What is a buck converter?
A buck converter, or stepdown voltage regulator, provides either isolated or nonisolated, switch-mode dc-dc conversion, reducing an input voltage to a regulated, lower output voltage. The figure shows a simplified non-isolated buck converter that accepts a dc input and uses pulse-width modulation (PWM) of switching frequency to control the output of an internal power MOSFET (Q1). An external Schottky rectifier diode, together with external inductor and output capacitors, produces the rectified, filtered dc output. The regulator IC compares a portion of the rectified dc output with a voltage reference (VREF) and varies the PWM duty cycle (on-time vs total switch period) to maintain a constant dc output voltage. If the output voltage increases slightly due to a reduced load, the PWM briefly lowers its duty cycle to reduce the regulated output, keeping it at its proper voltage level. Conversely, if the output voltage tends to go down, the feedback causes the PWM duty cycle to briefly incr
