Switching Regulator

Definition

A switching regulator is a circuit that uses a power switch, an inductor, and a diode to transfer energy from input to output. The power switch, usually a Field Effect Transistor (FET), is turned on and off by a switching controller IC that monitors the output of the switching regulator in a feedback control loop. This ensures that it maintains a constant output under normal operating conditions. In some switching regulators, the FET is a discrete component, external to the switching controller. In other versions, the FET and controller are in the same IC.

The basic components of the switching circuit can be rearranged to form a step-down (buck)converter, a step-up (boost) converter, or an inverter (fly back). These designs are shown in Figures 1, 2, 3, and 4 respectively, where Figures 3 and 4 are the same except for the transformer and the diode polarity.

Why Use a Switching Regulator instead of a Linear Regulator?

Switching regulators offer three main advantages compared to linear regulators. First, switching efficiency can be much better. Second, because less energy is lost in the transfer, smaller components and less thermal management are required. Third, the energy stored by an inductor in a switching regulator can be transformed to output voltages that can be greater than the input (boost), negative (inverter), or can even be transferred through a transformer to provide electrical isolation with respect to the input.

Given the advantages of switching regulators, one might wonder where can linear regulators be used? Linear regulators provide lower noise and higher bandwidth; their simplicity can sometimes offer a less expensive solution. There are, admittedly, disadvantages with switching regulators. They can be noisy and require energy management in the form of a control loop that requires a switching controller. Fortunately, the solution to these control problems is integrated in modern switching controller ICs.

Switching Regulators Diagrams

Synonyms