Chopper Control Strategies: A Comprehensive Guide

A chopper, also known as a DC-DC converter, is an electronic circuit used to control the power delivered to a load by intermittently interrupting the current using a switching device.

The main objective of chopper control is to regulate the average output voltage or current, and various control strategies are used to achieve this. Here are some common control strategies for choppers:

Pulse Width Modulation (PWM)

PWM is one of the most popular control strategies in chopper circuits. It works by varying the width of the pulse applied to the chopper switch while keeping the frequency constant. By adjusting the duty cycle (the percentage of time the switch is on), the average output voltage can be controlled. PWM offers good efficiency and is relatively simple to implement.

Voltage Mode Control

In voltage mode control, the output voltage is compared to a reference voltage. The resulting error signal is then used to adjust the duty cycle of the chopper. The goal here is to maintain the output voltage at a desired level.

Voltage mode control is effective in applications where precise voltage regulation is needed.

Current Mode Control

In current mode control, the current flowing through the load is sensed and compared to a reference current. The error signal generated from this comparison is used to control the duty cycle of the chopper. This strategy is particularly useful in applications where maintaining a constant output current is critical.

Hysteresis Control

Hysteresis control, sometimes called bang-bang control, compares the actual output voltage or current with upper and lower reference values. If the output goes beyond a certain hysteresis band, the chopper is either turned on or off to bring the output back within the desired range.

Hysteresis control is known for its simplicity and fast response.

Sliding Mode Control

Sliding mode control is a nonlinear control strategy that aims to force the system’s trajectory to “slide” along a predefined sliding surface. This approach provides robust performance and is well-suited for chopper control in applications with uncertain parameters.

Feedforward Control

Feedforward control involves anticipating load changes and adjusting the chopper control signals accordingly. By incorporating a feedforward control strategy, the chopper can respond more quickly to sudden load variations, improving overall performance.