In power electronics, a chopper circuit is a type of electronic switching device used in power control and signal applications). A chopper is a static device that converts fixed DC voltage/power to variable DC voltage or power. It is essentially a high-speed switch that connects and disconnects the load from the source at a high rate to get variable or chopped voltage at the output. The period of time for which the power switch stays ON or OFF is referred to as the chopper’s ON and OFF state times, respectively. Choppers are classified based on the voltage output as:
- Step-up chopper (boost converter)
- Step-down chopper (buck converter)
- Step-up/Step-down chopper (buck-boost converter)
A step-up chopper has an average voltage output greater than the voltage input, while a step-down chopper has an output voltage always less than the input voltage. A chopper can be used to increase or decrease the DC voltage level at its opposite side, making it a DC equivalent to an AC transformer having a continuously variable turn ratio.
Chopper circuits are used in various applications, including electric cars, conversion of wind and solar energy, DC motor regulators, and electronic instrumentation where stability and accuracy are essential. In electronic instrumentation, chopper circuits are used to break up the input signal so that it can be processed as if it were an AC signal, then integrated back to a DC signal at the output. This approach is often used to construct pico-voltmeters and Hall sensors).
The various power semiconductor devices used in chopper circuits include GTO, IGBT, power BJT, power MOSFET, and 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 the arrow only.
