A basic introduction is given for loop control theory from the perspective of a power supply. Namely, negative feedback loops as control loops are being used in almost every linear and switch mode power supply in order to stabilize the output. The major concepts like input, output, controlling element, controller, desired output value and error and feedback are presented in a simple fashion. As a real-life example the regulation of the output temperature of a shower is being used in order to explain the above concepts. The effect of an external perturbation is also shown after the system reached static equilibrium.
In a negative feedback control loop the controller will adjust the control element such, to keep the output stable. The controller is obtaining the control signal based on an error calculated between the expected value and the output value. As a function of the error, the controller will send feedback to the control element in a closed loop. This concept is being implemented to regulate the output of switch mode and linear power supplies, where the feedback is applied to a power transistor acting as control element.
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