Phase control circuits are electronic systems used to manage the power delivered to electrical devices by controlling the phase angle of the voltage and current. They are commonly found in applications like light dimmers, motor speed controllers, and heating systems. By adjusting the phase, these circuits can effectively regulate the amount of power consumed, leading to energy savings and improved performance. These circuits typically use components such as thyristors or triacs to switch the power on and off at specific points in the AC cycle. This allows for precise control over the output, making phase control circuits essential in various industrial and consumer applications.