below.
Step up Chopper or Boost Converter (DC DC BOOSTER):
Step up chopper or boost converter is used to increase the input voltage level of its output side. Its circuit diagram is shown in figure below.