What Is an Adjustable Buck Converter?

Primary Function

• Adjustable buck converters have the ability to adjust the current of any DC power supply. However, its main function is to limit current flow based on the exact amount of energy required by a device plugged into the power supply. Buck converters also have an inductor that stores energy and a capacitor that limits it, but supplies a constant flow of electricity. The system works by switching back and forth between the inductor and capacitor through a switching regulator.

Switching Regulator

• The switching regulator works by using a diode, a transistor and an inductor to transfer from input to output. The alternative to a switching regulator is a linear regulator. Adjustable buck converters use a switching regulator over a linear regulator for several reasons. First, linear regulators bleed off excess power and lose energy in the form of heat, making them significantly less efficient. Secondly, because switching regulators lose less energy, smaller components can be used and less thermal management is required. Third, the energy that is stored in the inductor can be released, providing more energy, if necessary, than the normal output of the DC power supply.

Charge and Discharge

• The switch regulator in a buck converter has two primary phases -- charge and discharge. During the charge phase the switch regulator is closed, which prevents the capacitor from discharging to ground, and input voltage is directed into the inductor. As a result, the current rises over time in the inductor. In a discharge phase the switch regulator opens, allowing the current flow from the inductor to enter the rectification diode. In the rectification diode the output current is charged by the energy from the inductor, which raises the voltage above regular output levels. In principle the higher the charge present in the inductor the faster and bigger the energy boost.

Efficiency

• In normal converters the most energy is lost in the rectification diode because a big portion of the charging energy is lost to heat. As a result, heat sinks or fans are necessary for thermal management, reducing efficiency. Switching regulators use Schottky rectifying diodes and metal--oxide--semiconductor field-effect transistor (MOSFET) switches, which reduces energy loss to heat. As a result, it is possible for adjustable buck converters to have above 90 percent efficiency ratings.