How Do Voltage Regulators Work?

Linear and switching are the two types of voltage regulators. It generates a fixed output voltage of a preset magnitude that remains constant despite everything on the changes to its load conditions or input voltage.

An active (BJT or MOSFET) pass device is employed by a linear regulator which is controlled by a high gain differential amplifier. A precise reference voltage and the output voltage are compared by the linear regulator. To maintain a constant output voltage, it adjusts the pass device.

Switching regulator on the other hand converts dc input voltage to a switch voltage applied to a power MOSFET or BJT switch. To keep the output remains constant regardless of input voltage or load current changes, the filtered power switch output voltage is fed back to a circuit that controls the power switch on and off times.

What are some of the switching regulator topologies?

The three common topologies are: buck (step-down), boost (step-up) and buck-boost (step-up/step-down). Some other topologies include the flyback, SEPIC, Cuk, push-all, forward, full-bridge and half-bridge topologies.

How does switching frequency impact regulator designs?

Higher switching frequencies mean the voltage regulator can use smaller inductors and capacitors. It also means higher switching losses and greater noise in the circuit. What losses occur with the switching regulator? Losses occur as a result of the power needed to turn the MOSFET on and off, which are associated with the MOSFET's gate driver. Also, MOSFET power losses occur because it takes a finite time to switch to/from the conduction to nonconduction states. Losses are also due to the energy needed to charge and discharge the capacitance of the MOSFET gate between the threshold voltage and gate voltage.

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